Detection of race-specific resistance against Puccinia coronata f. sp. avenae in Brachypodium species

Authors: OMIDVAR, VAHID - University Of Minnesota; DUGYALA, SHESHANKA - University Of Minnesota; LI, FENG - University Of Minnesota; ROTTSCHAEFER, SUSAN - University Of Minnesota; MILLER, MARISA - University Of Minnesota; AYLIFFE, MICHAEL - Commonwealth Scientific And Industrial Research Organisation (CSIRO); MOSCOU, MATTHEW - Sainsbury Laboratory; Kianian, Shahryar; FIGUEROA, MELANIA - University Of Minnesota

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/20/2018
Publication Date: 12/1/2018
Citation: Omidvar, V., Dugyala, S., Li, F., Rottschaefer, S.M., Miller, M.E., Ayliffe, M.A., Moscou, M.J., Kianian, S., Figueroa, M. 2018. Detection of race-specific resistance against Puccinia coronata f. sp. avenae in Brachypodium species. Phytopathology. 108(12):1443-1454. https://doi.org/10.1094/phyto-03-18-0084-r.
DOI: https://doi.org/10.1094/phyto-03-18-0084-r

Interpretive Summary: Oat crown rust caused by the obligate biotrophic rust fungus Puccinia coronata f. sp. avenae is the most widespread and damaging foliar disease of cultivated oat (Avena sativa L.). Symptoms of crown rust infection manifest in the foliar tissue, causing a reduction in the plant photosynthetic capacity and thus affecting grain size and quality. A method of choice to control this devastating disease is the use of genetic resistance, and therefore increasing our understanding of plant immunity can translate into novel crop protection strategies. The need for more durable resistance against oat crown rust prompts attempts to find potential genetic sources of immunity and advance our understanding of the molecular basis of rust recognition. Non-host systems offer an untapped source of potential resistance. In this study, we examined the interaction between the rust fungus and Brachypodium species. Our study shows that B. distachyon and B. hybridum can support colonization of the crown rust fungus, but not fungal sporulation. These findings provide the framework to conduct genetic inheritance studies to discover factors dictating the recognition of P. coronata f. sp. avenae in B. distachyon and B. hybridum and governing intermediate oat crown rust susceptibility.

Technical Abstract: Oat crown rust caused by Puccinia coronata f. sp. avenae, is the most destructive foliar disease of cultivated oat. Characterization of genetic factors controlling resistance responses to Puccinia coronata f. sp. avenae in non-host species could provide new resources for developing disease protection strategies in oat. We examined symptom development and fungal colonization levels of a collection of B. distachyon and B. hybridum accession infected with three North American P. coronata f. sp. avenae isolates. Our results demonstrated that resistance phenotypes are dependent on both host and pathogen genotypes, indicating a role for race-specific responses in these interactions. These responses were independent of the accumulation of reactive oxygen species. Expression analysis of several defense-related genes suggest that salicylic acid and ethylene-mediated signaling, but not jasmonic acid, are components of resistance reaction to P. coronata f. sp. avenae. Our findings suggest that effector-triggered immunity contributes to non-host resistance to P. coronata f. sp. avenae in Brachypodium species and provide the basis to conduct a genetic inheritance study to examine this hypothesis.