Characterization and selection of exploitable genetic diversity in soursop (Annona muricata Linn.) accessions based on phenotypic attributes and RAPD markers

Annona muricata is a tropical evergreen fruit tree species with great potential for food, industrial and medicinal uses, especially in the treatment of cancer. The crop, however, remains an underutilized tree species in most parts of the world due primarily to lack of commercial varieties, efficient conservation strategies and genetic characterization of the available germplasm. This study was, therefore, undertaken to characterize key phenotypic attributes and genetic diversity data from 42 representative accessions of the crop as a precursor to enhancing a systematic varietal improvement and selection programme that would support conservation. Phenotypic attributes based on stem, leaf, flower and fruit characteristics were evaluated in situ to complement molecular tools and data obtained demonstrated that differences amongst the accessions were highly significant (p < 0.001) for number of flowers and fruits, with 71.38 % of the total variability being accounted for by 3 principal components. Conversely, molecular characterization studies using random amplified polymorphic DNA markers produced a total of 65 reproducible bands. Of these, 59 amplified bands (90.77 %) were polymorphic while the remaining 6 were monomorphic loci. Analysis of the data generated from the phenotypic attributes and molecular markers revealed a high degree of divergence with 3 and 4 clusters, respectively, which exhibited continuous variation that was highly distinguishable. The genetic diversity identified here could offer yet-unknown traits of high value that would optimize varietal improvement and use of genetic resources amongst A. muricata accessions with great potential as raw material for the food and pharmaceutical industries.