The Biology of Sorghum bicolor (L.) Moench (Sorghum)

Biology Document BIO2017-01: A companion document to Directive 94-08 (Dir94-08), Assessment Criteria for Determining Environmental Safety of Plant with Novel Traits

Plant and Biotechnology Risk Assessment Unit
Plant Health Science Division,
Canadian Food Inspection Agency
Ottawa, Ontario

Table of contents

1. General Administrative Information

1.1 Background

The Canadian Food Inspection Agency's Plant and Biotechnology Risk Assessment (PBRA) Unit is responsible for assessing the potential risk to the environment from the release of plants with novel traits (PNTs) into the Canadian environment. The PBRA Unit is also responsible for assessing the pest potential of plant imports and plant species new to Canada.

Risk assessments conducted by the PBRA Unit require biological information about the plant species being assessed. Therefore, these assessments can be done in conjunction with species-specific biology documents that provide the necessary biological information. When a PNT is assessed, these biology documents serve as companion documents to Dir94-08: Assessment Criteria for Determining Environmental Safety of Plants with Novel Traits.

1.2 Scope

This document is intended to provide background information on the biology of cultivated Sorghum bicolor, its identity, geographical distribution, reproductive biology and ecology, related species, the potential for gene introgression from S. bicolor into sexually compatible relatives, and details of the life forms with which it interacts.

Such information will be used during risk assessments conducted by the PBRA Unit. Specifically, it may be used to characterize the potential risk from the release of the plant into the Canadian environment with regard to weediness/invasiveness, gene flow, plant pest properties, impacts on other organisms, and impact on biodiversity.

2. Identity

2.1 Name(s)

Sorghum bicolor (L.) Moench (USDA-ARS 2012)

2.2 Family

Poaceae (Gramineae) family, commonly known as the grass family.

2.3 Synonym(s)

Synonyms for S. bicolor are numerous and include (USDA-ARS 2012):

  • Andropogon arundinaceus Willd.
  • Andropogon drummondii Steud.
  • Andropogon sorghum (L.) Brot.
  • Andropogon stapfii Hook. f.
  • Andropogon subglabrescens Steud.
  • Andropogon verticilliflorus Steud.
  • Holcus bicolor L.
  • Holcus cernuus Ard.
  • Holcus dochna Forssk.
  • Holcus durra Forssk.
  • Holcus saccharatus L.
  • Holcus sorghum L.
  • Milium nigricans Ruiz & Pav.
  • Panicum caffrorum Retz.
  • Rhaphis arundinacea Desv.
  • Sorghum aethiopicum (Hack.) Rupr. ex Stapf
  • Sorghum arundinaceum (Desv.) Stapf
  • Sorghum basutorum Snowden
  • Sorghum brevicarinatum Snowden
  • Sorghum caffrorum (Thunb.) P. Beauv.
  • Sorghum caudatum (Hack.) Stapf
  • Sorghum cernuum (Ard.) Host
  • Sorghum conspicuum Snowden
  • Sorghum coriaceum Snowden
  • Sorghum dochna (Forssk.) Snowden
  • Sorghum × drummondii (Steud.) Millsp. & Chase
  • Sorghum durra (Forssk.) Stapf
  • Sorghum elegans (Körn.) Snowden
  • Sorghum gambicum Snowden
  • Sorghum guineense Stapf
  • Sorghum hewisonii (Piper) Longley
  • Sorghum japonicum (Hack.) Roshev.
  • Sorghum lanceolatum Stapf
  • Sorghum macrochaeta Snowden
  • Sorghum margaritiferum Stapf
  • Sorghum melaleucum Stapf
  • Sorghum mellitum Snowden
  • Sorghum membranaceum Chiov.
  • Sorghum miliiforme (Hack.) Snowden
  • Sorghum nervosum Besser ex Schult. & Schult. f.
  • Sorghum nigricans (Ruiz & Pav.) Snowden
  • Sorghum niloticum (Stapf ex Piper) Snowden
  • Sorghum notabile Snowden
  • Sorghum pugionifolium Snowden
  • Sorghum roxburghii Stapf
  • Sorghum saccharatum (L.) Moench
  • Sorghum simulans Snowden
  • Sorghum splendidum (Hack.) Snowden
  • Sorghum stapfii (Hook. f.) C. E. C. Fisch.
  • Sorghum subglabrescens (Steud.) Schweinf. & Asch.
  • Sorghum sudanense (Piper) Stapf.
  • Sorghum technicum Batt. & Trab.
  • Sorghum usambarense Snowden
  • Sorghum verticilliflorum (Steud.) Stapf
  • Sorghum virgatum (Hack.) Stapf
  • Sorghum vogelianum (Piper) Stapf
  • Sorghum vulgare Pers.

2.4 Common name(s)

S. bicolor is commonly known in English as broomcorn, chicken-corn, common wild sorghum, durra, feterita, forage sorghum, grain sorghum, sweet sorghum, great millet, milo, Rhodesian sudan grass, shallu, shattercane, sordan, sorghum, sorghum-Sudan grass, and Sudan grass (USDA-ARS 2012). French common names include gros mil, sorgho du Soudan, sorgho menu, and sorgho (USDA-ARS 2012).

Common names often only apply to some subspecies, working groups, races, or intended uses. For example, grain sorghum refers to cultivated S. bicolor subsp. bicolor.

2.5 Taxonomy and genetics

The genus Sorghum is a member of the tribe Andropogoneae of the grass family (Poaceae) (USDA-ARS 2012). Sorghum comprises approximately 25 species, and is divided into five subgenera: Chaetosorghum, Heterosorghum, Parasorghum, Stiposorghum, and Eusorghum (Garber 1950; De Wet 1978; USDA-ARS 2012). In addition to S. bicolor, the subgenus Eusorghum contains the agronomically-important species Sorghum propinquum (Kunth) Hitchc. and Sorghum halepense L. (Pers.) (derived from past hybridizations between S. bicolor and S. propinquum (Paterson et al. 1995)).

S. bicolor is a genetically diverse diploid (2n = 2x = 20) (Barkworth 2006; Smith and Frederiksen 2000). The classification of S. bicolor has been controversial and challenging due to high variability within the species (Wiersema and Dahlberg 2007). Snowdon (1936) defined a complex with annual members of Sorghum Moench subg. Sorghum comprising 7 weedy, 13 wild, and 28 cultivated species. All of these species, in addition to perennial members, were later grouped within the single species, S. bicolor (De Wet and Huckabay 1967). A review of the classification and recent refinements can be found in Wiersema and Dahlberg (2007). In the peer-reviewed literature and sources of grower information (seed companies, extension publications etc.) terminology use is inconsistent and it is often challenging to determine the species, subspecies, and race or working group being referenced.

Currently, S. bicolor has three recognized subspecies: subsp. bicolor, subsp. verticilliflorum (Steud.) de Wet ex Wiersema & J. Dahlb, and subsp. drummondii (Steud.) de Wet ex Davidse (Wiersema and Dahlberg 2007).The subspecies bicolor includes the domesticated sorghum used for grain. It is divided based on floral morphology into five interfertile races (Bicolor, Kafir, Caudatum, Durra, and Guinea) that can produce 10 intermediate races (Brown et al. 2011; Harlan and De Wet 1972; Morris et al. 2013). Wild types of S. bicolor are included in the subspecies verticilliflorum. Annual weedy derivatives arising from the hybridization of domesticated sorghum and subspecies verticilliflorum make up the subspecies drummondii. The intergrades of the subspecies drummondii are highly variable due to gene segregation and include shattercane (a feral form) and Sudan grass.

In this document, 'domesticated sorghum' refers to S. bicolor subsp. bicolor. 'Sudan grass' and 'shattercane' both refer to S. bicolor subsp. drummondii. 'S. bicolor' refers to all wild, weedy, and cultivated forms of Sorghum bicolor. The focus of this document is domesticated sorghum, however Sudan grass, sorghum × Sudan grass hybrids, and other cultivated sorghums are also considered.

Taxonomic position (USDA-ARS 2012):

  • Kingdom: Plantae (plants)
  • Subkingdom: Tracheobionta (vascular plants)
  • Superdivision: Spermatophyta (seed plants)
  • Division: Magnoliophyta (flowering plants)
  • Class: Liliopsida (monocotyledons)
  • Subclass: Commelinidae
  • Order: Cyperales
  • Family: Poaceae (Gramineae) (grass family)
  • Tribe: Andropogoneae
  • Genus: Sorghum Moench (sorghum)
  • Species: Sorghum bicolor (L.) Moench (sorghum)

2.6 General description

S. bicolor is a C4 annual or short-lived perennial grass that typically has one generation per growing season. It can produce tillers (adventitious stems originating from the plant base) but not rhizomes. The culms (stalks) typically reach heights from 50 to over 240 cm and are 1 to 5 cm thick, sometimes branching above the base. The nodes are glabrous or have appressed pubescent hairs. The internodes are glabrous. The ligules are 1 to 4 mm long. The leaf blades are 5 to 100 cm long and 5 to 100 mm wide. The inflorescence (panicle) is 5 to 60 cm long, 3 to 30 cm wide, and may be open or contracted. The primary panicle branches are compound, terminating in racemes with 2 to 7 spikelet pairs. The sessile spikelets are bisexual and 3 to 9 mm in length. The glumes are coriaceous to membranous and glabrous to densely hirsute or pubescent. The keels on the glumes (bracts) are usually winged. The upper lemmas vary from being awnless to having a geniculate, twisted, 5 to 30 mm awn. The anthers are 2 to 3 mm long. The pedicels are 1 to 3 mm long. The pedicellate spikelets are 3 to 6 mm long and are usually shorter than the sessile spikelets. The pedicillate spikelets may be staminate or sterile. (Doggett 1988).

