INFIVE   05416
Unidad Ejecutora - UE
congresos y reuniones científicas
Recent progress in the characterization of the Pyrenophora tritici-repentis-wheat interaction in Argentina.
Congreso; International Congress of Postharvest Pathology; 2011
Tan spot of wheat is caused by Pyrenophora tritici-repentis and is often a major constraint in argentinian wheat growing areas. The variable nature of the pathogen offers challenges to breed for resistance and to develop available cultivars effectively. Genetic diversity among 89 isolates of the tan spot of wheat pathogen P. tritici-repentis, from 14 geographically distinct regions of the wheat argentinian area of Argentina, was evaluated by RAPD markers and virulence characters on two differential genotypes (BIOINTA 1001 and Buck Mataco). RAPD analysis grouped the isolates into 7 different groups (43 % similarity). Group 1 (greatest) included all isolates from ecological region III (Entre Ríos Province); Group V involves all isolates from Alberti locality, and Group VII, with only three isolates, showed as the most different one including Bragado and Los Hornos localieties isolates. Differences between severity and lesion type were detected. ClN was the most common type showed (55%), following by Cl (13%) and no symptoms (3%). A same isolated induced low or high severity dependent on the inoculated wheat cultivar. Others produced always high or low severity on both cvs. No association between virulence phenotypes and molecular profiles was observed. Morphocultural and virulence features were employed to analyse 155 Pyrenophora tritici-repentis isolates obtained from wheat grown in distinct ecological areas in Argentina. The P. t and molecular diversityritici-repentis isolates used in this study were collected from 23 regions and 13 wheat cultivars of Argentina from 2004 to 2007. Variations in colony and conidial morphology were observed among isolates with no inclination to either host or geographical origin of the isolates. UPGMA cluster analysis of morphocultural characteristics delineated the isolates into distinct clusters. The dendrogram based on Jaccard?s coefficient showed 44 morphotypes encompassing isolates that were obtained from different localities and hosts. Pathogenicity tests performed on a set of 8 differential wheat genotypes showed the presence of physiological specialization in 33 isolates of P. tritici-repentis. No association between morphocultural or virulence phenotypes and geographical origin of the isolates was observed. The isolates tested appeared in different groups and most of the isolates which shared the highest similarity coefficient were collected from different regions and hosts.