Evaluation of Resistance of Some Soybean Genotypes to Charcoal Rot (Macrophomina phaseolina) Disease Under Field Conditions

Charcoal rot is one of important disease of soybeans. In this study, 130 different soybean genotypes were evaluated in a simple lattice design with two replications in 2014 and 2015 in Karaj, Iran. Grain yield and disease-related indices including lesion length, lesion length: plant length ratio, percentage of infected plants and number of microsclerota on stem were measured. The results showed that the lowest (1.11 percent) grain yield reduction was observed for genotype 45 whereas genotype 11 had the highest (60.96 percent) grain yield reduction. The results of this study also showed that genotypes 1, 3,4, 5, 10, 12, 20, 24, 30, 31, 32, 40, 41, 43, 45, 46, 50, 53, 54, 63, 64, 66, 74, 76, 77 and 115 were resistant with low percentage of grain yield reduction and were free of disease symptoms. Genotypes 6, 11, 13, 18, 25, 33, 35, 42, 55, 57, 58, 59, 62, 70, 72, 73, 78, 86, 93, 97, 109, 111, 113, 123, 124, 129 and 130 were identified as susceptible genotypes with high percentage of grain yield reduction and disease symptoms on stem. The correlation between percentage of grain yield reduction and lesion length (r = 0.62**) and percentage of infected plants (r = 0.53*) were positive and significant. The results of stepwise regression analysis showed that lesion length and percentage of infected plants could explain more than 61 percent of the variations observed in the performance of genotypes under disease stress conditions.