Temperature induction response (TIR) as a rapid screening protocol to dissect the genetic variability in acquired thermotolerance in rice and to identify novel donors for high temperature stress tolerance

Abstract

Rice is the major cereal food crop in the world. The predicted 2–4 °C increment in temperature by the end of the twenty-first century and the occurrence of drought coupled with high temperature stress situation poses a threat to rice production. There is a wealth of unexplored rice germplasm and landraces which show significant genetic variation in response to temperature stress. Hence, the present study was designed to develop a rapid screening protocol based on the principle of “acquired tolerance” in which seedlings were subjected to a gradual temperature increase from 38 to 48 °C for 3 h (induction treatment), immediately followed by challenging at 54 °C for 3 h. Among the landraces, Apo and Norungan showed a mortality of 12 %, coupled with a less reduction in percent root and shoot growth when subjected to induction treatments. Thus their intrinsic thermo-tolerance was found to be comparable with that of N22. The physiological basis of thermo-tolerance in these lines was further confirmed, as these lines recorded a higher chlorophyll stability index and a strong antioxidant enzyme system with lesser lipid peroxidation in terms of malondialdehyde content values. Finally, TIR studies revealed that, apart from N22, landraces such as Apo, Norungan, Ottadiayan and Vellaikudaivazhai can also be used as new sources of donors in breeding programmes to overcome combined drought and temperature stresses.