Resumen de Identificación de Pseudocercosporella herpotrichoides (Fron) Deighton, agente causal de la mancha ocular del trigo de la zona sur de Chile
Near the end of the 1994/95 season, in different localities of the IXth Region, Chile, a high incidence of lodged wheat (Triticum aestivum L.) fields were observed, with up to 70% of some fields having white spikes, rotten and broken stems at the base. The microscopic observation of affected tissue of wheat cvs. SNA 400 and Francia, collected near Traiguén (IX Region), as well as the isolates obtained in agar-water + streptomycin sulfate permitted the observation of slow-growing, green-grayish colonies with smooth borders and the presence of needle-like, straight or curved, hyaline conidia, with 4 to 6-septated spores, occasionally 7 septated spores, and with a length of 40.9-81.9 µ m and diameter of 1.6-2.3 µ m. Pathogenicity tests carried out with the isolated organism, by inoculating 12-day-old wheat seedlings of cv. Otto Baer grown in sterile soil, and inoculated at the base of the stem, resulted in the development of brown oval lesions at the inoculated point in contrast to the controls that did not develop symptoms. The examination of the internal sheaths of affected tissue, previously stained, revealed the development of "infection plaques" characteristic of Pseudocercosporella herpotrichoides as well as mucilage collars at the hyphae infection sites. The results permitted the identification of P. herpotrichoides (Fron.) Deighton, as the causal agent of wheat eyespot as being responsible for the symptoms. This is the first report of the presence of P. herpotrichoides affecting wheat in Chile.
