Changes of virulence in populations of Mycosphaerella graminicola fuck schroether on weath

摘要

Virulence variations in two populations (P_1 and P_3) of Mycosphaerella graminicola were studied by inoculation of sub-isolates-of several generations on differential wheat cultivars carrying Bobwhite "S' germplasm. Population P_1 and P_3 were isolated from wheat lines LAJ 3139 and LPI/Bbw "S", respectively, and the sub-isolates within each population obtained by isolation and single-spore culture from plants of the correspondant line. Plants of the differential cultivars were inoculated in the greenhouse and the amount of disease was estimated as the.percentage, of leaf surface covered by pycnidia 24 days after inoculation. Generally, virulence increased in succesive generations, this increase depending on sub-isolate and wheat cultivar. Isolates of the two populations also showed morphological variations between generations. The changes in virulence observed indicate vulnerability of the Bobwhite "S" germplasm carried by resistant wheat cultivars.