Specific Work Instructions: Field Corn Seed Crop

SWI 142.1.2-1

Date

This version of the Field Corn Seed Crop Inspection Procedures was issued March 15, 2011.

Contact

The contact for this Seed Program Specific Work Instruction (SWI) is the Chief, Seed Design and Delivery Office, Seed Section.

Review

This Seed Program Specific Work Instruction (SWI) is subject to periodic review. Amendments will be issued to ensure the SWI continues to meet current needs.

Endorsement

This Seed Program Specific Work Instruction is hereby approved.

Director, Field Crops Division

Date

The most up to date version of this document will be maintained on the CFIA Intranet site (Merlin) and Internet site. In addition, the signed original will be maintained by the National Manager, Seed Section.

0.0 Introduction

Pedigreed seed corn is inspected to provide an unbiased inspection and the completion of a report for the Canadian Seed Growers' Association (CSGA) on the isolation, condition, and purity of the crop. It is the inspector's responsibility to describe the crop as observed at the time of inspection.

1.0 Scope

This Seed Program Specific Work Instruction (SWI) outlines the procedures that a licensed or official crop inspector will follow in inspecting field corn seed crops for pedigreed seed status.

Licensed crop inspectors may only inspect crops producing Certified seed. Official crop inspectors may:

inspect crops producing Certified seed of hybrid or open-pollinated field corn at the request of the CSGA;
inspect crops producing Foundation seed, including seed of inbred lines;
inspect crops producing Registered seed of open-pollinated corn;
inspect crops producing Breeder seed of inbred or open-pollinated corn;
conduct crop inspections as part of a system audit of an accredited crop inspection service or of a licensed crop inspector.

The crop inspection and completed report assists the CSGA in determining whether the seed grown for pedigreed status meets the requirements for varietal purity and crop standards as specified by the CSGA Circular 6 Canadian Regulations and Procedures for Pedigreed Seed Crop Production.

2.0 References

The publications referred to in the development of this SWI are those identified in SPRA 111, SWI 142.1.1, QSP 142.1 Pedigreed Seed Crop Inspection Procedures and CSGA Circular 6 Regulations and Procedures for Pedigreed Seed Crop Production.

3.0 Definitions, Abbreviations and Acronyms

3.1 Definitions

For the purposes of this SWI the definitions given in SPRA 101 and the following apply,

Detasseling: The removal of the tassel or pollen producing organ at the top of a corn plant before pollen is shed.
Isolation: The distance between a source of contaminating pollen and the nearest seed parent plant. This includes sweet corn plants and volunteer plants in feed lots, around corn cribs and in surrounding crops, etc.
Male-Female Planting Pattern: Male (fertile/pollen) and female (sterile/seed) parent blocks may be produced in separate fields, separate blocks in the same field or alternated according to a definite pattern in the same field.
Planting Error: Planting errors include the misuse of seed stocks, a mixture of seed stocks and seed parent plants in border rows, or headland rows of pollen parent etc.
Pollen parent: The corn line used as a pollen source for the sterile female parent during the production of hybrid corn. The kernels formed on the pollen parent are not produced by cross pollination and may not be harvested as part of a hybrid variety.
Pollination: The process by which pollen is transferred from an anther to the stigmatic surface of the pistil of a flower (tassel to silk).
Pollination Uniformity: Uniform pollination depends on such factors as uniform soil topography, soil type, drainage, moisture, temperature, planting dates and seedling vigour.
Seed parent: The corn line whose pollination is controlled and the grain harvested, conditioned and sold as hybrid seed.
Shedding Tassel: Includes sucker tassels and/or portions of tassels on the main plants counted as shedding pollen when 5 cm (2 in) or more of the central stem and/or side branches have anthers extended from the glumes and are shedding pollen.
Sterile Female: A term used for the seed parent plant where the tassel does not shed any viable pollen and, therefore, requires pollen from another source to produce kernels on the ear.
Volunteer Corn on Corn: When corn is planted following a corn crop, an inspection must be made to determine the freedom of the seed crop from plants that may have volunteered from the previous crop.
Volunteer Plants: Unwanted corn plants growing from residual seeds from the previous crop or a replanted crop.