Domesticated sorghums produce large caryopses that are often exposed at maturity. Cultivars and environmental conditions affect the nutritional composition of the caryopses and the composition of their components including the pericarp (outer layer), the endosperm (storage tissue), and the germ (embryo). The protein content of the caryopsis ranges from 7.3 to 15.6%; fibre from 1.2 to 6.6%; lipids from 0.5 to 5.2%; and starch from 55.6 to 75.2% (Doggett 1988).

Sorghum used for grain has short panicles and panicle branches while sorghum used for forage is typically leafier, and late maturing (Harlan and De Wet 1972). Sorghum used for grain typically grows 60 to 120 cm tall (Carter et al. 1989) and is usually shorter than sorghums used for forage that can grow over 150 cm tall (Espinoza and Kelley 2004). Sudangrass and sorghum-Sudangrass hybrids are intermediate in height in between grain sorghums and forage sorghums. The distinguishing characteristics of the five interfertile domesticated sorghum races are described in Table 1.

Table 1. Characteristics of domesticated sorghum races adapted from Doggett (1988).
Race Distinct Characteristics
Bicolor
  • Open inflorescences with pendulous branches
  • Long, clasping glumes
  • Relatively small and elliptic grains
Kafir
  • Moderately compact, cylindrical inflorescences
  • Elliptic spikelets
  • Tightly clasping, long glumes
Caudatum
  • Compact to open inflorescences
  • Grains with one side flat, opposite side curved
  • Shorter glumes that expose grains
Durra
  • Compact inflorescences
  • Flat, ovate shaped sessile spikelets
  • Middle-creased lower glume
  • Distinct texture on tip of lower glume
Guinea
  • Large, open inflorescences with pendulous branches
  • Long, separated glumes that expose grains
  • Obliquely twisted grains

3. Geographical Distribution

3.1 Origin and history of introduction

S. bicolor originated in northeastern Africa, where large variability in wild and cultivated forms remains (Harlan and De Wet 1972; Shewale and Pandit 2011; Vavilov 1951). Archaeological evidence from near the Egyptian-Sundanese border supports that S. bicolor was first cultivated 8,500 to 4,000 years B.P. during the early Holocene period (Dahlberg and Wasylikowa 1996). S. bicolor cultivation likely spread from Ethiopia, where it is believed domestication occurred, to Africa, the Middle East, and India along trade and shipping routes over 3,000 years ago (Dahlberg et al. 2011; Shewale and Pandit 2011). Cultivation then spread from India to China along the silk route, and to southeast Asia with seed moving through coastal shipping routes (Shewale and Pandit 2011). S. bicolor was introduced into the United States (U.S.) for commercial cultivation from North Africa, South Africa, and India through the slave-trade at the end of the 19th century (Shewale and Pandit 2011). S. bicolor cultivation in South America and Australia became substantial beginning around 1950 (House 1985; Shewale and Pandit 2011). Currently, S. bicolor is widely cultivated in dry areas of Africa, Asia, the Americas, Europe, and Australia. Sorghum is cultivated between the latitudes of 50°N in North America and Russia and 40°S in Argentina (Smith and Frederiksen 2000).

There is little information on the cultivation of S. bicolor in Canada because production is minimal (Almaraz et al. 2009). Canadian field trials were conducted in the 1970s and 1980s assessing the suitability of domesticated sorghum as a crop (Hume and Kebede 1981). Interest in S. bicolor for forage, grain production, and use for bioenergy has increased in the past decade, especially in southwestern Ontario and Quebec (AERC 2008; Brouillet et al. 2010+; Thivierge et al. 2015). Approximately 5,000 to 8,000 acres of S. bicolor are grown annually in eastern Canada and production and demonstration plots have also been planted in western Canada. On marginal land in eastern Ontario, forage sorghum hybrid CFSH-30 was grown at 1.1 million plants per hectare and yielded 14.5 Mg/ha/year in one study and 1.6 to 4.8 Mg/ha/year in another study where crop establishment was poor (Rennie and Tubeileh 2011). For ethanol crops, a study with three sweet sorghum varieties and four planting densities showed a production potential of up to 16 Mg/ha (with cv. 'Bulldozer') and sugar content as high as 22 Brix (with cv. 'Sugargraze') (Saita et al. 2012). Yields can range considerably among sites and years.

3.2 Native range

Africa
Angola, Benin, Botswana, Burkina Faso, Cameroon, Central African Republic, Chad, Cote D'Ivoire, Egypt, Equatorial Guinea, Ethiopia, Gabon, Gambia, Ghana, Guinea, Kenya, Liberia, Mali, Malawi, Mauritania, Mozambique, Namibia, Niger, Nigeria, Senegal, Sierra Leone, Somalia, South Africa, Sudan, Swaziland, Tanzania, Uganda, Zaire, Zambia, Zimbabwe (USDA-ARS 2012)

3.3 Introduced range

S. bicolor is the world's fifth most important cereal crop after Oryza spp. (rice), Triticum spp. (wheat), Zea mays L. (maize), and Hordeum vulgare L. (barley) (FAO 2015). S. bicolor is widely cultivated throughout tropical, semi-tropical, arid, and semi-arid environments in over 120 countries throughout Africa, Asia, Australia, and Europe including those listed below (FAO 2015; USDA-ARS 2012; Shewale and Pandit 2011).

Oceania
Australia: Almost all production occurs in northeast Australia (Lobell et al. 2015). Naturalised (USDA-ARS 2012).
Asia

China: Production occurs throughout China, concentrated in the region north of the Yellow River and the Qinling Mountains (Gnansounou et al. 2005; Smith and Frederiksen 2000).

India: Naturalised (USDA-ARS 2012). Mainly cultivated on the Deccan Plateau, with minor production in northern India.

Pakistan, Saudi Arabia, Thailand, Yemen (FAO 2015).

Europe
France, Italy, Ukraine (FAO 2015).
Central America
El Salvador, Mexico, Nicaragua (FAO 2015).
South America
Argentina, Bolivia, Brazil, Colombia, Venezuela (FAO 2015).
North America

Canada: Naturalised (USDA-ARS 2012). S. bicolor is infrequently grown in Ontario and Quebec. S. bicolor is not recommended as a forage in Manitoba and Saskatchewan unless the climate warms to where 2700 crop heat units are consistently accumulated during the growing season (May et al. 2007; McCaughey et al. 1996).

United States: Naturalised (USDA-ARS 2012). The U.S. is a global leader in S. bicolor breeding, seed production, and commercial production. Production is concentrated in Texas, Kansas, Nebraska, and Oklahoma (FAO 2015; Smith and Frederiksen 2000).

3.4 Potential range in North America

S. bicolor grows in plant hardiness zones 7 to 13; zones 7 and 8 are present in Canada (Magarey et al. 2008). Based on these plant hardiness zones, the potential range of S. bicolor in Canada includes southern Ontario, the west coast of British Columbia, and small areas of southern Nova Scotia and Newfoundland. S. bicolor may also be suited to areas of Quebec and Alberta (Almaraz et al. 2009; Gaudet and Kokko 1986; Major and Hamman 1981).

3.5 Habitat

Domesticated sorghum does not typically survive in natural environments outside agricultural production. Primarily a crop of hot, semi-arid tropical environments with optimum growth temperatures of 25 to 31°C, domesticated sorghum is also grown in temperate regions (Balole and Legwaila 2006). Domesticated sorghum is drought tolerant with an extensive root system, a waxy bloom on the leaves that reduces water loss, and the ability to stop growth in periods of drought and resume growth under suitable environmental conditions. It requires rainfall of 500 to 800 mm throughout the growing season, and can withstand temporary waterlogging (Balole and Legwaila 2006). Domesticated sorghum tolerates a range of soil types including heavy vertisols, light sandy soils, loams, and sandy loams and soil pH levels from 5.0 to 8.5 (AERC 2008; Balole and Legwaila 2006). Domesticated sorghum and sorghum Sudan grass hybrids are sensitive to cold temperatures and frost (Singh 1985; Verhallen et al. 2003).

S. bicolor subsp. verticilliflorum (wild sorghum) is introduced in most areas that sorghum is cultivated and can occur alongside the crop as an annual weed (Doggett 1988).

S. bicolor subsp. drummondii (shattercane) is widespread in Africa, Asia, Australia, and southern and central Europe. In North America, shattercane can be found from southern Maine through southern Ontario to southern Michigan, westward to southwest British Columbia, and south to Florida and Mexico (Defelice 2006). Reports of shattercane in Canada are rare. However, shattercane is an increasing weed problem in some U.S. states, and is listed as a state noxious weed in Indiana, Maryland, Ohio, and Pennsylvania. Shattercane is also listed a state noxious weed in Iowa when not cultivated (USDA-NRCS, 2012; Brenly-Bultemeier et al. 2002). Shattercane grows in recently abandoned fields, field margins, and cultivated fields, often sympatric with domesticated sorghum (Defelice 2006; Fellows and Roeth 1992).

S. bicolor subsp. drummondii (Sudan grass) is found throughout Africa where domesticated sorghum is grown, it is also cultivated in temperature regions (Andersson and de Vicente 2010; Ejeta and Grenier 2005). It is the name generally applied to weedy derivatives of hybridization between the crop plant S. bicolor and S. arundinaceum. These plants occur in fields of the crop, and may persist for a while in abandoned cultivations (Phillips 1995).

