Effect of the level of “Candidatus Liberibacter solanacearum” infection on the development of zebra chip disease in different potato genotypes at harvest and post storage

Zebra Chip disease is a serious threat to potato production. The pathogen, the phloem-limited bacterium ‘Candidatus Liberibacter solanacearum,’ is vectored by the potato and tomato psyllid Bactericerca cockerelli to potato and tomato. Patterns of pathogen translocation through phloem in potato and tomato plants were examined to determine whether rate or direction of translocation vary by host species or potato cultivars. Two insects were given a 7-day inoculation access period on a single leaf. Weekly, leaves from upper-, middle-, and lower-tier branches were tested for the presence of ‘Ca. L. solanacearum’ by polymerase chain reaction (PCR). In tomato and potato, ‘Ca. L. solanacearum’ was detected 2 to 3 weeks after infestation, most frequently in upper- and middle-tier leaves. In potato, the pathogen was detected in leaves on a second, noninfested stem when the stems remained joined via the tuber. Although rates of pathogen movement were similar among potato cultivars, symptoms developed earlier in more susceptible cultivars. Quantitative PCR indicated that bacterial titers were frequently low in tomato and potato samples (<20 genome units per nanogram of DNA). Results establish that, for improved detection, samples should include newly developing leaves and consider that, under low insect pressure, the pathogen may be undetectable by PCR until 3 weeks after infestation.

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Characterization of the Serralysin-Like Gene of ‘Candidatus Liberibacter solanacearum’ Associated with Potato Zebra Chip Disease

Phytopathology ◽

10.1094/phyto-02-17-0064-r ◽

2018 ◽

Vol 108 (3) ◽

pp. 327-335 ◽

Cited By ~ 5

Author(s):

Aravind Ravindran ◽

Panatda Saenkham ◽

Julien Levy ◽

Cecilia Tamborindeguy ◽

Hong Lin ◽

...

Keyword(s):

Gene Expression ◽

Expression Analysis ◽

Skim Milk ◽

Type I ◽

Zebra Chip ◽

Candidatus Liberibacter Solanacearum ◽

Intact Proteins ◽

Zebra Chip Disease ◽

Genes Encoding ◽

Candidatus Liberibacter

The nonculturable bacterium ‘Candidatus Liberibacter solanacearum’ is the causative agent of zebra chip disease in potato. Computational analysis of the ‘Ca. L. solanacearum’ genome revealed a serralysin-like gene based on conserved domains characteristic of genes encoding metalloprotease enzymes similar to serralysin. Serralysin and other serralysin family metalloprotease are typically characterized as virulence factors and are secreted by the type I secretion system (T1SS). The ‘Ca. L. solanacearum’ serralysin-like gene is located next to and divergently transcribed from genes encoding a T1SS. Based on its relationship to the T1SS and the role of other serralysin family proteases in circumventing host antimicrobial defenses, it was speculated that a functional ‘Ca. L. solanacearum’ serralysin-like protease could be a potent virulence factor. Gene expression analysis showed that, from weeks 2 to 6, the expression of the ‘Ca. L. solanacearum’ serralysin-like gene was at least twofold higher than week 1, indicating that gene expression stays high as the disease progresses. A previously constructed serralysin-deficient mutant of Serratia liquefaciens FK01, an endophyte associated with insects, as well as an Escherichia coli lacking serralysin production were used as surrogates for expression analysis of the ‘Ca. L. solanacearum’ serralysin-like gene. The LsoA and LsoB proteins were expressed as both intact proteins and chimeric S. liquefaciens-‘Ca. L. solanacearum’ serralysin-like proteins to facilitate secretion in the S. liquefaciens surrogate and as intact proteins or as a truncated LsoB protein containing just the putative catalytic domains in the E. coli surrogate. None of the ‘Ca. L. solanacearum’ protein constructs expressed in either surrogate demonstrated proteolytic activity in skim milk or zymogram assays, or in colorimetric assays using purified protein, suggesting that the ‘Ca. L. solanacearum’ serralysin-like gene does not encode a functional protease, or at least not in our surrogate systems.

