Variation of ribosomal gene spacer length among wild and cultivated banana.

The diversity of rDNA spacer length (IGS) of 107 wild and cultivated clones of banana belonging to different genetic groups, was studied using a sulphonated wheat rDNA probe. The length of the rDNA unit was between 10 and 12.6 kb and was highly variable. Fifteen different types of IGS could be observed. IGS diversity within the acuminata complex was greater among the diploid cultivars than among the triploid cultivars. Variation was also found among BB genotypes and confirms the diversity of this species. As opposed to previous studies, based on enzymatic or poly-phenolic markers, there was no obvious relation between the rDNA structure and the classification into genetic groups. More particularly, the IGS variations did not differentiate between the A and B genomes. This analysis, however, indicates a relationship between the geographical origin and the IGS structure of Thai and Indonesian clones.