Potato Psyllid Bactericera Cockerelli Research Articles

Hiding in plain sight: a widespread native perennial harbors diverse haplotypes of 'Candidatus Liberibacter solanacearum' and its potato psyllid vector.

The unculturable bacterium 'Candidatus Liberibacter solanacearum' (CLso) is responsible for a growing number of emerging crop diseases. However, we know little about the diversity and ecology of CLso and its psyllid vectors outside of agricultural systems, which limits our ability to manage crop disease and understand the impacts this pathogen may have on wild plants in natural ecosystems. In North America, CLso is transmitted to crops by the native potato psyllid (Bactericera cockerelli). But the geographic and host plant range of the potato psyllid and CLso beyond the borders of agriculture are not well understood. A recent study of historic herbarium specimens revealed that a unique haplotype of CLso was present infecting populations of the native perennial Solanum umbelliferum in California decades before CLso was first detected in crops. We hypothesized that this haplotype, and other potentially novel CLso variants, are still present in S. umbelliferum populations. To test this, we surveyed populations of S. umbelliferum in Southern California for CLso and potato psyllid vectors. We found multiple haplotypes of CLso and the potato psyllid associated with these populations, with none of these genetic variants having been previously reported in California crops. These results suggest that CLso and its psyllid vectors are much more widespread and diverse in North American natural plant communities than suggested by data collected solely from crops and weeds in agricultural fields. Further characterization of these apparently asymptomatic haplotypes will facilitate comparison with disease-causing variants and provide insights into the continued emergence and spread of CLso.

Sub-optimal temperatures lead to altered expression of stress-related genes and increased 'Candidatus Liberibacter solanacearum' accumulation in potato psyllid.

The potato psyllid Bactericera cockerelli is the insect vector of the fastidious bacterium 'Candidatus Liberibacter solanacearum'. The bacterium infects both B. cockerelli and plant species, causing zebra chip (ZC) disease of potato and vein-greening disease of tomato. Temperatures are known to influence the initiation and progression of disease symptom in the host plant, and seasonal transitions from moderate to high temperatures trigger psyllid dispersal migration to facilitate survival. 'Ca. L. solanacearum' -infected and uninfected psyllids were reared at previously established 'permissible', optimal, and 'non-permissible' and temperatures of 18°C, 24°C, and 30°C, respectively. Gene expression profiles for 'Ca. L. solanacearum'-infected and -uninfected adult psyllids reared at different temperatures were characterized by Illumina RNA-Seq analysis. Bacterial genome copy number was quantified by real-time quantitative-PCR (qPCR) amplification. Relative gene expression profiles varied in psyllids reared at the three experimental temperatures. Psyllids reared at 18°C and 30°C exhibited greater fold-change increased expression of stress- and 'Ca. L. solanacearum' invasion-related proteins. Quantification by qPCR of bacterial genome copy number revealed that 'Ca. L. solanacearum' accumulation was significantly lower in psyllids reared at 18°C and 30°C, compared to 24°C. Temperature is a key factor in the life history of potato psyllid and multiplication/accumulation of 'Ca. L. solanacearum' in both the plant and psyllid host, influences the expression of genes associated with thermal stress tolerance, among others, and may have been instrumental in driving the co-evolution of the pathosystem.

Accumulation and Transmission of 'Candidatus Liberibacter solanacearum' Haplotypes by the Nymphs of Two Psyllid Vectors.

