Drought tolerance of soybean genotypes at early vegetative stage

Soybean (Glycine max L. Merr.) is one of the major sources of protein for human and animal nutrition as well as a source for vegetable oil. Drought is a major limiting factor that can drastically reduce soybean yield. Due to climatic changes, periods of severe drought can occur at germination and early vegetative stage. The objective of this study was to screen 32 soybean genotypes for drought tolerance in early vegetative stage in controlled conditions. Seeds were germinated in moist silica sand and seedlings transplanted in tubes filled with vermiculite. The tubes were placed in a containers filled with a half strength Hoagland solution (control) or the same solution with 6% of diluted polyethylene glycol (PEG) 8000 (drought). Plants were grown in growth chamber at 22°C, 60% air humidity under cool-white light and 16/8 day/night photoperiod for 26 days. The following traits were measured: root and shoot length, fresh weight and dry weight. PEG-treated plants showed decrease in all measured traits with significant difference among genotypes. Drought tolerant genotype no. 3, 8, 11, 15, 22 and 25 with the highest drought tolerance efficiency (DTE) and the lowest decrease of shoot and root fresh and dry weight in drought were identified. These traits were highly positively correlated while root length negatively correlated with them. In conclusion, soybean genotypes that attained high root biomass without compromising shoot biomass are considered as drought tolerant.