Studies On Growth And Development Of Seed And Genetic Diversity Of Edible Seed-Watermelon Germplasm Resource

Edible seed-watermelon (Citrullus lanatus ssp. vulgaris var. megalaspermus Lin et Caho.) is one of the important economical crop, whose seed is the main edible part. The kernel is very full and contains high content of protein and crude fat. In the history of 400 years cultivation, edible seed-watermelon has evolved many ecological types which plant in different places in China, it belongs to edible seed-watermelon variety in watermelon classifucation. It is benefit for production, collection, conservation and ultilization through the research on growth and development of seed and genetic diversity of germplarsm resource, even more provide the foundation for genetic breeding. In this study, it simplely probed the growth and development of seed, and the genetic diversity in 44 edible seed-watermelon,4 wild watermelon,2 vegetable-using watermelon and 1 watermelon were assessed via morphological and RAPD markers. The main results were as follows:1. During the development of seed, morphological and qualified indices showed the "slow-fast-slow" process, but the notably changing period of them were different. Seed size which was account for 75% of the final size increased most in 14 days after pollination. Water content decreased and dry matter content increased at the most fast speed from day 14 to 21. Day 14 to 35 was the main accumulation stage of protein and crude fat, and weight of 100 seeds growed most at the same time.2. The statistical result of genetic diversity parameters based on morphological characters showed that:the average of CV was 28.44%, and the amounts of seed per fruit had the maximum of 66.95% as well as seed index had the minimum of 5.37%. The average of Shannon information index was 1.55, which ranged from 0.32(seed cover lines) to 2.16(length of seed).3. The cluster analysis based on morphological characters demonstrated that:each wild and vegetable-using watermelon germplasm was clustered into one group separately, the edible seed-watermelon germplasms were clustered into a group; The result of principal component analysis was that the first three principal component reflected the quantitative characters of fruit, seed size and the thickness of pericarp and seed respectively. The cluster result between them was mainly same.4. A total of 80 distinct bands were detected by 12 RAPD primers choosen from 80 primary primers. Among them,74 bands (92.5%) were polymorphic. The average of Shannon information index of primers was 0.73, and the primer PA-059 had the maximum of 1.31.5. The cluster analysis based on RAPD marker demonstrated that:the similarity coefficient among germplasms ranged from 0.41 to 0.99. It had distant genetic relationship between wild and vegetable-using watermelon and edible seed-watermelon, and edible seed-watermelon germplasms had very narrow genetic background. At a point of 0.812,51 inbred lines were clustered into 8 groups, and wild watermelon germplasms, vegetable-using watermelon and edible seed-watermelon were divided clearly.6. The principal component analysis based on RAPD marker demonstrated that:the inbred lines ZG0009、ZG0038、ZG0041 and ZG0042 were divided separately from the whole, other 37 germplasms polymerized tightly.