Genetic diversity and morphological variation of aibika [Abelmoschus manihot (L.) Medik.] in Melanesia

Abstract Aibika [ Abelmoschus manihot (L.) Medik.], also known as island cabbage, is a highly nutritious leafy vegetable crop which is traditionally cultivated in Southwest Pacific countries. The study presents the results of genetic analyses of 227 aibika accessions conserved in the genebanks of three Melanesian countries (New Caledonia, Papua New Guinea, and Vanuatu), and French Polynesia. Genotyping with 21 novel microsatellite markers revealed that 216 accessions had a diploid genome, while eleven exhibited a third allele at one locus or more. Among the diploid accessions, we observed a total of 196 unique multilocus genotypes. Using K-means clustering method, we identified six genetic groups, including one specific to Papua New Guinea. Discriminant analysis of principal components revealed the relations between these groups, the probability of membership, and the level of admixture of the accessions. Genetic analyses by country also shown that Papua New Guinea accessions exhibited the highest genetic diversity, allelic richness, and number of private alleles, which is consistent with the history of the introductions of the crop in the Pacific. The genetic diversity observed is likely the result of a cultivation process combining selection of seedlings issued from natural sexual reproduction and clonal propagation. Morphological analyses of 76 accessions conserved in Vanuatu national ex situ germplasm collection were also conducted using a set of four quantitative and five qualitative morphological descriptors. We further discussed future challenges for the conservation and breeding of this neglected crop that contributes to the diversification and quality of the diets of Pacific Islands communities.