Trichothecene production by Fusarium graminearum isolates from Argentina and its relationship with aggressiveness and fungal colonization of the wheat spike

ISMAEL MALBRÁN; CECILIA A. MOURELOS; PEDRO A. BALATTI; QUIRICO MIGHELI; GLADYS A. LORI

Boredaux

Seminario; 12th European Fusarium Seminar; 2013

Institut national de la recherche agronomique

In Argentina, at least 20 epidemics of Fusarium Head Blight (FHB) of wheat, caused by Fusarium graminearum, have been registered in the last 50 years. The damages induced by the disease are further aggravated by the frequent presence in affected grains of mycotoxins, mostly deoxynivalenol (DON), which may cause health problems to human and animals. In the present work we investigated the correlation between the aggressiveness of F. graminearum isolates from Argentina, its capacity to colonize the spike and the accumulation of DON in wheat grains. Fourteen isolates of F. graminearum were tested for aggressiveness in point inoculated (PI) spikes of field grown wheat in two years of trials. Inoculated spikes were hand threshed and the resulting rachis were superficially disinfected, cut in their component parts and plated on potato dextrose agar medium (PDA) to analyze the colonization of the vascular system. Grains were ground and DON was quantified by means of the RIDASCREEN® FAST DON ELISA kit (R-Biopharm). Isolates significatively differed in the severity of the symptoms of FHB (F = 7.34; p < 0.01), DON production (F = 5.91; p < 0.01) and percentage of colonized portions of the rachis (F = 7.22; p < 0.01). A close correlation was found between the severity of FHB and DON (r = 0.9073), colonization and severity (r = 0.7106), and colonization and DON (r = 0.8081). The presence of the pathogen in the rachis was verified even in asymptomatic spikes in a percentage that was highly superior to that of symptomatic spikelets for all treatments. Furthermore, even isolates with a limited capacity of induction of visible symptoms of FHB were able to colonize the vascular tissue of wheat spikes and to produce considerable amounts of DON.