Molecular Investigations on Thermotolerance of Three Tomato (Solanum lycopersicum) Landraces in Sudan

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Aida Ali Elsharief Mohamed, Mohamed
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The objective of this work was to identify the effects of heat stress and heat shock treatment, on three landraces of tomato collected from different geographical sites of Sudan compared to a commercial cultivar and to detect polymorphism among the four genotypes using RAPD markers. Plant height, Days to 50% flowering, days to physiological maturity, fruit size and fruit weight were compared between plants grown under normal temperatures ( 37 0C/ 23 0C day and night, respectively) in the nursery for two successive seasons (2007 and 2008) and plants grown inside green house under heat stress (45 oC/ 29 oC day and night, respectively) and another group subjected to heat shock treatment (48 oC) then left to grow under heat stress conditions (45 oC/ 29 oC day and night, respectively). With regard to the nursery experiments, no significant differences were found in plant height between the four genotypes in the first season, while significant differences were obtained in the second season. Significant differences were found between genotypes in the remaining pre mentioned growth parameters in both seasons. Heat stress led to significant differences in plant height, fruit size and fruit weight while time to 50% flowering and time to maturity showed highly significant differences between genotypes grown under normal temperatures compared to those under heat stress. Plant height, time to 50% flowering and time to physiological maturity increased markedly due to heat stress, while fruit size and fruit weight decreased. Heat stress had their most effects on the reproductive stage, which were reflected in delay of flowering and maturity and reduction in fruit size and weight. Heat shock treatment did not improve thermotolerance, although different types of heat shock proteins (HSPs) were induced to provide tomato plants with thermoprotection under heat stress. Heat shock suppressed some genes which was reflected on degradation of some proteins and enhanced expression of other genes to produce HSPs belonging to diverse groups. The use of 16 RAPD primers gave 61 polymorphic fragments, and there was a wide range of variations in polymorphism percent per primer. Genetic relationship between genotypes was determined using similarity matrix. RAPD proofed to be a powerful measure for the detection of polymorphism in tomato
Molecular Investigations on Thermotolerance of Three Tomato (Solanum lycopersicum) Landraces in Sudan