Characterisation of bell pepper (Capsicum annuum L. var. grossum Sendt.) accessions for genetic diversity and population structure based on agro-morphological and microsatellite markers

Abstract

Bell pepper (Capsicum annuum L. var. grossum Sendt.) is a leading Solanaceous vegetable crop across the world with immense therapeutic and export potential. Such wide cultivation exposes the crop to various biotic and abiotic stresses. Genetic diversity is one of the major prerequisites for any crop breeding programme. Hence, in this study, an attempt was made to evaluate the genetic diversity and population structure of 24 bell pepper genotypes using 25 agro-morphological [9 distinctness, uniformity and stability (DUS) descriptors; 13 quantitative traits; and 3 quality traits] and 82 microsatellite or simple sequence repeat (SSR) markers. Eight DUS descriptors showed polymorphism with maximum morphological variation (H = 1.29) for fruit shape in longitudinal section. Multivariate analysis using Mahalanobis D2 statistic distinguished the genotypes into 11 clusters. With a mean of 4.08 alleles per locus, a total of 151 alleles were generated from 37 polymorphic SSR primers. The polymorphic information content (PIC) ranged from 0.14 (CAMS 451) to 0.76 (CA 525390) with an average of 0.54. The genotypes were divided into two major clusters based on cluster analysis using the unweighted pair group method with arithmetic mean (UPGMA) algorithm, whereas the cluster tree using the neighbour-joining (NJ) method identified three major groups. The population was classified into three groups based on structure analysis. On comparing agro-morphological and molecular clusters, 11 genotypes viz., BWT-39, BWT-39-BR, BWT-39-DR, BWT-29, BWT-3Y, BWT-3Y-4L, Kandaghat Selection, BWT-48-AC, BWT-49-AC, EC-464107, and EC-464115, were found common. These genotypes also exhibited considerable resistance to bacterial wilt disease. Mantel's test showed a moderate positive correlation between agro-morphological (DUS descriptors) and molecular data. Therefore, a combined approach of agro-morphological and molecular evaluation can facilitate the selection of diverse parental lines followed by subsequent hybridisation between them to introduce new traits in bell pepper.