3.2 Abbreviations and Acronyms

CFIA: Canadian Food Inspection Agency
CSGA: Canadian Seed Grower's Association
OECD: Organisation for Economic Co-operation and Development
QSP: Quality System Procedure
SPRA: Seed Program Regulatory Authority
SWI: Specific Work Instruction

4.0 Specific Inspection Procedures

4.1 Assessment of Application for Crop Inspection

The inspector must first review the submitted application and/or preprinted forms. In addition to the standard application information, the application should also be reviewed for the following additional information specific to corn:

field location including the name of the grower
number of acres planted including field layout of parental lines, plant population, and description of barrier rows for hybrid and open pollinated corn production
a diagram of the field indicating:
1. the number of border barrier rows, where applicable;
2. direction of planting;
3. area in corn last year or replanted this year;
4. description of adjoining crops and other corn crops within 200 metres of the seed field, and the types of corn (sweet corn, popcorn, seed corn);
5. distance in feet or metres to sources of potentially contaminating pollen;
6. planting pattern of fertile (male) and sterile (female) seed parent rows and male pollen parent rows, where applicable;
7. how the male pollen parent rows are marked, where applicable;
8. planting dates;
9. seed parent designations or coded equivalent, where applicable;
10. pedigreed status for which the field is being inspected i.e. Breeder, Foundation, Registered, Certified;
11. designated entrance of seed field.

If any of the above information are missing, the applicant should be contacted to ensure that all necessary information are present before the initial inspection of the crop.

4.2 Inspection Requirements

One inspection for open-pollinated corn must be made at the time when the silks are receptive in order to determine whether appropriate isolation has been provided and to identify detectable off-types. A minimum of three inspections must be conducted during the pollination period for both inbred and hybrid seed corn. Additional inspections are required only if the crop is planted on land that produced corn in the previous year and are required to verify the freedom of the seed crop from volunteer corn. If required, these inspections are to be conducted when the crop is well emerged (more than 50 cm. tall).

Inspection for the production of hybrid and inbred field corn seed differs in some ways from the inspection of other cereal and forage kinds. These differences from cereal and forage inspections are based on regulations that take into account the particular characteristics of corn, the method of producing and distributing the basic seed stocks and the procedures followed in processing and packaging the seed. In the inspection of pedigreed seed corn, a few facts must be recognized with respect to its reproduction. The male reproductive organs are located in the tassel and the female reproductive organs are located in the ear. As the plant matures, the tassels emerge from the leaf whorl and the anthers are extended from the glumes by their threadlike filaments. As the anthers ripen, the pollen is expelled and falls on the silks which by this time have emerged from the developing ear which develops somewhat slower than the tassel. Appendix VII provides further information on the biology of corn.

4.3 Field Inspection

4.3.1 Seed Source Verification for Hybrid Production

For hybrid field corn seed crops, official inspectors do NOT need to check parent seed tags unless directed to do so by the CSGA (i.e., OECD status production). The rationale for this different approach with hybrid crops is that the growers of hybrid crops are required to identify and verify to CSGA, at the time of application for crop inspection, the pedigree of parent seed planted (usually with copies of Foundation tags or with Foundation crop certificates). For hybrid field corn seed crops, official inspectors may obtain from the CSGA the variety descriptions for the male and/or female parent lines being inspected. The same is true for open-pollinated varieties. Licensed crop inspectors must obtain characteristics for the male and females interplanted to produce hybrid from the grower or contractor, who is generally their employer.

4.3.2 Seed for Export under OECD Rules

The Application for Crop Inspection should indicate if the crop from this field is designated to be sealed under the rules of the OECD. If the resultant crop is to be inspected and tagged under OECD rules, the local CFIA office must have on file or have access to:

the proof of pedigree of each parent; and
the variety description for each parent prior to the completion of the hybrid field corn seed crop inspection.

