Physiological Characterization of Diverse Landraces of Rice to Identify Donors for High Temperature Stress Tolerance Based on First Spikelet Opening Time

Abstract

Rice is susceptible to heat stress at flowering, where temperatures above 33 °C during anthesis causes spikelet sterility. Heat-induced spikelet sterility at flowering is associated with reduction in grain yield. So far only N22 has been used as universal donor for heat stress. One of the major traits employed in N22 in mitigating the impact of high temperature is the early morning flowering (EMF). Hence, the present study was designed to identify novel donors from the indigenous landraces of rice available at TNAU. The physiological basis of flower opening time (FOT) showed early flowering lines had higher transpiration rate coupled with low photosynthetic rate and stomatal conductance during anthesis. The transpiration rate also led to a reduction in panicle temperatures in these lines. It was concluded that at the time of anthesis, the panicle temperatures were 24 °C and less which led to advanced FOT. The results revealed that among the 21 lines, seven landraces, namely Thatan samba, Panamara samba, Thooyamali, Norungan, Mattikar, Sornavari and Seakar, flowering (9.30 to 10.00 IST). Hence, the lines Thatan samba, Panamara samba which flowered before 9.40 IST can be used as potential donors of EMF trait to develop heat-tolerant varieties.