Vol. 17 No. 2
Validation of temperature induction response technique on combined effect of drought and heat stress in rice (Oryza sativa L.)
Author(s): M. RESHMA, R. BEENA, M.M. VIJI, R.V. MANJU AND S. ROY
Abstract: Acquired tolerance traits can be evolved in plants by gradual induction of stress in a progressive manner. Here, we demonstrate a significant genetic variability in acquired tolerance traits among rice genotypes against combined effect of heat and drought stress after standardizing temperature induction response technique protocol.Expression of stress responsive genes during the sub-lethal induction stress and differences in the expression of these genes is the reason for observed genetic variability for stress tolerance. Five days germinated seedlings of rice varieties Jyothi (Ptb-39) and Vaishak (Ptb-60) were exposed to different temperatures to standardize both the lethal and induction temperature for TIR technique. Seedlings exposed to 52°C for 3 hr showed 100% mortality was selected as lethal temperature. TIR induced as well as non-induced plants of ten rice varieties (Nagina 22, Apo, CR Dhan 305, CR Dhan 307, Ptb-7, Ptb-15, Ptb-30, Ptb-39, Ptb-43 and Ptb-60) were exposed to both the abiotic drought and heat stress and were used to study the morpho-physiological and molecular responses. Based on the percentage of seedlings survival rate lethal temperature was standardized as 52°C for 3 h. Standardized induction temperature was 32-42ºC for 5 h and 42-52ºC for 30 min followed by 52ºC for 3 h based on the recovery growth of varieties. TIR induced plants exhibited better performance on morphological and physiological traits than non-induced plants in all the genotypes based on better stress tolerance and yield parameters. Nagina 22 and Apo were selected as the best genotypes for stress related traits. Tolerance of genotypes towards stress has been attributed to changing transcript levels of stress induced genes. The results revealed that temperature induction response technique can be used as a prospective tool for improving the performance of high yielding susceptible genotypes under stress conditions.
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