Anther characteristics and spikelet fertility in rice (Oryza sativa L.) under high temperature stress at anthesis

The effect of high temperature at anthesis on spikelet fertility was studied in 22 rice genotypes selected from 98 heat tolerant genotypes. Genotypes were grown in field under natural conditions in Randomized Block Design replicated twice till vegetative stage. Before booting stage, few plants were transferred to pots and placed in polyhouse for high temperature treatments. On the first day of anthesis (i.e. the appearance of anthers), plants were transferred into polyhouse with temperatures gradually increasing from 29°C to 40°C and maintained at 40°C until 15 h, with a relative humidity of 75 percent. Seven genotypes viz., IR 86970-145-1, IR 86977-140-2, IR 86977-141-3, IR 86977-95-1, IR 86970-126-3, IR 86977-92-3 and IR 86977-104-1 exhibited 20 to 40 per cent spikelet fertility after exposure to high temperature of 40°C.The pollen fertility ranged from 39.0 to 90.5 per cent. The genotype IR 86970-145-1 had significant value for anther length (2.125) and anther breadth (0.320). Anther dimensions seem to have an influence on anther dehiscence, pollen and spikelet fertility. All other genotypes were found to be sterile with no seed set. Exposure to high temperature during heading has significantly reduced the spikelet fertility but there were genotypic differences.