INHERITANCE OF ALBINISM IN BANANA AND PLANTAIN (MUSA SPP) AND ITS SIGNIFICANCE IN BREEDING

Few genetic markers are available in Musa spp. as a result of a lack o f inheritance studies. Full-sib diploid (2n = 2x = 22) plantain-banana hybrids of the International Institute of Tropical Agriculture were s elfed or outcrossed with other diploid bananas, one of which is an imp roved selection from Central America. Three populations having albinos (complete lack of chlorophyll in any plant tissue) were produced. The segregation ratios for albinism suggested that this deleterious trait is controlled by one or two recessive alleles. The small sample sizes (a problem inherent in the low reproductive fertility of cultivated p arthenocarpic Musa) in two of these three populations did not allow fo r conclusiveness between the one or two genes model. However, a distin ction was possible with the third population, consisting of 64 seedlin gs, of which four were albinos. The segregation ratio for albinism fit the 15:1 ratio (chi2 = 0.07, P = 0.79) and not the 3:1 ratio (chi2 = 11.02, P < 0.01), suggesting that albinism in Musa spp. is under the g enetic control of at least two independent recessive alleles with comp lementary gene action. This finding also demonstrates that deleterious recessive alleles are present in the cultivated AAB plantain gene poo l and in cultivated and advanced AA banana breeding populations. The l atter suggests that population improvement through phenotypic recurren t selection for agronomic traits might be based on the elimination of deleterious recessive genes.