Studies On Mechanisms Of Low Temperature Tolerance And Its Inheritance In Tomato

The purpose of this paper was to study some problems that mainly existing in low temperature tolerance in tomato breeding. 2 low temperature tolerance stains "97-66, 97-69" and 3 low temperature sensitive stains "97-71, 97-65, 97-72" were screened by using an useful appraisal method as selection criterion. A better understanding of physiological, biochemical and botanical causes of injury and tolerance mechanisms would enable the breeder to develop more tomato tolerance. The main results obtained were as follows:1. Seedlings relative growth rate ( RGR ) was significantly correlated with low temperature tolerance. Y= -0.1084+1.3325X( RGR ) could be applied to estimate low temperature tolerance in tomato. The importance to low temperature tolerance was RGR >root vigor >soluble sugar >Vc >MDA >electrolyte exosmosis >carotenoid >soluble protein >seeds germination index. Basing on all the characters, more important characters should be mainly considered in order to reduce the amount of breeding work.2. Day/night temperature of (13 ± l)℃/(7± 1)℃ could not cause irreversible damage to physiological metabolism of tomato. Though physiological metabolism and assimilates translocation decreased, the inhibition degree was small. Short treatment period of low temperature induced antioxidants system, USFA content, protoplasm concentration and enzyme system increasing. Low temperature induced not only the increasing of enzyme activity but also the changes of its composition. Physiological metabolism was inhibited beyond 3-6 days. Low temperature exercise time of tomato seedlings under this condition between 3 days and 6 days was best.3. There was difference between inhibition of physiological metabolism under low temperature and irreversible chilling injurymechanism in tomato. The decrease of assimilates translocation and partition ability, physiological ? metabolism and enzyme activity was important physiological mechanism of tomato in low temperature.4. Effect and susceptibility of low temperature tomato in tomato during seedling stage and fruit setting stage were same. Low temperature tolerance during fruit setting stage was lower than seedling stage, but the inducing effect was same. It was important to pay attention to low temperature experiment during fruit setting stage.5. There was heterosis in low temperature tolerance of tomato, so the low temperature tolerance breeding should adopt crossbreeding primarily. In physiological mechanism, the heterosis of membrane permeability, enzyme system and chlorophyll content was higher. In tomato growth and development, the heterosis of seeds germination and fruit growth rate was higher.6. Low temperature tolerance of tomato fitted for the "additive— dominance" model with partial dominance. Back crossing effect was significant whereas reciprocal crossing effect was not significant. !r(N)=93.98%. To assure offsprings with high low temperature tolerance, we must pay attention to select high low temperature tolerance varieties(stains)as parents, esp. as female parent in tomato breeding.