Fusarium graminearum: Dynamic And Survival In Plant Debris And Detection By Polymerase Chain Reaction (PCR)

CECILIA A. MOURELOS; ISMAEL MALBRÁN; D.L. MENGUAL GÓMEZ; PEDRO A. BALATTI; P.D. GHIRINGHELLI; 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 (FHB) is caused by Fusarium graminearum Schwabe [teleomorph Gibberella zeae (Schwein.) Petch], is one of the most important fungal diseases affecting wheat in all cropping areas around the world, including those in Argentina. Damage from head blight, involves shrunken and discolored kernels that results in reductions in yield and grain quality. F. graminearum produces mycotoxins such as the trichothecenes, deoxinivalenol and nivalenol, and an estrogenic metabolite, zearalenone. FHB is influenced by weather conditions and agronomic factors, such as tillage and crop rotation. In South America the sources of primary inoculum are different plant debris as well as, weeds. The weeds with summer growth habits, that remain dry during winter and early spring when wheat flowering/heading, have an epidemiological role in production systems in Argentina. Knowing the different sources and the amount of primary inoculum present in the field is a crucial factor for the management of the FHB. Therefore the aim of this work was to analyze, the dynamics and survival of F. graminearum on the different sources of inoculum based on conventional and molecular methods.Plant debris of bread and durum wheat, rye, barley, tritordio (Triticum x Hordeum), maize and soybean were sampled of naturally infected field plots. Initially, the presence of F. graminearum was evaluated on PDA media supplemented with pentachloronitrobenzene (PCNB 75% wettable powder) and antibiotics. The colonies of the pathogen were identified based on their morphological and cultural characteristics. To perform the PCR identification, DNA was isolated by a CTAB method modified with a high EDTA concentration and successive steps of precipitations, which were aimed at reducing PCR inhibitors. A 280 bp fragment specie-specific of F. graminearum was amplified by means of a pair of primers (Fg16N) using as template DNA isolated from the different samples. In all plant debris taken during 2010/11, when analyzed by PCR standard, the pathogen could be detected indirectly in an agarose gel 1.5%. By conventional methods, F. graminearum was found in all samples. The results obtained were variable in the time showing a considerable inoculum reduction within the winter interval. The tritordio debris presented the highest number of primary inoculum, while barley and soybean presented the lowest.Considering the results observed and their importance, we are currently developing a real time PCR protocol in order to augment the sensibility of the reaction. The aim is to be able to more accurately quantify the dynamics of the Fusarium graminearum inoculum, since such a tool will allow us to perform epidemiological studies aimed at establishing the importance of the different sources of inoculums.