The Analysis Of Germplasm Resources Genetic Diversity And Evaluation Of Abiotic Stress Tolerance In Rootstock-Used Pumpkins

The selection and use of good rootstock is a major guarantee of cucumber grafting. Rootstock germplasm resource evaluation and study is the premise of great rootstock selection and new variety breeding. Rootstock-used pumpkins collected from domestic market were studied in this research. Analysis of genetic diversity was done with phenotypes and SSR markers. And on this basis we evaluated abiotic stress tolerance of different rootstock germplasm resources under salt stress, low temperature, and high temperature. Concrete results are as follows:1. Analysis of genetic diversity in 47 rootstock-used pumpkin germplasm resources was done with 63 phenotypes. It was observed that the genetic diversity of collected rootstock-used pumpkin germplasms was low; and eight quality traits as well as most of the quantitative traits could be used as morphological markers, as an auxiliary means of rootstock-used pumpkin germplasms evaluation and breeding of new varieties.2. Three groups were divided by 40 screened higher polymorphic SSR primers, similar to the result of morphology. And rootstock-used pumpkin cultivars with stronger resistance to different abiotic stress were distributed in every clusters. Also found that the genetic diversity of collected rootstock-used pumpkin germplasms was low in the molecular level, and SSR marker CMTmll, with a high polymorphism, could be used in molecular marker assisted selection.3. Forty-eight rootstock-used pumpkin varieties were treated with 125 mmol/L NaCl at germination stage, and 80 mmol/L NaCl at seedling stage, and screened for salt tolerance using clustering analysis of average membership function. In both development stages, there were 9 salt tolerant varieties (samples 12,14,23,30,31,34,45,47,48) and 9 salt sensitive varieties (samples 3,4,6,9,15,16,29,36,43).4. Forty-eight accessions of rootstock-used pumpkin were treated with low temperature to screen for chilling tolerance in terms of principal component analysis and cluster analysis. In both germination stage and seedling stage, there were 9 chilling tolerant varieties including samples 1,2,3,6,13,17,26,27,33 and 11 chilling sensitive varieties including samples 21,22,23,24,32,34,37,40,42,44,46.5. In a search for thermotolerance and morphological index,48 specimen rootstock-used pumpkins were treated with high temperature. Growth indexes were evaluated, and UPGMA cluster analysis was done. The results showed that the thermotolerance of 48 rootstock-used pumpkin varieties could be divided into 4 types at germination stage and seedling stage, while the classification results of different stages were inconsistent. In both development stages, there were 2 moderately heat susceptible cultivars (samples 26 and 27) and 11 heat sensitive cultivars (samples 6,9,10,11,13,14, 17,20,36,47 and 48). The relative value of germination potential, germination index, vigor index, dry weight were credible indexes for identification.