High-temperature stress in rice [study conducted at IRRI, Philippines]

Abstract

When rice is exposed to air temperatures higher than 35 C, heat injuries occur. Clear varietal differences are observed for high temperature injuries at different growth stages. The rice plant appears to be most sensitive to high temperature at flowering. The second most sensitive stage is about 9 days before flowering. High temperature during anthesis induces high percentages of spikelet sterility. The occurrence of sterility can be attributed to disturbed pollen shedding and impaired pollen germination but not to inactivated pistil. Early morning anthesis is considered one way to avoid high temperature stress. Oryza glaberrima flowers open 3 hrs earlier than IR 36, O. sativa. Some O. sativa and O. glaberrima crosses have anthesis earlier than IR 36. Studies of the genetics of high temperature-induced sterility indicate that heat tolerance has a fairly high heritability and that most genetic variation is additive. There are clear varietal differences in high temperature-induced sterility at anthesis. Both heat-tolerant and early-maturing varieties can be found from the existing variety stocks. A comparison between phytotron and field experiments confirmed that the phytotron can be used for screening for heat tolerance