Analysis Of Genetic Variation In Some Cucurbita Spp Resources From China

More than 80 accessions of Cucurbita spp were collected from different provinces in China and planted in Chengdu in 2003. The relationship among species of Cucurbita spp collected from China was studied and classified by the inspection of morphological characteristies and RAPD markers. Cucurbita moschata and Cucurbita ficifolia from China were estimated the genetic diversity by RAPD. . Objectives of these studies were to: (1) find new idea and new way for the collection, preservation and breeding of pumpkin by analyzing the amount of genetic variation in Cucurbita spp grown in China; and (2) make preparation for using DNA markers assistant breeding technique in pumpkin. The results were as follow:1. There were four cultivated species: C. moschata, C. maxima, C. pepo and C. ficifolia, and no other cultivated and wild species of cucurbita spp were found in Cucurbita spp landraces of China. The diversity of morphological characteristic of these Cucurbita spp landraces was very great. Except few traits (such as female lines), Cucurbita spp landraces of China had total traits that have been reported. But there were some traits only in certain species, not in the four species. For example:only C. moschata and C. pepo possess the bush trait. Some important economic traits (such as large fruit) were not expressed, for the limitation of the cultivated condition of the experimentation.2. Using RAPD markers, all the accessions could be clustered rightly according to different species, but the accessions could't be grouped together in terms of fruit weight, shape or color.3. The degree of polymorphism obtained by RAPDs among different accessions of C. moschata collected in China was great. The genetic distance among accessions had no relationship with geographic distance and latitude, but with isolated zones since all Cucurbita spp of China originated from America and were introduced into China. We thought that the genetic variation of these accessions might be mainly induced by genetic drift.4. Both the results of the RAPDs and morphological data indicated that the genetic diversity of Cucurbita ficifolia found in China was very poor, and also much lower than other three species of Cucurbita spp in China. So, introduction of new varieties of Cucurbita ficifolia is important for improvement programs.5. All the accessions could be clustered rightly into four groups: C. moschata, C. maxima, C. pepo and C. ficifolia by RAPDs, according to the traditional morphological way. It was suggested that the RAPDs analysis system formed in our study was good in evaluating the genetic variation of Cucurbita spp accessions, and might provide a new method in pumpkin germplasm collection, group and exploitation in further study.