Genetic Analysis of Bacterial Wilt Resistance Mutants 486-K and 117-K in Tobacco

Tobacco bacterial wilt is a typical vascular bundle bacterial disease that seriously affects tobacco production in China. In order to understand the genetic basis of tobacco bacterial wilt resistance mutants and develop molecular markers related to resistance, and to provide theoretical basis for breeding high quality resistant varieties, in this study, tobacco bacterial wilt resistance mutants 486-K and 117-K obtained by EMS mutagenesis of flue-cured tobacco variety Cuibi 1 were selected as research objects, and Cubi 1 and the two mutants were used as parents to construct two different hybrid combinations. The analysis method of population genetic effect was carried out by using the analysis method of Chi-square test and "major-gene + polygene" mixed genetic model of plant quantitative traits. The results showed that, based on the Chi-square test, the number of disease-level strains of F2 generation of mutants 486-K and 117-K showed a normal distribution, and showed some trait separation. Analysis of the "major-gene + polygene" mixed model showed that 2MG-A was the optimal genetic model for resistance in mutant 117-K, with two pairs of major genes showing additive effects without dominant or epistatic effect, and the genetic efficiency of major genes being 78.57%. The optimal resistance genetic model for mutant 486-K was 2MG-ADI, or the two pairs of additive-dominant-epigenetic master gene model. Among the epistatic effects, the dominant×dominant interaction and dominant×additive interaction effects were larger, and the genetic efficiency of the main genes was 88.34%. It was indicated that the inheritance of tobacco bacterial wilt resistance mutants was dominated by main gene effect and less affected by the environment.