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Relative Abundance of Potato Psyllid Haplotypes in Southern Idaho Potato Fields During 2012 to 2015, and Incidence of ‘Candidatus Liberibacter solanacearum’ Causing Zebra Chip Disease

Plant Disease ◽

10.1094/pdis-05-16-0668-re ◽

2017 ◽

Vol 101 (5) ◽

pp. 822-829 ◽

Cited By ~ 11

Author(s):

Jennifer Dahan ◽

Erik J. Wenninger ◽

Brandon Thompson ◽

Sahar Eid ◽

Nora Olsen ◽

...

Keyword(s):

Potato Industry ◽

Potato Psyllid ◽

Bactericera Cockerelli ◽

Zebra Chip ◽

Spatial And Temporal Patterns ◽

Candidatus Liberibacter Solanacearum ◽

South Central ◽

Zebra Chip Disease ◽

Four Seasons ◽

Candidatus Liberibacter

Zebra chip (ZC) disease, a serious threat to the potato industry, is caused by the bacterium ‘Candidatus Liberibacter solanacearum’ (Lso). Five haplotypes (hapA to hapE) of this pathogen have been described so far in different crops, with only hapA and hapB being associated with ZC in potato. Both haplotypes are vectored and transmitted to a variety of solanaceaeous plants by the tomato/potato psyllid, Bactericera cockerelli (Šulc). Psyllids are native to North America, and four haplotypes have been identified and named based on their predominant geographic association: Northwestern, Central, Western, and Southwestern. Although all psyllid haplotypes have been found in southern Idaho potato fields, data on relative haplotype abundances and dynamic changes in the fields over time have not previously been reported. Here, psyllid samples collected in Idaho potato fields from 2012 to 2015 were used to clarify spatial and temporal patterns in distribution and abundance of psyllid and Lso haplotypes. A shift from hapA toward hapB population of Lso was revealed during these four seasons, indicating possible evolution of Lso in Idaho fields. Although we confirmed that Western psyllids were the most abundant by far during the four seasons of observation, we also observed changes in abundance of other haplotypes, including increased diversity of psyllid haplotypes during 2015. Seasonal changes observed for the Northwestern and Central haplotypes could potentially be linked to psyllid migration and/or habitat changes. South-central Idaho exhibited more diversity in psyllid haplotypes than southwestern Idaho.

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Similarities and Differences in Physiological Responses to ‘Candidatus Liberibacter solanacearum’ Infection Among Different Potato Cultivars

Phytopathology ◽

10.1094/phyto-05-13-0125-r ◽

2014 ◽

Vol 104 (2) ◽

pp. 126-133 ◽

Cited By ~ 23

Author(s):

C. M. Wallis ◽

A. Rashed ◽

A. K. Wallingford ◽

L. Paetzold ◽

F. Workneh ◽

...

Keyword(s):

Amino Acids ◽

Physiological Responses ◽

Zebra Chip ◽

Candidatus Liberibacter Solanacearum ◽

Russet Norkotah ◽

Zebra Chip Disease ◽

Candidatus Liberibacter ◽

Similarities And Differences ◽

Cultivar Responses ◽

Fastidious Bacterium

Zebra chip disease (ZC), putatively caused by the fastidious bacterium ‘Candidatus Liberibacter solanacearum’, is a threat to potato growers worldwide. However, little is known about biochemical shifts in different potato genotypes in response to ‘Ca. L. solanacearum’ infection. To address this, ‘Red La Soda’, ‘Russet Norkotah’, and ‘FL 1867’ potato were infected with ‘Ca. L. solanacearum’ 4, 3, 2, and 1 weeks before harvest to observe variability in cultivar responses to ‘Ca. L. solanacearum’ infection. ZC symptoms, ‘Ca. L. solanacearum’ titers, and tuber biochemistry were assessed. Red La Soda tubers exhibited greater symptoms when infected for 4 weeks than Russet Norkotah or FL 1867 tubers. ‘Ca. L. solanacearum’ titers did not vary among cultivars. Tuber levels of amino acids, carbohydrates, and phenolics varied among cultivars but no consistent trends were observed. Individual amino acids and phenolics were greater in FL 1867 than Red La Soda, whereas others were greater in Red La Soda or Russet Norkotah than FL 1867. Most amino acids, carbohydrates, and phenolics were positively associated with infection duration and symptoms regardless of cultivar. Associations between most of the evaluated compounds and ‘Ca. L. solanacearum’ titer were positive in Red La Soda. However, no associations between ‘Ca. L. solanacearum’ quantity and compounds were observed in FL 1867 and Russet Norkotah.

