Phylogeny of Kluai Tani Musa balbisiana Colla, its related cultivars and hybrids and based on DNA analysis

Abstract

Bananas is one of the oldest cultivated crops. It is widely believed that edible seedless banana cultivars have been derived from or are hybrids of two wild diploid species, namely Musa acuminata Colla (AA) and M balbisiana Colla (BB). Though the banana domestication is believed to have occurred in the Southeast Asian region, the genomic and geographical origin (s) of the ancestral bananas are still uncertain. We are exploring DNA sequence polymorphism to determine the domestication history of bananas with special emphasis on the Southeast Asian triploid ABB/BBA complex; ‘Hin’ / ‘Saba’ / ‘Namwa’. Four chloroplast (cp-) non-coding loci-rp116 and ndhA introns, psaA-ycf3 and petA-psbJ-psbL spacers-and a nuclear (nu-) locus, GBSS or waxy, markers have been developed. By analyzing the four cp-loci combined sequences, the A and B genome derived alleles could be relatively easily distinguished. Polymorphism within each genome included nucleotide substitutions and insertion/deletions (indels). In the hybrid cultivars, the alleles derived from each of the contributing genomes could be separated. Phylogenetic analyses based on these DNA sequence data with different treatments of indels resulted in the discovery of a distinct population of wild M. balbisiana in northern Thailand. This finding rejected the hypothesis that this species was not native. Diversity within triploid hybrids was found and particular B genome-rich triploids (ABBs) were given new genome designation as BBAs to indicate their maternal genealogy. In the investigation of the nuclear (nu-) genome, three GBSS alleles were found in triploid hybrids ‘Namwa’ cultivars and one among the three can be designated as B allele. In order to estimate the influence of agricultural selection on the evolutionary history of banana, more samplings and further investigation are required.