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United States Department of Agriculture

Agricultural Research Service

Research Project: EPIDEMIOLOGY AND MANAGEMENT OF XYLELLA FASTIDIOSA (XF) AND OTHER EXOTIC AND INVASIVE DISEASES AND INSECT PESTS

Location: Crop Diseases, Pests and Genetics

Title: Detection, Distribution and Genetic Variability of 'Candidatus Liberibacter’ Species Associated with Zebra Complex Disease of Potato in North America

Authors
item Wen, Aimin -
item Mallik, Ipsita -
item Alvarado, Valvarado -
item Pasche, Julie -
item Wang, Xiaoyun -
item Li, Wenbin -
item Levy, Laurene -
item Lin, Hong
item Scholthof, Herscho -
item Mirkov, Emirkov -
item Rush, Charlie -
item Gudmestad, Neil -

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 16, 2009
Publication Date: October 13, 2009
Citation: Wen, A., Mallik, I., Alvarado, V.Y., Pasche, J.S., Wang, X., Li, W., Levy, L., Lin, H., Scholthof, H., Mirkov, E., Rush, C.M., Gudmestad, N.C. 2009. Detection, Distribution and Genetic Variability of 'Candidatus Liberibacter’ Species Associated with Zebra Complex Disease of Potato in North America. Plant Disease. 93:1102-1115.

Interpretive Summary: The presence of ‘Candidatus Liberibacter solanacearum’ (CLs) and ‘Candidatus Liberibacter psyllaurous’ (CLp) were confirmed in potato plants affected with zebra chip/zebra complex (ZC) disease throughout Texas potato production areas in 2005-2008, in seed tubers produced from Wyoming in 2007, and in Colorado, Kansas, Nebraska and Mexico potato production areas in 2008 using CLp/CLs specific primers in PCR assays. The PCR assays were capable of detecting 0.19 to 1.56 ng of total DNA per reaction, depending on the primer set used. The overall efficiency associated with the detection of true positives was generally less than 60%. Detection efficiencies were much higher for below ground portions of plants, such as stolons and tubers, as opposed to leaves, leaf petioles and above ground stems. The ‘Candidatus Liberibacter’ species detected in all samples divided into two clusters sharing similarity of 99.8 % in their partial 16S rDNA sequences and 99.3 % in their partial ISR-23S rDNA sequences. Genetic variations in the 16S rDNA region consistently matched with those of the ISR-23S rDNA region. Preliminary studies suggest silverleaf nightshade (Solanum elaeagnifolium Cav.), wolfberry (Lycium barbarum L.), black nightshade (S. ptychanthum Dun.), and jalapeno pepper (Capsicum annuum L.) as potential reservoir hosts for the ZC bacterium.

Technical Abstract: The specificity and sensitivity of PCR primers developed for ‘Candidatus Liberibacter solanacearum’ (CLs) and ‘Candidatus Liberibacter psyllaurous’ (CLp) were evaluated in conventional and real-time PCR assays. All PCR primers were specific for CLp and CLs insomuch as they did not detect other prokaryotic plant pathogens that affect potato except for psyllid yellows and haywire. Conventional PCR assays were capable of detecting 0.19 to 1.56 ng of total DNA per reaction and real-time PCR was found capable of detecting 1.56 to 6.25 ng of total DNA per reaction, depending on the specific PCR primer set used. ‘Ca. Liberibacter’ species associated with ZC was confirmed in plants affected with this disease from throughout Texas from 2005 to 2008, 25 in seed tubers produced from Wyoming in 2007, and in Colorado, Kansas, Nebraska and 26 Mexico in 2008. Preliminary studies suggest silverleaf nightshade (Solanum elaeagnifolium Cav.), wolfberry (Lycium barbarum L.), black nightshade (S. ptychanthum Dun.), and jalapeno pepper (Capsicum annuum L.) as additional solanaceaous hosts for the ZC bacterium. The ‘Candidatus Liberibacter’ species detected in all samples divided into two clusters sharing similarity of 99.8 % in their partial 16S rRNA gene sequences and 99.3 % in their partial intergenic spacer region (ISR)-23S rRNA gene sequences. In this partial 16S-ISR-23S rDNA region there were a total of 8 single nucleotide polymorphisms among the CLp/CLs ‘isolates’ investigated in this study.

Last Modified: 7/11/2014
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