Studies on Genetic Diversity among Okra (Abelmoschus esculentus) genotypes using SSR markers

Abstract

Twenty-eight genotypes of Okra used in the current investigation were collected from ICAR-NBPGR, New Delhi. Genomic DNA was isolated from 10 to 14 days old Yellow and etiolated fresh leaves from all the genotypes of Okra using the SDS lysis buffer method. Genomic DNA was quantified by using Nanodrop to estimate concentration and purity. Agarose gel electrophoresis was used to quantify DNA based on molecular weight. The purified DNA was amplified using PCR with 15 SSR primers. The banding pattern was recorded in the form of a 0-1 sheet which was analyzed using UPGMA-based Jaccard’s similarity coefficient. The results were obtained and presented in the form of a dendrogram for SSR analysis. SSR analysis generated a total of 452 bands from 15primers. Among the 15 SSRs primers, 10 SSR primers showed 100% polymorphism while one SSR primer showed 50% polymorphism. Four primers showed no polymorphism. Genetic diversity using SSR data as estimated by PIC value for the SSR loci ranged from 0.40 (AVRDC OKRA 77) to 0.88 (OKRA 157). The resolving power (RP) value varied from 0.11 (OKRA 157) to 1.00 (OKRA 144, OKRA 151, OKRA 164, and OKRA 126). The cluster dendrogram of SSR primers revealed two major clusters; Cluster A consisted of seven genotypes, and cluster B was the largest and included twenty-one genotypes. On the basis of PIC values SSR primers namely OKRA 109, OKRA 157, OKRA 120, OKRA 137, and OKRA 175 provide maximum accession coverage in Okra genome. The cluster A consist of seven genotypes namely IC128071, EC305618, EC305631, EC169504, EC305611, EC280756, and EC305632 with similarity coefficient ranging from 0.71 to 0.96. Cluster B consists of 21 genotypes namely IC128070, IC128072, IC128087, IC128089, EC169505, EC169511, EC169513, EC169948, EC177900, IC128080, EC284327, EC305609, IC128123, IC128892, IC128127, IC128146, IC128143, IC128142, IC128891, EC305609, and IC128893 with similarity coefficient ranges from 0.66 to 0.88. Dendrogram revealed that genotype IC128142 is distantly related to IC128143, IC128127, and IC128146, with a similarity coefficient of 0.72. Genotype namely IC128893 was found distantly related to IC128891 and EC305609 with a similarity coefficient of 0.75. EC169511 and EC169513 were very close to each other with a similarity coefficient of 0.92. IC128127 and IC128146 were very close to each other, with a similarity coefficient of 0.93. In subgroup II of cluster B, IC128087 and IC128089 were very close to each other with a similarity coefficient of 0.96. In subgroup III of cluster B, EC284327 and EC305609 were very close to each other with a similarity coefficient of 0.96. The cluster analysis and PCO analysis shows similar results, lead to infer that ample genetic variation existed at the molecular level in relation to okra genotypes. It can be concluded from the current investigation that the genotypes were clearly distinguishable from each other when grouping was carried out using SSR markers. Thus, these SSR primers are of high importance in the characterization of Okra genotypes. The information generated from current studies can be used in future breeding programs for Okra improvement for various traits.