VIEW ARTICLE

Genetics

Genetics of Pathogenicity in Puccinia coronata: Pathogenic Specialization at the Host Genus Level. N. Eshed, Instructor, Department of Plant Pathology and Microbiology, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel; A. Dinoor, associate professor, Department of Plant Pathology and Microbiology, Faculty of Agriculture, The Hebrew University of Jerusalem, Rehovot, Israel. Phytopathology 70:1042-1046. Accepted for publication 14 May 1980. Copyright 1980 The American Phytopathological Society. DOI: 10.1094/Phyto-70-1042.

Physiologic forms of Puccinia coronata in Israel were isolated and characterized as a prelude to genetical studies of their pathogenicity. Seven forms were identified from representative species of grass genera recognized as primary hosts for crown rust forms elsewhere. Four additional forms were isolated from oats. The host range of these 11 forms on the original eight gramineous species was determined and found to be overlapping to a greater or lesser degree. The host range of single-spore cultures of certain forms isolated from grasses in Israel was wider and exhibited greater overlap than the host ranges combined from representatives of the same forms elsewhere in the world. This is a clear reflection of the dynamic host-parasite relationships existing in an area where hosts and parasites have co-evolved. The forms could be distinguished from each other when their main hosts were used as differentials. Apart from the fact that races are identified on crop plant cultivars and forms are identified on plant genera, there was no difference between races and forms. Isolates from one host were as different from each other as from isolates from other hosts. Strict specificity could not be detected by applying the criterion that a species is susceptible when some individuals in it are susceptible. The simultaneous inoculation technique revealed plants among the individuals within the host species that could serve as classical, very specific differential hosts. On the other hand, this method also revealed reliable common hosts that were useful for the propagation of hybrid rusts.