Analysis Of Genetic Diversity Based On Botanical Traits And SCoT Markers In Seed-used Pumpkin And Preliminary Screening Of Pumpkin Stocks Resources

Seed-used pumpkin refers to the kind of pumpkin with seeds for the main edible object.It is a kind of vegetable crop of high economic value and rich nutritional value in Cucurbitaceae Cuczarbita cultivars.Academically it can be divided into C.moschata,C.pepo and C.maxima.The study on genetic diversity of seed-used pumpkin is beneficial to the scientific classification and identification of seed-used pumpkin germplasm resources,and to the improvement and breeding of seed pumpkins.And the process of variety improvement and breeding was accelerated.The initial selection of different pumpkin rootstock resources provides more alternative materials for further breeding of pumpkin rootstock.In this study,the genetic diversity of 44 seed-used pumpkin materials was analyzed by SCoT molecular marker and morphological marker;Preliminary screening of watermelon grafted rootstock was performed on 14 pumpkin ingredients.The main conclusions are as follows:(1)The range of coefficient of variation of botanical characters in the materials was 8.52%-86.29%.The melon shape index has the largest coefficient of variation(86.29%)and seed kernel rate has the smallest's(8.52%).The average Shannon's information index is 3.55,ranging from 3.37 to 3.63.(2)The 50 morphological traits of the seed-used pumpkin materials was divided into three categories with R-type cluster analysis.The largest Euclidean distances among the traits are the pod characteristics(X28)and the seed rim(X29),which is 11.2360.Except for two indicators with significant correlation between single total weight and seed thousand kernel weight,the smallest Euclidean distance is 1.1117 which is between seed weight(X49)and kernel weight(X45).(3)Based on morphological marker system clustering,38 seed pumpkin materials were divided into four categories: The first category belongs to the C.maxima;the second category includes 31 and 32 materials,which belong to C.maxima and C.pepo respectively;the third category belongs to C.moschata;the fourth category belongs to C.pepo.Principal component analysis showed that the variance contribution rates of the first,second and third principal components were 26.53%,11.64% and 9.95% respectively.The cumulative variance contribution rate is 48.12%,and the test materials are divided into 5 categories,which are basically consistent with the results of system cluster analysis.(4)24 primers with good polymorphism were screened out from 62 primers by using SCoT molecular markers.A total of 228 effective DNA sites were amplified,of which 168 were polymorphic and the percentage of polymorphic sites was 73.68%.The mean Nei's gene diversity coefficient of the 44 seed-used pumpkin varieties was 0.3055,and the average Shannon's information index was 0.4425.(5)UPGMA cluster analysis based on SCoT marker divided 44 seed-used pumpkin cultivars into three major groups.The first group consisted of 29 C.pepo cultivars,the second group consisted of 4 C.moschata varieties,and the third group consisted of 11 C.maxima varieties.According to the principal coordinate analysis,the variance contribution rates of the first,second and third principal components were 29.21%,8.26% and 4.47%,respectively.The cumulative variance contribution rate was 41.94%,and the test materials are divided into 3 categories,which are consistent with the results of SCoT molecular marker clustering.(6)From the initial screening test of rootstock including 14 different pumpkin varieties which grafted watermelon,it shoued that the types of pumpkins suitable for grafting rootstocks of watermelon seedlings were ranked as follows: C.moschata > C.ficifolia > C.maxima > C.pepo.And C.moschata No.8 and Tokoto black squash are the primary rootstocks that have been initially selected in this experiment.