Aggressiveness, In Vivo, And In Vitro Deoxynivalenol Production Of Fusarium graminearum Isolates From Argentina

ISMAEL MALBRÁN; MARIANELA B. LANDA; CECILIA A. MOURELOS; PEDRO A. BALATTI; GLADYS A. LORI

Mendoza

Conferencia; ISM Conference 2011 "Strategies to reduce the impact of mycotoxins in Latin America in a global context"; 2011

Fusarium head blight of wheat (FHB), caused by Fusarium graminearum Schwabe [teleomorph Gibberella zeae Schweinitz) Petch], is one of the most important diseases of wheat in Argentina. FHB causes yield and quality losses and infected grains may contain significant levels of trichothecenes which are hazardous to animals, making the grain unfit for food or feed. Field tests were conducted in point inoculated (PI) spikes of wheat genotype Klein Chajá to analyze the variation in aggressiveness of 112 isolates of the pathogen from 27 localities of Buenos Aires province. Sixteen isolates that spanned through the entire variation in aggressiveness found in the field tests were selected to analyze the relationship between the severity of FHB symptoms induced and the production of mycotoxins both in vivo and in vitro. The ability to produce deoxynivalenol (DON) and/or nivalenol (NIV) by the isolates was evaluated by PCR using primer pairs 3551H/4056H and Tri7F340/Tri7R965, respectively. Primers were as follows: 3551H: 5?-ACT TTC CCA CCG AGT ATT TT-3?, 4056H: 5?-CAA AAA CTG TTG TTC CAC TGC C-3?, Tri7F340: 5?-ATC GTG TAC AAG GTT TAC G-3?, Tri7R965: 5?-TTC AAG TAA CGT TCG ACA AT-3?. Based on the PCR results obtained, all sixteen F. graminearum isolates tested corresponded to the DON chemotype and the amount of the trichothecene produced by the strains both in vivo and in vitro was evaluated using a commercially available enzyme immunoassay (enzyme-linked immunosorbent assay [ELISA]) (RIDASCREEN FAST DON; R-Biopharm GmbH, Darmstadt, Germany). To test in vivo DON production, the point inoculated spikes from each of the four blocks from the field tests were handthreshed and 5 gr of the grounded samples were used for determination. To test for in vitro DON production, isolates were cultured in triplicate on rice (80% relative humidity) for 21 days, air dried and 5 gr of the grounded samples were used for testing. Aggressiveness differed significantly between the isolates (F = 6.21, p < 0.01) and so did both in vivo and in vitro toxin production (F = 7.82, p < 0.01 and F = 6.77, p < 0.01, respectively). No correlation was found between the amount of toxin produced by the isolates in vivo and in vitro (r = 0.15, p > 0.05). Furthermore, even though a strong correlation was found between the severity of the disease induced by the isolates in the field and in vivo DON production (r = 0.9, p < 0.01), no correlation was observed between the former and in vitro production of mycotoxins (r = 0.11, p > 0.05). According to our findings, under field conditions the ability of F. graminearum to produce and accumulate DON in wheat spikes is highly related to the aggressiveness of the isolates but not to its capacity to produce DON in vitro.