'Candidatus Liberibacter solanacearum' (Lso) is a plant pathogenic bacterium transmitted by psyllids that causes significant agricultural damage. Several Lso haplotypes have been reported. Among them, LsoA and LsoB are transmitted by the potato psyllid Bactericera cockerelli and infect solanaceous crops, and LsoD is transmitted by the carrot psyllid B. trigonica and infects apiaceous crops. Several studies evaluated the transmission of these haplotypes by adult psyllids. However, fewer data are available on the transmission of different Lso haplotypes by psyllid nymphs. In this study, we investigated the transmission of these three haplotypes by psyllid nymphs to expand our basic understanding of Lso transmission. Specifically, the objective was to determine if the haplotypes differed in their transmission rates by nymphs and if LsoA and LsoB accumulated at different rates in the guts of nymphs as it occurs in adults. First, we quantified LsoA and LsoB titers in the guts of third- and fifth-instar potato psyllid nymphs. We found similar LsoA titers in the two nymphal stages, while LsoB titer was lower in the gut of the third-instar nymphs compared to fifth-instar nymphs. Second, we assessed the transmission efficiency of LsoA and LsoB by third-instar nymphs to tomato plants, revealing that LsoA was transmitted earlier and with higher efficiency than LsoB. Finally, we examined the transmission of LsoD by carrot psyllid nymphs to celery plants and demonstrated an age-related difference in the transmission rate. These findings provide valuable insights into the transmission dynamics of different Lso haplotypes by nymphal vectors, shedding light on their epidemiology and interactions with their psyllid vectors.

Individual and Combined Effects of Predatory Bug Engytatus nicotianae and Trichoderma atroviride in Suppressing the Tomato Potato Psyllid Bactericera cockerelli in Greenhouse Grown Tomatoes

The tomato potato psyllid (TPP) Bactericera cockerelli is a serious pest of the Solanaceae family. The management of this pest using synthetic pesticides is problematic because of the development of pesticide resistance and environmental concerns including impacts on non-target organisms. The predatory bug Engytatus nicotianae has recently been identified as a useful biocontrol agent for TPP in greenhouses. The soil fungus Trichoderma Pers. is commonly used as a plant growth enhancer and biocontrol agent against phytopathogenic fungi. Therefore, there could be advantages associated with the combined use of these biocontrol agents. Some reports in other systems suggest that Trichoderma inoculation may alter the behaviour of pests and their natural enemies by modifying plant defence metabolites such as volatile organic compounds (VOCs). For this reason, this study aimed to investigate the individual and combined efficacy of these biocontrol agents (i.e., Trichoderma atroviride and E. nicotianae) against TPP in greenhouse grown tomatoes (Solanum lycopersicum cv. Merlice). To this end, we compared the effect of each biocontrol agent and their combination on TPP abundance across different developmental stages (egg, nymphs, adults) and the number of infested leaves. We also investigated plant VOC emissions under the different treatments. Across all measured TPP stages, the treatments tested (E. nicotianae alone, T. atrovirdae alone, and T. atrovirdae + E. nicotianae) significantly reduced mean TPP counts relative to the control, and no significant differences were observed in VOC emissions among treatments. Overall, T. atrovirdae alone was less effective than E. nicotianae alone and its combination with T. atrovirdae in suppressing TPP populations. However, the combined use of Trichoderma + E. nicotianae did not show significant advantages over the use of E. nicotianae alone in controlling TPP. Therefore, their combined use needs to be further assessed in light of other advantages of Trichoderma to the crop (e.g., growth promotion or pathogen defence).

Catch of the Potato Psyllid Bactericera Cockerelli (Hemiptera: Triozidae) with Yellow Sticky Traps Covered with Mesh of Different Color and Size

Catch of the Potato Psyllid Bactericera Cockerelli (Hemiptera: Triozidae) with Yellow Sticky Traps Covered with Mesh of Different Color and Size

A high-throughput plate method for nucleic acid extraction from beet leafhopper (Hemiptera: Cicadellidae) and potato psyllid (Hemiptera: Triozidae) for pathogen detection.

