DEVELOPMENT OF PSEUDOCERCOSPORELLA-HERPOTRICHOIDES (FRON) DEIGHTON VAR HERPOTRICHOIDES AND VAR ACUFORMIS ON WHEAT PLANTS MEASURED BY ELISA

Using the ELISA method, the development of Pseudocercosporella herpotr ichoides var. herpotrichoides and var. acuformis in a susceptible cult ivar of winter wheat was compared under controlled and field condition s. In the greenhouse, var. acuformis grew less vigorously, was slower in penetrating the coleoptile and the successive leaf sheaths and in c olonizing the stem tissue than var. herpotrichoides. In the field, the se differences were confirmed on the last leaf sheaths and the stem. A t ripening stage, however, identical ELISA values were measured for bo th varieties. Moreover, a significant variation was observed between t he individual isolates of each variety. Comparison of the effect of bo th varieties of P. herpotrichoides on 20 wheat cultivars characterized by different resistance levels showed significant interactions. The c ultivars carrying the Pch-1 gene always remained the less diseased gen otypes. In general, var. acuformis developed less antigen in the culti vars than var. herpotrichoides. It is concluded, that in tests for res istance to P. herpotrichoides mixtures of many highly pathogenic isola tes of both fungus varieties should be used. Less complex mixtures or single isolates may result in wrong estimates of resistance.