4. Biology

4.1 Reproductive biology

S. bicolor is predominantly self-pollinating, but under specific conditions wind-mediated cross-pollination can occur over 60%, depending on the genotype, and average about 6% (Ellstrand and Foster 1983; House 1985; Pedersen et al. 1998; Schertz and Dalton 1980). As a result of self-pollination and outcrossing, most sorghum landraces grown by subsistence farmers are mixtures of inbred and partially inbred lines (Singh et al. 1997). The level of outcrossing varies and is influenced by the panicle type of the cultivar; typically outcrossing is higher in loose-panicled grassy sorghum and lower in compact-panicled domesticated sorghum. The estimated outcrossing rate in domesticated sorghum under field conditions ranges from 5% to over 40% (Barnaud et al. 2008; Djè et al. 2004; Doggett 1988; Ellstrand and Foster 1983; Schmidt and Bothma 2006). Several pollinator species have been observed consecutively visiting domesticated sorghum flowers (Immelman and Eardley 2000; Schmidt and Bothma 2006). Upon insect collection, sorghum pollen grains were found on all of the insects. However, it was not determined if insect movement resulted in cross-pollination. More studies are needed to determine the extent of insect pollination in S. bicolor.

The flowering and pollination of S. bicolor is described in House (1985), Singh et al. (1997), and Srinivasa Rao et al. (2013). Inflorescence development begins when a floral initial forms 30 to 40 days after germination. Domesticated sorghum normally flowers 55 to 70 days after germination in warm climates, but depending on the genotype, flowering may occur 30 to 100 days after germination. Wet and cool weather can also delay flowering. Flowers begin to open two days after the emergence of the inflorescence from the boot. Flowering starts in the sessile spikelets (multiflowered subdivisions of the inflorescence) at the tip of the inflorescence and progresses downwards over 4 to 5 days. A single panicle may have up to 6,000 florets (Quinby and Karper 1947). All heads do not flower at the same time in a field, so pollen is usually available for 10 to 15 days. Flowering time varies based on the genotype and climate, usually occurring from midnight to mid-morning and peaking around sunrise. The swelling of the lodicules facilitates flower-opening. When the stigma becomes visible, the stamen filaments elongate and the anthers become pendent. When the anthers are dry they dehisce and pollen is shed through the apical pore. Most pollen from a head fertilizes eggs on the same head. Cross-pollination can occur if pollen is blown into the air. The stigma is pollinated before the emergence of the anthers from the spikelets. Pollen grains drift to the stigma and germinate. A pollen tube develops with two nuclei and grows down the style to fertilize the egg. A sperm nucleus fertilizes the egg to form a 2n embryo and the other nucleus fuses with the polar nuclei to form a 3n endosperm. After pollination, the glumes close and the empty anthers and stigmas usually protrude. Some long-glumed varieties are cleistogamous (the florets do not open for fertilization). Unpollinated stigmas remain receptive for up to 16 days. After fertilization, organ differentiation occurs over approximately 12 days. Seeds pass through three development stages: milk, early dough, and late dough, and reach maturity after about 30 days. S. bicolor reproduces through seeds.

4.2 Breeding and seed production

Most improvements to S. bicolor have been achieved using conventional breeding (Grootboom et al. 2010). Conventional sorghum breeding methods include germplasm evaluation and enhancement, backcrossing, pedigree selection, recurrent selection and hybrid development using cytoplasmic and genetic male sterility (House 1985; Huang et al. 2013). Limited genetic variation is found in sorghums in many locations (i.e. the germplasm base is narrow), so crosses between, or selection from collections made within the same area usually result in minimal yield increase (House 1985). To increase desirable traits, collections from other breeding programs, and breeding procedures including the formation of composites, which retain more variability are often used (House 1985). One major crop improvement was the introduction of chemically induced brown midrib mutants that have less lignin in the stalk and, therefore, have improved fibre digestibility (Dowd et al. 2016; OMAFRA, 2009).

Plant biotechnology is increasingly used for S. bicolor improvement with the application of molecular genetics, genomics, and plant transformation. Transgenic traits have been added to S. bicolor using Agrobacterium-mediated transformation and particle bombardment (Casas et al. 1993; Zhao et al. 2000). S. bicolor has been highly recalcitrant to genetic transformation and until recently the transformation efficiency was less than 10% (Andersson and de Vicente 2010). Liu and Godwin (2012) optimized transformation variables and reported transformation efficiencies of over 20% in an inbred sorghum line.

Future traits added to the S. bicolor germplasm will likely improve agronomic performance and increase resistance to insects and diseases. Traits that may be introduced include increased potential yield, increased yield stability, resistance to lodging, resistance to drought, aluminium tolerance, shorter photoperiod (suitability for growing in northern regions), good threshability, larger head size, erect heads, good tillering, improved grain quality, cold tolerance during early development and flowering, increased biomass, improved photosynthetic ability, and a larger root system (House 1985; Huang et al. 2013; Rakshit et al. 2014; Windpassinger et al. 2015). Bacillus thuringiensis Berliner (Bt) genes that confer Lepidopteran resistance have been deployed experimentally in S. bicolor (Girijashankar et al. 2005). Particle bombardment of shoot apices with a synthetic Cry1Ac Bt gene controlled by a promoter from the maize protease inhibitor gene (mpiC1) led to development of sorghum resistant to Chilo partellus Swinhoe (spotted stem borer larvae) (Girijashankar et al. 2005). Other pests of S. bicolor may be targeted using a similar approach. Breeding for disease resistance is underway and the transformation of S. bicolor to increase resistance to anthracnose, a fungal disease caused by Colletotrichum sublineolum P. Henn. Kabat et Bub., and to stalk rot-causing fungi like Fusarium thapsinum, has had some success (Kosambo-Ayoo et al. 2013; Krishnaveni et al. 2001). Future breeding programs may target other major diseases.

Some breeding projects aim to develop nutritionally enhanced domesticated S. bicolor with increased lysine content, protein digestibility, and bioavailability of iron and zinc (Zhao 2007). Biofortified S. bicolor has not been a focus of Canadian breeding programs.

Similar traits to those listed above, are likely to be selected to increase the suitability of S. bicolor as a bioenergy crop specifically increased yield, increased biomass quality, and lignin modification (Basu et al. 2011; Rooney et al. 2007; Saballos 2008). Seed composition, seed structure, and other physical features can affect the conversion of grain to ethanol and may be targeted by breeding programs (Wu et al. 2007). Two lines of transgenic S. bicolor with lignin composition altered to increase the bioenergy production efficiency have been developed using Agrobacterium-mediated transformation (Basu et al. 2011).

In Canada, as of February 2016, S. bicolor seeds do not require variety registration. Varietal purity standards for pedigreed seed production of both foundation and certified domesticated sorghum seed have been developed by the Canadian Seed Growers' Association (Canadian Seed Growers' Association 2010).

4.3 Cultivation and use as a crop

S. bicolor is grown for grain, forage, sugar, bioenergy, brooms, and as a cover crop (Smith and Frederiksen 2000; Verhallen et al. 2003). This document focuses on commercial cultivation. Globally, 50% of domesticated sorghum is used for human consumption; in the U.S., 90% of domesticated sorghum is used for livestock feed (Hamman et al. 2001). Desirable crop characteristics of S. bicolor include its ability to become dormant during drought conditions and resume growth under favorable conditions, and its tolerance of salinity and temporary waterlogging (Heuzé et al. 2012; Srinivasa Rao et al. 2013). In semi-tropical climates, S. bicolor may be double-cropped (Banks and Duncan 1983). Under favorable conditions, domesticated sorghum has a yield potential comparable to rice, wheat, and maize (House 1985).

In Canada, interest in S. bicolor production is increasing, especially in southwestern Ontario and Quebec for use as a bioenergy crop (CFIA 2011; Rooney et al. 2007; Tubeileh et al. 2014). The potential use of S. bicolor for ethanol production is reviewed in Serna-Saldívar et al. (2012). Domestic use of S. bicolor in Canada is primarily for animal feed in the poultry, beef, pork, and pet food industries (AERC 2008; Meja and Lewis 1999). Domesticated sorghum can be ground into flour and used in breakfast cereals, breads, pastries, beer, gluten-free and other food products (Hamman et al. 2001). Forage sorghum is used for green chop, hay, silage and pasture (OMAFRA 2009). Sweet sorghum is grown for the production of syrup (Srinivasa Rao et al. 2013). Also, the dried, stripped panicles of some varieties are used for making brooms (CFIA 2011). S. bicolor is imported to Canada from the U.S. in small quantities (less than $10,000 per year from 2007 to 2009) for brooms (finished and unfinished), propagation, and grain for human consumption or livestock feed (CFIA 2011). The low value of imports suggests that S. bicolor is not being imported for industrial processes.

S. bicolor hybrids can be selected based on the production region, field conditions, intended use, and desired characteristics including yield potential, lodging, maturity, insect resistance, disease resistance, and cold tolerance (Cothren et al. 2000). Management practices are not well developed for S. bicolor in temperate climates; more research is needed to adapt practices from other row and forage crops and optimize them for the Canadian environment (Zegada-Lizarazu and Monti 2012). Agronomic practices vary based on the intended use and hybrids; the following sections summarize common practices. Seed dealers, agronomists, extension personnel, or other experts should be consulted for specific recommendations.

Seedbed preparation begins with harvesting the previous crop to allow time for the control of weeds, decay of crop residue, infiltration and storage of soil moisture, and application of fertilizer (Cothren et al. 2000; Doggett 1988). Land preparation practices include shredding the stalks of the previous crop; disking, chiseling, rotary hoeing, plowing or bedding the land; bed reshaping; and applying herbicides (Cothren et al. 2000). S. bicolor can be grown in conventional or no-till systems (Banks and Duncan 1983). Most S. bicolor cropping systems involve crop rotation. Crop rotation can improve weed control, reduce disease and insect pressure, enhance the physical characteristics of soil, and utilize residual nutrients (Cothren et al. 2000). Common crops grown in a rotation with S. bicolor include winter wheat, Gossypium spp. L. (cotton), and Glycine max (L.) Merr. (soybean) (Cothren et al. 2000).

