Genetic Association Among Morpho-Physiological Attributes Against Heat Tolerance in Rice Genotypes

Asia produces the majority of the world's rice (Oryza sativa L.), one of the utmost vital fundamental food crops, with 90% of worldwide production. Because of increases in average temperature, climate change has a negative impact on rice yield. It is essential to develop such verities of rice that have potential to meet challenges of environmental changes like heat stress etc. This research was approved to investigate heat tolerance ability of rice genotypes on the basis of morpho-physiological attributes at the experimental field area of Islamia University of Bahawalpur. Using a randomized complete blocked design (RCBD) and two sets of plots (one in early sowing rice, other plot goes under late sowing rice condition) with five replications was applied to study 102 genotypes of rice under heat stress. The days to heading, days to maturity, no. of panicles, flag leaf area, grain weight per panicle, no. of grains per panicle, 1000 grain weight and grain yield per plant were positively correlated among themselves under both early sowing and late sowing conditions. Results revealed that, out of 14 principal components (PCs), the first five PCs were showed significant genetic variation under both conditions. The first five PCs displayed 71.1% and 68.9% total variance in the examined germplasm under early and late sowing locations respectively. Based on PCA, 05 heat-tolerant and five heat-susceptible genotypes were identified. There is a significant difference in all the studied rice morphological and physiological traits. Effect of high temperature (heat stress) was observed in both early (normal) and late sowing (heat stress) environments. As a result of these findings selection based on these qualities is not appropriate for heat tolerance. The best performing germplasm under heat stress can be a desirable genotype to generate high yield and used for future breeding programs and early sowing of rice genotypes recommended in this study will be effective for developing heat tolerant rice varieties.