Resistance Genetic Analysis Of Tomato Late Blight Disease

Tomato late blight disease is a worldwide fatal disease for vegetable production,often break out, and cause great crop loss. Lacking of efficient prevent and cure chemicals currently ,the utilization of late blight resistant varieties is the most economic and efficient method. There are no tomato late blight- high resistant varieties to provide tomato production in our country. In order to increase late blight-resistant variety breeding process, provide theoretical support for tomato late blight resistance breeding, four tomato varieties 04957 (S) ,04968 (S) ,L3708 (R) å’Œ Wva700 (R) were selected to study the genetic mechanism. According to Griffing(â… ) complete Diallel crossing design, and use self cross and back cross to generate F₂,BC₁ and BC₂ populations,and evaluate their reaction to late blight by artificial inoculation at the seeding stage. Using Griffing(â… ) and Hayman's methods,get the grade of the disease, and analyze the regulation of inheritance of resistance to late blight.The main results were as followed:1. The phenotypic resistance of different varieties were stable highly significant differences were among varieties and different crosses.2. The difference of general combining ability (GCA) and specific combining ability (SCA) among varieties were highly significant. Wva700 and L3708 which showed excellent GCA were high value parent for late blight resistant. The result showed both general combining ability (GCA) and special combining ability(SCA) were very obvious, the ratio of GCA/SCA was as high as 27.3,this result proved that the additive effect was much more predominant than other effects. So GCA evaluation was important in the breeding for late blight resistance. Crosses Wva700×04957 and Wva700×04968 had highly SCA, and have potential value for utilization study. Effect of reciprocal cross is obvious , resistance was dominated by nuclear gene and cytoplasm gene.3. Heritability in the broad(90.64%) and narrow(81.48%) sense were all mach higher, showed parents have a great Influence on progenies Resistant genes could be expressed in the offspring through gene accumulation, early generation selection is suitable.4. The tomato Late blight-resistant genotype additive effect was the main effect ,part of dominance effect were also existed, no epistatic interaction effect was found Accord with additive-dominant model.5. Inheritance of resistance to tomato late blight is controlled by major gene and polygene together, fitted to the major gene and polygene mixed inheritance model., Major genes were identified.