Ecophysiology of Fusarium graminearum main pathogen associated to Fusarium head blight in Latin America

Abstract

In Argentina, the main pathogen associated with Fusarium Head Blight (FHB) is Fusarium graminearum Schw, perfect stage Gibberella zeae (Schw.) Petch. Prevention of mycotoxin contamination of food raw materials is now considered more important than subsequent cure. Accurate information is therefore needed on the impact of key environmental factors such as water availability and temperature and their interactions, and the identification of marginal and optimum conditions for growth and toxin production. Studies done in Argentina were focused on the impact of different abiotic factors (a W, temperature and fungicides) on F. graminearum growth rates and deoxynivalenol production. The impact of 5 fungicides (prochloraz, propioconazole, epoxiconazole, tebuconazole and azoxystrobin, 0.5-50 mg/ ml) on growth of F. graminearum isolated from wheat in Argentina were evaluated in relation to water activity (a W; 0.99, 0.97, 0.95) and temperature (15 and 25 °C) on wheat-based media (in vitro) and on wheat grains (in situ). Also the effect of osmotic (NaCl, glycerol) and matric (PEG8000) water stress on temporal germination and growth by F. graminearum strains isolated from wheat in Argentina over the water potential range of -0.7 to -14.0 MPa at 15 and 25 °C. The effect on endogenous water potentials and accumulation of sugars and sugar alcohols were also evaluated. The results showed that water potential and solute type have a significant effect on germination, germ tube extension, growth rates, germination, internal cell water potential and endogenous accumulation of sugars and sugar alcohols in F. graminearum.