The optimal planting date for domesticated sorghum varies based on soil temperature, air temperature, soil moisture, and short-term weather predictions (FAO Undated; Duke 1983; Mahmood 2012). In temperate climates, planting occurs in the spring or early summer, whereas in tropical climates planting occurs in the wet season, so moisture is available during plant growth and restricted during harvest (Doggett 1988). Domesticated sorghum germinates when soil temperatures are over 10°C (Anda and Pinter 1994; Mahmood 2012). It is recommended to plant domesticated sorghum when soil temperature at the planting depth reaches 10°C for three consecutive days and the five day projected forecast is acceptable (Anda and Pinter 1994). In Canada, planting in late May or early June when temperatures are over 12°C and the risk of frost has passed is recommended (AERC 2008; OMAFRA 2009). Seeding rates range from 8.5 to 40 kg/ha (AERC 2008; OMAFRA 2009; Kim et al. 1989; Mahmood 2012). Lower seeding rates can be used in ideal planting conditions and when row widths are wide. Higher seeding rates can be used in poor seeding conditions and when row widths are narrow. Domesticated sorghum seeds are planted at depths of 2.5 to 7.5 cm; deeper planting depth is recommended for quick drying soil (Cothren et al. 2000). AERC (2008) recommends shallow planting of 2 to 3 cm in a good seedbed for domesticated sorghum, and 2 cm, or 4 cm in sandy soils, for forage sorghum and sorghum-Sudan grass hybrids. Planting S. bicolor too deep (more than 3.8 cm) may cause poor seedling survival and vigor, while planting too shallow (less than 1.3 cm) may cause poor rooting and lodging of the mature crop (Cothren et al. 2000; Hergert et al. 1993; Mahmood 2012). S. bicolor can be planted using a maize planter with sorghum plates or sorghum cups. For smaller seeds typical of sorghum-Sudan grass hybrids, a grain drill with a grass box or conventional grain drill may be used (AERC 2008). Broadcasting seeds may result in an uneven stand.

Despite the high water use efficiency of S. bicolor, irrigation may be used to increase yield (Cothren et al. 2000). S. bicolor should be fertilized with phosphorus and potash as needed based on soil test results. In Ontario, the recommended nitrogen rate is 100 kg/ha for S. bicolor developed for use as a forage, and 50 to 100 kg/ha for sorghum-Sudan grass hybrids (OMAFRA 2009). A split application of nitrogen is recommended, half at seeding and half after the first cut, to optimize yield and quality (OMAFRA 2009). Fertilizers are applied at-planting, and phosphorous and potassium fertilizers may be applied in fall if ground is not frozen (Cothren et al. 2000). For domesticated sorghum, AERC recommends applying 40 kg/ha nitrogen, 30 kg/ha phosphorus, and 30 kg/ha potassium at-planting, followed by side dressing with 40 kg/ha nitrogen four to five weeks after planting (AERC 2008).

Insect pests and diseases affecting cultivated S. bicolor are discussed in Section 6.

Weeds can decrease yield and affect crop quality. To control weeds, herbicides are applied to almost all domesticated sorghum acres and are essential in most no-till production systems (Stahlman and Wicks 2000). Early in the season, S. bicolor seedlings grow slowly and are weak competitors with many weed species (Espinoza and Kelley 2004). Thus, early season weed control is essential to the successful establishment of seedlings and should start before planting (Stahlman and Wicks 2000). Weed control can be achieved using integrated weed management (IWM) practices, including a combination of mechanical, biological, cultural, and chemical practices (Stahlman and Wicks 2000). Pre-plant tillage is a common means of mechanical weed control. In addition to tillage, other cultural methods can minimize the impact of weeds on S. bicolor including crop rotation, manipulation of crop row spacing and plant population, hybrid selection, and fertilizer timing and placement (Stahlman and Wicks 2000). Cultural control methods are usually used in combination with chemical control in integrated production systems (Stahlman and Wicks 2000). In Canada, the herbicides 2,4-D (group 4), bromoxynil and bentazon (group 6), atrazine (group 5), and prosulfuron (group 2) are registered for post-emergence weed control in S. bicolor (Health Canada 2015).

Typically, the first cut of S. bicolor developed for use as a forage is harvested 60 to 65 days after planting (usually late July or early August) and a second cut is ready 30 to 35 days after the first cut. S. bicolor for use as forage can be cut one to three times per cropping season (AERC 2008; OMAFRA 2009). Regrowth will be faster if at least 10 cm of stubble is left when cutting, or 15 to 20 cm when grazing (OMAFRA 2009). A one-cut silage system will increase yield but decrease feed quality because feed quality drops dramatically after heading. The crop should be wilted and ensiled at approximately 65% moisture content after harvest with a regular forage harvester (AERC 2008; OMAFRA 2009). S. bicolor developed for use as a forage can also be used for green chop, hay, baleage, or pasture (AERC 2008). Also, sorghum-Sudan grass hybrids can be incorporated into cover crops or underseeded with crops such as alfalfa (Verhallen et al. 2003).

Domesticated sorghum is usually harvested from September to November (NASS-USDA, 1997). Domesticated sorghum can be combined using a grain combine with proper adjustments once grain moisture is below 18 to 22% (AERC 2008; McNeill and Montross 2003). At harvest, domesticated sorghum is usually cut as close to the panicles as possible (McNeill and Montross 2003). The grains are free-threshing, with the glumes, lemma and palea removed during combining (Carter et al. 1989). Pre-harvest losses often exceed economic levels if the crop is left standing until moisture levels are suitable for direct marketing (14.0%) or safe storage (13.5% or lower) (AERC 2008; McNeill and Montross 2003). High pre-harvest losses occur because kernels are not completely enclosed by the glumes and are borne in apical panicles, making them susceptible to birds, insects, moulds, and unfavourable weather (McNeill and Montross 2003). To accelerate drying a pre-harvest desiccant can be used (i.e. glyphosate) and grain can be dried after harvest (Health Canada 2015).

In S. bicolor, prussic acid (hydrogen cyanide) and nitrate poisoning can be a concern when the crop is used for forage or ensiling. Prussic acid levels may be higher in young or immature plants, plants suffering from drought stress, plants where a high rate of nitrogen fertilizer was applied, and frost damaged plants. High nitrate levels can lead to nitrate poisoning in livestock and formation of silo gas (nitrogen dioxide, NO2) if the crop is ensiled. Human exposure to silo gas can result in severe respiratory distress, permanent damage to lungs, and death. Of the forages, sorghum-Sudan grass hybrids and cereal crops can accumulate higher nitrate levels than forage grasses and legumes. Steps to reduce prussic acid and nitrate levels in feed are outlined in OMAFRA (2009).

4.4 Gene flow during commercial seed and biomass production

Gene flow from cultivated S. bicolor to other wild and cultivated populations of S. bicolor is likely. S. bicolor is primarily self-pollinating; however, when plants flower simultaneously wind-mediated cross-pollination can occur. S. bicolor pollen does not remain viable for more than a few hours after release, limiting long distance dispersal to a few kilometers (Lansac et al. 1994; Schmidt and Bothma 2006). Cross-pollination may facilitate gene flow to wild, weedy, and cultivated S. bicolor nearby. Bees have been observed in domesticated sorghum fields, but the extent of insect pollination in sorghum is not established (Schmidt and Bothma 2006). Crop-to-crop gene flow can occur among S. bicolor plants grown in the same, or nearby fields, the extent varying based on factors including flowering synchrony, inflorescence morphology, distance, wind, and the fertility of male pollen (Schmidt and Bothma 2006). The estimated outcrossing rate in domesticated sorghum plants under field conditions ranges from 5% to over 40%; though few studies have empirically measured crop-to-crop gene flow (Barnaud et al. 2008; Djè et al. 2004; Doggett 1988; Ellstrand and Foster 1983; Schmidt and Bothma 2006). Factors influencing the outcrossing rate are discussed in the following paragraphs. Because S. bicolor is primarily self-pollinated, and there are few deleterious alleles, S. bicolor is less likely to be affected by inbreeding depression, and hybrids may not outcompete self-pollinated seeds (Barnaud et al. 2008).

The inflorescence morphology (shape of the panicle) and other floral traits vary among landraces, and largely impact the outcrossing rate. Loose panicles, such as those of guinea landraces, favour outcrossing, whereas very compact panicles, such as those typical of durra landraces, impede outcrossing (Djè et al. 2004). The more compact panicles of the race durra, which is commonly used in commercial production, contribute to a relatively low outcrossing rate of about 7% in this race (Djè et al. 2004). Floral traits can also impact the outcrossing rate by imposing a partial barrier to pollen flow. Cleistogamy (flowers that remain enclosed) reduces pollen flow, and long glumes can prevent pollen movement and result in effectively cleistogamous flowers (Djè et al. 2004).

An experiment by Schmidt and Bothma (2006) was laid out with the pollen donors (male-fertile B-line) grown in a 30 × 30 metre block, from which eight arms of the pollen receptors (male-sterile A-line) radiated out at distances from 13 to 158 metres. The average outcrossing rate, across directions, declined from 2.54% at 13 metres to 1.00% at 26 metres and 0.06% at 158 metres. The use of male sterile receptors eliminated pollen competition and increased the length of time female flowers remained receptive in the absence of pollination; therefore the outcrossing rate under normal growing conditions would likely be lower. Based on this, authors used mathematical models to estimate that the maximum gene flow distance for domesticated sorghum is 200 to 700 metres. In addition to separation distance, wind direction during pollination affected the outcrossing rate for separation distances between 13 and 117 meters.

