Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

First report of natural infection by 'Candidatus Liberibacter solanacearum' in bittersweet nightshade (Solanum dulcamara) in the Columbia basin of Eastern Oregon.

Abstract

Potatoes are a major crop in the Columbia Basin of Oregon and Washington, representing an annual farm gate value of almost $750 million. Zebra chip disease (ZC), a new and economically important disease of potato, was first reported in Oregon and Washington in 2011. The disease is caused by the bacterium 'Candidatus Liberibacter solanacearum' (Lso, also referred to as 'Candidatus L. psyllaurous'), which is vectored by the potato psyllid (Bactericera cockerelli). The perennial weed, bittersweet nightshade (Solanum dulcamara), is a year-round host of the potato psyllid and is also a suspected host of Lso. However, little is known about the role of this weed in ZC epidemiology. Naturally occurring bittersweet nightshade plants (n=21) were sampled at 6 different locations near Hermiston, Oregon, between May and October in 2012. These plants exhibited several symptoms associated with Lso, ranging from asymptomatic to slight purpling, chlorosis, or scorching of the foliage. Sequence analysis of 16S rDNA and outer membrane protein genes confirmed the identity of the pathogen. The results showed that bittersweet nightshade may be an important annual source of Lso in the region, particularly since it serves as a host for the potato psyllid. This is thought to be the first report of Lso causing natural infections in S. dulcamara in the United States.