Susceptibility of Selected Potato Varieties to Zebra Chip Potato Disease

Zebra chip (ZC), an emerging and serious disease of potato has caused millions of dollars in losses to the potato industry in the United States, Mexico, Central America, and New Zealand. The disease has recently been associated with a previously undescribed species of liberibacter tentatively named “Candidatus Liberibacter solanacearum” transmitted to potato by the potato psyllid, Bactericera cockerelli (Šulc). At present, applications of insecticides targeted against the potato psyllid are the only means to manage ZC. Given the low psyllid density and short inoculation access period required to induce the disease, insecticides may not act fast enough to prevent transmission of liberibacter to potato by the psyllid and development of ZC. Identification and development of ZC-resistant or tolerant varieties may offer the most efficient and sustainable way to manage this potato disease. Susceptibility of selected potato varieties to ZC was evaluated under controlled field cage conditions in 2009 and 2010 in WA by inoculating potato plants with “Ca. L. solanacearum” using infective potato psyllids and monitoring them for ZC symptom development. All potato varieties evaluated in both years of the study were determined to be very susceptible to the disease, with almost 100% of the inoculated plants developing severe ZC foliar and tuber symptoms. Potato yield in all tested varieties was significantly affected by ZC, with yield losses ranging from 49.9% to 87. 2%. Information from this research suggests that there is an urgent need to develop new potato varieties that are resistant or tolerant to this damaging potato disease

Latent Period and Transmission of “Candidatus Liberibacter solanacearum” by the Potato Psyllid Bactericera cockerelli (Hemiptera: Triozidae)

"Candidatus Liberibacter solanacearum" (Lso) is an economically important pathogen of solanaceous crops and the putative causal agent of zebra chip disease of potato (Solanum tuberosum L.). This pathogen is transmitted to solanaceous species by the potato psyllid, Bactericera cockerelli (Šulc), but many aspects of the acquisition and transmission processes have yet to be elucidated. The present study was conducted to assess the interacting effects of acquisition access period, incubation period, and host plant on Lso titer in psyllids, the movement of Lso from the alimentary canal to the salivary glands of the insect, and the ability of psyllids to transmit Lso to non-infected host plants. Following initial pathogen acquisition, the probability of Lso presence in the alimentary canal remained constant from 0 to 3 weeks, but the probability of Lso being present in the salivary glands increased with increasing incubation period. Lso copy numbers in psyllids peaked two weeks after the initial pathogen acquisition and psyllids were capable of transmitting Lso to non-infected host plants only after a two-week incubation period. Psyllid infectivity was associated with colonization of insect salivary glands by Lso and with Lso copy numbers >10,000 per psyllid. Results of our study indicate that Lso requires a two-week latent period in potato psyllids and suggest that acquisition and transmission of Lso by psyllids follows a pattern consistent with a propagative, circulative, and persistent mode of transmission

Assessing Potato Psyllid Haplotypes in Potato Crops in the Pacific Northwestern United States

The potato psyllid, Bactericera cockerelli (Šulc), is a vector of the bacterium ‘Candidatus Liberibacter solanacearum’ (Lso) that has been linked to the economically devastating zebra chip disease of potato. To date, four haplotypes of the potato psyllid have been identified and include Central, Western, Northwestern, and Southwestern haplotypes. Zebra chip was reported in potato crops in the Pacific Northwestern United States for the first time in 2011, and the Lso-infected psyllids collected from zebra chip-affected fields were identified as the Western haplotype. Additional studies have reported a mix of the Western and Northwestern psyllid haplotypes in the Pacific Northwest. The present study further examined psyllid population dynamics over the duration of the 2012 potato season in the Pacific Northwest by haplotype analysis of 864 potato psyllids collected from potato fields in Washington, Oregon, and Idaho. In the Yakima Valley of Washington and the lower Columbia Basin of Washington and Oregon, the Northwestern haplotype was predominant (78%), and was detected earlier in the season than the Western haplotype. Interestingly, in south-central Idaho, all four psyllid haplotypes were identified, but the predominant haplotype was the Western haplotype (77%). Here, Northwestern psyllids were detected early in the season from June to mid-August, whereas Central psyllidswere detected in late July and thereafter. These results suggest that haplotype composition of psyllid populations in potato fields throughout the 2012 growing season in south-central Idaho differed greatly from those in Washington and Oregon. Additionally, all psyllids were analyzed for the presence of Lso, and no Lso-positive psyllids were found in Washington and Oregon, whereas Lso-positive psyllids were found in south-central Idaho. These Lso-positive psyllids consisted of the Western, Northwestern, and Central haplotypes

Association of "Candidatus Liberibacter solanacearum" with the Psyllid, Trioza apicalis (Hemiptera: Triozidae) in Europe

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"Candidatus Liberibacter solanacearum" titer over time in Bactericera cockerelli (Hemiptera: Triozidae) after acquisition from infected potato and tomato plants

The potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) is a serious pest of potato and other solanaceous crops. B. cockerelli has been associated with the bacterium "Candidatus Liberibacter solanacearum" (Lso), the causal agent of zebra chip, a new and economically important disease of potato in the United States, Mexico, Central America, and New Zealand. The biology of liberibacter transmission to potato and other host plants by the potato psyllid is largely unknown. The current study determined Lso acquisition by adult psyllids following different acquisition access periods (AAP) on potato and tomato, quantified Lso titer over time in postacquisition psyllids, determined Lso-acquisition rate in psyllids at each AAP on each source of inoculum, and determined influence of host plant Lso titer on Lso acquisition rates and postacquisition titer in psyllids over time. Results showed that Lso detection rates and titer increased over time in psyllids following AAPs of 8, 24, and 72 h on tomato and potato and Lso titer was highest when psyllids acquired Lso from tomato versus potato. Lso titer ranged from 200- to 400-fold higher in tomato leaves, petioles, and stems than those of potato. The increase of Lso titer in the insects reached a plateau after an average of 15 d following 24 and 72 h AAP on potato or tomato. At this 15-d plateau, Lso titer in postacquisition psyllids was comparable with that of infective psyllids from the Lso-infected laboratory colony. Lso-acquisition rate in psyllids fed on potato and tomato increased up to 5 and 20, 15 and 35, 35 and 75, and 80 and 100%, respectively, when the insects were allowed access to plants for 4, 8, 24, and 72 h, respectively

Desmanthus virgatus Willd.

原著和名: タチクサネム科名: マメ科 = Leguminosae採集地: 沖縄県 沖縄本島 中頭郡 読谷村 (琉球 沖縄本島 中頭郡 読谷村 )採集日: 1986/2/28採集者: 萩庭丈壽整理番号: JH006479国立科学博物館整理番号: TNS-VS-95647

Carrot plants exhibiting characteristic symptoms of ‘<i>Candidatus</i> Liberibacter solanacearum’ (Lso) infection, following exposure to Lso-infected potato psyllids (<i>Bactericera cockerelli</i>) under controlled field cage conditions.

<p>The symptomatic plants were collected in August (A) and October (B) 2010, respectively, from a field trial conducted at USDA-ARS Wapato facility.</p

A new haplotype of "Candidatus Liberibacter solanacearum" identified in the Mediterranean region

Candidatus Liberibacter solanacearum", a phloem-limited and Gram-negative bacterium that is spread from infected to healthy plants by psyllid insect vectors, is an economically important pathogen of solanaceous and carrot crops in the Americas, New Zealand and Europe. Three haplotypes of "Ca. L. solanacearum" have previously been described, two (LsoA and LsoB) in relation to solanaceous crops in the Americas and New Zealand and the third (LsoC) to carrots in Finland. Herein, we describe a fourth haplotype of this 'Candidatus Liberibacter' species (LsoD), also associated with carrots, but from Spain and the Canary Islands and vectored by the psyllid Bactericera trigonica. In addition, LsoC was confirmed in carrot and psyllid samples recently collected from Sweden and Norway. Phylogenetic analysis of the 16S rRNA gene suggests that two of the haplotypes, one in the Americas and the other in northern Europe are closer to each other in spite of a large geographic separation and host differences. Furthermore, during this study, potatoes with symptoms of zebra chip disease recently observed in potato crops in Idaho, Oregon and Washington states were analyzed for haplotype and were found to be positive for LsoA. This liberibacter haplotype was found in psyllids associated with the diseased potato crops as well. This finding contrasts with an earlier report of LsoB from psyllids in Washington which came from a laboratory colony originally collected in Texas.Financial support for this work was partially provided by USDA-ARS, USDA-RAMP (Project # 2009-51101-05892) and USDA-SCRI (Project # 2009-51181-20176). We also would like to thank Agricola Villena Coop. V. for collecting Spanish carrot samples and for their financial support.Nelson, WR.; Sengoda, VG.; Alfaro Fernández, AO.; Font San Ambrosio, MI.; Crosslin, JM.; Munyaneza, JE. (2013). A new haplotype of "Candidatus Liberibacter solanacearum" identified in the Mediterranean region. European Journal of Plant Pathology. 135(4):633-639. https://doi.org/10.1007/s10658-012-0121-3S6336391354Alfaro-Fernández, A., Cebrián, M. C., Villaescusa, F. J., Hermoso de Mendoza, A., Ferrándiz, J. C., Sanjuán, S., et al. (2012a). First report of ‘Candidatus Liberibacter solanacearum’ in carrot in mainland Spain. Plant Disease, 96, 582.Alfaro-Fernández, A., Siverio, F., Cebrián, M. C., Villaescusa, F. J., & Font, M. I. (2012b). ‘Candidatus Liberibacter solanacearum’ associated with Bactericera trigonica-affected carrots in the Canary Islands. Plant Disease, 96, 581.Brown, J. K., Rehman, M., Rogan, D., Martin, R. R., & Idris, A. M. (2010). First report of “Candidatus Liberibacter psylaurous” (syn. “Ca. 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Primers and probes used in this study.

a<p>Conventional PCR of Lso.</p>b<p>Quantitative real-time PCR of Lso.</p>c<p>Quantitative real-time PCR of potato psyllid.</p>d<p>Lso haplotype differentiation, 240 bp  =  Lso haplotype A; 180 bp  =  Lso haplotype B.</p>e<p>Fluorescence <i>in situ</i> hybridization of Lso.</p>f<p>Psyllid haplotyping primers.</p