Résumé
The many edible bananas originated primarily in tropical regions and the crop thrives best in the humid tropics. Banana cultivation in subtropical regions faces numerous abiotic constraints like droughts, poor quality of irrigation water, wide daily and/or seasonal temperature variations and winds. Pests and diseases (like Panama disease, virus and nematodes) are locally present and often represent a serious constraint to banana production. Banana genetic diversity in subtropical regions remains limited. Intensive banana cultivation relies mainly on varieties belonging to the Cavendish (AAA) subgroup. Their cultivation requires great farmer skills and high level of inputs (in terms of irrigation, nutrition, greenhouses ...) for commercial productivity. Nevertheless, the sustainability of these production systems is questionable, in particular in terms of water use. In the subtropics, farmers also grow more hardy varieties with relatively rustic methods. These varieties which belong to AAB and ABB groups are less productive and sometimes of poorer quality, but appear more tolerant to abiotic stresses than the Cavendish cultivars. This brief diagnostic suggests that the genetic improvement of banana for the subtropics should have as an objective to select new varieties representing a good compromise between criteria of productivity and quality fruit on the one hand and tolerance to difficult growing conditions on the other. In pursuit of this objective, breeders could initially recommend the introduction of existing varieties better adapted putatively than the current varieties. The development of new breeding strategies looking for better adaptability of varieties to the subtropics, a longer term approach, requires specific background research. In particular, investigations have to elucidate what are relationships between intra- and inter-specific heterozygosis and plant adaptability to specific environments in Musa. The contribution of M. balbisiana genome for better tolerance to hard conditions should also be clarified. Some working hypothesis and preliminary results will be presented during the seminar. (Texte intégral)