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SESSION 3: PATHOGENESIS – EPIDEMIOLOGY AND POPULATION
GENETICS
P47 - Trichothecene production by Fusarium
graminearum isolates from Argentina and its
relationship with aggressiveness and fungal
colonization of the wheat spike
I. Malbrán 1 , C. A. Mourelos 1 , P. A. Balatti 1 , Q. Migheli 2 , G. A. Lori 1
1 Centro de Investigaciones de Fitopatología, Facultad de Ciencias Agrarias y Forestales, Universidad
Nacional de La Plata, 60 y 119, CC 31, (1900) La Plata, Buenos Aires, Argentina; 2 Dipartimento di
Agraria - Plant Pathology and Entomology Unit, Università degli Studi di Sassari, Via E. De Nicola 9, I
- 07100 Sassari, Italy
E-mail: imalbran@yahoo.com.ar
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.
Keywords: Fusarium head blight, deoxynivalenol, wheat
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