Stability of Seed Yield and Reaction to Charcoal Rot Disease of New Soybean Genotypes in Some Northern Regions of Iran

Seed yield in soybean is a complex trait and is influenced by multiple genetic and environmental factors. In this research, 13 cultivars and advanced genotypes with two control cultivars (Sari and Katul) were cultivated in three warm and humid regions of the north of Iran, including Gorgan, Sari and Mughan, during the two cropping years of 2013 and 2014 in a randomized complete block design with three replications. Mean comparison in different years and locations showed that G15 genotype had the highest seed yield, followed by G2, G4 and G9 genotypes. Correlation coefficients showed that the number of seeds per m2 (R² = 0.77) and the number of pods per plant (R² = 0.66) had a positive and significant correlation with seed yield, while the correlation between 100 seed weight and seed yield was insignificant (R²=0.02). G2 and G3 genotypes had the highest percentage of charcoal rot and G4 genotype showed the lowest percentage of infection. Regarding the percentage of infection with charcoal rot disease, all the investigated genotypes are below 10% and are considered tolerant genotypes for this disease. GGE biplot analysis indicated that the first and second principal components explained 70.6% of total yield variation. According to which-won-where pattern of GGE biplot, G4, G15, G12 and G7 genotypes had the longest distance from the origin of the biplot and were placed in the group of reactive genotypes to the environment and G2, G3 and G1 genotypes were classified as stable group. Genotype G4 performed well in Mughan1 and Mughan2 whereas, G15 genotype showed the best performance in Sari1 and Gorgan2, and G12 genotype was the best genotype in Sari2 environments. According to the genotypes comparison with ideal genotype, G15, G9, G2 and G1 genotypes had the shortest distance from the ideal genotype and were, hence, included in the group of stable genotypes. The simultaneous GGE biplot of seed yield and stability displayed graphically that G2 genotype had superior performance and broad adaptation to the diverse environments. Sari1(Sari 2013) was the most discriminating and representative environment and is classified as the superior environment and Gorgan 2 (Gorgan 2014) was ranked second. Based on tolerance to charcoal rot disease, average seed yield, as well as different GGE biplot graphs, G2 genotype incorporated both high mean yield and yield stability and can be released as a new soybean variety.