Abstract

MARTINEZ-BOLANOS, Luciano et al. Fungicides resistance on Mycosphaerella fijiensis populations of southeastern México. Agrociencia [online]. 2012, vol.46, n.7, pp.707-717. ISSN 2521-9766.

The control of black Sigatoka (Mycosphaerella fijiensis) of banana (Musa acuminate Colla AAA) and (Musa balbisiana Colla AAB) requires numerous applications of fungicides, mainly of the triazoles group that impose high selection pressure in populations of this pathogen. The aim of the this study was to determine the response of strains of Mycosphaerella fijiensis isolated from banana plantations of Tabasco and Chiapas, México, to propiconazol and tridemorph. The bioassays were carried out in potato dextrose agar (PDA^®) culture medium added with different concentrations of these fungicides. The media were inoculated with 100 µL of a conidial suspension and mycelia fragments of the fungus, and incubated in darkness at 26 °C for 7 d. The effective concentration 50 (EC₅₀) and 95 % (EC₉₅) was estimated through Probit analysis of the percentage of inhibition of the relative growth of the pathogen. The EC₅₀ values in propiconazol varied from 0.0001 to 0.95 mg L^-1 and those of EC₉₅ from 0.006 to 12.51 mg L^-1. The resistance ratio at the level of EC95 was higher than 2085x, for the isolate MF-RmC₂ of the Remedios plantation from Teapa, Tabasco. The values for EC₅₀ in tridemorph varied from 0.00001 to 0.002 mg L^-1 and those of EC₉₅ from 0.03 to 0.85 mg L^-1. The resistance ratio to level EC95 between the sensitive isolate of reference and the least susceptible (MF-RcC₅ of the Recreo plantation, Tabasco) was higher than 28.3x. The positive correlation between the number of applications and the values of EC₅₀ and of EC₉₅ are indicative that the selection pressure exerted in this plantation generated resistance to the propiconazol.

Keywords : Black Sigota; propiconazol; tridemorph; banana; plantain.