HEAT SHOCK INDUCED MORPHO-PHYSIOLOGICAL RESPONSE IN INDICA RICE (ORYZA SATIVA L.) AT EARLY SEEDLING STAGE

Heat stress is a serious threat for rice production in various localities around the world. Present research was conducted to explore the mechanism of heat tolerance in rice at early seedling stage. Forty six rice genotypes including 39 mutants (Msgeneration) of super basmati and 7 varieties were subjected to heat stress (45 +/- 2 degrees C) for 12 h followed by three days recovery under normal temperature (28 +/- 2 degrees C). The relative heat tolerance of genotypes was assessed on the basis of various morphological (fresh and dry leaf weight, fresh and dry weight of seedlings) and physiological (relative water contents (RWC), cell membrane thermo-stability (CMTS), photosynthetic pigments and malondialdehyde (MDA)) parameters. Significant variation was observed among the tested rice genotypes for morpho-physiological response. Based on relatively higher CMTS, RWC and photosynthetic pigments along with higher fresh and dry weights of leaves and seedlings, and less MDA content, fifteen genotypes including 11 mutants and four varieties were identified as heat tolerant. HTT-1 was identified as moderately heat sensitive mutant. In conclusion, tested morpho-physiological markers were useful to screen rice germplasm for heat tolerance at early growth stage. In addition, Kashmir basmati and HTT-114 can be used as heat tolerant check and HTT-1 can be used as heat sensitive check in screening experiments at early growth stage.