Analysis of genetic diversity and phylogenetic relationships among indigenous and exotic Silk (AAB) group of bananas using RAPD markers

Natural transgression between Musa acuminata and Musa balbisiana, the well accepted progenitors of Musa spp., has led to the evolution of modern bananas and plantains with various ploidy levels and genomic constitutions. Silk is an important group of triploid, dessert bananas of bispecific origin (AAB). Though it has wide geographic distribution across the globe, the variability seems to be very limited. This study was undertaken with 25 Silk group representatives of both indigenous and exotic origins. The genetic variation and phylogenetic relationships were analysed using Random Amplified Polymorphic DNA (RAPD) markers. Out of the 80 primers screened, 34 primers produced reproducible bands and only four primers were selected for the polymorphic study. A total of 35 DNA fragments across all materials were amplified with four random primers, averaging 8.75 per primer. Within the amplified fragments, 18 showed polymorphism with an average of 4.5 per primer. The average polymorphism among the amplified products was 51.2% indicating the existence of considerable variation at the DNA level among the test accessions. Most of the commercial Silk clones formed only two clusters and the extent of variability ranged only between 0-30%. The results indicate, irrespective of wider distribution of Silk group members across the globe, the spectrum of variability is very narrow.