Reaction to septoria leaf blotch in a number of elite genotypes of bread wheat

Septoria leaf blotch disease (STB) caused by the fungus Mycosphaerella graminicola (Fuckel) J. Schroeter (Anamorph: Septoria tritici Roberge), is one of the most destructive foliar diseases of wheat in the world, that its worldwide damage in outburst years is about 30 to 50 per cent. The pathogen is a bipolar heterotallic ascomycete that its sexual life cycle is repeating during the cropping season when environmental conditions are favorable for disease development. Due to evolution of resistance to fungicides in fungus strains and harmful effects of fungicides for environment, planting resistant cultivars is the most effective method to manage the disease. However, the disease has been spreading around the world due to use of susceptible, premature and semi-stunt cultivars that have been cultivated broadly during the last decade, because of high yield and resistance to some diseases such as rusts. Identify to resistance source to pathogens and selection of resistant genotypes is one of the most basic components in breeding programs for disease resistance. The purpose of this study is comparing the resistance of different wheat lines and identification of cultivars with the highest level of resistance to septoria leaf blotch. In this study the reaction of 40 lines from north humid climate of wheat genotypes and Tajan cultivar for control was evaluated by artificial inoculation in tillering stage in field during 2013-2014 cropping season. For this purpose, separation and purification of the fungus was carried out and prepared inoculation was used for inoculating. Then artificial inoculation was done in cultivated genotypes using infected leaves and spore suspension. Finally, statistical analysis of recorded data and means comparison was performed using SAS software and LSD test. The reaction of wheat genotypes were evaluated by assessing leaf necrosis area and calculate of Area Under the Disease Progress Curve (AUDPC). Analysis of variance showed significant differences among genotypes for leaf necrosis area at 1% level. The difference is representative of genetic variants between genotypes in susceptibility and resistance to disease. Mean comparison of leaf necrosis area in genotypes according to LSD test put the genotypes in different groups. Evaluation of means comparison showed that line 27 (N-91-6) and 10 (N-92-9) were the most susceptible and the most resistant in leaf necrosis area and infection intensity, respectively. The highest AUDPC was calculated for line 27 and the lowest for line 10. The cluster analysis of genotypes according to the average percentage of pycnidia coverage on leaf surface put the genotypes in two groups. Genotypes with sensitive reaction were in the first group, and the second group included genotypes with moderately resistance reaction. Due to the results of this study, from the used lines, two lines number 10 (N-92-9) and 19 (N-92-18) showed moderately resistance reaction to septoria leaf blotch and other lines placed in susceptible and moderately susceptible groups. Then two lines number 10 and 19 can be used in biotechnology to make resistant cultivars to the septoria leaf blotch disease.