EST-SSR based genetic polymorphism among Lablab (Lablab purpureus L. Sweet) accessions contrasting for drought stress at seedling stage

Lablab is a multipurpose and the most drought-tolerant (DT) crop compared with its relatives. Despite its potential, Lablab is still an underutilized crop with a lack of improved varieties in many countries. The DT (D349, D147, HA4, D363, D352, D359, D348, D311, D55 and D250) and drought-susceptible (DS) (D271, D66, D106, D6, D26, D255, D28, D186, D95, and D258) accessions were earlier identified according to their morphological and biochemical responses to moisture stress at the seedling stage. These accessions were used to establish genetic polymorphism among the accessions contrasting for drought stress based on the Expressed Sequence Tag-Simple Sequence Repeats (EST-SSR) markers. The CTAB protocol was employed for the genomic DNA extraction. After DNA quality and quantity verification, the PCR was conducted using 16 EST-SSR primer pairs specific to the Lablab. The products were separated through the horizontal polyacrylamide gel electrophoresis (hPAGE). Discriminating ability of the markers and primers' efficiency were evaluated based on various genetic parameters. Principal Coordinate Analysis (PCoA) was performed to estimate the distance matrix among the population and among the accessions. While cluster analysis was processed to trace the genetic relationship among the accessions, dendrogram was constructed to decipher their genetic relationship. Analysis of Molecular Variance (AMOVA) was finally computed to quantify the diversity level and genetic relationship among the population, and among the accessions. A low polymorphism (GD = 0.19) was observed between the DT and DS accessions, likely due to limited discriminatory power of the EST-SSR markers. However, the PCoA, cluster analysis and AMOVA identified DT (D147, HA4, and D349) and DS (D106, D95, and D271) accessions as strongly contrasting populations under drought stress, with D147, HA4, D349, D363, D359, D352, and D348 further recommended as DT accessions. Given the low polymorphism observed, further validation using more informative molecular markers and advanced genomic approaches is recommended to improve the identification of drought-tolerance genes and related QTLs to support Lablab breeding programs.