Effects of Septoria nodorum Berk. on yield and yield components of spring wheat

Data from two experiments was analysed in order to determine the effects of Septoria nodorum Berk. on the yield of spring wheat. In the first experiment the cultivar Hankkija’s Taava was artificially inoculated with low spore concentration suspensions of S. nodorum. The resulting disease reduced grain yield by 10%, 1000-grain weight by 14%, and hectorlitre weight by 5.7 %. An examination of the ears from the main stems revealed that the pathogen induced a reduction in all yield components but especially in grain number/ear and grain weight. In the second experiment a total of 28 cultivars or lines were studied and the correlation between grain yield/ear and disease severity was found to be negative but low. No consistent trend among the correlations was seen and some susceptible cultivars suffered only slightly from the disease while other fairly resistant cultivars showed great losses. The results are discussed in relation to compensatory mechanisms and potential disease tolerance in wheat