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Scab-Resistant Wheat Varieties: Just Around the Corner,
Or Way Down the Road?

Fred Kolb
Fred Kolb
Professor of Plant Breeding
Department of Crop Sciences
(217) 333-9485; f-kolb@illinois.edu

Diseases infecting wheat often cause economic losses for wheat producers in Illinois. One of the most damaging diseases of wheat in Illinois is head scab (also called Fusarium head blight). Wet, rainy weather at flowering favors infection with scab. This occurred in part of the wheat production area in southern Illinois in 2003. Symptoms of scab infection are not evident until several weeks after flowering, when heads (or parts of heads) turn prematurely tan, and a pinkish-orange color may be visible at the base of some spikelets. The fungus not only causes reduced grain yield and test weight, but it also produces a mycotoxin called deoxynivalenol (DON), which is detrimental to humans and livestock.

Scab infection symptoms on a wheat head
Figure 1. Scab infection
symptoms on a wheat head.

Development of scab-resistant varieties is a major breeding objective in many wheat breeding programs, including the one at the University of Illinois. A misted, inoculated disease evaluation nursery is used to evaluate scab resistance of wheat experimental breeding lines and wheat varieties. Material to be evaluated is planted in short rows. The field is inoculated with infected corn fodder and also by scattering wheat grain (on which the fungus has been grown) in the field. The nursery is mist-irrigated twice daily from just before the earliest lines begin to flower until a week or more after the latest material has flowered. This technique allows for the production of many fungal spores and provides an opportunity for all of the experimental breeding lines and varieties to be infected with scab.

About three to four weeks after flowering, the breeding lines and varieties are evaluated for scabresistance. Resistance is evaluated by assessing the incidence (what percentage of the heads are infected and showing symptoms?), severity (how much of a head is showing the premature tan color?), and quality of a grain sample (how much of the grain is shriveled?). The experimental breeding lines with resistance are evaluated further; other traits also are evaluated in these lines. For an improved variety, scab resistance must be combined with many other traits, such as high yield potential, high test weight, earliness, winter hardiness, good milling and baking quality, and resistance to other important diseases.

To minimize risk from scab, wheat producers should:

Some varieties with moderate to good scab resistance include Agripro Gibson, Agripro Patton, Allegiance - Kentucky American Seed, Coker 9474 - Syngenta NK, Ernie, and Pioneer Brand 25R42.

In summary:

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