2018 ASHS Annual Conference

Perennial ryegrass (Lolium perenne, L.) is an important cool-season turfgrass species which is widely cultivated around the world. Perennial ryegrass is very fast to establish, which makes it very favorable for ornamental use. Crown rust (Puccinia coronata Corda f. sp. lolii) is one of the most devastating fungal diseases of perennial ryegrass, causing significant economic losses worldwide. Rust infections can be controlled by fungicide chemicals, but the approach is pollutive and expensive. However, breeding rust resistance cultivars of perennial ryegrass may provide a better solution. We have isolated 16 dwarf mutants from an ethyl methanesulfonate (EMS)- and gamma-treated population of “Fiesta 4” cultivar of perennial ryegrass. Under a field condition, we have observed that the wildtype “Fiesta 4” plants were severely infected by rust with an average score of 4.9 (a score of “5” indicates all leaves were infected by rust while “0” is indicative of no infection). Meanwhile, under the same condition, some mutant plant lines scored 0 on average, and the others had an average score of 1-3. It appears that the rust resistance is related to the degrees of dwarfness of the mutant lines. We are currently further evaluating a small number of the rust resistant mutant lines under growth chamber conditions. The mutants identified from this study may provide valuable resources for understanding of the mechanism of rust resistance observed in our dwarf mutants and also for breeding of novel rust resistant perennial ryegrass cultivars.