Abstract:

To investigate the genetic polymorphism of the inbred lines and hybrids derived from Cucurbita moschata (MO)×Cucurbita maxima (MA),the genetic diversity of 53 pumpkins,including commercial varieties,core parent materials and inter-specific hybrids offspring,were investigated by thirty morphological traits and twenty SSR markers.The results showed that the core parent materials and offspring of inter-specific hybrids had more polymorphism in plant type,growth vigor,fruit skin color and shape than commercial varieties.Twenty SSR primers were screened and showed 90% of polymorphism ratio.Based on the principal components,the cluster results of morphological and SSR markers were consistent with each other very well.The two methods and three times cluster results showed that the commercial varieties and core parent materials of Cucurbita maxima were clustered into one group,firstly.This mean the commercial varieties and core parent materials of Cucurbita maxima had relatively close genetic distance and shared the severely homogenized genetic background.It's very hard to produce the new and different varieties in this situation.Secondly,the offspring of inter-specific hybrids derived from MO×MA were clustered into one group,which was distinguished from commercial varieties and core parent materials of Cucurbita maxima and the genotypes of Cucurbita moschata.The offspring of inter-specific hybrids had relatively long genetic distance and more polymorphism than commercial varieties.It's possible to derive the new and different pumpkin varieties by crossing with the genotypes having the heterogeneous genes produced from interspecies hybrids.Meanwhile,the 6 principal component factors derived from principal component analysis would be used to simplify the edible pumpkin survey indicators.

Key words: Pumpkin, Inter-specific hybrids, Commodity homogenization, Genetic diversity, Cluster analysis