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Development of Primers for Improved PCR Detection of the Potato Zebra Chip Pathogen, ‘Candidatus Liberibacter solanacearum’

Plant Disease ◽

10.1094/pdis-05-11-0386 ◽

2011 ◽

Vol 95 (12) ◽

pp. 1542-1546 ◽

Cited By ~ 28

Author(s):

Aravind Ravindran ◽

Julien Levy ◽

Elizabeth Pierson ◽

Dennis C. Gross

Keyword(s):

Control Strategies ◽

Housekeeping Gene ◽

Potato Production ◽

Pcr Detection ◽

Zebra Chip ◽

Rdna Genes ◽

Candidatus Liberibacter Solanacearum ◽

Zebra Chip Disease ◽

Candidatus Liberibacter ◽

Primer Sets

Zebra chip disease poses a major economic threat to potato production. The causative agent is a phloem-limited bacterium identified as ‘Candidatus Liberibacter solanacearum’ that is transmitted by the potato/ tomato psyllid. Currently, there are no effective controls and existing control strategies depend largely on the early detection of the pathogen via polymerase chain reaction (PCR) assays. Most primer sets used for PCR detection target a region of the bacterial 16S rDNA gene, and detection of the pathogen in symptomatic potato tissue with existing primers has been variable depending on the specific primer sets used. This study describes the development of two new primer sets that target a conserved intergenic region between the 16S and 23S rDNA genes and a conserved bacterial housekeeping gene, adenylate kinase (adk). Results demonstrate that the new primer sets are more reliable in detecting ‘Ca. L. solanacearum’ in field and glasshouse samples than the currently used LsoF/OI2 primers. The newly developed primers differentiated between ‘Ca. L. solanacearum’ and a closely related ‘Ca. Liberibacter’ spp. and were more sensitive than the LsoF/OI2 primers. The low detection limit for the new primers was four times lower (0.65 ng) than the limit (2.5 ng) for the LsoF/OI2 primers.

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Characterization and Epidemiological Significance of Potato Plants Grown from Seed Tubers Affected by Zebra Chip Disease

Plant Disease ◽

10.1094/pdis-94-6-0659 ◽

2010 ◽

Vol 94 (6) ◽

pp. 659-665 ◽

Cited By ~ 19

Author(s):

D. C. Henne ◽

F. Workneh ◽

A. Wen ◽

J. A. Price ◽

J. S. Pasche ◽

...

Keyword(s):

United States ◽

The United States ◽

Zebra Chip ◽

Candidatus Liberibacter Solanacearum ◽

Potato Plants ◽

Seed Tubers ◽

Zebra Chip Disease ◽

Candidatus Liberibacter ◽

Epidemiological Significance

An emerging disease of potato in the United States, known as “Zebra Chip” or “Zebra Complex” (ZC), is increasing in scope and threatens to spread further. Here, we report on studies performed to understand the role of tuberborne ZC in the epidemiology of this disease. Depending on variety, up to 44% of ZC-affected seed tubers (ZCST) were viable, producing hair sprouts and weak plants. Chip discoloration in progeny tubers of ZCST was more severe than those from ZC-asymptomatic seed tubers but varied depending on whether progeny tubers or foliage were positive or negative for ‘Candidatus Liberibacter solanacearum’. A low percentage of greenhouse-grown plants produced by ZCST tested positive for ‘Ca. Liberibacter’. No adult potato psyllids became infective after feeding upon these plants but they did acquire ‘Ca. Liberibacter’ from field-grown plants produced by ZCST. Plants with new ZC infections near plants produced by ZCST were not significantly different from healthy plants, whereas plants affected with ZC from infectious potato psyllids had significantly more ZC infections near either plants produced by ZCST or healthy plants. We conclude that, in areas where ZC is currently established, plants produced by ZCST do not significantly contribute to ZC incidence and spread within potato fields.

