Comparative stress physiological analysis of indigenous rice cultivars of Eastern Himalayan Region under elevated temperature of changing climate

Rice (Oryza sativa L.) is the major staple crop of Eastern Himalayan Region (EHR) and its cultivation and productivity is severely constrained by elevated temperature (T) in cooler mountain regions like EHR. Present study on stress physiological response of indigenous rice cultivars (68no.) of EHR for elevated T of Carbon dioxide temperature gradient chamber (CTGC) revealed that leaf chlorophyll and leaf T has varied significantly with chlorophyll content index (CCI) of 35.05 and 28.34 °C canopy temperature (CT) and range of 25.0–49.3CCI and 23.1–35.9 °C CT. Higher chlorophyll of 35.02–40.0 CCI and cooler canopy T of 26.0–29.0 °C under elevated T was recorded by 45.0% and 51.0% rice cultivars against 35.0% and 65.0% cultivars under ambient T. Under elevated T high photosynthetic types had 23.5% and 60.4% higher photosynthetic rate over moderate and low photosynthetic types, respectively. Cultivar TRC2016-14 had highest SLW (Specific leaf weight) and leaf carotenoids, whereas Saplani and Anjali recorded highest LT (Leaf thickness) and highest Chl a/b ratio under elevated T. CMS (Cell membrane stability) and LRWC (Leaf relative water content) under elevated T was 29.8% and 24.2% lower in low tolerant types (LTT) compared to high tolerant types (HTT). Grain chaffiness was lower in HTT (73.7%) compared to LTT (113.5%), whereas the grain yield was 47.8% lower in LTT than HTT (23.4%). TRC 2016-14 and Anjali showing higher yield of 11.7 and 11.3qt/ha respectively under elevated T are promising for crop stress improvement and cultivation in EHR.