Effects of sharp eyespot (Rhizoctonia cerealis) on yield and grain quality of winter wheat

Sharp eyespot caused by Rhizoctonia cerealis was assessed in four winter wheat crops surveyed at four locations in north-central Poland in 2006-2009. At the four locations symptoms developed on 41.9-67.7 % of shoots of all plants (average of 4 years) and on 49-73.5 % of shoots of diseased plants (average of 4 years). Slight (category 1) disease was most frequent, occurring on 24.4-41.3 % of shoots (range 14.8-51.3 %); moderate (category 2) disease was less frequent, occurring on 16.9-25.5 % of shoots (range 8.9-32.4 %); severe (category 3) disease was least frequent, occurring on 3.2-7.1 % (range 0-22.0 %) of shoots. Sharp eyespot affected wheat growth and yield, and grain quality. Disease, especially in the severe category, was associated with significant decreases in plant and ear dry weights, number of grains per ear, grain dry weight per ear and thousand-grain weight, and with increases in grain protein and wet gluten contents, Hagberg falling number and sedimentation value. There was an association between occurrence of sharp eyespot in stems and colonization of grain by fungi. Alternaria alternata and E. nigrum were the most common species.