Populations study of Mycosphaerella fijiensis and genetic improvement of bananas for resistance to black leaf streak disease

Knowledge of the extent and distribution of variability within #M. fijiensis# is necessary for efficient genetic improvement of banana for a durable resistance to black leaf steak disease. The population genetic structure of #M. fijiensis# has been studied at a global, country and field scale using molecular markers. These studies have shown that populations of #M. fijiensis# can maintain a high level of genetic diversity at a small scale, and that recombination plays an important role in this pathogen. The Australasia Southeast Asia region is the centre of #M. fijiensis# diversity. The founder effects that have accompanied the introductions of #M. fijiensis# to Latin America, the Pacific Islands, and Africa have led to a reduction of genetic diversity in these regions. The implications of these results for resistance breeding and disease management will be discussed. Population analysis of #M. fijiensis# should include pathogenic variability studies. The characterization of disease resistance in banana germplasm is also essential for banana breeding. To this order, we are developing an inoculation technique for #M. fijiensis#, using banana leaf pieces. Similar infection patterns and symptom evolution to that observed under field conditions have been obtained. All of the different stages of the #M. fijiensis# life cycle have been reproduced in the leaf piece assay, and resistant phenotypes of cultivars were expressed. The first results obtained of #M. fijiensis# pathogenic variability, and the characterization of resistance within banana, using this technique will be presente