Browsing by Author "Greatens, Nicholas"
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Item Aecial and telial host specificity of Puccinia coronata var. coronata, a Eurasian crown rust fungus of two highly invasive wetland species in North America(Plant Disease, 2023-08) Greatens, Nicholas; Jin, Yue; Pablo, D. OliveraThe Eurasian crown rust fungus Puccinia coronata var. coronata (Pcc) was recently reported in North America and is widespread across the Midwest and Northeast United States. Pcc is a close relative of major pathogens of oats, barley, and turfgrasses. It infects two highly invasive wetland plants, glossy buckthorn (Frangula alnus) and reed canarygrass (Phalaris arundinacea) and could be useful as an augmentative biological control agent. We conducted large greenhouse trials to assess the host specificity of Pcc and determine any threat to cultivated cereals, turfgrasses, or native North American species. A total of 1,830 accessions of cereal crop species and 783 accessions of 110 other gramineous species were evaluated. Young plants were first inoculated with a composite uredinial inoculum derived from aecia. Accessions showing sporulation were further tested with pure urediniospore isolates. Sixteen potential aecial hosts in the families Rhamnaceae and Elaeagnaceae were tested for susceptibility through inoculation with germinating teliospores. Thirteen grass species within five genera in the tribe Poeae, Apera, Calamagrostis, Lamarckia, Phalaris and Puccinellia, and four species in Rhamnaceae, Frangula alnus, F. californica, F. caroliniana and Rhamnus lanceolata, were found to be susceptible to Pcc, with some species native to North America. All assessed crop species and turfgrasses were resistant. Limited sporulation, however, was observed on some resistant species within Poeae and four other tribes, Brachypodieae, Bromeae, Meliceae, and Triticeae. Among these species are oats, barley, and Brachypodium distachyon, suggesting the possible use of Pcc in studies of non-host resistance.Item Puccinia coronata var. coronata , a Crown Rust Pathogen of Two Highly Invasive Species, Is Detected Across the Midwest and Northeastern United States(Plant Disease, 2023-07) Greatens, Nicholas; Klejeski, Nick; Szabo, Les J; Jin, Yue; Olivera, Pablo DPuccinia coronata var. coronata (Pcc) causes crown rust disease of glossy buckthorn (Frangula alnus) and reed canarygrass (Phalaris arundinacea), two highly invasive plant species in North America. Pcc is closely related to major pathogens of cereals, turfgrasses, and forage grasses. It occurs throughout Europe but was first recorded in North America in 2013. Where its hosts co-occur, such as in wetlands in the Twin Cities metro area in Minnesota, we have observed Pcc causing significant infection that results in defoliation and fruit loss in glossy buckthorns and premature leaf senescence in reed canarygrass. In this research, we mapped the distribution of this likely recently introduced rust fungus and provided a description of disease signs and symptoms and pathogen morphology. Samples were acquired by two primary means: by surveys in Minnesota and by correspondence with users of iNaturalist.org, a social network for nature enthusiasts and community scientists. With an Oxford Nanopore MinION, we sequenced two to four loci from 22 samples across 13 states and identified samples by phylogenetic analysis and sequence similarity. Notably, four pure isolates appear to have intragenomic variation of the ITS region. We found that Pcc is present throughout the range of glossy buckthorn in the eastern United States. In Minnesota, Pcc is not common outside the range of glossy buckthorn despite the presence of susceptible grass hosts.Item Studies on Puccinia coronata var. coronata and other recently observed rust fungi in Minnesota(2023-07) Greatens, NicholasIn the spring of 2017, a prolific crown rust fungus was observed on the highly invasive glossy buckthorn (Frangula alnus) around Central Park, Roseville, MN. Field observation and greenhouse studies established the grass host as another invasive species, reed canarygrass (Phalaris arundinacea), and sequencing identified the rust fungus as Puccinia coronata var. coronata sensu stricto (Pcc), a taxon of likely Eurasian origin not previously known in Minnesota. Curiously, this new pathogen appeared to have a desirable effect locally, strongly affecting only two invasive plant species. In a research project that began in 2019 and was funded in 2020 by the Minnesota Invasive Terrestrial Plants and Pests Center, we pursued three goals, which correspond to the first three chapters of this dissertation: 1) to determine the distribution of Pcc in Minnesota and North America; 2) to assess its host specificity on potential buckthorn and grass hosts; and 3) to evaluate its potential as an augmentative biological control agent of one or both of its invasive hosts. We report Pcc across the range of glossy buckthorn in the Midwest and Northeastern U.S. but find that it is absent on susceptible reed canarygrass outside the range of glossy buckthorn within Minnesota. Cereal crop and turfgrass species were highly resistant to Pcc, but other grass and buckthorn species were susceptible, including some native North American species. In greenhouse trials, Pcc significantly reduced the height and biomass of both reed canarygrass and glossy buckthorn, supporting its use as a possible biological control agent of one or both of its hosts, although non-target effects and deployment strategies would require further consideration. Chapter four describes a similarly designed study around another crown rust fungus, Puccinia digitaticoronata, which we confirm for the first time in North America. We investigate its relation to other crown rust fungi and its pathogenicity on grass and buckthorn species. In greenhouse studies, the popular turfgrass species Kentucky bluegrass (Poa pratensis) is broadly susceptible, along with numerous other native and weedy Poa spp. Common buckthorn (Rhamnus cathartica), another widespread invasive species, is an aecial host of the rust fungus and likely facilitates its sexual cycle locally. Chapter five combines the results of two small projects published as plant disease notes: first reports of Puccinia glechomatis, a rust of creeping Charlie (Glechoma hederacea) in Minnesota and of a Puccinia sp. causing rust of lemongrass in Minnesota.