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Zebra Chip Disease Development in Relation to Plant Age and Time of ‘Candidatus Liberibacter solanacearum’ Infection

Plant Disease ◽

10.1094/pdis-04-13-0366-re ◽

2014 ◽

Vol 98 (1) ◽

pp. 24-31 ◽

Cited By ~ 23

Author(s):

A. Rashed ◽

F. Workneh ◽

L. Paetzold ◽

J. Gray ◽

C. M. Rush

Keyword(s):

Population Growth ◽

Incubation Period ◽

Leaf Tissue ◽

Yield Reduction ◽

Tuber Quality ◽

Zebra Chip ◽

Pathogen Population ◽

Candidatus Liberibacter Solanacearum ◽

Zebra Chip Disease ◽

Candidatus Liberibacter

A 2-year field study was conducted to evaluate plant susceptibility to ‘Candidatus Liberibacter solanacearum’, the putative causal agent of zebra chip disease (ZC). Incubation period of ZC, the rate of symptom progress, and the rate of pathogen population growth were evaluated for individual plants infested on different weeks after emergence. In foliage, incubation period was between 21 and 28 days. The pathogen was detected within leaf tissue in 3 to 4 weeks, regardless of the time of infestation. The rates of foliar symptom progress and pathogen population growth were uniform among all infestations. Although symptoms were observed in only 1.3% of tubers from plants infested 2 weeks before harvest, 74% of these tubers tested positive for the pathogen. There was a positive correlation between symptom severity and titer in the foliage. Within tubers, however, the relationship was negative but nonsignificant. Pathogen titer reached detectable levels some time between 7 to 14 days following infestation. Although yield reduction was significant only in plants infested during early stages of their growth, chemical management of potato psyllids needs to be continued until at least a week before harvest to minimize ZC impact on the tuber quality.

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First Report of Zebra Chip Disease and “Candidatus Liberibacter solanacearum” on Potatoes in Idaho

Plant Disease ◽

10.1094/pdis-10-11-0853 ◽

2012 ◽

Vol 96 (3) ◽

pp. 453-453 ◽

Cited By ~ 48

Author(s):

J. M. Crosslin ◽

N. Olsen ◽

P. Nolte

Keyword(s):

16S Rdna ◽

The United States ◽

Zebra Chip ◽

Candidatus Liberibacter Solanacearum ◽

Russet Norkotah ◽

Sequence Identity ◽

South Central ◽

Zebra Chip Disease ◽

Candidatus Liberibacter ◽

Central Idaho

In September 2011, potato (Solanum tuberosum L.) tubers graded in a packing facility in south-central Idaho were observed with internal discolorations suggestive of zebra chip disease (ZC). Symptoms were observed in 1 to 2% of tubers of cv. 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 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 cv. Russet Norkotah were cloned and three clones of each were sequenced. The 16S sequences (1,071 bp; GenBank Accession Nos. JN848755 and JN848756) from the two tubers varied by one nucleotide and had 99 to 100% sequence identity to numerous “Ca. L. solanacearum” sequences in GenBank (e.g., Accession Nos. HM246509, FJ957897, and EU935004). Sequences of the two OMB clones (605 bp; GenBank Accession Nos. JN848757 and JN848758) had 97% sequence identity to the two “Ca. L. solanacearum” OMB sequences in GenBank (Accession Nos. CP002371 and FJ914617). Six of eight additional symptomatic field-collected cv. Russet Norkotah tubers corresponding to tubers collected in the packing facility were also positive for “Ca. L. solanacearum” by PCR. Additional severely symptomatic tubers of cvs. Russet Burbank, Yukon Gold, and raw cut French fries of Ranger Russet produced in south-central Idaho were subsequently tested by PCR and were found to be positive for “Ca. L. solanacearum” as well. On the basis of the symptoms, specific PCR amplification with two distinct primer pairs and DNA sequence analysis, zebra chip disease caused by “Ca. L. solanacearum” was determined to be present in Idaho. This disease has caused significant economic damage to potatoes in many regions, including Texas, Mexico, Central America, and New Zealand (1). Idaho is the largest potato-producing state in the United States, with over 150,000 ha planted this year, and therefore, ZC potentially poses a significant risk to agriculture in this state. References: (1) J. M. Crosslin et al. Online publication. doi:10.1094/PHP-2010-0317-01-RV, Plant Health Progress, 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.

