Aecial and telial host specificity of Puccinia digitaticoronata, a new crown rust fungus of Kentucky bluegrass in North America

Authors: GREATENS, NICHOLAS - University Of Minnesota; MILLER, KARL - University Of Minnesota; WATKINS, ERIC - University Of Minnesota; Jin, Yue; OLIVERA, PABLO - University Of Minnesota

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2023
Publication Date: N/A
Citation: N/A
DOI: https://doi.org/10.1094/PDIS-04-23-0776-RE

Interpretive Summary: In North America, crown rust has emerged as a common disease of Kentucky Bluegrass (Poa pratensis) and may cause significant damage. After observing crown rust on plants of Poa spp. in the Twin Cities, MN and aecia on three East Asian buckthorns (Rhamnus crenata, R. davurica, and R. japonica) in North Dakota, we analyzed DNA sequences collected from the field and determined that the rust pathogen is Puccinia digitaticoronata. Previous studies showed that a rust fungus of a different clade was the cause of crown rust of Kentucky bluegrass. This study revealed there are two two different crown rust fungi causing crown rust in Kentucky bluegrass in North America. To assess the pathogenicity on potential telial and aecial hosts, 789 accessions of 98 gramineous species were evaluated for rust reaction. Eleven species of plants in families of Rhamnaceae and Elaeagnaceae were evaluated for potential aecial hosts by inoculation with germinating teliospores. Cereal crops and turfgrasses other than Poa were highly resistant. Twenty-two of the tested gramineous species were susceptible, including 12 Poa spp., and several other native and introduced species in North America. In addition to the three East Asian buckthorns, the native R. lanceolata and the widespread invasive common buckthorn (R. cathartica) are susceptible and may serve as the aecial hosts of the rust fungus. This research will be useful for plant pathologists, horticulturists, ecologists and gardeners in disease identification and management.

Technical Abstract: In North America, crown rust has emerged as a common disease of Kentucky Bluegrass (Poa pratensis) and may cause significant damage. After observing crown rust on plants of Poa spp. in the Twin Cities, MN and aecia on three East Asian buckthorns (Rhamnus crenata, R. davurica, and R. japonica) in North Dakota, we sequenced one to four loci of nine samples for identification and to determine their placement within the Puccinia series Coronata. Sequnce analysis identified Puccinia digitaticoronata to be the rust pathogen on these samples. This crown rust fungus is known only in northeast China reported recently. Previous studies showed that a pathogen in the P. coronata var. avenae f. sp. avenae clade was the cause of crown rust of Kentucky bluegrass. Thus, two different crown rust fungi cause disease in Kentucky bluegrass in North America. To assess the pathogenicity on potential telial and aecial hosts, 789 accessions of 98 gramineous species were evaluated with two inocula: one field collection and one pure isolate. Eleven species in Rhamnaceae and Elaeagnaceae were evaluated for potential aecial hosts by inoculation with germinating teliospores. Cereal crops and turfgrasses other than Poa were highly resistant. Twenty-two of the tested gramineous species were susceptible, including 12 Poa spp., and several other native and introduced species in North America. In addition to the three East Asian buckthorns, the native R. lanceolata and the widespread invasive common buckthorn (R. cathartica) are susceptible and may serve as the aecial hosts of the rust fungus.