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ARS Home » Northeast Area » Frederick, Maryland » Foreign Disease-Weed Science Research » Research » Publications at this Location » Publication #420232
Research Project: Developing Genomic and Biological Resources to Characterize, Diagnose and Detect Emerging and Invasive Vectored Bacterial and Viral Plant Pathogens for Safeguarding U.S. Agriculture

Location: Foreign Disease-Weed Science Research

Title: Seed gall nematodes and their association with toxigenic bacteria

Author
item MURRAY, TIMOTHY - Washington State University
item DAMASO DUARTE, AIDA - Animal And Plant Health Inspection Service (APHIS)
item Luster, Douglas
item MCKIRDY, SIMON - Murdoch University
item Rogers, Elizabeth
item SCHROEDER, BRENDA - University Of Idaho
item SUBBOTIN, SERGI - California Department Of Food And Agriculture

Submitted to: Annual Review of Phytopathology
Publication Type: Review Article
Publication Acceptance Date: 1/17/2025
Publication Date: 5/21/2025
Citation: Murray, T.D., Damaso Duarte, A., Luster, D.G., Mckirdy, S., Rogers, E.E., Schroeder, B.K., Subbotin, S.A. 2025. Seed gall nematodes and their association with toxigenic bacteria. Annual Review of Phytopathology. https://doi.org/10.1146/annurev-phyto-121823-033153.
DOI: https://doi.org/10.1146/annurev-phyto-121823-033153

Interpretive Summary: Annual ryegrass toxicity (ARGT) is a disease which arises from interaction of a bacterium that produces a toxin, a nematode that grows in developing grass seeds, and the grasses that host both. This interaction results in grass and hay containing enough toxin to fatally poison grazing livestock like sheep, cows, and horses. ARGT has caused significant livestock losses and economic damage in Australia as well as sporadic poisonings in South Africa; to date, it has not been found in the U.S. The bacterium, Rathayibacter toxicus, has been listed as a Select Agent by the US Dept. of Agriculture. This review covers newly identified species of Rathayibacters and new interactions between these bacteria and seed gall nematodes. It also summarizes methods of detecting and identifying Rathayibacters and seed gall nematodes and control measures found to be effective in Australia. This information is important for assessing the risk of ARGT to U.S. livestock and grass seed production and for detection, eradication, and management should ARGT be found in the U.S.

Technical Abstract: Gall-forming nematodes are widespread in nature but rarely of economic importance in modern agriculture. Three seed gall nematodes, Anguina agrostis, A. funesta, and A. tritici are potentially invasive and quarantine pests in several countries due to their economic impact. Anguina tritici and A. agrostis are pests of small grains and turfgrasses, respectively, and cause direct damage to their hosts. However, A. funesta is of concern because it is the primary vector of Rathayibacter toxicus, a Gram-positive, coryneform bacterium that produces a tunicamycin toxin in the heads of several grasses including ryegrass, that results in the death of grazing animals when consumed. This syndrome, known as Annual Ryegrass Toxicity, has caused significant economic damage in Australia; as a result, Rathayibacter toxicus has been listed by USDA APHIS as a Plant Pathogen Select Agent in the U.S. Research over the past 40 years has revealed several new Rathayibacter species and nematode associations, as well as a greater understanding of toxin production among other members of the genus. This review focuses largely on new information about R. toxicus, other Rathayibacter species and their nematode vectors, providing important information for pathogen risk assessment, surveillance and management of ARGT.