Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/16/2011
Publication Date: 11/14/2011
Citation: Beirn, L., Moy, M., Meyer, W., Clarke, B., Crouch, J. 2011. Molecular analysis of turfgrass rusts reveals the widespread distribution of Puccinia coronata as a pathogen of Kentucky Bluegrass in the United States. Plant Disease. 95:1547-1557. Interpretive Summary: The diseases of turfgrass on golf courses and lawns cause millions of dollars of damage each year. These diseases are caused by fungi including several similar looking rust fungi. Knowing exactly which rust fungi is present is essential for treating the disease. In this research samples of turfgrasse were tested for the presence of rust fungi using DNA sequences. Three rust fungi were found to be associated with different cultivars of Kentucky bluegrass. For the first time a rapid DNA-based diagnostic test was developed to accurately identify each rust species. This research will be used by plant pathologists to determine the cause of turfgrass diseases and thus provide effective treatment of the disease.
Technical Abstract: Over the past ten years, rust diseases have become increasingly prevalent'on certain cultivars of Kentucky bluegrass. This pattern suggests that new'races or new species of rust fungi may have emerged. To test this'hypothesis, 66 samples of turfgrass rust fungi collected from across the'U.S. were evaluated using rDNA internal transcribed spacer region (ITS) 'sequence data. Phylogenetic analysis revealed three species: Puccinia'coronata, P. graminis, and P. striiformis, comprising 67%, 28%, and 5% of'the samples, respectively. P. coronata was frequently found in association'with Kentucky bluegrass, a host/pathogen relationship that has not been'previously reported. Comparison of molecular analyses with the use of'standard field identification techniques – host association and pustule'pigmentation – showed that 58% of the Kentucky bluegrass samples would'have been incorrectly diagnosed using non-molecular criteria. To avoid such'misidentifications, a real-time PCR diagnostic protocol was developed for'turfgrass-associated P. graminis, P. coronata, and P. striiformis using ITS'sequence data. Accurate, reproducible, species-specific identifications'were made using as few as 50-150 urediniospores, even in mixed infections.' This study represents the first DNA-based evaluation of turfgrass rust'fungi and provides a quick and reliable sequence-based protocol as an'alternative to error-prone field-based identification techniques.