4.3.3 Orientation

The inspector must check the application for previous land use and the potential for volunteer plants. For those crops not requiring corn on corn inspection (volunteer), the information on the application should be reviewed, then each field located to verify the planting pattern, border rows and adjacent crops. If the cross or either of the parental lines require inspection as Foundation status, then the Record and Report of Inbred Seed Crop Inspection - Corn should be completed (Appendices II and VI). When inspecting open-pollinated corn, the inspector must report the findings on the Report of Seed Crop Inspection (CFIA/ACIA 1115).

Whenever practical, the inspector should conduct an orientation visit to the field before 5% of the female plants have receptive silks. During this visit, the inspector may:

match the information from the application form and field map with the field site;
verify isolation distances from potential sources of contamination.

Where this is not practical, the orientation must be conducted at the time of the first inspection.

Where corrective action is required with respect to isolation, the first formal inspection should take place to verify the timely performance of this corrective action. Subsequent inspections occur throughout the pollination period.

4.3.4 Conducting the Inspection

The inspector selects a travel pattern to ensure the best inspection of the crop. The crop should be walked according to the selected travel pattern noting the isolation distances, presence of off-types and volunteer plants as well as the uniformity of the crop that may affect the length and timing of the pollination period. Deviations from the selected travel pattern may be required to verify the isolation distances to contaminating corn, number and condition of the border rows, and the detasselling of each female row. The crop should always be entered at the posted entry point to the field since entry restrictions due to a pesticide application may apply.

CSGA Circular 6, Section 8 may be referred to for isolation distances for hybrid and open-pollinated field corn seed crop production.

The following procedure should be used to perform counts. Unless otherwise specified, these procedures apply to hybrid and inbred seed corn:

It will be up to each inspector to ascertain when pollination will be starting in each crop. The actual length of time when silks of the seed parent are receptive (pollination period) in any one crop is variable. It may be less than one week or it may be spread over a three week period. Each detailed inspection should be spaced several days apart (2 to 5 days) depending on how fast the crop is developing. Three detailed inspections during the pollination period are necessary.
The inspector selects the count areas, randomly scattering them throughout the crop to give an accurate picture of the crop. Count areas should be determined before entering the crop. If the inspector varies the travel pattern significantly from the first inspection and the resulting counts do not fall within the normal pollination pattern, the inspector should make a comment on the report as to why this occurred.
The minimum number of counts the inspector must take is twelve, 100 plants per count. Six counts are taken for:
a) female plants with receptive silks; and
b) female plants with tassels shedding.
A second series of six counts of 100 plants is taken for male parents shedding pollen.

When 5% or more of seed parent silks are receptive, not more than 1% of seed parent tassels should be shedding pollen on any one visit of the inspector, or if the total of three inspections on different dates exceeds 2%. This verifies the detasselling meets the CSGA standards. Male sterile seed parent lines should be checked for fertile out-crosses or incomplete sterility. The content of pollen shedding tassels is determined by counting such tassels on 100 consecutive stalks on each of six rows at random in the crop or portion of the field. When the inspection is part of a system audit, a greater number of counts is to be performed to overcome lack of uniformity or discrepancy between locations of counts. Tassel development is most rapid in periods of rainy weather and high temperatures. Tassel growth is more rapid at night and in the early morning when the predominance of pollen is produced. Pollen shedding tassels in the male sterile lines are more easily detected in the early morning as their filaments are not very sturdy and are quickly removed by daytime breezes. Such tassels will most likely be found in areas where growing conditions are abnormal, either good or bad, and they may occur towards the end of the pollinating period. Appendix IV provides information on female parent plant standards.