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Transmission Efficiency of ‘Candidatus Liberibacter solanacearum’ and Potato Zebra Chip Disease Progress in Relation to Pathogen Titer, Vector Numbers, and Feeding Sites

Phytopathology ◽

10.1094/phyto-04-12-0094-r ◽

2012 ◽

Vol 102 (11) ◽

pp. 1079-1085 ◽

Cited By ~ 21

Author(s):

A. Rashed ◽

T. D. Nash ◽

L. Paetzold ◽

F. Workneh ◽

C. M. Rush

Keyword(s):

Plant Pathogens ◽

Transmission Efficiency ◽

Bactericera Cockerelli ◽

Zebra Chip ◽

Candidatus Liberibacter Solanacearum ◽

Feeding Site ◽

Disease Progress ◽

Zebra Chip Disease ◽

Candidatus Liberibacter ◽

Inoculation Study

With diseases caused by vector-borne plant pathogens, acquisition and inoculation are two primary stages of the transmission, which can determine vector efficiency in spreading the pathogen. The present study was initiated to quantify acquisition and inoculation successes of ‘Candidatus Liberibacter solanacearum’, the etiological agent of zebra chip disease of potato, by its psyllid vector, Bactericera cockerelli (Hemiptera: Triozidae). Acquisition success was evaluated in relation to feeding site on the host plant as well as the acquisition access period. Inoculation success was evaluated in relation to vector number (1 and 4) on the plants. Acquisition success was influenced by the feeding site on the plant. The highest acquisition success occurred when insects had access to the whole plant. The results of the inoculation study indicated that the rate of successfully inoculated plants increased with the vector number. Plants inoculated with multiple psyllids had higher bacterial titer at the point of inoculation. Although disease incubation period was significantly shorter in plants inoculated with multiple psyllids, this effect was heterogeneous across experimental blocks, and was independent of pathogen quantity detected in the leaflets 3 days postinoculation. Disease progress was not affected by bacterial quantity injected or psyllid numbers.

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Seasonal Occurrence of Potato Psyllid (Bactericera Cockerelli) and Risk of Zebra Chip Pathogen (Candidatus Liberibacter Solanacearum) in Northwestern New Mexico

Insects ◽

10.3390/insects11010003 ◽

2019 ◽

Vol 11 (1) ◽

pp. 3

Author(s):

Koffi Djaman ◽

Charles Higgins ◽

Shantel Begay ◽

Komlan Koudahe ◽

Samuel Allen ◽

...

Keyword(s):

New Mexico ◽

Pest Management ◽

Growing Season ◽

Management Decision ◽

Potato Psyllid ◽

Bactericera Cockerelli ◽

Zebra Chip ◽

Candidatus Liberibacter Solanacearum ◽

Zebra Chip Disease ◽

Candidatus Liberibacter

Potato psyllid (Bactericera cockerelli) is one of the most important pests in potatoes (Solanum tuberosum L.) due to its feeding behavior and the transmission of a bacterium (Candidatus Liberibacter solanacearum) that causes zebra chip disease, altering the quality of the potato tuber and the fried potato chip or french fry. This pest is thus a threat to the chip potato industry and often requires preventive measures including the use of costly insecticides. The objectives of this research were to monitor the variation in B. cockerelli adult abundance and to evaluate the risk of zebra chip disease in northwestern New Mexico, USA. Yellow sticky traps were used to collect the pest at the Agricultural Experiment Station at Farmington, NM and in nearby commercial fields at the Navajo Agricultural Products Industry (NAPI) and Navajo Mesa Farms during the 2017–2019 period. The collected adult pests were analyzed at Texas A & M University for the presence of Candidatus L. solanacearum (Lso). The results showed field infestation by B. cockerelli in early June and that the population peaked during the second half of July and decreased as the potato growing season progressed. However, a second less important peak of the pest was revealed around mid- to late-August, depending on the growing season and field. While the B. cockerelli population increased linearly with average air temperature, it showed strong third order polynomial relationships with the accumulated thermal units and the Julian days. The test of B. cockerelli for the Lso infection revealed a low incidence of the pathogen varying from 0.22% to 6.25% and the infected adult B. cockerelli were collected during the population peak period. The results of this study may be helpful to potato growers in pest management decision-making and control. However, more study is needed to evaluate zebra chip disease in terms of its prevention and economic impact, and to develop economic thresholds and pest management programs for northwestern New Mexico and neighboring regions.

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