Under the OECD Seed Scheme, sorghum must be at least 200 meters from a contaminating pollen source to produce Certified Seed and 400 meters to produce Basic Seed (OECD 2008). Similar isolation distances apply to Canadian sorghum production (Canadian Seed Growers' Association 2010). Some certification associations require greater isolation distances. For example, the Arizona Crop Improvement Association requires a minimum isolation distance for Foundation and Certified Seed of up to approximately 800 meters (ACIA 2014).

Adugna and Bekele (2013) evaluated crosses between domesticated sorghum and S. bicolor subsp. drummondii and found flowering periods usually overlapped. Schmidt (2010) estimated gene flow between domesticated sorghum and shattercane, using domesticated sorghum as the pollen source and shattercane as the pollen receptor. When shattercane occurred in the same field as domesticated sorghum, 4 to 16% of shattercane was pollinated by domesticated sorghum; when plants were separated by 200 meters almost no shattercane was pollinated by domesticated sorghum.

Pedersen et al. (1998) evaluated natural outcrossing rates in Sudan grass. In Sudan grass, the level of outcrossing was affected by pollination date. In both years, the middle pollination date had the highest rate of outcrossing (57% in 1991 and 39% in 1992). Outcrossing ranged from 0 to near 100% on individual Sudan grass plants and was highly variable. The more compact grain sorghum panicles outcross at lower rates than the more open Sudan grass panicles (Barnaud et al. 2008; Djè et al. 2004; Doggett 1988; Ellstrand and Foster 1983; Schmidt and Bothma 2006).

The survival and maintenance of new genetic combinations from outcrossing events depends on the fitness of outcrossed seeds. Sahoo et al. (2010) estimated the fitness of hybrids between an inbred shattercane line and domesticated sorghum by measuring characteristics including: temperature requirements for germination, seed viability, germination rate, dormancy, vegetative growth, and seed production. Overall, the estimated fitness of F1 hybrids was similar to shattercane. F1 hybrids exhibited heterosis, growing taller and producing more biomass than either parent. Temperature affected the seed viability, germination rate, and length of dormancy. At lower temperatures F1 hybrids behaved similarly to shattercane; at higher temperatures F1 hybrids behaved similarly to domesticated sorghum. More research is needed to extrapolate results to other shattercane lines and environments.

Werle et al. (2017) developed a simulation model to investigate management options to mitigate the risk of gene flow from herbicide tolerant sorghum to shattercane. Evolution of herbicide tolerant shattercane was predicted to occur rapidly when herbicide tolerant sorghum was planted continuously as a result of high selection pressure and crop-to-weed gene flow. The rotation of herbicide tolerant sorghum with conventional sorghum did not improve shattercane management. Rotating herbicide tolerant sorghum with non-sorghum crops, where effective herbicide options were available, was the most effective management option for controlling shattercane.

Crop-to-crop gene flow can be reduced by altering planting times, selecting varieties that will flower at different times, selecting varieties with compact panicles and long glumes, and spatially isolating sorghum away from other sorghum fields. Gene flow from cultivated S. bicolor to wild and weedy S. bicolor can be reduced through selecting varieties with compact panicles and long glumes for cultivation and controlling weeds in and around fields. Using clean, certified seed can reduce the occurrence of weedy S. bicolor in a field.

4.5 Cultivated Sorghum bicolor as a volunteer weed

Seed dormancy in domesticated sorghum is present for the first month after harvest (Shanmugavalli et al. 2007; Simpson 2007). Shanmugavalli et al. (2007) tested fresh seeds of S. bicolor and found that both physical and physiological dormancy are present.

Domesticated sorghum is harvested with a grain combine, and seed losses can occur from the header, cylinder, or the shoe. Adjusting the combine ground speed, cylinder speed, and clearance can help to reduce harvest losses (AERC 2008). Unharvested S. bicolor seed may become a volunteer weed in subsequent crops. S. bicolor cover crops may set seed if not mowed (Verhallen et al. 2003). The potential for volunteer S. bicolor to grow and persist in Canada as a troublesome weed is low because seeds have poor ability to overwinter in temperate regions and seedlings are not highly competitive with weed species or other crops (Andersson and de Vicente 2010). Under winter burial conditions, Fellows and Roeth (1992) observed domesticated sorghum germination rates of 0 and 5% in 1988 and 1989, respectively. Burial sites were in Nebraska U.S. and would have experienced similar winter conditions to those in southwestern Ontario. Similarly, Jacques et al. (1974) found that only 0.13% of domesticated sorghum seed survived a 4-month winter burial, and 0% survived an 8-month winter burial. Mild winters will likely increase the overwintering survival of domesticated sorghum seeds. Volunteer S. bicolor primarily grows in the year following sorghum cultivation but is reported persisting for several years in some U.S. growing regions including Oklahoma (McCoy et al. 1992; Wicks and Klein 1991). It is unclear if S. bicolor found over two years from the time it was planted as a crop results from seeds persisting in the seed bank, or from volunteers that have reproduced. Volunteer sorghum will likely be controlled by a weed management program for other grassy weeds and will not require special consideration (Wicks and Klein 1991).

Shattercane has characteristics that increase overwintering survival relative to cultivated S. bicolor including seed shattering, retention of the glumes that enclose the caryopsis, and slower seed demise in soil (Fellows and Roeth 1992). In field trials in Nebraska, U.S., shattercane seed tightly enclosed by glumes averaged 5 and 53% germination after 4-months of winter burial in 1988 and 1989, respectively (Fellows and Roeth 1992).

4.5.1 Cultural/mechanical control

Tillage is the most common mechanical practice to control volunteer S. bicolor. Disking fields after harvest may reduce the development of S. bicolor volunteers (Matocha et al. 2008) or may increase volunteer S. bicolor germination, allowing later control by sweep and rod tillage (Greb and Black 1962). A rolling cultivator will also control volunteer S. bicolor (Allen et al. 1980). No-till is the most challenging system in which to manage S. bicolor volunteers, and often chemical options are solely relied on (Allen et al. 1980). In-season control of weedy relatives is currently limited to hand weeding.

4.5.2 Chemical control

No herbicides are currently registered in Canada for the control of volunteer S. bicolor, however, volunteer populations of S. bicolor in crops can be controlled using herbicides registered for weed control in those crops (Health Canada 2015). In the U.S., volunteer S. bicolor is controlled with herbicides including clethodim (group 1), fluazifop (group 1), imazethapyr (group 2), primisulfuron (group 2), dicamba (group 4), atrazine (group 5), glyphosate (group 9), and S-metolachlor (group 15), alone or in mixtures ([US-EPA] United States Environmental Protection Agency 2014; Wicks and Klein 1991). Volunteer S. bicolor can be controlled with either pre- or post- emergent herbicide applications.

4.5.3 Integrated weed management (IWM)

Integrated weed management (IWM) uses a combination of biological, cultural, mechanical, and chemical weed control tactics to manage weed populations and maximize economic returns. IWM strategies are not specifically developed for the control of S. bicolor volunteers. S. bicolor volunteers will likely be controlled by IWM programs used for managing other grassy weed species. Development of an IWM plan specific to S. bicolor may become necessary if herbicide-tolerant S. bicolor varieties are planted that limit chemical control options, or if the overwintering rate and seed survival increase.

4.5.4 Biological control

No biological control methods for S. bicolor volunteers exist.

4.6 Means of movement and dispersal

S. bicolor seeds are dispersed by organisms that consume the seeds, such as birds (Stubbendieck et al. 2003) and mammals, or by humans during cropping, harvesting, handling, storage, and transport of the crop (Andersson and de Vicente 2010). Viable seeds of S. bicolor have been documented in pellets of white-tailed deer (Odocoileus virginianus Zimmerman); modeling suggests that 95% of seeds ingested by deer are carried more than 100 meters, and 30% are carried more than one kilometer (Myers et al. 2004).

5. Related species of Sorghum bicolor

In the Sorghum genus, the subgenus Eusorghum includes the rhizomatous taxa johnsongrass (S. halepense) and S. propinquum, and Columbus grass (S. almum Parodi) (De Wet et al. 1976). Weedy sorghums can exist alongside cultivated sorghums as perennial rhizomatous forms derived from S. propinquum or as annual grassy weeds resulting from hybridization between cultivated and wild forms of S. bicolor (Ejeta and Grenier 2005).

Johnsongrass is the primary weedy relative of S. bicolor that affects agriculture, due to its invasiveness and propensity to develop herbicide resistance (Heap et al. 2012; Holm et al. 1977). It is wind-pollinated and often found to be sympatric with cultivated S. bicolor (Holm et al. 1977). The geographical range of winter-hardy rhizomatous johnsongrass is expanding in North America; johnsongrass was documented at 38°N latitude in 1926 (Burt 1974), 40°N latitude in 1971 (Burt 1974), and 43°N in 1979 (Warwick and Black 1983). In Canada, johnsongrass has been introduced to some temperate regions, including southwestern Ontario. In 2000, johnsongrass was known to occur in 13 Ontario counties including Brant, Bruce, Elgin, Essex, Huron, Chatham-Kent, Middlesex, Peel, Waterloo, and York (OMAFRA 2000; OMAFRA 2015; Warwick and Black 1983). While most rhizomes are killed by Ontario winters, a few stands of johnsongrass act as true perennials with rhizomes capable of overwintering (OMAFRA 2000; OMAFRA 2015). The weed can overwinter near protected areas such woodlots or river valleys, though it is more commonly found in agricultural fields, field edges and irrigation ditches (OMAFRA 2000; OMAFRA 2015; Alex et al. 1979; Warwick and Black 1983).

