Molecular Characterisation Reveals the Existence of a Hybridogenous Intermediary Form between Sweet Watermelon and Cow Melon Forms of Watermelon

Abstract

Watermelon research in Southern Africa, has predominantly observed the clear existence of the sweet watermelon and cow melon forms of watermelon, cultivated on farm and even some occurring in the wild. Molecular characterization of 48 watermelon accessions collected from National Genebank of Zimbabwe using 9 SSR markers generated a total of 49 putative alleles. The average number of alleles detected by each primer was 5.4. Analysis of molecular variance within and among accessions of watermelons revealed that only 39% of the total variation resides between these two groups (cow-melons and sweet watermelons), 24% between accession within groups and 37% within accessions. Multivariate analyses employed provide evidence of the existence of introgression between sweet water melons and cow melons, as reflected by some accessions of cow melons, clustering into a hybridogenous group. Most of watermelon accessions within the hybridogenous group [A (II)] were collected from drier communal areas, while those accessions within the cow melon group [A (I)] are mostly from research centers. The separation of cow melons into distinct groups could be indicative of a possible formation of an isolated evolutionary unit.