Inheritance of albinism in banana and plantain (Musa spp.)

Abstract

Few genetic markers are available in Musa spp. as a result of a lack of inheritance studies. Full-sib diploid (2n = 2x = 22) plantain-banana hybrids of the International Institute of Tropical Agriculture were selfed or outcrossed with other diploid bananas, one of which is an improved 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 parthenocarpic Musa) in two of these three populations did not allow for conclusiveness between the one or two genes model. However, a distinction was possible with the third population, consisting of 64 seedlings, of which four were albinos. The segregation ratio for albinism fit the 15:1 ratio (χ2 = 0.07, P = 0.79) and not the 3:1 ratio (χ2 = 11.02, P < 0.01), suggesting that albinism in Musa spp. is under the genetic control of at least two independent recessive alleles with complementary gene action. This finding also demonstrates that deleterious recessive alleles are present in the cultivated AAB plantain gene pool and in cultivated and advanced AA banana breeding populations. The latter suggests that population improvement through phenotypic recurrent selection for agronomic traits might be based on the elimination of deleterious recessive genes.