Plantain-derived Diploid Hybrids (TMP2x) with Black Sigatoka Resistance

Abstract

Plantain (Musa spp., AAB group), a triploid (2n = 3x = 33) giant perennial herb of the tropics, is a natural interspecific hybrid between the two wild banana species M. acuminata Colla. and M. balbisiana Colla. These diploid species contributed the A and B genomes, respectively (Simmonds, 1962). Triploidy makes plantain crossbreeding difficult but not impossible (Swennen and Vuylsteke, 1993). As such, plantain progenies were obtained when triploid plantains were crossed with diploid M. acuminata clones (Vuylsteke et al., 1993c). Genetic improvement of plantain is required because its sustainable production is threatened by increasing disease and pest pressure (Vuylsteke et al., 1993b). One of the major constraints is the black sigatoka leaf spot disease (Mycosphaerella fijiensis Morelet), which causes yield losses of at least 33% (Mobambo et al., 1993). Production and cultivation of resistant cultivars are generally considered the most appropriate means to control the disease. The International Institute of Tropical Agriculture (IITA) targets the development of improved plantain germplasm. So far, 14 improved plantain-derived tetraploid (4x) hybrids with black sigatoka resistance have been selected for multilocational testing and further cultivar release by national agricultural research programs (Vuylsteke et al., 1993d). In addition to the tetraploid hybrids, progenies with other ploidies were also recovered from the 3x x 2x crosses, diploids (2x) being most numerous (Vuylsteke et al., 1993c). Plantainderived diploids play an important role in