Drought tolerance in Malawian soybean (Glycine Max L.) germplasm

Water-limited stress (WLS) is associated with adverse changes at morphological, physiological, biochemical and molecular levels among genotypes, which consequently affects crop growth and productivity. These changes are useful indicators in breeding of drought tolerant genotypes. This study was, therefore, carried out to identify genotypes that are good performing under WLS conditions and to determine traits’ response to WLS using a combination of morphological traits, physiological traits, water use efficiency and grain yield. In addition, interrelationships among morphological traits, physiological traits and water use efficiency were determined in order to identify traits that contribute to grain yield under WLS conditions. The study also elucidated the association between drought tolerance indices and grain yield under WLS conditions in separating tolerant genotypes from sensitive genotypes. It further looked at the impact of drought on grain yield of soybean with change in environment and season. The study also tried to understand the mode of gene action considering that the majority of the characteristics of importance in a crop are inherited quantitatively. Genotypes showed significant variability in tolerance levels to WLS. Genotypes with a high drought tolerance level generally exhibited a higher grain yield, 100-seed weight, plant height, number of pods per plant, minimal grain yield reduction, maintained a higher relative chlorophyll content, quantum yield of efficiency for photosystem II and water use efficiency under severe WLS compared to genotypes with a low drought tolerance level. Among the physiological traits, relative chlorophyll content was most significantly associated with genotype, while quantum yield of efficiency for photosystem II, photoprotective nonphotochemical quenching and non-photochemical quenching basal dissipation of light energy for other unregulated process were more frequently and significantly associated with WLS. Plant height