Link to home

Genetic characterization of Rathayibacter spp. present in the United States of America (USA).

Brenda Schroeder: University of Idaho

<div><span><em>Rathayibacter toxicus</em></span><span> is a Gram-positive plant pathogen that infects <em>Lolium rigidum</em> and other grass species in Australia; it is also a USDA APHIS–listed Select Agent in the USA because it produces corynetoxins <em>in planta</em> that are fatal to grazing animals. None of the other six validly described <em>Rathayibacter</em> species are known to produce toxin, but anecdotal reports of animal deaths raise concerns that a toxigenic <em>Rathayibacter</em> sp. already may be present in the USA. Of the seven species<em>,</em> <em>R. rathayi </em>and <em>R. agropyri</em> are present in the US. Knowing which other species of <em>Rathayibacter</em> are present is important for developing detection and discrimination methods to help prevent introduction and establishment of <em>R. toxicus</em> in the USA. The goal of this study was to characterize 114 <em>Rathayibacter</em> strains isolated from various grass species collected in the Pacific Northwest US since 2013. To do so, the </span>16S rRNA gene and four housekeeping genes (<em>rpoB</em>, <em>gyrB</em>, <em>recA</em>, and <em>ppk</em>) were amplified and sequenced from all strains and seven reference isolates. <span>Phylogenetic analysis of the sequences suggests that there are several undescribed <em>Rathayibacter</em> species present in the USA and there is significant within species diversity. One clade of strains originating in the USA are closely related to the toxigenic strain <em>Rathayibacter</em> sp. EV isolated from <em>Ehrharta villosa</em> var. <em>villosa</em> in South Africa, suggesting that strains present in the USA may be capable of toxin production as well. </span></div>