Development of dwart plantain hybrids with resistance to black leaf streak and high yield: lessons learnt and outlooks

Plantain (Musa, AAB group) is an important food and cash crop in the humid lowlands of Sub-Saharan Africa, Central/South America and the Caribbean where it is mainly cultivated by smallholders. Plantain is threatened by severe diseases and pests and generally exhibits weak root branching. Nematode and weevil attacks weaken the anchoring of the plant, thus increasing its susceptibility to strong winds. Therefore, dwarf, robust and resistant cultivars seem to offer an appropriate and environmentally friendly solution for sustainable yield improvement. A breeding strategy based on multisite hybridizations allowed the identification of 50 seed-fertile plantain cultivars. Pollination of several French-type plantains by diploid banana (AA group) has resulted in the production of diploid, triploid and tetraploid hybrids. On average, seed set was higher when plantains were pollinated during the dry season. The dwarf plantain 'Red Yade' produced numerous viable seeds at middle altitude (400 masl) whereas it appears totally sterile at sealevel. When pollinated by the wild diploid banana 'Calcutta 4', this dwarf plantain landrace generated mainly dwarf tetraploid hybrids with black leaf streak resistance and higher female fertility. In addition, very few dwarf diploids and triploids were generated. Although tetraploid hybrids express periodically streaks caused by banana streak viruses (BSV), they produce a normal bunch. Among the predominant triploids resulting from crosses between dwarf tetraploid and improved diploids, several hybrids exhibited dwarf stature, black leaf streak resistance and big bunches. Hence, the dwarfism in 'Red Yade' appears to be a stable and genetic trait. These results show that a dwarf banana with big bunches can be created by conventional breeding and opens prospects for generating appropriate segregating populations for genetic analysis of dwarfism in banana. Promising dwarf hybrids which do not express symptoms of BSV will be shared as parental clones or as final products with the international community. (Résumé d'auteur