Cold temperature under aerobic conditions increases spikelet sterility in rice (Oryza sativa L.)

Aerobic rice production (well-watered, non-flooded) has been proposed to improve water productivity. However, little research has been conducted on the effect aerobic conditions have on cold induced spikelet sterility. Two glasshouse experiments were conducted to examine the interaction between genotypes and water availability under cold temperatures. In each experiment, four genotypes were grown under aerobic and flooded conditions and half of all plants were exposed to cold temperatures (15/21°C) for a minimum of 14 days during the late booting stage. Water use was measured weekly until harvest and spikelet sterility was determined on the main stem panicle. Pollen number, anther size and stigma size were quantified. Under warm conditions, reductions in water use in aerobic conditions ranged from 58 to 85% compared to flooded (26L plant-1). When plants were exposed to cold temperatures, flooded conditions (34-48%) resulted in a significantly lower sterility than aerobic (70-80%). The genotypic effect in the cold treatment was significant in both experiments and sterility ranged between 36-78%. The lack of a significant interaction in both experiments indicates the mechanism for cold tolerance may be similar for flooded and aerobic conditions. Within the cold treatment, spikelet sterility was negatively correlated with the % viable pollen (r=-0.51*) and mean area of viable pollen (r=-0.60*) which reaffirms that the failure of the pollen grains is the leading cause for cold induced spikelet sterility at the late booting stage.