RAPD analysis of genetic diversity among clones of the Ethiopian crop plant Ensete ventricosum

Random amplified polymorphic DNA (RAPD) was used to estimate genetic variability among 111 different clones of Ensete ventricosum, cultivated at 9 different collection sites in southwestern Ethiopia. PCR conditions were optimized for the amplification of DNA fragments in this crop. Out of 126 oligonucleotide primers initially screened, 12 were chosen that together generated 97 reproducible polymorphic bands. Each clone proved to have a unique DNA profile, in spite of 8 duplications among the vernacular names represented in this material. The high level of genetic variability encountered is in good accordance with an outcrossing breeding system, and is also indicative of gene flow from wild enset and possibly from other Ensete species. Genetic variation within collection sites was relatively high, with values for the Shannon-Weaver diversity index ranging from 0.44 to 0.55. A PCA (principal component analysis) demonstrated some differentiation among sites but also considerable overlapping. Partitioning the total variability at different levels with the Shannon-Weaver index shows that only 14% was attributable to differences between sites and 86% to variation within sites. Pairwise comparisons of the 9 sites yielded values for Nei's unbiased genetic distances that ranged from 0.054 to 0.225. Cluster analysis as well as PCO (principal co-ordinate analysis) showed that Bonga and Chencha form a nucleus within a loose cluster, which also comprises Wolkitae, Worka, Shonae and Wondo. The remaining three sites, Answae, Setunae and Seltae, take quite isolated positions. Estimates of genetic distances did not correspond with geographical distances between collection sites. Genetic distances, as well as amount of within-site diversity, may instead be connected with the pattern of distribution for various ethnic groups in the enset-based agricultural system, and their dependency on enset as a staple food. This study is the first of its kind on enset.