Assessment of Drought Tolerance in Soybean Genotypes Using Multivariate Statistical Methods in Greenhouse Conditions

Soybean (Glycine max L.) is one of the most important oil crops whose yield can be affected by drought stres

In order to investigate the drought stress tolerance as well as yield and yield components of 45 soybean genotypes in greenhouse conditions, an experiment was conducted as a factorial arrangement in a completely randomized design (CRD) with three replications at Sari University of Agricultural Sciences and Natural Resources during 2019. The experimental treatments included different soybean genotypes and three levels of irrigation regimes include normal condition, moderate and severe drought stresses with 15, 40 and 75% soil moisture depletion, respectively.

The results of variance analysis indicated that the interaction between genotype and stress were significant for all the studied traits and also means comparisons of the traits shows that the negative effects on yield and yield components are more evident with increasing stress intensity. The highest seed yield in normal irrigation and moderate drought was related to Columbus genotype, whereas higher yield under severe drought stress was obtained for the OhioFG2 genotype, which is due to an increase in number of pods, number of seeds per pod and seed weight. Correlation between agronomic traits indicates that in all three stress levels, seed yield has a positive and highly significant (p<0.01) correlation with number of pods per plant and number of seeds per plant. Based on the results of regression analysis, in each of stress levels, seeds number per plant and seed weight were entered into regression model, and in normal condition, moderate and severe drought stresses justified 97, 84 and 97% of the changes related to the seed yield, respectively. The means comparisons of the tolerance indices in normal condition-moderate drought stress showed that the highest indices for mean productivity (MP), harmonic mean (HM), stress tolerance index (STI) and geometric mean productivity (GMP) were related to genotypes Columbus and Hill, while genotypes Emperor and Bonus had greatest value for the indices in normal condition-severe drought stress, which indicates the existence of resistance potential for these genotypes. Based on the results of cluster analysis of the tolerance indices in normal condition-moderate drought stress and normal condition-severe drought stress, genotypes are placed in three separate groups. Accordingly, genotypes placed in the first, second and third groups were identified as tolerant, semi-tolerant and sensitive genotypes, respectively. The result of principal components analysis showed that two components justified 93.34% in normal condition-moderate drought stress and 96.54% in normal condition-severe drought stress of total variations. Also, first component of geometric mean productivity (GMP) and the second component of stress susceptibility index (SSI) had highest values in both conditions. By using biplot analysis based on the first and second components, Columbus, Hill and Williams genotypes were placed in high yielding and stress tolerant area.

The cultivars of Columbus, Hill, Williams, Bonus, Emperor and Ohio FG2 have tolerance potential compared with other genotypes and are suggested as tolerant genotypes to drought stress.