Anatomical, agro-morphological and physiological changes in rice under cumulative and stage specific drought conditions prevailed in eastern region of India

Abstract

Under the climate change scenario, the occurrence of drought at any developmental stage of rice can cause significant yield loss in rainfed areas. Thus, the present study was conducted to explore the cumulative and stage-specific effects of drought on rice genotypes sown under field conditions. Preliminary screening of 32 rice genotypes for multi-stage drought (MSD) tolerance resulted in the identification of five promising genotypes based on yield and component traits and physiological parameters. These five promising genotypes along with checks (Sahbhagi Dhan and IR64) were grown further in a detailed study to establish their level of MSD tolerance based on physiological, biochemical and anatomical parameters. The mean grain yield of tested genotypes declined significantly (85.7%) under cumulative drought (MSD) compared to non-stress conditions. Further, MSD caused significant reduction in spikelet fertility (35.2%), test weight (16.1%), tillers m−2 (45.4%), grains panicle-1 (21.45%), flag leaf length (FLL) (13.9%), relative water content (27.3%) and membrane stability index (28.1%). Chemometric analysis also confirmed the relative MSD tolerance of promising genotypes. Photosynthetic rate (PN), stomatal conductance, total chlorophyll, protein and starch content significantly (P < 0.05) declined under MSD conditions. The contents of total chlorophyll, protein and starch were augmented from seedling to vegetative stage, and thereafter reduced at reproductive stage both under non-stress and MSD conditions. However, the level of lipid peroxidation measured in terms of thiobarbituric acid reactive substances (TBARS) and peroxidase activity increased from seedling to reproductive stage under both conditions. Among the five promising genotypes, IR84899-B-179-16-1-1-1and IR84894-143-CRA-17-1 maintained their PN rate, total chlorophyll, proline and protein contents under drought irrespective of growth stage. Moreover, drought-induced defective sugar mobilization led to the loss of pollen viability, thereby decreasing grain yield. Overall, the study established that MSD significantly affected agronomic, physiological and biochemical traits of rice plants at different developmental stages, but the tolerant genotypes sustained their yield by maintaining their efficient physiological functions and pollen viability through effective sugar mobilization.