Studies On Genetic Diversity Of Cucurbita Moschata Germplasm Resources

Cucurbita Moschata is one of the three main cultivars in Cucurbita. Cucurbitamoschata is an important horticultural plant and have many various fruit colour. Thestudy on the genetic diversity of Cucurbita moschata can benefit the conservation,classification, identification, genetic enhancement and effective utilization of theCucurbita moschata germplasm resources. Molecular marker, which can detect thegenetic diversity at DNA level, is a powerful tool to study genetic diversity. RAPDmarkers have been popularized for their simplicity, rapidity and non-specialty amongdifferent genus. In this study, the genetic diversity in 70 Cucurbita Moschata. Theseaccessions from different regions of China were assessed using agronomic traits andRAPD markers, and the genetic relationship among the accessions was revealed bycluster analysis, principal components analysis and principal coordinates analysis atvarious level. The main results were as follows:1. A total of 56 agronomic traits were measured, 31 quantitative and 25 qualitative,for assessing genetic diversity of 70 Cucurbita Moschata germplasm. The averagecoefficient of variation was 37.50%. They ranged from 6.60% in aspect ratio ofcotylendon to 97.44% in lengthwise diameter pulp thickness of ripe pumpkin based on the31 qualitative descriptors and from 9.68% in circumference colour of seed to 262.22% inbisexual flower based on the 25 quantitative descriptors. The average Shannon'sInformation index among the accessions was 1.39 based on the data of 56 morphologicaldescriptors. They varied from 0.22 to 1.45 based on quantitative descriptors. They variedfrom 1.43 to 2.49 based on qualitative descriptors. All the results above confirmed thatthe Shannon's Information index based on quantitative descriptors was higher than basedon qualitative descriptors.2. Except the 5 germplasm, the cluster analysis divided the 65 germplasm into 2major groups based on agronomic traits. One was round pumpkin and another was longpumpkin. Round pumpkin was divided into existing bump around fruit surface andsmooth fruit surface. The results of principal components analysis accorded with clusteranalysis.3. 21 primers were screened from 100 arbitrary primers, and a total of 167 DNAbands were amplified, 130 (73.23%) of which were polymorphic. The number of bands perprimer was 8 and the average of Shannon's information index was 0.286.4. The cluster analysis divided the germplasm into 5 groups based on RAPD markers.The germplasm 19,27 and 64 were classified into one group. The resuts almost accordedwith agronomic traits.5. All the results above confirmed that the RAPD clusters were greatly associatedwith the morphologic characters and both not with the origins of the germplasm. We candivided the germplasm into round pumpkin and long pumpkin. The results accorded with traditional sorting process. It is indicated that the traditional sorting process was scientificand reasonable. The results indicated that Cucurbita moschata could subdivided existingbump around fruit surface or not.6. According to the analysis of the main nutrition contents in 70 Cucurbita moschata,the average coefficient of variation was 31.70%. They ranged from 1.52% in watercontent of light fruit to 60.07% in Vc content of light fruit. In general, solubility solids,protein content and soluble sugar content of ripe fruit were higher than light fruit. Bycontrast, water content was lower of ripe fruit. The correlation coeficients among Vccontent, protein content, solubility solids and soluble sugar content were at the significantor very significant level. Whereas the water content of light fruit was at the negativesignificant with the others. The resuts based on ripe fruit accorded with light fruit.7. To selected quality traits connected by soluble sugar content of ripe fruit bystepwise regression. Abtained a complex equation of linear regression, Y=0.899-0.648X₁-0.019X₄+0.683X₅-0.285X₆+0.014X₈+0.015X₉8. The cluster analysis divided the germplasm into three Groups and theâ…¡Group wasbest. Vc, solubility solids, protein content and soluble sugar content of the germplasm 18and 70 were higher than the others. Therefore, the germplasm 18 and 70 were bettervarieties in pumpkin breeding for quality.