In determining the percentage of receptive silks, usually only the silk on the primary ear is counted. Second and subsequent ear shoots seldom produce an ear of desirable quality and usually only when the primary ear shoot has been removed or injured. Silks are considered to be receptive when they first emerge and as long as they are fresh or green and waxy. When fertilization has occurred the silk becomes dry, brown and lifeless. Fertilization occurs within 8-12 hours after the pollen falls on a receptive silk. Silks may remain receptive for a prolonged period awaiting the arrival of pollen.
Inspectors must be observant as to plants that appear between the rows or slightly out of the male or female rows. These plants may be volunteer plants that germinated from seeds left from a corn crop planted in the previous year or a crop planted during the current year and then replanted to the current seed crop. Volunteer corn plants can become visible anytime during the season. If suspicious plants are noted, rough counts should be made. If these are believed to be volunteer plants and present at the rate of more than 1 in 2000 as specified in CSGA Circular 6, official counts must be made as described in Appendix III during the pollination period if these plants produce a tassel that sheds pollen. If these volunteer plants exist but do not shed pollen, they should still be recorded in the "Comments" section of the report by the inspector with a statement that the plants did not shed pollen during the pollination period.
Inspectors must be observant as to plants in the rows that appear different from the majority of other male and female plants in the crop. Off-types and variants can become visible anytime during the season. If suspicious plants are noted, the inspector should make some rough counts. If these are believed to be actual off-types and are present at the rate of more than 1 in 1000 for hybrid and inbred corn as specified in CSGA Circular 6, official counts must be made as specified in Appendix III during the pollination period. Counts should be taken for off-type pollen parent plants that have shed or are shedding pollen during the pollination period and/or off-type seed parents plants that remain during the final detailed inspection. A description of the plant type must be included on the appropriate Record of Inspection. Appendix VII provides a brief description of the traits that may indicate off-types. In the case of open-pollinated corn, CSGA specifies that the maximum allowable level of detectable plants of other varieties or off-type plants is 1 plant in 2000.
If off-types are found in a number of crops of a variety, the licensed inspector should contact his/her supervisor for further action. Official crop inspectors should notify their Area Program Specialist as it may be indicative of contaminated parental lines.
For the three detailed inspection visits during the pollination period, the inspector must record the information, as required, on the Record of Hybrid Seed Crop Inspection - Corn, (Appendix I) or the Record of Inbred Seed Crop Inspection - Corn (Appendix II).
If a problem is noted such as contamination by an adjacent source, borders have been destroyed, or official counts are over the standards allowed, take detailed counts in the problem area and then contact your nearest program specialist for further information or instruction. There must be 5% receptive silk in the seed parent plants in the area of possible contamination.

For hybrid and inbred corn, a Non-Conformance Report (Appendix VIII) must be completed and attached to the final report. For hybrid corn, additional counts must be taken to calculate the percent (%) plants with shedding tassels in the border rows.

For open pollinated corn, the minimum number of counts to be taken is six. The count area is 2000 plants.

4.4 Completion of the Report of Seed Corn Crop Inspection

When three detailed inspections have been completed during the pollination period, and detasselling is completed, the crop inspection can be finalized by completing a final report (as long as there are no problems such as delayed tassel emergence in male and female rows, delayed silk emergence in female rows, correction after a detasselling problem, adjacent contaminating sources, etc.). It is not necessary to wait until the majority of female silks are starting to turn brown.

The report (Appendix V for hybrid corn or Appendix VI for inbred lines) should be completed by the crop inspector as soon as possible after the three detailed inspections. Key factors to report include:

date and time of visits;
map inaccuracies;
volunteer corn check;
border rows checked;
distances verified to comply with field map;
potential contaminating sources identified;
planting pattern compared and verified with application;
sterile seed parent location identified;
counts for:
- female receptive silks;
- males shedding pollen;
- female tassels shedding;
- contaminating corn shedding tassels;
- sterile seed parent shedding tassels;
off-types and description (male and female);
did pollen parent rows and border rows shed pollen simultaneously with silk emergence of female parent rows?

All information should be clear and legible.

The Report of Seed Crop Inspection - Corn consists of a copy of the final report (Appendix V for hybrid corn or Appendix VI for inbred corn), a copy of the record of inspection and a corrected copy of the field map and all non-conformance reports that have been generated.

