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United States Department of Agriculture

Agricultural Research Service

Research Project: EVALUATION AND IMPROVEMENT OF CEREAL GERMPLASM FOR DISEASE RESISTANCE AND WINTER-HARDINESS Title: Fusarium graminearum infection and deoxynivalenol concentrations during development of wheat spikes

Authors
item Cowger, Christina
item Arellano, Consuelo -

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 5, 2012
Publication Date: April 8, 2013
Citation: Cowger, C., Arellano, C. 2013. Fusarium graminearum infection and deoxynivalenol concentrations during development of wheat spikes. Phytopathology. 103:460-471.

Interpretive Summary: Fusarium head blight (FHB), also known as head scab, affects whole heads of small grain plants. Yet little is known about how concentrations of the mycotoxin deoxynivalenol (DON) change during disease development. Fusarium mycotoxin levels in small-grain heads are of concern to producers of whole-crop silage, as well as users of straw containing chaff for animal bedding or winter livestock rations. A two-year field experiment was carried out in Kinston, North Carolina. Eight winter wheat lines with varying levels of FHB resistance were used in the 2006 experiment, and four of them were used again in 2007. Plots were sprayed with Fusarium spores at flowering, and then misted for either 0, 10, 20 or 30 days. Head samples were collected at 15, 25, 35, 45, 55, and 65 days after flowering and separated into grain, glume, and rachis components. Increasing durations of post-flowering moisture elevated grain DON and reduced the effect of variety resistance on DON in all spike tissues. Fusarium-damaged kernels (FDK) increased from early kernel-hard to harvest-ripe in both years. Percent infected kernels (PIK) increased from medium-milk to harvest-ripe. During grain-fill, DON concentrations declined in grain, but increased in rachises and glumes, peaking at early kernel-hard, before declining again. Higher DON levels were observed in rachises and glumes than in grain. Estimated whole-head DON peaked at early kernel-hard stage. In a high-scab year, whole-plant harvest for forage should be conducted as early as possible. Straw that may be consumed by livestock could contain significant amounts of DON in chaff, and DON can be minimized if straw is sourced from crops with fewer symptoms at milk stage.

Technical Abstract: Fusarium head blight (FHB) affects whole spikes of small grain plants, yet little is known about the timecourse of FHB development following infection, nor about the concentration or progression of the mycotoxin deoxynivalenol (DON) in non-grain spike tissues. Fusarium mycotoxin levels in whole small-grain spikes are of concern to producers of whole-crop silage, as well as users of straw containing chaff for animal bedding or winter livestock rations. A two-year field experiment was performed in Kinston, North Carolina, to reveal the timecourse of FHB development. Plots were spray-inoculated with F. graminearum macroconidia at mid-anthesis. Eight winter wheat cultivars with varying levels of FHB resistance were used in the 2006 experiment, and four of them were used in 2007. Four durations of post-anthesis mist were applied: 0, 10, 20, or 30 d. Spike samples were collected and bulked by plot at 15, 25, 35, 45, 55, and 65 d after anthesis (daa); samples were separated into grain, glume, and rachis fractions. Increasing durations of post-anthesis moisture elevated grain DON and reduced the effect of cultivar on DON, presumably by breaking down resistance, in all spike tissues. Fusarium-damaged kernels (FDK) increased from early kernel-hard to harvest-ripe in both years. Percent infected kernels (PIK) increased from medium-milk to harvest-ripe. During grain-fill, DON concentrations declined in grain, but increased in rachises and glumes, peaking at early kernel-hard, before declining again. Higher mean and maximum DON levels were observed in rachises and glumes than in grain. Estimated whole-spike DON peaked at early kernel-hard. In a high-FHB year, whole-plant harvest for forage should be conducted as early as possible. Straw that may be consumed by livestock could contain significant amounts of DON in chaff, and DON can be minimized if straw is sourced from low-FHB-index crops. Cultivar FHB resistance ratings and disease index data should be useful in predicting whole-spike DON levels. Overall, associations between grain DON levels in harvest-ripe and prior samples were stronger the later the prior samples were collected, suggesting limits to the possibility of predicting harvest-ripe grain DON from earlier levels.

Last Modified: 11/24/2014
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