| Seed watermelon(Citrullus lanatus var.megulasnemus Lin et Chao),belonging to the Cucurbitaceae,seed as the main edible organs.It is full of nutrition,have a high edible value.Seed watermelon has abundant germplasm resources,but with the wrong conventional breeding for a long time,there has bad phenomenon of mixed varieties of seed watermelon across the country,the different names of the same substance and the different meaning oft.It lead to decline in the quality and yield instability and it restricts the development of industry seriously.The study combined the phenotypic traits with SCoT molecular markers to analyze the genetic diversity and genetic relationship of 48 seed watermelon germplasm resources,and construct the core collection.The main results of the study are as follows:1.The cluster analysis was built by 48 seed watermelon materials based on 39 phenotypic traits,the results showed that the genetic distance is 3.1449～15.6997.When the genetic distance is 9.83,the 48 seed watermelon materials could be classified into six classes,the kinship between common watermelon germplasm with seed watermelon germplasm is farther,the genetic distance is very large,and they were separated obviously.2.In the principal component analysis by 39 phenotypic traits of 48 seed watermelon germplasm resources,it showed that the first principal component mainly reflected the characteristics of seed,the second principal component mainly reflected the characteristics of flesh,and the third principal component mainly reflected the characteristics of plant leaves.3.Based on the sampling proportions of 10%to 35%,six core subsets(XT10～XT35)were constructed by UPGMA and preferred sampling.They were compared by MD%,VD%,CR%,VR%of four evaluation parameters,and combined with the principal component analysis,the results showed that the core subset of XT25 could be regarded as core collection,it can represent the genetic diversity of initial collection.4.20 SCoT primers were selected from 51 SCoT primers to PCR for 48 seed watermelon materials,237 DNA bands were amplified,and 220 were polymorphic bands among them,the percentage of polymorphic bands was up to 92.83%.And the number of alleles was 1.9283,effective number of alleles was 1.4865,Nei’s diversity index was 0.2994,Shannon information index was 0.4596,which indicated the genetic diversity of 48 seed watermelon germplasm is abundant.5.The cluster analysis was built based on SCoT molecular markers,it showed that Loci Loci%the genetic similarity coefficient among germplasms range from 0.59 to 0.95,thekinship between common watermelon germplasm with seed watermelon germplasm is more far,and the common watermelon were not be well separated.The 48 seed watermelon materials could be classified into six groups when the Gs=0.662.The distribution pattern of all materials in the chart of principal component analysis was similar to the cluster analysis.6.The core collection was constructed by Least Dinstance Stepwise Sampling(LDSS)based on SCoT molecular markers,six core subsets(FZ10～FZ35)were constructed based on the sampling proportions of 10%to 35%.The core subset of FZ25 could be regarded as core collection by comparing gentic diversity of each core subset.And by comparison the results showed that the retention of polymorphic loci and percentage of polymorphic loci of the core collection was up to 99.55%,and other gentic diversity indexs were also high.Therefore,further prove that the core collection of FZ25 could represent the genetic diversity of the initial collection.7.By comparing the core collection based on two markers,in terms of phenotypic traits,XT25 have more representive than FZ25;in terms of SCoT molecular markers,FZ25 have more representive than XT25. |
