XVI International Botanical Congess

The invasion of a host by rust and powdery mildew fungi requires the development of specialized infectional structures from the germinating spore. Various kinds of deviations in morphology of infectional structures of pathogen from normal, genetically conditioned pathway of development could be observed on the resistant varieties. Morphometric studies of E.graminis and P.graminis development on prepenetration stage and on reproductive stage have revealed positive correlation of normal primary infection structures and amount of fungus pustul formation. Our experiments showed that variety can be considered resistant to penetration of pathogen when less than 30% of normal infectional structures are formed. Hence, it is possible to use the relative amount of normal primary infectional structures of fungus as an index of resistance of the plants to penetration of causative agents of infectional diseases during obligate parasitism on cereals. Supported by RFFI, project N 96-04-48581, N 96-15-97778.