Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2001
Publication Date: 9/30/2001
Interpretive Summary: In the Pacific Northwest region of the USA, cool-season grasses grown for seed can be severely damaged by Puccinia graminis subsp. graminicola, causal agent of stem rust. To effectively devise management strategies, including development of host genetic resistance, it is necessary to know whether there are subgroups within the pathogen population that differ in the host species they can infect. In this study, spores of the pathogen collected from each of the two major grass hosts were inoculated onto a range of host species. The rust spores from perennial ryegrass could infect more species of grass than could the spores from tall fescue. However, spores from perennial ryegrass could not infect tall fescue. Spores from the two sources differed also in size and in development rate of infections they caused. The results demonstrate that there are distinct subgroups within the grass stem rust species that differ in host range. This information will be useful in developing genetic host resistance to stem rust and in devising agronomic management strategies for the disease.
Technical Abstract: Urediniospores of Puccinia graminis subsp. graminicola, collected either from perennial ryegrass (Lolium perenne) or tall fescue (Festuca arundinacea), were tested for host range among selected grasses and cereals. Under greenhouse conditions, the inoculum from perennial ryegrass could also infect Dactylis glomerata, Lolium multiflorum, Poa pratensis, and Festuca rubra subspp. rubra and commutata; it caused only limited infection (low incidence and/or infection type) on tall fescue (F. arundinacea), F. ovina subsp. hirtula, Poa annua, Hordeum vulgare, and Secale cereale. The inoculum from tall fescue had a host range that included itself, D. glomerata, L. perenne, L. multiflorum, and F. rubra subspp. rubra and commutata; there was no sign of infection on Poa species or the cereal grains tested (Triticum aestivum, Avena sativa, S. cereale, H. vulgare). The two urediniospore populations differed also in latent period on most of their common hosts. There was a small, but statistically significant, difference in spore size. No recommendation is made for separate taxonomic status of populations from tall fescue and perennial ryegrass, but the adaptation of each to its own host should be considered when devising management strategies and studying host genetic resistance.