Genetic diversity analysis of pomelo germplasm resources based on leaf phenotype and SCoT markers

Pomelo is an important horticultural cash crop in China, and it is of great significance to conserve and characterize its rich germplasm resources. There are few studies using SCoT molecular markers for genetic diversity analysis in pomelo germplasm, therefore, this study aimed to combine leaf phenotypic traits and SCoT molecular markers to characterize the genetic diversity and relatedness of pomelo varieties. In this study, 11 leaf phenotypic traits from 84 pomelo germplasm resources were analyzed for diversity, correlation and principal components. The average genetic diversity indices of qualitative and quantitative traits were 4.233 and 4.3624, respectively, and the average coefficients of variation were 51.98 % and 22.73 %, respectively, indicating that all the observed traits differed significantly among pomelo populations, and that phenotypic genetic diversity was rich. Correlation analysis revealed that all traits except leaf shape and leaf base traits were significantly correlated with them( P < 0.05), and therefore, these traits could provide improved materials for pomelo breeding. Principal component analysis extracted four principal components from 11 leaf phenotypic traits with a cumulative contribution of 73.76 %, indicating that these traits are the main indicators for pomelo variety identification and evaluation. In addition, 19 primers with clear and stable bands and good polymorphic specificity were selected from 80 SCoT primers in this study, and a total of 467 bands were amplified with an average polymorphism ratio (PPB) of 88.54 %. The average polymorphism ratio (PPB) was 88.54 %. The number of alleles in the population (Na) was 1.8908; the number of effective alleles (Ne) was 1.5296; the gene diversity index (H) was 0.3092; and the Shannon's diversity index(I) was 0.4625, which indicated that there was abundant genetic diversity among the test materials, and that the differences among pomelo germplasm could be effectively distinguished. Finally, comparing the phenotypic data and molecular marker clustering results, both could be categorized into five major taxa, but there was no correlation between the clustering results of the two methods ( r = -0.00729, P = 0.4270>0.05). The information on morphological phenotypes and genetic diversity of SCoT molecular markers obtained in this study provides a basis for future breeding programs for pomelo.