Proper Management Improves Seedling Survival and Growth during Early Flooding in Contrasting Rice Genotypes

Flooding following direct seeding reduces germination and emergence in rice (Oryza sativa L.); however, crop establishment can be enhanced through genetic improvement and proper management. This study describes the effects of selected management practices on seedling survival of rice genotypes that vary in tolerance of flooding during germination. Seeds were sown in pots and submerged, and seedling survival was determined 21 d later. Extent of lipid peroxidation and activity of reactive oxygen-scavenging enzymes in dry seeds and amylase activity in germinating seeds were assessed. Flooding decreased survival in old seeds and in seeds stored at warmer temperature, and this reduction was associated with a decrease in activities of superoxide dismutase and catalase and an increase in lipid peroxidation. Survival, shoot and root growth, and activities of amylase enzymes measured 3 d after sowing were highest when floodwater temperature was 24 to 26 degrees C. Survival decreased with increasing water depth and algal growth and correlated positively with total amylase activity and negatively with lipid peroxidation. Apparently, floodwater conditions and seed handling affects survival in direct-seeded rice subject to early flooding, and tolerant genotypes are more responsive to such conditions. Sowing properly stored, fresh seeds in a well-prepared seedbed to control flooding depth and irrigating with water at optimum temperature will further enhance the establishment of tolerant genotypes.