Effect of stage-specific and multi-stage drought on grain nutrient quality in rice

Drought is a multidimensional stress that affects the grain nutritional quality of high yielding rice genotypes. The present study evaluated the impacts of stage-specific (seedling, vegetative, and reproductive stages) and cumulative (multi-stage) drought on ionome, starch, and protein contents in grains of two rice genotypes of eastern Indo-Gangetic plain, viz. Sahbhagi Dhan and IR64 with contrasting drought tolerance. The study showed drought to negatively affect the physiological and nutritional traits of rice grains. Following the study, stage-specific and multi-stage drought caused significant reduction in grain size, test weight, starch, amylose, amylopectin, and total soluble protein contents of rice grains. Drought during different developmental stages of rice caused significant variations in micro- (Cu, Fe, Mn, Na, Zn) and macro-nutrient (P, K, Ca, Mg) contents in the grains. Stage-specific and cumulative drought exposure of the rice genotypes also governed the ionomes in grains resulting in specific ionomic networks. Hierarchical cluster analysis showed two discrete clusters for elements as well as different drought treatments in the studied rice genotypes, which supported the results obtained from the principal component analysis, displaying five clusters based on stage-specific and multi-stage drought treatments. Variation in drought treatments and elements in different rice genotypes also altered the ionomic interactions represented by differential ionomic networks. In this study, Sahbhagi Dhan maintained the morphological and nutritional qualities of grains across the drought treatments and therefore, can be used as a suitable donor in breeding for stage-specific and cumulative drought tolerance with superior grain quality for eastern Indo-Gangetic plain.