S. propinquum is not present in Canada. The range of S. propinquum is restricted to parts of Sri Lanka, southern India, and southeast Asia where it readily crosses with domesticated sorghum (Doggett 1988; Ejeta and Grenier 2005).

Columbus grass is not present in Canada (USDA-NRCS 2012). Columbus grass is a short-lived perennial with a rhizomatous growth habit. Originally used as a summer forage and fodder crop in southern regions of the U.S., it is now listed as a noxious weed in four U.S. states (USDA-NRCS 2012; Eberlein 1987).

USDA-ARS (2012) lists 19 crop wild relatives in the tertiary gene pool of S. bicolor, no records of these species were found in North America. The tertiary gene pool includes species more distantly related to members of the primary gene pool. Gene flow can occur between the primary and tertiary gene pool only with the use of artificial measures. Some grassy species including Sorghum arundinuceuin and Sorghum verticillijlorum, have the same chromosome number (2n = 2x = 20) as S. bicolor.

5.1 Inter-species/genus hybridization

S. bicolor can interbreed with its congeners in the Eusorghum subgenus. Members of the Sorghum genus outside Eusorghum are more distantly related to S. bicolor and, therefore, less likely to interbreed. There are no known species outside Eusorghum likely to interbreed with S. bicolor under typical agricultural conditions (Hodnett et al. 2005). Inter-species hybridization occurs between S. bicolor and species in its primary and secondary gene pools.

The primary gene pool includes species that are fully interfertile when crossed; when species distributions overlap under favorable conditions frequent gene introgression is expected (Andersson and de Vicente 2010; Ejeta and Grenier 2005). The primary gene pool of S. bicolor includes the diploid (2n = 2x = 20) species S. propinquum from the section Eusorghum (Ejeta and Grenier 2005). Grassy species such as S. arundinuceuin also have the same chromosome number (2n = 2x = 20), and can be crossed with S. bicolor (Arriola and Ellstrand 1996).

S. bicolor can outcross with species in the secondary gene pool despite ploidy level differences, producing either sterile triploids or somewhat fertile tetraploids (Arriola and Ellstrand 1997; Morrell et al. 2005). The secondary gene pool includes the two tetraploid (or higher) (2n = 4x = 40) species of Eusorghum, Columbus grass and johnsongrass.

The tertiary gene pool includes species from sections of Sorghum outside Eusorghum. Outcrossing of S. bicolor with members of this gene pool is highly unlikely under natural conditions, and crosses produced through human intervention are anomalous, lethal, or almost completely sterile (Ejeta and Grenier 2005). USDA-ARS (2012) lists 19 crop wild relatives in the tertiary gene pool of S. bicolor. While the flowering times may overlap for some of these species, hybridization between S. bicolor and species outside Eusorghum has not been successful due to strong reproductive barriers (Adugna and Bekele 2013; Doggett 1988; Garber 1950; Hodnett et al. 2005). A study by Hodnett et al. (2005) tried to form hybrids between S. bicolor and 14 related Sorghum species. Pollen–pistil incompatibilities were the primary reason that hybrids could not be obtained with any of the species tested. Growth of pollen tubes in sorghum pistils was inhibited and tubes rarely grew past the stigma. In three species, pollen tubes grew into the ovary of S. bicolor. However, fertilization and subsequent embryo development were uncommon. All seeds with developing embryos aborted before maturation, apparently because of the breakdown of the endosperm.

Inter-genus hybridization between sorghum and other closely related genera is unlikely to result in viable offspring without human intervention (Bernard and Jewell 1985; De Wet et al. 1976; Nair 1999; Reger and James 1982). With the goal of introducing new agronomic traits, crosses between other members of the tribe Andropogoneae including maize (Zea mays), sugarcane (Saccharum spp.), and millets (Pennisetum, Eleusine, Eragrostis, Setaria, etc.) have been attempted. Hybridization did not occur in maize or millet. In the case of maize, pollen substances are capable of inducing stimulation of maternal tissues, leading to nucellus' hypertrophy and possibly apomixis. Evidence does not indicate that maize and S. bicolor in proximity under field conditions will hybridize (Bernard and Jewell 1985; Reger and James 1982). S. bicolor × sugarcane crosses have a low success rate but are possible (De Wet et al. 1976). Nair (1999) obtained five hybrid seedlings from 3,670 sorghum florets pollinated by sugarcane. The sorghum × sugarcane hybrids lacked vigour and were slow to establish.

5.2 Potential for introgression of genetic information from Sorghum bicolor into relatives

Many wild relatives of S. bicolor are not present in Canada, and geographical isolation will prevent outcrossing to these species. This section focuses on johnsongrass, the only species present in Canada where introgression from S. bicolor is believed to be likely. The potential of S. bicolor and johnsongrass to cross is well established (Arriola and Ellstrand 1996; Arriola and Ellstrand 1997; Morrell et al. 2005). The flowering time of S. bicolor and johnsongrass overlap (Holm et al. 1977), and both species can be wind-pollinated (Arriola and Ellstrand 1996; Holm et al. 1977).

Hybridization between S. bicolor and johnsongrass under controlled conditions has been completed with varied success (Bennett and Merwine 1966; Dweikat 2005). Phenotypic characteristics in resulting hybrids (i.e. seed production, number of panicles per plant, number of tillers per plant, above- and belowground biomass production) can range from intermediate between the parent species to very similar to johnsongrass (Jessup et al. 2012). The progeny of johnsongrass × S. bicolor crosses are often sterile, rhizomatous triploids that can persist in the environment through vegetative reproduction. S. bicolor × johnsongrass F1 offspring have similar fitness when compared to either parent, suggesting that either neutral or beneficial crop genes would persist in johnsongrass populations (Arriola and Ellstrand 1996; Arriola and Ellstrand 1997; Sahoo et al. 2010; Sangduen and Hanna 1984).

The distance between johnsongrass and the pollen source (S. bicolor) is the primary factor affecting gene flow with more hybrids being produced when johnsongrass is closer to the pollen source. Arriola and Ellstrand (1996) investigated the level of spontaneous hybridization between johnsongrass and sorghum in the field when plants were separated by up to 100 meters. Hybrid production decreased as the distance from the crop increased, but crop-to-weed hybrid seedlings were still detected at the furthest distance tested. Measured rates of hybridization ranged from 0 to 100% per plant, with hybridization levels as high as 2% occurring at a distance of 100 metres from the pollen source.

Traits introduced into S. bicolor have a high potential for transfer into johnsongrass populations (Hoang-Tang and Liang 1988; Morrell et al. 2005). Evidence indicates that putatively neutral allelic variants from S. bicolor persist in johnsongrass populations for long periods, and at a considerable geographical distance from cultivated fields where the initial introgression likely occurred (Morrell et al. 2005). Crop-specific alleles have been found in samples of johnsongrass. Morrell et al. (2005) surveyed restriction fragment length polymorphisms (RFLPs) allelic diversity in five johnsongrass accessions from different parts of the U.S. Among them, the frequency of individuals carrying at least one crop-specific allele ranged from 0.79 to 0.91 in Texas and Nebraska where sorghum is more frequently grown, and from 0.27 to 0.47 in New Jersey and Georgia where domesticated sorghum is less common. These results suggest that when johnsongrass is in proximity to domesticated sorghum, higher rates of crop-to-weed gene flow are likely in the absence of management practices designed to reduce it, despite the two species having different ploidy levels.

Increased distance between S. bicolor and johnsongrass is an effective mitigation technique to limit crop-to-weed gene flow because greater distances are associated with a reduction in pollen density from the source (Arriola and Ellstrand 1996; Schmidt and Bothma 2006). In Canada, the isolation distance required between S. bicolor and non-pedigreed S. bicolor, Sudan grass, or broomcorn is 200 or 400 meters for Certified and Foundation seed, respectively (Canadian Seed Growers' Association 2010). In most cases, isolation distances have sufficiently reduced outcrossing to less than 0.1% (Andersson and de Vicente 2010).

A summary of proposed strategies to mitigate crop-to-weed gene flow, including physical and biological containment, are outlined in Gressel (2015). Where physical isolation is not feasible, ensuring different flowering times is the most effective way to reduce the likelihood of gene flow. However, high temperatures or drought may induce flowering among late- or non-flowering sorghum lines and increase the likelihood of outcrossing. Genetic or cytoplasmic male sterility could be used to create barriers to outcrossing as viable pollen would not be available to initiate spontaneous hybridization (pollen donors without novel genes should also be planted) (Pedersen et al. 2003; Schmidt and Bothma 2006). High temperatures or drought may cause plants with cytoplasmic male sterility to become fully or partially fertile (Schmidt and Bothma 2006). Thus, cytoplasmic male sterility could reduce crop-to-crop gene flow but not eliminate it (Pedersen et al. 2003). Further research on cytoplasmic male sterility and its limitations is required before it can be applied as a risk management tool for domesticated S. bicolor with novel traits.

5.3 Summary of the ecology of relatives of Sorghum bicolor

The closest relatives of S. bicolor include johnsongrass (S. halepense) and Columbus grass (S. almum Parodi). Columbus grass is not present in Canada. Johnsongrass is an aggressive, perennial grass that can reproduce through both rhizomes and seeds (De Wet et al. 1976; Holm et al. 1977). Winter-hardy rhizomatous johnsongrass is expanding its range in North America. Johnsongrass was introduced to southwestern Ontario, and its rhizomes are capable of overwintering. Johnsongrass is the primary weedy relative of S. bicolor affecting agriculture, due to its invasiveness and propensity to develop herbicide tolerance (Heap et al. 2012; Holm et al. 1977). Johnsongrass is considered self-compatible with an outcrossing rate below 10% (Burke et al. 2007; Warwick and Black 1983). It is wind-pollinated and often found to be sympatric with S. bicolor (Holm et al. 1977). Gene flow is likely to occur between S. bicolor and johnsongrass.