The original report should be forwarded to CSGA office, with a copy sent to the grower representative. A copy is also kept in the office file of the crop inspector along with the rough field notes of the inspector. These must be retained in the office for two years. The CSGA determines the eligibility of the status of the crop as pedigreed corn seed.

Appendices

Appendix I: Record of Hybrid Seed Crop Inspection - Corn

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Form - Record of Hybrid Seed Crop Inspection - Corn

Appendix II: Record of Inbred Seed Crop Inspection - Corn

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Form - Record of Inbred Seed Crop Inspection - Corn

Appendix III: Maximum Impurity Levels for Corn

For the production of hybrid field corn

Volunteer plants must not exceed 1 plant in 2,000 plants in the seed crop immediately prior to detasselling or the commencement of the pollination period.The inspector must examine an area of 200 parent seed plants, randomly selected, for volunteer corn plants within or between the rows. This represents one count. Ten counts must be taken randomly in each inspected crop. The total of the ten counts is reported. Clusters or groups of volunteers must be reported as more than one plant.

Unless otherwise specified by the breeder of the inbred, a crop may not be eligible for pedigreed status if:

more than 1 plant in 1,000 (0.1%) obvious off-type plants in the pollen (male) parent have shed pollen;

more than 1 plant in 1,000 (0.1%) obvious off-type plants are found in the seed (female) parent at the time of last inspection.

The inspector must examine 100 plants in one, randomly selected, row of parent seed plants. The inspector must count the number of off-type plants, in the 100 plants inspected, and describe their deviant morphological characteristics. This represents one count. Ten counts must be taken randomly in each inspected crop. The average of these ten counts is the percentage reported.

For the production of open-pollinated corn

A crop inspection must be made at the time the silks are receptive to determine whether isolation has been provided in accordance with the CSGA standards and whether there are any detectable off-type plants. A crop or a portion of a crop may be eligible for pedigreed status but the reject parts of the crop must be removed, and confirmed by an inspector.

There shall not be more than 1/20 of 1 per cent (1 plant per 2000) detectable admixture with plants of other varieties or off-type plants in the variety being inspected.

Open-pollinated corn must be isolated by a minimum of 200 meters from any contaminating corn. The isolation distance may be modified by designating certain rows of the same variety for pollen shedding purposes only. The minimum isolation and border requirements appearing in the CSGA Circular 6 table for hybrid field corn seed production also apply to open-pollinated corn.

Rows that function to provide isolation shall not be harvested for seed purposes and their removal shall be confirmed by an inspection by an authorized crop inspector.

Appendix IV: Female (Seed) Parent Plant Standards for Hybrid Corn

The following applies when 5% or more seed (female) parent plants have receptive silks.

A crop may not be eligible for pedigreed status if on any one inspection more than 1% of the seed (female) parent plants possess tassels which have shed or are shedding pollen, or if the total for three inspections on different dates exceeds 2%.

Sucker tassels and/or portions of tassels on the main plants will be counted as shedding pollen when 5 cm (2 in) or more of the central stem and/or the side branches have their anthers extended from their glumes and are shedding pollen.

Sterile seed parent lines should be checked for fertile out-crosses or incomplete sterility. The content of pollen shedding tassels is determined by counting such tassels on 100 consecutive stalks on each of a minimum of six rows at random in the field or portion of the crop. A greater number of counts is preferred to overcome lack of uniformity in such discrepancy. Tassel development is most rapid at night and in the early morning when the predominance of pollen is produced.

Appendix V: Final Report of Hybrid Seed Crop Inspection - Corn

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Form - Final Report of Hybrid Seed Crop Inspection - Corn

Final Reports: Documents required to be sent into the local CFIA office are:

A completed copy of the Application for Hybrid Seed Crop Inspection - Corn corrected and signed.
A completed Report of Hybrid Seed Corn Crop Inspection - CSGA 142.121A for each crop.
A copy of the Record of Inspection for Hybrid Seed Corn and any rough notes

Notes to assist in completing report of hybrid seed crop inspection - corn form (CSGA 142.121A)

Company Name Block: Please use full company name.

