Evaluation of Reaction in Soybean Elite Genotypes to Charcoal Rot under Field Conditionsύ.

The charcoal rot caused by the fungus Macrophomina phaseolina is the most common diseases of soybean in many parts of the world. The charcoal rot is one of the most important fungal diseases of soybean in soybean fields in the north of Iran. The use of resistant and tolerant cultivars, is the most effective, economical and environmentally safe way to control of this disease. Therefore, the response of maturity in late elite genotypes of soybean in contaminated field to Macrophomina phaseolina were evaluated for two year. Each line of soybean in four lines of five meters to the distance of 50 cm together in in randomized complete block design with three replications were planted. At the end of the season and maturity stage R7, reaction of lines to disease were measured as a percentage of infected plants in each plot and disease severity per plant based on the percentage height of internal stem discoloration from ground level. Due to unfavorable weather conditions in summer 1390 (continuously and high rainfall) that leading to increas soil moisture and decreas soil temperatures, so the charcoal rot was not created and genotypes were not infected. In the summer of 1391 due to favorable climate for growth and development of soybean and pathogen and also changes in the way run of projects, acceptable results were obtained by reaction of genotypes to the disease. Based on these results, the genotype Davis / Williams with 52/2 % had the maximum and genotypes (cultivar) Saman with 7% had the minimum percentage of infected plants. Genotype Davis / Williams with 49/8 % and genotype (cultivar) Saman with 17/1 % had the highest an lowest disease severity, respectively. Genotypes (cultivar) Katul with 194 gram and genotypes (cultivar) Williams with 116/7 gram had the highest and lowest 1000 seed weight, respectively. Genotypes (cultivar) Katul with 1324 kg/ha had the maximum and genotypes (cultivar) Williams with 674/7 kg/ha had the minimum seed yield.