Genetic Analysis of Resistance to Triazoles in Isolated of Mycosphaerella fijiensis from Ecuadorian Populations

Banana crops are severely affected by "Black Sigatoka” disease, caused by Mycosphaerella fijiensis, an ascomycete fungi. Control systems are generally determined by the use of chemical formulations that may be linked to the molecular changes that have been described into genes associated to the action sites of pesticides. In this work we try to determinate the relationship between genetic variations with the pressure from the conventional control to the populations. We made an in vitro analysis of the sensitivity with two types of fungicides from the group of triazoles (Epoxiconazole and propiconazole), also we made a genetic characterization of 60 isolates of M. fijiensis isolates from Ecuador and isolates used as reference strains from Costa Rica and Cameroon, to understand the diversity among each genotype, within and between populations. Samples were taken from the provinces of Guayas, Los Ríos and El Oro, the areas of major production of banana in the country. The characterization was made with 30 microsatellite markers, and 23 isolates were selected for sequencing of the CYP51 gene. The isolates obtained high levels of LC -50 (≥ 20 mg / L) for chemical fungicides studied. The populations obtained high genetic diversity values of h= 0.4202 (Nei’s genetic diversity of 1973’s), Shannon index= 0.7766 and 0.2465 Gst with low genetic distance between populations of Guayas and El Oro (0.12 was found). The sequences of CYP51 gene of selected isolates showed some mutations in the corresponding positions G313A, D461Y, H463Y, N463Y and S463Y of lanosterol 14α demethylase.