Comparative analysis of phenotypic and genotypic diversity among plantain landraces (Musa spp., AAB group)

Genetic diversity amongst 76 plantain landraces has been studied using RAPD analysis at two levels of intensity and compared with groupings based on p henotypic indices and morphotype. There was a good correlation (R-2=0.78) b etween estimates of genetic diversity based on 76 RAPD bands and 164 RAPD b ands. However, there was a poor correlation between RAPD-based estimates of genetic diversity and a phenotypic index based on argonomic characters. Th ere was also a poor correlation between RAPD analyses and morphotype group (based on bunch type and stature). These results suggest that the tradition al designations of plantain landraces based on morphotype do not provide a true reflection of overall genetic divergence. Similarly, classification sy stems using phenotypic indices based on agronomic characters may not provid e accurate taxonomic differentiation. The level of genetic divergence withi n morphogroups based on bunch type suggests that True Mom plantains are der ived from False Horn plantains which in turn are derived from French planta ins. Genetic divergence was found to be generally quite low within the plan tain landrace genepool, which is consistent with the proposed evolution of this germplasm through somatic mutation of a relatively small number of int roductions. However, putative synonyms/duplicates have been shown to be gen etically distinct. In contrast, a group of 12 landraces have been identifie d that are highly distinct from one another (showing 20-35% dissimilarity). Fertile members of this group may be useful for generating genetically div erse 2x and 4x breeding populations that can be used in breeding secondary triploid hybrid plantain varieties.