The Study On Quantitative Genetics Of Resistance To Bacterial Wilt And Phytophthor Capsici In Pepper Rootstock Germplasms And Their Grafting Applications

Fifteen pepper rootstock germplasms were used as materials in this study. The method of indoor inoculation was applied to identify the resistance to bacterial wilt and phytophthora capsici. The rootstock gerplasms F05which is resistant to bacterial wilt, D15and D35which were susceptible to bacterial wilt, D15which is resistant to phytophthora capsici (P. capsici), and F05which is susceptible to P. capsici, were used as parents to build the generation groups and for identification of their resisitence. We studied the quantitative genetic characteristics of the resistances to these two diseases in rootstock germplasms according to the resistant phenotypes from the generation groups.Also, we used three germplasms named F05, D15and J7with tolerance to these two diseases as the rootstocks, two pepper cultivars J5and TY which were susceptible or highly susceptible materials as the scions to construct different grafted combinations. We compared the resistances to the bacterial wilt and P. capsici in different grafted combinations, as well as their fruit yiled and quality. Our results were as following:1. The results of seedling inoculation identification showed that among the fifteen pepper rootstock germplasms, three had the highly resistant (HR) level, four showed the medium resistant (MR) level and eight were susceptible (S) or highly susceptible (HS) to the bacterial wilt. As to the P. capsici, three showed the medium resistant (MR) level while the others were susceptible (S) levels. There were two rootstock germplasms showed the medium resistant (MR) level to these two diseases, five had the over medium resistant (MR) level to the bacterial wilt but they were susceptible to the P. capsici. One rootstock germplasm had medium resistance to the P. capsici but it was susceptible to the bacterial wilt.2. The results of genetic analysis of resistance to these two diseases showed that the resistance to the bacterial wilt in germplasm resources F05was mainly controlled by two dominant genes and possibly influenced by modified genes. Its heredity was in agreed with the Additive-Dominant genetic model and mainly influenced by the additive effect. The resistance to P. capsici in pepper rootstock germplasm D15was controlled by a recessive gene and was possibly influenced by the cytoplasm. The heredity was agreed with the Additive-Dominant-Epistasis genetic model and mainly influenced by the additive effect. The result of heterosis analysis showed that the F1generations had more strong resistance to the bacterial wilt when F05and D35were used to be female parents and the F1generations had more strong resistance to the P. capsici when D15was used to be female parents. Moreover, the F1generations had no heterosis in the resistance to the P. capsici when F05was used to be female parents3. The results of the identification of the resistances to these diseases showed that the resistant rootstocks grafting could significantly improved the resistances to these two diseases in grafted pepper plants. And the resistances to these two diseases were enhanced by34.4%～50.0%and42.2%～77.0%, respectively. The results of field cultivations showed that the single plant yield of grafted plant was higher than that of own-rooted plant, and that of the grafted plant with F05rootstock was significantly higher. The fruit quality of grafted plants is better than own-rooted ones or with no significant difference. It suggested that disease resisitent rootstock grafting cultivation could protect pepper from damage from bacterial wilt and P. capsici, and also increase the production, while had no adverse effects on fruit quality.The above results could provide scientific evidences for the reasonable utility of rootstock germplasms with the different resistances to the bacterial wilt and P. capsici. It could also guide the breeding of hybrid rootstocks with resistance to both diseases.