Verticillium longisporum Fact Sheet

Background

Verticillium longisporum is a plant pathogen that can cause early death and reduced yield in crops. It is one of three species in the genus Verticillium that causes a disease commonly known as verticillium wilt. Verticillium longisporum infects a broad range of crops, but the most severe impact is on oilseed rape (canola). In Europe, verticillium wilt is considered one of the most important diseases of crucifers.

Plant Pest Credit Card- Verticillium wilt on canola PDF (1.1 mb)

Where is Verticillium longisporum found?

  • Europe: Belgium, Czech Republic, France, Germany, Netherlands, Poland, Russia, Sweden, United Kingdom (England and Wales)
  • Asia: Japan
  • North America: United States (California, Illinois)

Biology

The disease cycle of V. longisporum happens in two phases. First, the fungus grows inside the vascular (water conducting) tissues of the plant. Then, it has a necrotrophic stage, which involves tissue rot and the production of microsclerotia in dying plant tissues. Microsclerotia are the survival structures of the pathogen. They are tolerant of many environmental conditions.

The first phase of the disease cycle requires microsclerotia to germinate in the soil. This occurs when they are in close proximity to plant roots. The fungus grows in plant roots and spreads up into the above-ground vascular tissues of the plant, including the stem and leaves. As the disease progresses into the second phase, the fungus causes the stem and leaves to prematurely degenerate. Microsclerotia form on the stem (see Figure 1), and when infected plant debris is incorporated into the soil, these survival structures can stay in the soil until there is another host plant available to colonize.

Symptoms

Disease symptoms include yellowing of leaves and lateral branches, early degeneration, drying out of stems and leaves, and, potentially, plant death. Yellowing and stem symptoms tend to occur on one side of the plant (see Figure 2). Symptoms may also include early ripening of seeds on infected branches. Reduced plant biomass and smaller seed sizes have also been reported on canola as a result of infection with V. longisporum.

How does the pathogen spread?

The pathogen is primarily spread through the movement of infested soil or diseased plant parts. There is also some evidence that seed from heavily infected crops may introduce the pathogen to new areas.

Management and Control

Survival structures of this fungus (microsclerotia) can stay in the soil and remain infective for many years, even without a host plant. This makes eradication a difficult process, and requires that host plants of the fungus are not grown on infected fields for several years. In countries in which V. longisporum is present, in-field control measures concentrate on reducing the number of microsclerotia in soil and include tilling plant residue into the soil to reduce wind-blown spread of infected debris, clearing fields of susceptible weed species, and extended crop rotations.

Figures

Figure 1: Layers of blackish microsclerotia underneath disrupted epidermis on the stem of a mature rapeseed plant
(Photo: A. V. Tiedemann, Göttingen, 2006)
Figure 1: a mature rapeseed plant with layers of blackish microslerotia underneath disrupted epidermis

Source: Department of Crop Sciences - Division of Plant Pathology and Crop Protection

Figure 2: Field symptoms of Verticillium longisporum infection on Brassica napus showing one-sided stem discolouration
(Photo: A. v. Tiedemann, Göttingen, 2006)
Figure 2: Verticillium longisporum infection on Brassica napus showing one-sided stem discolouration

Source: Department of Crop Sciences - Division of Plant Pathology and Crop Protection

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