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Genetics

Genetics of Pathogenicity in Puccinia coronata: The Host Range Among Grasses. 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 71:156-163. Accepted for publication 23 June 1980. Copyright 1981 The American Phytopathological Society. DOI: 10.1094/Phyto-71-156.

The host range of eight forms of Puccinia coronata Cda. among 106 grass species in Israel was determined at the seedling stage. A few species were not susceptible to any of these cultures. Most species were susceptible to more than one culture and many were to all eight cultures. Many common hosts were found, which is very important for genetical studies and for the development of hybrid rust in the field. Grasses vary in responses to the various forms of the rust pathogen; some individuals within a species being susceptible to one form and others to another form of P. coronata. The simultaneous inoculation technique was very useful for identifying real common hosts. Host range for two forms was also determined at the adult stage. Many hosts reacted the same way at both stages. Some species, however, differed at the two stages, indicating some difficulties for further studies, but also suggesting the possible importance in nature of disengagement between the reactions at both stages. Several new host species and even genera were found. The host range of P. coronata in Israel was found to be much wider than in all previous studies combined. Host ranges of the forms differed no more widely than did host ranges of races within one form. The use of host range of forms as an aid in the taxonomy of their hosts was invalid for P. coronata because of its very wide host range which represents all the tribes of the Festucoideae. It is postulated that the chance of the host’s exposure to the pathogens’ attack is as important in the evolution of host range as host phylogenetic relationships. The long-term association of hosts and parasites brought about this adaptation.