Floriane Lawac

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.

Aibika ( Abelmoschus manihot ) is a tropical leafy vegetable with great potential in the prevention of malnutrition. Its high fibre and micronutrient content makes it a valuable complement to staple foods such as rice and starchy crops consumed in South Asia and the Pacific. The present study is the first to report the development of a set of 21 nuclear single sequence repeat (SSR) markers of A. manihot from genomic sequence data obtained using NGS technology. The DNA library was prepared from a pool of four aibika accessions and sequenced using an Illumina MiSeq system. A total of 1,295,217 pair-end reads were generated. Raw data are available in the European Nucleotide Archive (accession number PRJEB88210; https://www.ebi.ac.uk/ena/browser/view/PRJEB88210 ). The sequences were assembled using the ABySS software. In total 651,320 contigs were generated. Using MISA Perl script and Primer3 software, we identified 8014 SSR motifs, of which 4637 had a suitable primer design. The contigs were blasted with NCBI-BLAST on okra reference genome. After selection based on motif type, repeat length, amplicon size and occurrence blast, we retained 91 candidate SSR loci, which were tested on 23 aibika accessions. Finally, we validated 21 high quality SSR loci by genotyping 45 accessions from three Pacific countries. The number of alleles per locus ranged from 3 to 21 with an average of 7.81 alleles/locus. The 21 selected SSRs were found to be useful in discriminating between accessions and revealing the diversity structure of A. manihot . They will help to optimize genebanks management and breeding programmes, and guide future collection activities.

The Pacific Islands (Melanesia, Micronesia, Polynesia) were the last region in the world to be colonized by modern humans. In their migrations, they dispersed asexually propagated food plants that were first domesticated in Melanesia and exposed them to further selection in diverse insular environments. Later, staple food crops were introduced from South America. In our search for research on genetic resources characterization and breeding conducted between 1950 and 2022, we retrieved 338 references on 13 crop species. All studies were examined, and a review is presented here. Relatively few were on genetic improvement (92 references) compared to those on morphological diversity (246 references). The paradox is that the Pacific is considered a region exposed to the climatic crisis, perhaps more vulnerable than any other region in the world. This paradox is surprising when we consider that most people in the Pacific are growing staple food crops, for household use and/or for local markets, and occasionally for export. In some countries, it involves more than 75% of the population with a considerable contribution to gross domestic product (GDP). Plant breeding has not been considered a priority to mitigate against forthcoming changes in climate, which is likely to be detrimental to crops with a narrow genetic base. We suggest several possible reasons and that conventional plant breeding should be given high priority based on new approaches that include geographical distribution of allelic diversity.