A. G. SHANKAR, A. G.LOKESHA, A.N.2020-10-062020-10-062019-10-05Th-12505https://krishikosh.egranth.ac.in/handle/1/5810152608Temperature is one of the important environmental factors which affect the plant growth and development. In order to assess the high temperature tolerance mechanism in tomato, three susceptible and three tolerant genotypes were grown under high temperature conditions (40±2°C). Susceptible genotypes showed significant decrease in photosynthetic rate and Fv/Fm ratio under high temperature stress. Fruit quality parameters like TSS, acidity, Vitamin C content, total phenols and flavonoids, total carotenoids and lycopene were also highly affected in the susceptible genotypes compared to tolerant genotypes under stress. Pollen germination and viability were significantly reduced thereby fruit yield was also markedly decreased in susceptible genotypes. The tolerant genotypes recorded significantly better root growth compared to susceptible genotypes. With regard to metabolomics, sugars, amino acids, phenols, flavonoids, polyamines and some of the stress related hormones were highly accumulated in tolerant genotypes compared to susceptible genotypes under stress. Some of the vitamins and organic acids were also up regulated under stress in tolerant genotypes. GC-MS/MS data revealed that tolerant genotype recorded higher content of aroma compounds compared to susceptible genotype under stress. This study provides a compendium of metabolite levels from leaves and flowers of tolerant and susceptible genotypes of tomato under control and high temperature stress. The qRT-PCR study clearly showed genes like NCED, P5CS, spermidine synthase, TPS12 and TPS20 were highly up regulated at different stages of high temperature stress in tolerant genotype compared to susceptible genotype. Further, there is an urgent need to analyze all the metabolites of biosynthetic pathway (including intermediates) to understand the rate limiting step of each pathway both under control and high temperature stress conditions.EnglishThesis