ABSTRACT
Banana and plantain (Musa spp.) are perennial, giant herbs grown mostly in small plots and orchards. The main centers of Musa diversity are in the tropics: from South Asia to Polynesia. All edible cultivars derived from the diploid species M. acuminata and M. balbisiana, which contribute the A and B genomes, respectively. Advances in DNA-aided analysis of diversity are providing new insights into Musa diversity, filling gaps and unraveling relationships among species and cultivars, which are often complex owing to interspecific hybridization, heterozygosity, and polyploidy. Seed set in triploid bananas and plantains – whose fruit develop through parthenocarpyis very low due to high levels of sterility, thus making crossbreeding of both cultigens difficult, although some cultivars produce seed after crossing with diploid bananas. The genetic enhancement of banana and plantain is aimed at triploid cultivars whose multiplication is by vegetative means. The challenge is to breed using triploid cultigens – which are mostly sterile – as source populations, then release genetic variation by interploidy 3x × 2x crossing involving interspecific hybridization to obtain tetraploid hybrids, and thereafter using interploid 4x × 2x crossing with the aim of producing a non-seed bearing triploid cultivar. Interspecific hybridization, ploidy manipulations via 2n gametes, embryo culture, rapid in vitro multiplication, field-testing and selection led to development and identification of suitable plantain bred-germplasm for the West and Central Africa lowlands, and of beer or cooking bananas for the East African highlands. Genetic knowledge gives essential information to design crossing blocks targeting specific trait improvement according to combining ability, and may allow breeding gains to be predicted based on heritability and genetic correlations among traits.