Johnsongrass is hard to control in S. bicolor fields because both are susceptible to the same herbicides (Paterson et al. 1995). Gene flow from herbicide-tolerant S. bicolor to johnsongrass may affect weed control in S. bicolor, and in other crops including maize and soybean.

Johnsongrass produces large numbers of shattering seeds that can be carried by wind and animals. Seed remains viable in the soil for over five years (Egley and Chandler 1983). Johnsongrass seed survival is higher at depths greater than 22 centimetres, and seed banks can accumulate when seeds are sufficiently buried (Andersson and de Vicente 2010). Even sterile johnsongrass with herbicide-tolerance may be difficult to control because johnsongrass can reproduce vegetatively through rhizomes (Egley and Chandler 1983).

6. Potential Interaction of Sorghum bicolor with Other Life Forms

Because of the limited acreage of S. bicolor in Canada, little research has focused on the pest and beneficial organisms that interact with this crop. There are no known, consistently present insect pests currently requiring control in Canadian S. bicolor cultivation. In this section, most information is drawn from the northern U.S. states where agronomic practices and species composition are similar to Canadian environments suitable for cultivation of S. bicolor.

Agriculture Environmental Renewal Canada Inc. (AERC) reports that some silage varieties do not require insect control. If sorghum acres increase, we can expect pest species and populations will also increase. This will require more intensive management and consideration. Most insect pests of domesticated sorghum are distributed widely, are not host specific, and do not coevolve with the crop (Teetes and Pendleton 2000). Insect pests that consistently require control in many areas where sorghum is cultivated include: greenbug (Schizaphis graminum Rondani), sorghum midge (Contarinia sorghicola Coquillett), shoot fly (Atherigona soccata Rondani), and stalk-borers. Several other species, including Banks grass mite (Oligonychus pratensis Banks) and corn earworm (Helicoverpa zea Boddie), are secondary pests that may become injurious following application of insecticides targeting a primary pest (Teetes and Pendleton 2000). Other species are considered occasional pests that cause economic damage only in localized areas, or during some years. Pests of sorghum should be managed using integrated pest management, including a combination of cultural, biological, and chemical control methods. Cultural control methods include crop rotation, variety selection, and seedbed preparation; biological methods include the use of natural enemies including predators, parasites, or pathogens; and chemical methods include aerial sprays, seed treatments, and soil-applied insecticides (Teetes and Pendleton 2000).

S. bicolor is susceptible to bacterial, fungal, nematode, plant, phytoplasma, and viral diseases that can damage, weaken, or reduce the value and productivity of the sorghum crop (Frederiksen 2000). Poor seedling emergence and stand failure has been a persistent problem in southern Alberta and may be caused by a combination of seedborne and soilborne fungi, pathogenic bacteria, and weather conditions (Cuarezma-Teran et al. 1984; Gaudet and Kokko 1986). Plant-parasitic nematodes are poorly documented in Canadian fields of S. bicolor, but may limit uniform plant establishment and decrease yield (Gaudet and Kokko 1986). Diseases can be managed by rotating crops, maintaining soil organic matter and soil structure, altering the density of plants, and applying fungicides (Craig and Odvody 1992; Frederiksen 2000).

S. bicolor has allelopathic effects that may suppress weeds and affect subsequent crops in the rotation, including wheat, maize, and S. bicolor (Khaliq et al. 2013; Panasiuk et al. 1986; Razzaq et al. 2012; Roth et al. 2000). Above-ground and below-ground sorghum tissues produce phenolic acids that contribute to the allelopathic potential of S. bicolor. Levels of allelopathic compounds can vary based on environment, year, and variety. Phenolic acids in the roots may contribute to the allelopathic nature of S. bicolor during growth and after harvest if residues remain on the soil surface or are incorporated prior to planting a subsequent crop (Ben-Hammouda et al. 1995).

For a list of species associated with domesticated sorghum, please refer to Table 3.

Table 3. Examples of potential interactions of cultivated Sorghum bicolor L. with other life forms present in Canada during its life cycle.

Note: Abbreviations denote Canadian provinces: BC - British Columbia; AB - Alberta; SK - Saskatchewan; MB - Manitoba; ON - Ontario; QC - Quebec.

