Genetic characterization of banana cultivars (Musa spp.) from Brazil using microsatellite markers

Microsatellite markers were used to characterize 35 banana (Musa spp.) genotypes cultivated in Brazil, including triploid cultivars and tetraploid hybrids. A total of 33 Musa-specific primers were tested, and 11 produced clear, reproducible and discrete bands. The average number of alleles amplified per primer was 6.1, ranging from 4 to 8, with a total of 67 alleles identified. Phenetic analysis based on Jaccard similarity index derived from presence or absence of the alleles agreed with the morphological classification. Bootstrap analysis divided the genotypes into four clusters, according to genomic group and subgroup classification. The first cluster contained the majority of cultivars which have 'A' genome alone; while the second contained all triploid cultivars of the subgroup Prata (Pome) and their tetraploid hybrids. The third cluster contained cultivar 'Maca' together with other genotypes considered for breeding purposes as similar to the Silk subgroup. These last two clusters formed a larger group including the majority of genotypes that resulted from hybridization between M. acuminata and M. balbisiana. The microsatellite loci were highly informative, with some pair of primers generating an unique fingerprinting for each genomic group and discriminating a genotype of doubtful classification, although somatic mutants from a subgroup were seldom distinguished from their original clone. Tetraploid hybrids exhibited distortion in the proportion of alleles donated by their triploid female parent. For a few primers, some genotypes exhibited a higher number of alleles than expected from their ploidy level, suggesting the occurrence of duplicated alleles or duplicated chromosomal regions.