Effect of elevated temperature regimes on growth and yield of rice cultivars under temperature gradient tunnel (TGT) environments

The effect of elevated temperature on rice were studied during kharif 2013 and 2014 using six cultivars of rice (PR-116, PR-118, PR-113, PR-115, PR-121 and PR-122) with two replications within a temperature gradient tunnel in which temperature was elevated from the ambient level (+4.5, +5.0, +5.3, +5.5 and +5.8 °C) for the entire crop growth period. The results revealed that the plant height increasedunder elevated temperature regimes, although the rate of change varied with cultivars as well as the stages of the crop. Amongst the six cultivars, the plant height was maximum for cv PR-118 (13.9 cm in vegetative stage (VS) and for cv PR-113 (58.5 cm in grain development stage (GDS) and minimum for cv PR-121 (12.4 cm in VS and 51.8 cm in GDS). The overall tiller number under elevated temperature regimes was maximum for cv PR-122 followed by PR-121, PR-113, PR-116, PR-115 and PR-118 in decreasing order. The 1000-grain weight was reduced from the ambient temperature regime by 8.7 to 14.5 per cent and number of grains per panicle was reduced by 30.6 to 46.7 per cent under elevated temperature of 4.5 to 5.8 oC from ambient. Similarly, the grain yield was reduced by 38.3 to 54.5 per cent and biomass yield reduced by 19.7 to 33.6 per cent with increase under temperature 4.5 to 5.8 oC from theambient environment. Amongst the six cultivars the harvest index was maximum in cv PR-122 (33.0%), i.e., it is most tolerant to heat stress followed by PR-121 (28.3%) and least tolerant were cv PR-116 (20.2%) and PR-115 (18.9%).