Bacteria
Other Life Forms Interaction with sorghum
(pathogen; beneficial organism; consumer; gene transfer)
Presence in Canada Reference(s)
Dickeya dadantii
(bacterial top and stalk rot)
Pathogen Present; ON and BC (Frederiksen 2000; Joshi 2000)
Pseudomonas andropogonis Smith
(bacterial leaf strip)
Pathogen Present; widespread (Centre for Biosciences and Agriculture International 2012a; Frederiksen 2000)
Pseudomonas syringae pv. syringae
(bacterial leaf spot)
Pathogen Present; widespread (Centre for Biosciences and Agriculture International 2015; Frederiksen 2000; Gaudet and Kokko 1986)
Fungi
Other Life Forms Interaction with sorghum
(pathogen; beneficial organism; consumer; gene transfer)
Presence in Canada Reference(s)
Acremonium strictum
W. Gams, (acremonium wilt)
Pathogen Present; widespread (Agriculture and Agri-Food Canada 2011; Frederiksen 2000)
Alternaria alternata (Fr.)
Keissl.
(sorghum grain mold)
Pathogen Present; widespread (Agriculture and Agri-Food Canada 2011; Frederiksen 2000)
Ascochyta sorghina Sacc.
(rough leaf spot)
Pathogen Present; prairie provinces (Agriculture and Agri-Food Canada 2011; Frederiksen 2000)
Colletotrichum graminicola
(Ces.) Wils. (anthracnose
and sorghum grain mold)
Pathogen Present; widespread (Agriculture and Agri-Food Canada 2011; Centre for Biosciences and Agriculture International 2012b; Frederiksen 2000)
Colletotrichum gloeosporioides Penz.
(anthracnose)
Pathogen Present; widespread (Agriculture and Agri-Food Canada 2011; Frederiksen 2000)
Curvularia lunata (Wakker) Boedijn
(sorghum grain mold)
Pathogen Present; widespread (Bolton and Cordukes 1981; Clear and Patrick 1995b; Frederiksen 2000)
Exserohilum turcicum (Pass.) K.J. Leonard & Suggs
(leaf blight)
Pathogen Present; ON, QC, and MB (Desjardins et al. 2009; Frederiksen 2000; Zhu et al. 2007)
Fusarium moniliforme
J. Sheld.; ascomycetous perfect state; Gibberella fujikuroi (Sawada) Wollenw.
(fusarium root and stalk rot; pokkah boeng – twisted top)
Pathogen Present; widespread (Basu et al. 2001; Duthie et al. 1986; Frederiksen 2000; Gordon 1959)
Fusarium proliferatum (Matsush.) Nirenberg
(pokkah boeng – twisted top)
Pathogen Present; widespread (Clear and Patrick 1995a; Frederiksen 2000; Gilbert et al. 2011; Mathur and Utkhede 2004)
Fusarium semitectum Berk. & Ravenel
(sorghum grain mold)
Pathogen Present; widespread (Agriculture and Agri-Food Canada 2011; Frederiksen 2000)
Fusarium spp.
(seedling disease)
Pathogen Present – Some species of Fusarium are present in Canada (Frederiksen 2000; Gaudet and Kokko 1986)
Macrophomina phaseolina (Tassi) Goid.
(charcoal rot)
Pathogen Present; widespread (Basu et al. 2001; Desjardins et al. 2001; Gourley 1983)
Pythium arrhenomanes Drechsler
(pythium root rot)
Pathogen Present; widespread (Agriculture and Agri-Food Canada 2011; Centre for Biosciences and Agriculture International 2012b; Frederiksen 2000)
Pythium graminicola Subraman.
(pythium root rot)
Pathogen Present; widespread (Elmhirst et al. 1999; Frederiksen 2000; Hsiang et al. 1995; Sampson and Watson 1981; Sprague 1950)
Pythium spp.
(pythium root rot)
Pathogen Present; widespread Several Pythium spp. are present in Canada (Centre for Biosciences and Agriculture International 2015; Frederiksen 2000; Vaartaja and Salisbury 1961)
Rhizoctonia solani J.G. Kühn
(banded leaf and sheath blight)
Pathogen Present; widespread (Centre for Biosciences and Agriculture International 2015; Frederiksen 2000)
Sclerophthora macrospora (Sacc.) Thirum
(crazy top)
Pathogen Present; widespread (Centre for Biosciences and Agriculture International 2015; Frederiksen 2000)
Sclerotium rolfsii Sacc.
(southern sclerotial rot)
Pathogen Present; widespread (Elmhirst and Joshi 1996; Frederiksen 2000; Gilbert et al. 2010)
Sporisorium reilianum (J.G. Kühn) G.P. Clinton (head smut) Pathogen Present; widespread (Agriculture Canada 1988; Elmhirst and Joshi 1996; Frederiksen 2000; Zhu et al. 2007)
Sporisorium sorghi Ehrenb. ex Link
(covered kernel smut)
Pathogen Present; widespread (Bisby 1938; Fischer 1953; Frederiksen 2000; Zundel 1953)
Viruses
Other Life Forms Interaction with sorghum
(pathogen; beneficial organism; consumer; gene transfer)
Presence in Canada Reference(s)
Barley yellow dwarf virus (BYDV) Pathogen Present; widespread (Centre for Biosciences and Agriculture International 2015; Jensen and Giorda 2008)
Brome mosaic virus (BMV) Pathogen Present – however there is only one record of this virus occurring in Canada in MB (Haber and Hamilton 1989; Jensen and Giorda 2008)
(Haber and Hamilton 1989; Jensen and Giorda 2008) Pathogen Present; widespread (Centre for Biosciences and Agriculture International 2015; Creelman 1962; Jensen and Giorda 2008; Platford 1988; Seaman 1970)
Maize dwarf mosaic virus (MDMV) Pathogen Present; ON (Centre for Biosciences and Agriculture International 2015; Jensen and Giorda 2008)
Sugarcane mosaic virus (SCMV) Pathogen Present; ON and QC (Jensen and Giorda 2008; Zhu et al. 2002)
Wheat streak mosaic virus (MYSV) Pathogen Present; widespread (Centre for Biosciences and Agriculture International 2015; Jensen and Giorda 2008)
Nematodes
Other Life Forms Interaction with sorghum
(pathogen; beneficial organism; consumer; gene transfer)
Presence in Canada Reference(s)
Criconemella xenoplax
Raski (Luc and Raski)
Consumer Present; ON (Bird and Boekhoven 1968; Cuarezma-Teran et al. 1984)
Helicotylenchus dihystera
(Cobb) Sher.
Consumer Present; ON (Centre for Biosciences and Agriculture International 2015; Cuarezma-Teran et al. 1984)
Hoplolaimus galeatus
Steiner
Consumer Present; ON and MB (Cuarezma-Teran et al. 1984; MacNay 1957; Townshend 1967)
Meloidogyne spp. Consumer Present; widespread (Centre for Biosciences and Agriculture International 2015; Cuarezma-Teran et al. 1984)
Paratrichodorus minor
(Colbran)
Raski.
Consumer Present; ON (Centre for Biosciences and Agriculture International 2015; Cuarezma-Teran et al. 1984)
Pratylenchus zeae Graham Consumer Present; ON (Cuarezma-Teran et al. 1984; Yu 2008)
Quinisulcius acutus (Allen) Siddiqi Consumer Present; AB and MB (Centre for Biosciences and Agriculture International 2012b; Cuarezma-Teran et al. 1984)
Xiphinema americanum Cobb Consumer Present; widespread (Cuarezma-Teran et al. 1984; Ebsary et al. 1984; Shoemaker and Creelman 1958)
Insects
Other Life Forms Interaction with sorghum
(pathogen; beneficial organism; consumer; gene transfer)
Presence in Canada Reference(s)
Blissus leucopterus
(Say)
(chinch bug)
Consumer Present; widespread (Centre for Biosciences and Agriculture International 2015; Teetes and Pendleton 2000)
Braconidae family
(braconid wasps)
Beneficial organism Present; widespread (Masner 1979; Teetes and Pendleton 2000; Wahl and Sharkey 1993)
Carabidae family
(ground beetles)
Beneficial organism Present; widespread (Bousquet et al. 2013; Teetes and Pendleton 2000)
Chalcididae family
(chalcid wasps)
Beneficial organism Present; widespread (Gibson 1993; Teetes and Pendleton 2000; Yoshimoto 1984)
Chlorochroa ligata (Say)
(conchuela)
Consumer Present; widespread (Rider 2009; Teetes and Pendleton 2000)
Chrysopa spp. and
Chrysoperla spp.
(green lacewings)
Beneficial organism Present; widespread (Garland 1985; Teetes and Pendleton 2000)
Corcyra cephalonica (Stainton)
(rice moth)
Consumer Present; ON (Centre for Biosciences and Agriculture International 2015; Haines 1991; Handfield 2002; Teetes and Pendleton 2000)
Cryptolestes ferrugineus (Stephens)
(rusty grain beetle)
Consumer Present; widespread (Bousquet et al. 2013; Canadian Grain Commission 2015; Teetes and Pendleton 2000)
Cryptolestes pusillus (Schnherr)
(flat grain beetle)
Consumer Present; widespread (Bousquet et al. 2013; Canadian Grain Commission 2015; Teetes and Pendleton 2000)
Diabrotica undecimpunctata howardi
Barber (southern corn rootworm)
Consumer Present; widespread (Bousquet et al. 2013; Teetes and Pendleton 2000)
Elateridae family and Tenebrionidae family
(true and false wireworms)
Consumer Present; widespread (Bousquet et al. 2013; Teetes and Pendleton 2000)
Geocoris bullatus (Say)
(large big-eyed bug)
Beneficial organism Present; widespread (Mead 2014; Teetes and Pendleton 2000)
Helicoverpa zea (Boddie)
(corn earworm)
Consumer Present; widespread (Bousquet et al. 2013; Centre for Biosciences and Agriculture International 2015; Teetes and Pendleton 2000)
Hippodamia convergens (Guerin-Meneville)
(convergent lady beetle)
Beneficial organism Present; widespread (Bousquet et al. 2013; Teetes and Pendleton 2000)
Ichneumonidae family
(ichneumonid wasps)
Beneficial organism Present; widespread (Masner 1979; Mead 2010; Teetes and Pendleton 2000; Wahl and Sharkey 1993)
Nabis americoferus (Carayon)
(common damsel bug)
Beneficial organism Present; ON and BC (Canadian Biodiversity Information Facility 2015; Rockburne and Lafontaine 1976; Teetes and Pendleton 2000)
Agrotis spp. and Euxoa spp.
(cutworms)
Consumer Present; widespread (Canadian Biodiversity Information Facility 2015; Rockburne and Lafontaine 1976; Teetes and Pendleton 2000)
Nysius raphanus Howard
(false chinch bug)
Consumer Present; widespread (Maw 2000; Teetes and Pendleton 2000)
Orius tristicolor (White)
(minute pirate bug)
Beneficial organism Present; widespread (Kelton 1978; Teetes and Pendleton 2000)
Oryzaephilus mercator (Fauvel)
(merchant grain beetle)
Consumer Present; widespread (Bousquet et al. 2013; Centre for Biosciences and Agriculture International 2015; Teetes and Pendleton 2000)
Oryzaephilus surinamensis (L.)
(sawtoothed grain beetle)
Consumer Present; widespread (Bousquet et al. 2013; Canadian Grain Commission 2015; Teetes and Pendleton 2000)
Plodia interpunctella
(Hubner)
(Indian meal moth)
Consumer Present; widespread (Canadian Grain Commission 2015; Teetes and Pendleton 2000)
Rhopalosiphum maidis
(Fitch)
(corn leaf aphid)
Consumer Present; widespread (Capinera 2008; Teetes and Pendleton 2000)
Rhyzopertha dominica
(Fabricius) (lesser grain borer)
Consumer Present; widespread (Bousquet et al. 2013; Canadian Grain Commission 2015; Fields et al. 1993; Teetes and Pendleton 2000)
Schizaphis graminum
(Rondani) (greenbug)
Consumer Present; widespread (Centre for Biosciences and Agriculture International 2015; Teetes and Pendleton 2000)
Sitophilus granarius (L.)
(granary weevil)
Consumer Present; widespread (Bousquet et al. 2013; Canadian Grain Commission 2015; Teetes and Pendleton 2000)
Sitophilus oryzae (L.) (rice weevil) Consumer Present; widespread (Bousquet et al. 2013; Campbell et al. 1989; Canadian Grain Commission 2015; Teetes and Pendleton 2000)
Sitophilus zeamais
Motschulsky (maize weevil)
Consumer Present; MB, ON, and QC (Bousquet et al. 2013; Canadian Grain Commission 2015; Teetes and Pendleton 2000)
Sitotroga cerealella
(Olivier) (angoumois grain moth)
Consumer Present; ON (Canadian Grain Commission 2015; Teetes and Pendleton 2000)
Spodoptera frugiperda
(J. E. Smith) (fall armyworm)
Consumer Present; widespread (EPPO 2015; Centre for Biosciences and Agriculture International 2015; Teetes and Pendleton 2000)
Syrphidae family (syrphid flies) Beneficial organism Present; widespread (Marshall 2012; Teetes and Pendleton 2000)
Tachinidae family (tachinid flies) Beneficial organism Present; widespread (Teetes and Pendleton 2000; Wood 1987)
Tribolium castaneum
(Herbst) (red flour beetle)
Consumer Present; widespread (Bousquet et al. 2013; Canadian Grain Commission 2015; Smith and Frederiksen 2000)
Tribolium confusum
(Jacquelin du Val) (confused flour beetle)
Consumer Present; widespread (Bousquet et al. 2013; Canadian Grain Commission 2015; Teetes and Pendleton 2000)
Phyllophaga crinita
(Burmeister) (white grub)
Consumer Present; widespread (Teetes 1973)
Lysiphlebus testaceipes
(Cresson)
Beneficial organism Present; AB, BC, and SK (Fernandes et al. 1998; Global Biodiversity Information Facility)
Plants
Other Life Forms Interaction with sorghum
(pathogen; beneficial organism; consumer; gene transfer)
Presence in Canada Reference(s)
Sorghum bicolor subsp. drummondii (Steudel) de Wet (shattercane) Gene transfer Present; ON and QC (Brouillet et al. 2010+; Pedersen et al. 2010)
Sorghum halepense L. Pers. (jonhsongrass) Gene transfer Present; ON (Alex et al. 1979; Arriola and Ellstrand 1996; Brouillet et al. 2010+)
Animals
Other Life Forms Interaction with sorghum
(pathogen; beneficial organism; consumer; gene transfer)
Presence in Canada Reference(s)
Birds Consumer Present; widespread (Doggett 1988)
Odocoileus virginianus
Zimmerman (white-tailed deer)
Consumer Present; widespread (Doggett 1988) (Myers et al. 2004)

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