PEG-Induced Drought Stress During Germination: Effects on Soybean Germplasm

Soybean is the one of the most important oilseed and protein sources worldwide. Among environmental stresses negatively affecting soybean, drought is considered as the most limiting factor in terms of yield losses encountered. In view of the need for improving drought tolerance, this study aimed at determining the seed germination and seedling growth potential under drought conditions as an approach to identify tolerant genotypes at early growth stages. The genetic material consisted of a set of commercial and pre-commercial varieties (Adonai, Neoplanta, Celina, Zora, PR92M22, P21T45, PR92M35, PR92B63, PR91M10). Drought stress was induced by different concentrations of polyethylene glycol (0, 5, 10 and 20 % PEG-6000). Genotype performance was assessed on the basis of Germination Percentage (GP), seed Water Uptake (WU), seedling Water Content (WC), root and shoot length and number of seedlings with abnormal phenotype. Stress substantially affected all traits associated to germination and seedling growth, with its effects though differing significantly among genotypes. Overall findings point to the superiority of varieties Neoplanta, Adonai, PR92M22 and Celina. Further, it was evidenced that GP as well as root and shoot length form suitable criteria for drought tolerance, while WU and WC did not allow the classification of genotypes in terms of drought tolerance. Our findings provide conclusive evidence that traits associated to germination and growth potential may be employed for revealing genetic variability related to drought tolerance, thus enabling their exploitation as screening criteria for drought tolerance. Upon confirmation of its validity, such short-cut selection approach may considerably upgrade the efficiency of breeding procedures targeted at the improvement of drought tolerance in soybean.