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Title: First report of zebra chip disease and Candidatus Liberibacter solanacearum on potatoes in Idaho

Author
item Crosslin, James
item OLSEN, NORA - University Of Idaho
item NOLTE, PHIL - University Of Idaho

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/18/2011
Publication Date: 2/10/2012
Citation: Crosslin, J., Olsen, N., Nolte, P. 2012. First report of zebra chip disease and Candidatus Liberibacter solanacearum on potatoes in Idaho. Plant Disease. 96:453.

Interpretive Summary: The zebra chip (ZC) disease is a serious and emerging disease of potatoes. The disease has been reported in various parts of the south-western US, Mexico, Central America, and recently in New Zealand. In September of 2011, symptoms consistent with the ZC disease were observed in Russet Burbank potato tubers grown in south-central Idaho. Tissue samples were tested by the polymerase chain reaction for “Candidatus Liberibacter solanacearum”, the bacterium associated with ZC. Nearly all of these samples were positive for the bacterium. DNA sequence analysis confirmed “Ca. L. solanacearum”. Later, additional symptomatic tubers of Yukon Gold and Ranger Russet also tested positive for “Ca. L. solanacearum”. These results provided the first evidence that zebra chip disease has spread to Idaho. Idaho is the largest potato-producing state in the United States, with over 150,000 hectares planted this year, and therefore ZC poses a significant risk to agriculture in this state.

Technical Abstract: In September of 2011, potato (Solanum tuberosum) tubers in a packing facility in (Idaho Falls???) were observed with internal discolorations suggestive of the zebra chip disease (ZC). Symptoms were observed in 1-2% of tubers of Russet Burbank and Russet Norkotah and included brown spots and streaks especially in and near the vascular tissue. Some tubers also showed a dark and sunken stolon attachment typical of ZC (1). Initially, tissue samples were taken from seven symptomatic tubers and tested by polymerase chain reaction (PCR) for “Candidatus Liberibacter solanacearum”, the bacterium associated with ZC. Primers specific for the 16S rDNA (primers CLipoF (4) and OI2c (3) and the outer membrane protein (OMB 1482f and 2086r) (2) were used. Six of these samples were positive for the bacterium. The amplified 16S rDNA and OMB products from two symptomatic tubers of Russet Norkotah were cloned and three clones of each were sequenced. BLAST analysis of the consensus sequences confirmed “Ca. L. solanacearum”. The 16S sequences (1,071 bp) from the two tubers varied by one nucleotide and were 99-100% identical to a number of “Ca. L. solanaceaum” sequences in GenBank. These were deposited in GenBank as accessions wwww and xxxx. Sequences of the two OMB clones (605 bp; deposited in GenBank as accessions yyyy and zzzz) showed 97% identity to the two “Ca. L. solanacearum” OMB sequences in GenBank (CP002371 and FJ914617). Additional severely symptomatic tubers of Yukon Gold and cut French fries of Ranger Russet produced in eastern Idaho were subsequently tested and were positive for “Ca. L. solanacearum”. Based on symptoms, specific PCR amplification with two distinct primer pairs, and DNA sequence analysis, zebra chip disease and “Ca. L. solanacearum” are present in Idaho. This disease has caused significant economic damage to potatoes in many regions, including Texas, Mexico, Central America, and recently in New Zealand (1). Idaho is the largest potato-producing state in the United States, with over 150,000 hectares planted this year, and therefore ZC poses a significant risk to agriculture in this state. (1) J.M. Crosslin et al. Plant Health Prog. doi: 10.1094/PHP-2010-0317-01-RV, 2010. (2) J.M. Crosslin et al. Southwest. Entomol. 36:125, 2011. (3) S. Jagoueix et al. Mol. Cell. Probes 10:43, 1996. (4) G.A. Secor, Plant Dis. 93:574, 2009. .