BENHERLAL, P.S.SHILPA, C.2023-01-142023-01-142022-06-20Th-13245https://krishikosh.egranth.ac.in/handle/1/5810192259Frequent extreme high temperature events are one of the consequences of climate change and hence, heat stress has become a major abiotic stress to crop plants. Heat stress tolerance and yield are quantitative traits. Many component traits, including the traits that are closely related to the quantitative trait and other apparently unrelated traits, are involved in the integrated traits. Therefore, basal thermotolerance by vegetative growth, antioxidant defense response (related trait) and ability to protect DNA from oxidative damage (apparently unrelated trait) etc. were studied in eight paddy genotypes. Eight paddy genotypes were assessed for basal thermotolerance and found genotypes GR_214 and GR_531 as highly tolerant. In the assessment of antioxidant defense response, highest superoxide radical scavenging potential in GR_470, GR_531 and GR_823; and highest hydrogen peroxide depletion potential in GR_601 and GR_823 were observed. To understand the effect of heat stress induced oxidative DNA damage, the marker 8-oxoG was quantified using GCMS. Higher level of 8-oxoG was found in GR_456, GR_660 and GR_285 that were grown at 48°C, 46.5°C and 46.5°C respectively. On analysis of the basal thermotolerance, antioxidant defense response and 8-oxoG levels, it was found that these traits are independently existing and regulated among eight paddy genotypes studied. Therefore, while exploring for developing heat tolerant crop genotypes, screening genetic resources only based on growth and yield is not sufficient to fulfill the future crop improvement. Hence, exploration, annotation and marking of component traits associated/ apparently associated with targeted integrated trait may help in more efficient crop improvement.EnglishThesis