ATYPICAL, GREEN LEAF BLOTCH LESIONS ON BARLEY LEAVES INFECTED BY RHYNCHOSPORIUM-SECALIS (OUD) DAVIS

Atypical, green leaf blotch lesions were observed on senescent leaves in winter barley crops and sometimes developed on barley leaves inocul ated with conidia of Rhynchosporium secalis in a glasshouse. Similar a typical lesions were induced on barley leaves inoculated with conidia of R. secalis and then grown in controlled environments at 10 degrees C and 80% rh. Microscopic examination of green lesions from these thre e sources showed that hyphae of R. secalis had colonized the subsidiar y cells of stomata so that guard cells were swollen, resulting in enla rged stomatal pores. Additionally, spore initials had erupted through the leaf cuticle of some leaves. Most spore initials did not develop i nto mature conidia when leaves were incubated for 24 h at 20 degrees C in a closed chamber at 100% rh, but aerial hyphae grew out from the l eaf surface. Thus, atypical green lesions produced a much smaller numb er of spores than typical leaf blotch lesions.