Characterization of Fusarium graminearum isolates in relation to their enzymatic activities as estimation of aggressiveness to evaluate the differential behavior of wheat genotypes to fusariosis

ORTEGA LEONEL; KIKOT, GISELE E; ASTORECA L ANDREA; ALBERIONE ENRIQUE; ALCONADA MAGLIANO, TERESA M.

Mar del Plata

Congreso; 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, si; 2012

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. Hence, the importance of characterizing the enzymatic activities of the fungus in relation to the establishment of infection and the changes observed in the structure and composition of infected grains. The aim of this work was to select F. graminearum isolates potentially aggressive according to the in vitro enzymatic production (proteases and polygalacturonases). In this work, 155 Fusarium spp isolates were obtained from samples of wheat grains belong Pampas region from 6 locations distributed in Buenos Aires, Entre Ríos, Santa Fe and Córboba provinces during 2010 and 2011 wheat-growing season. The identification of species from monosporic isolates was carried out by morphological and molecular characterization using species-specific PCR-based assays. From these monosporic isolates, eight were selected according to presence and abundance of F. graminearum and analysed for enzymatic production.The enzymatic activity (proteases and polygalacturonases) was assayed in liquid culture media saline with the addition of specific inducers 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 during incubation time, diverses F. graminearum isolates for inoculation on wheat were selected. These inoculum could be highly infective, and therefore used for the detection of new sources of resistance among a large number of genotypes of wheat through further patogenicity test to be carry out in the experimental station of EEA-INTA (Marcos Juarez).