Thesis (Ph.D.) - Cairo University - Faculty of Agriculture - Department of Vegetable

Experiments were carried out during the period from 2016 to 2019 at the Faculty of Agriculture, Cairo University, Giza, Egypt, to evaluate field performance of 10 tomato accessions and their hybrids for fruit set heat tolerance and related characters in two plantings under each of high and moderate growing conditions. Characters measured were fruit set (%), number of seeds per fruit, number of locules per fruit, proline content of fresh leaves and flowers and total soluble carbohydrates of fresh leaves and flowers for both accessions and hybrids. Combined analysis of the evaluated accessions of the two plantings of each of the two evaluation conditions showed that the highest significant values of fruit set percentage were for LAs 0816, 1310, 2661 and 3008. LAs 3320, 3213 and 2661 had the highest content of seeds in both seasons. Evaluated accessions exhibited no significant differences in the number of locules under both evaluation conditions. LAs 0816, 2661, 2662 and 3120 recorded the highest content of proline in both fresh leaves and fresh flowers. LAs 1995, 2661, 2662 and 2706 had the highest content of leaf total soluble carbohydrates under both evaluation conditions. LAs 2661, 2662, 3120 and 1310 were superior in their content of total soluble carbohydrates in fresh flowers. Fruit set percentage, number of seeds per fruit, and total soluble carbohydrates content of both fresh leaves and flowers were higher under moderate temperature than under high temperature. Proline content in both fresh leaves and flowers were higher under high temperature conditions than under moderate temperature. A positive correlation was found between fruit set and proline content in both fresh leaves and fresh flowers. An increase in proline content was noticed under heat stress conditions

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