Genetic diversity and population structure of Ethiopian taro Colocasia esculenta (L.) Schott) as revealed by SSR markers

Abstract

Abstract Taro (Colocasia esculenta (L.) Schott) is an important root and tuber crop that contributes to food security and livelihoods, but its genetic diversity remains poorly characterized in Ethiopia. This study assessed Ethiopian taro genetic diversity and population structure using simple sequence repeat (SSR) markers. We analyzed 119 accessions, 79 collected from farmers fields and 40 from the Ethiopian Biodiversity Institute (EBI), representing three regional populations: South Ethiopia Regional State (SERS), South West Ethiopia Peoples Regional State (SWEPRS), and Oromia. Fifteen polymorphic SSR markers produced 199 reproducible polymorphic loci, with 100% polymorphism. Polymorphism information content (PIC) ranged from 0.300 to 0.888 (mean 0.583). Diversity based on scored binary marker states was relatively low, with a mean effective number of alleles (Ne) of 1.077 and expected heterozygosity (He) of 0.066. Across populations, He ranged from 0.047 to 0.061, and the percentage of polymorphic loci ranged from 37.14% to 82.57%. Analysis of molecular variance showed that 98% of molecular variation occurred within populations and 2% among populations. Genetic differentiation ({Phi}PT, proportion of molecular variation among populations) was weak but significant ({Phi}PT = 0.016, P = 0.016). Principal coordinate analysis, neighbor-joining (NJ), and unweighted pair-group method with arithmetic mean (UPGMA) clustering showed extensive overlap among accessions and no clear geographic structuring. Bayesian clustering identified two groups as the strongest partition according to the {Delta}K criterion, but substantial admixture occurred, and groups did not correspond clearly to geographic populations. Despite relatively low diversity at individual scored loci, all 119 accessions had unique multilocus genotypes, indicating high multilocus genotypic diversity. Most molecular variation occurred within rather than among regional populations, potentially reflecting planting-material exchange and predominantly clonal propagation. These findings provide a basis for conserving, characterizing, and utilizing Ethiopian taro germplasm in crop improvement.