Genetic diversity in melon (Cucumis melo L.):: An evaluation of African germplasm

The genetic diversity among 126 exotic (108) and reference array (RA) melon (Cucumis melo L.) accessions (18) was assessed by variation at 49 random amplified polymorphic DNA marker bands (putative loci) using 29 10-mer primers. African accessions of unknown melon market classes were compared to the RA accessions from a broad range of C. melo subsp. melo groups (Cantalupensis, Conomon, Inodorus and Flexuosus). Although differences in groupings occurred after multidimensional scaling and cluster analysis, both analyses placed African accessions into two groups, which were separate from RA groupings. One African group of 33 accessions containing accessions from Zimbabwe (5), Zambia (24), Mali (1). one of two Senegal accessions and two of three South African accessions examined. The second group, which consisted of 67 accessions containing collections from Egypt (40), Tunisia (6). Libya (13), Morocco (1), Algeria (2), Ethiopia (1), Niger (1), Sierra Leone (1), S. Africa (1), Zambia (1) and Zimbabwe (1). Depending on the multivariate analysis technique employed, accessions from Kenya, Senegal and Ghana formed either unique groupings or were grouped with accessions (Cantalupensis) from the RA. Both analyses indicate that the genetic differences inherent between the African gene pools is associated with the geographic proximity of African countries (northern vs. central-southern Africa) in the germplasm array examined. Moreover., these data indicate that the genetic diversity of U.S. and European commercial RA germplasm (Cantalupensis and Inodorus) could be enhanced by the introduction of genetic variation from African accessions, and that it would be advantageous to acquire more accessions from this geographically and ecologically varied region to ensure the retention of existing genetic diversity.