Questions:

1. A slight omission, e.g. an adjacent crop is not considered an inaccuracy.

3 and 4: If NO, then complete the Table below on the report.

7. Answer is NO in most cases. If YES, then full details must be given in the tables below.

Dates of Regular Inspections - Record dates for detailed inspections only. Do not include dates for spot checks. Do not include volunteer inspection date. If more than 3 dates of detailed inspections are shown, then put the reason in the "Comments" section, e.g. uneven growth, excessive tiller growth, removal of rogues in female, etc.

Volunteer Corn on Corn - The acreage figure is for only corn on corn that may or may not be the entire field.

Comments are helpful such as: uneven growth, excessive tiller growth, part of crop later maturing, second planting of male will tassel very late, etc.

Appendix VI: Inbred Seed Crop Inspection Report - Corn

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Form - Inbred Seed Crop Inspection Report - Corn

Appendix VII: Facts and Observations to Assist in the Inspection of Hybrid Seed Corn

Unlike most other crop kinds, the reproductive structures in corn are housed on different parts of the same plant. The male organ, the tassel, which produces pollen is located at the top of the plant. The female organs, the ears, are located in the leaf axils and produce the kernels which can be planted as seed. If the silks are in a receptive condition, they accept the pollen and direct it to the ovaries where the embryo kernels are produced. Corn is wind pollinated. Both cross- and self-fertilization may be possible when both organs are present and functional on the plant. Self-pollination is also dependent on whether the time of receptivity of the silk occurs at the same time as the plant is shedding pollen.

Since the 1940s, it has been recognized that superior performance can be obtained from hybrid corn varieties. In order to produce hybrid field corn seed, the seed must result from the crossing of two genetically different inbred lines. In order to produce hybrid field corn seed, pollination by the same plant or by other plants of the female line must be prevented. Pollination by other than the male parent must also be prevented by use of isolation distances, use of border rows and removal of volunteers and off-types. Male and female plants are interplanted in rows or bays (blocks). The proportion of male to female plants is designed to result in the maximum pollination of the line or variety used as the female, or seed, parent.

The most common method of preventing self or sib pollination is by completely detasselling the female lines, while allowing the male plants to shed pollen. The male plants are then removed following pollination. The introduction of "cytoplasmic" or genetic male sterility into the female line results in plants that do not produce tassels that produce pollen that is capable of fertilization. It should be noted that some forms of male sterility will "break down" or not function under some environmental conditions. As a result, incompletely sterile tassels will need to be removed.

In contrast to hybrid field corn seed production, inbred field corn seed production is dependent on complete self-fertilization. In breeding nurseries, receptive ear shoots are protected from unwanted pollination by ear shoot bags that cover the silks. Pollen is contained and collected in bags that cover the tassels. Controlled hand pollinations are then made by exposing the ear shoot only to pollen produced on the same plant. In larger scale production of inbred lines, the crop must contain only plants of the specific inbred. Off-types must be accurately identified in a timely manner and removed. Breeder or Foundation seed is produced from self-pollinated seed after the eighth or ninth generation of self-pollination (inbreeding). Inbred lines are often stunted and less vigorous.

For all types of corn, one may prevent the introduction of contaminating pollen by producing a variety with a widely differing pollinating period to the source of possible contamination.

Off-types in hybrid corn may have one or more traits differing from the normal plant type of the variety or inbred line. Traits showing differences include, but are not limited to: plant height, intensity of colour of various plant parts, the shape, width and overall structure of the leaf, the presence and size of ear wings, tassel structure and colour, brace root colour and development, sucker plant development, silk colour and the shape and attitude of the ears. Kernel type may also be used to identify off-types but is not available at the time of seed corn inspection. Appendix IX provides diagrams of distinguishing characteristics in corn.