Poster Session: Diseases of Plants - New and Emerging Diseases
522-P
Preliminary assessment of differential susceptibility of soft red winter wheat cultivars to Lolium and Triticum pathotypes of Magnaporthe oryzae.
K. MILLS (1), P. Paul (2), L. Madden (2), G. Peterson (3)
(1) Ohio State Univ, Orrville, OH, U.S.A.; (2) The Ohio State University, Wooster, OH, U.S.A.; (3) USDA ARS Foreign Disease-Weed Science Research Unit, Fort Detrick, MD, U.S.A.
In South America, wheat blast epidemics caused by the Triticum pathotype of Magnaporthe oryzae (MoT) have resulted in yield loss as high as 40-100%. In 2011, wheat blast, incited by the Lolium pathotype of M. oryzae (MoL) was identified on a spike in Kentucky, suggesting that MoL could pose a threat to wheat production in the US. Subsequent pathogenicity studies have shown that some MoL isolates were indeed just as virulent as MoT on US hard red winter wheat. Two studies were conducted to compare the reactions of 86 northern soft red winter wheat (SRWW) cultivars to a Brazilian MoT isolate (T-25) and a US MoL isolate (P2-1). The MoT study was conducted in a BSL-3 facility at Fort Detrick, MD, and the MoL study in growth chambers in Wooster, OH. In both studies, 5-25 spikes of each cultivar were spray-inoculated, and then incubated for 48 hrs at high relative humidity and temperatures between 24 and 26°C. Blast severity was quantified as percent diseased spikelets. SRWW cultivars exhibited a wider range of reactions to MoL than to MoT. For MoL, average severity ranged from 2 to 78%, with a mean of 27%, compared to 70 to 100% for MoT, with a mean of 92%. These results suggest that some SRWW cultivars may be partially resistant to MoL but less so to MoT. MoL may pose a threat to SRWW production in the US if conditions are conducive for disease development and a susceptible cultivar is planted.