Differential Responses of Selected Soybean Cultivars to Drought Stress and Their Drought Tolerant Attributions

Abstract

Seven soybean cultivars in Thailand were evaluated under well-watered and drought- stressed regimes. A randomized complete block design with three replications in greenhouses was used. Control pots were kept well watered. Imposing drought stress commenced at the vegetative growth stage 3 (V3) for 15 d and then pots were re-watered. Shoot dry matter (SDM), root dry matter (RDM), nodule dry matter (NDM), shoot tissue moisture content (STM%) and electrolyte leakage from leaf tissue (EL%) of each tested cultivar under both water regimes were investigated. Physiological responses of the cultivars and their relationship were identified. Their drought tolerances were examined using a stress susceptibility
index (SSI), mean productivity (MP), geometric mean productivity (GMP), stress tolerance (TOL) and a stress tolerance index (STI). SDM, RDM and NDM decreased with increasing water stress. SDM, NDM, STM%, and EL% showed significant correlations with seed yield. On the basis of the physiological responses and drought tolerance attributes of the cultivars studied, SJ-4 was the most drought tolerant cultivar indicating that SJ-4 is not only the appropriate genotype for cultivar improvement but also for cultivation in drought-prone areas. STI had a highly significant correlation with seed yield (r=0.66) and could distinguish better yielding genotypes under the drought-stress environment. The results also showed that STI was the most appropriate index to attain better yielding cultivars for a drought-stress environment, followed by GMP.