Characterization of F. graminearum isolates in relation to their enzymatic activities to evaluate the differential behavior of wheat genotypes to Fusariosis

ORTEGA LEONEL; KIKOT GISELE ; ALBEREONE ENRIQUE ; ASTORECA ANDREA; ALCONADA TERESA

Mar del Plata

Congreso; VIII CONGRESO ARGENTINO DE MICROBIOLOGÍA GENERAL; 2012

SAMIGE

Fusarium Head Blight (FHB) on wheat is one of the most devastating diseases, causes by several Fusarium species being in Argentina, F. graminearum (Schwabe) anamorph of Gibberella zeae (Schw.) Petch, the dominant fungal agent. This disease causes both, significant yield losses and quality technology of grain and also high risk for human and animal health by associated mycotoxin action. To colonize of the grain occurs; the fungus produces extracellular enzymes that degrade the plant cell wall at an early stage which are also responsible for the degradation of grains proteins, altering the quality parameters of raw material. Different studies indicate that the secretion of enzymes in vitro is a good indicator of the kind of enzymes that a pathogen could produce in relation to disease. For this, the importance of characterizing the enzymatic activities of the fungus in the establishment of infection and in these structural changes that causes in the composition of infected grains. The aim of this work was to select F. graminearum isolates potentially aggressive according to their in vitro enzymatic production (proteases and polygalacturonases). Out of 182 Fusarium isolates obtained from samples of wheat grains from Pampas region from 10 locations distributed in Buenos Aires, Entre Ríos, Santa Fe and Córboba provinces harvested in 2010 and 2011 wheat-growing seasons, eight isolates were selected according to their occurrence. The identification of species from monosporic isolates was carried out by morphological and molecular characterization using species-specific PCR-based assays. The enzymatic activity (proteases and polygalacturonases) was assayed in liquid culture media saline with and without the addition of specific inducers as appropriate and incubated under agitation (150 rpm) at 28 °C in darkness for 10 days. Samples were taken every day and the supernatant stored at -20 °C until use. Proteases and polygalacturonases activity were determined using 0.5% casein and 0.1% polygalacturonic acid as substrate, respectively. From the enzymatic curves obtained, a F. graminearum isolate for inoculation was selected in this study. This F. graminearum inoculum proved to be highly infective to detect new sources of resistance among a large number of lines and cultivars of wheat through further patogenicity test to be carry out in the experimental station of EEA-INTA (Marcos Juarez).