Genetic diversity and population structure analysis of Ethiopian mustard ( Brassica carinata A. Braun) accessions using simple sequence repeat markers

Abstract

Brassica carinata A. Braun is an oilseed that originated in Ethiopia with a wide range of industrial and food applications. Exploring the genetic structure of the crop is crucial for breeding and conservation measures. Despite the fairly large number of B. carinata collections in the national genebank at the Ethiopian Biodiversity Institute, information on the extent of their genetic variability is quite limited. The objective was to analyze genetic diversity and population structure of 92 B. carinata accessions representing six populations using eight polymorphic microsatellite markers. The results revealed that all the microsatellite loci were highly informative, exhibiting a polymorphic information content that varied between 0.48 and 0.79. Moreover, a high genetic diversity within population was confirmed with the gene diversity index (h), which ranged from 0.49 to 0.74 with an overall mean of 0.65. Analysis of molecular variance indicated a moderate and significant genetic differentiation (PhiRT = 0.09, p =  0.001), with 91% of the total genetic variation occurring within populations and only 9% difference among populations. Clustering, principal coordinate analysis, and STRUCTURE analyses did not categorize the populations into clearly defined clusters based on their geographical origins, maybe due to high gene flow (Nm = 2.60). Brassica populations from Oromia and Amhara regions showed greater genetic diversity as compared to other populations. As a result, these areas could be regarded as hot spots for identifying genotypes with valuable alleles for breeding programs and conservation measures.