Screening of Resistant Genotypes to Septoria Leaf Blotch in Preliminary and Advanced Regional Wheat Yield Trials (PRWYT & ARWYT), and Selected and International Cultivars and Lines in 1392-93

Screening of plant material based on their reaction to plant pathogens could result in selection of resistant genotypes in breeding programs for disease resistance. In this study, reaction of 810 wheat genotypes was evaluated to septoria tritici blotch (STB) in adult plant stage under artificial inoculation in field condition of Gorgan and Dezful. The plant material includes genotypes from preliminary and advanced regional wheat yield trials (PRWYT & ARWYT) of four climate zones, some selected lines and cultivars from breeding programs of 2013-14 cropping season in the Department of Cereal Research, and CIMMYT screening nursery and differential cultivars of STB. Each line was linearly planted in two rows of 1 m with 30 cm space. Susceptible local cultivars were placed between 20 experimental lines, as well as field borders in order to increase disease incidence. Nurseries were artificially inoculated by spreading infected plant debris (from last growing season) at tillering stage and by several sprays of spore suspension with concentration of 106 per ml until emerging flag leaves. Disease severity was evaluated prior to ripening when at least four leaves are alive and green, based on 00-99 double digit scale of modified Saari & Prescott (Eyal et al., 1987). Wheat lines were classified in groups of immune (00), highly resistant (11-14), resistant (15-34), moderately resistant (35-44), moderately susceptible (45-64), susceptible (65-84) and highly susceptible (85-99). Based on the results of Gorgan, 19, 3 and 3% of wheat genotypes (25% in total) were classified as immune, resistant, and moderately resistant, whereas 36 and 39% (75% in total) were moderately susceptible and susceptible, respectively. In Dezful, only 8% of the genotypes were immune, while 10 and 82% (92% of whole material) displayed reactions of moderately susceptibility and susceptibility, respectively. Based on these results, wheat breeders screened the genotypes possessing an acceptable resistance in both locations for next breeding steps