Dry matter production, water use and water efficiencies of PhilRice drought resistant strains during early vegetative drought stress

Drought is one of the abiotic stresses negatively affecting rice growth and development. This study was conducted in greenhouse to determine the relationship among plastic root system development responses. Water use, water use efficiency and dry matter production under vegetative drought stress using drought resistant strains (DRS) identified during reproductive drought stress. Six genotypes were grown under continuously waterlogged control for 29 days and waterlogged for 14 days before being droughted for another 25 days. There was significant genotypic variations in dry matter production, water use and water use efficiency and root system development under vegetative drought stress. Generally, DRS had less reduction in shoot dry weight than the resistant check PSB RC14 and susceptible check IR64. Among DRS, DRS904 and DRSIII had less reduced shoot dry weight than DRS40 and DRS578. Genotypic variations in dry matter production were closely related to the variations in water use but not water use efficiency. Furthermore, genotypic variations in water use were closely related to the variations in root system development response to drought based on total root length. The overall root system development response to drought was significantly influenced by the ability to maintain nodal roots production and plasticity in L-type lateral root production. Overall, the results indicate that drought resistance mechanism during early vegetative drought was through dehydration avoidance mechanism brought about by plastic root system development which consequently contributed to the maintenance of shoot dry matter production. The selection for drought resistance during reproductive stage does not guarantee identifications of genotypes with drought resistance to early vegetative stage as resistance mechanism to drought may differ between the two stages of rice growth.