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First report of non-2NS resistance to wheat head blast

Giovana Cruppe: Kansas State University

<div>Wheat blast, caused by the fungus <em>Magnaporthe oryzae Triticum</em> (MoT), is a devastating emerging disease affecting S. America and S. Asia. Despite 30-yrs of intensive effort, the 2NS translocation from <em>Aegilops ventricosa</em> contains the only source of useful head blast resistance identified to date. Our goal was to identify non-2NS resistance to MoT. At least 1000 elite cultivars, breeding line materials, and wild accessions were tested at 2 biosafety level-3 laboratories in the US and under controlled and field conditions in Bolivia. In controlled conditions, heads were inoculated after full emergence and individually rated for percentage of diseased spikelets. Under field conditions, susceptible spreaders were inoculated at tillering to guarantee sufficient inoculum. Disease incidence and severity were evaluated as the average rating for each meter-row plot. The diagnostic marker Ventriup-LN2 was used to test for the presence of the 2NS translocation. Among the germplasm tested, four non-2NS CIMMYT lines (i.e., CM22, CM36, CM58, and CM61) averaged 6.5, 17.5, 6.7, and 0% of disease severity under controlled conditions. Under field conditions, averages of two locations (2017 growing season) were 3, 18.5, 0, and 12%. Meanwhile, susceptible checks averaged 91% (controlled-environment) and 34% (field). Additional experiments are being conducted to validate our results. New resistance sources from this study can be incorporated into wheat head blast breeding programs.</div>