Plant pathogens that are transmitted by insect vectors cause considerable damage to crops when pests or pathogens are not detected early in the season and populations are not controlled. Knowledge of pathogen prevalence in insect pest populations can aid growers in their insect pest management decisions but requires the timely dissemination of results. This process requires that specimen capture, identification, nucleic acid extraction, and molecular detection of a pathogen(s) occur alongside a platform for sharing results. The potato psyllid (Bactericera cockerelli, Sulc; Hemiptera: Triozidae) and beet leafhopper (Circulifer tenellus, Baker; Hemiptera: Cicadellidae) transmit pathogens to potato and other vegetable or seed crops each season in the northwestern United States. While the potato psyllid has been tested for pathogen occurrence for the past decade, testing of the beet leafhopper is a new endeavor and substantially increases the specimen number that must be tested by our laboratories each season. To aid in the rapid processing of individual insect specimens, we optimized and validated a new high-throughput 96-well plate nucleic acid extraction method for use in place of a standard 1.5-ml single-tube extraction method. Processing efficiency, in terms of total specimens processed over a 2-day period, improved 2.5-fold, and the cost associated with processing a single sample was nearly cut in half with this newly developed plate nucleic acid extraction method. Overall, this method has proven to be an excellent tool for the rapid testing of large numbers of small, individual insect vectors to enable timely dissemination of data on pathogen prevalence to growers.

Flight Performance of the Potato Psyllid (Bactericera cockerelli) is Negatively Affected by ‘Candidatus Liberibacter solanacearum’ Infection

Flight Performance of the Potato Psyllid (Bactericera cockerelli) is Negatively Affected by ‘Candidatus Liberibacter solanacearum’ Infection

Development and reproduction of a native generalist predator, Coccinella transversalis (Coleoptera: Coccinellidae), on the tomato potato psyllid, Bactericera cockerelli, with a greenhouse assay of biocontrol potential

The tomato potato psyllid (Bactericera cockerelli Šulc (Hemiptera: Triozidae)) can cause significant losses to Solanaceous crop via direct feeding and by transmitting the bacterium Candidatus Liberibacter solanacearum. In the present study, an Australian native ladybird beetle, Coccinella transversalis Fabricius, was examined as a potential biological control agent of B. cockerelli. An age-stage, two sex life table of C. transversalis was constructed, demonstrating that C. transversalis could survive, develop, and reproduce successfully when fed B. cockerelli as a monotypic diet. Predation on B. cockerelli by C. transversalis third and fourth instar larvae and adults fit the Holling 'type II' disc equation. In a glasshouse trial using B. cockerelli-infested tomato plants, C. transversalis larvae reduced the population growth of B. cockerelli larvae by 66% and adults by 59% over one month, reducing loss of leaf chlorophyll and increasing plant biomass relative to controls. The results of the present study were compared with a previous study for the resident ladybird beetle species against B. cockerelli. Whereas C. transversalis suppressed B. cockerelli populations, the impact was less than that of the introduced ladybird, Hippodamia variegata Goeze, which showed higher voracity in previous work. However, B. cockerelli is a suitable prey for C. transversalis and this species should aid in its biological control in agricultural ecosystems in Australia.

Value‐adding in biosecurity surveillance and monitoring: Testing colour and non‐target semiochemical lures on Psylloidea and Pentatomoidea

AbstractCost efficiency in biosecurity surveillance is vital, and the ability to survey multiple pest species using just one trap is, therefore, highly appealing. The Psylloidea, or plantlice, contain significant horticultural pest species that act as vectors for a number of deleterious plant bacteria. We examine the efficacy of using two different coloured sticky traps, and two semiochemical lures on the general Psylloidea and Pentatomoidea fauna, and a target extant pest psyllid; tomato potato psyllid (TPP) Bactericera cockerelli (Šulc) in Western Australia. Specifically, we test the effect of semiochemical lure (no lure, Asian citrus psyllid ACP lure, brown marmorated stink bug BMSB lure, combined lures), sticky trap colour (yellow‐green vs yellow) and sentinel plant (tomato vs citrus) on psyllid and pentatomid species in 104 urban backyards across Perth, Australia. We found that tomato sentinel host plants and yellow‐green traps significantly increased the capture rate of TPP, but that lures decreased the capture of TPP constraining their use. Yellow‐green traps also increased the capture rate of all other Psylloidea. Although BMSB lures reduced TPP capture, these lures increased the abundances of other Psylloidea and the pest stinkbug Plautia affinis (Dallas) on traps. Thus, our experiment demonstrates that increased efficiencies can be gained with multi‐species traps and semiochemical lures for particular groups, provided that they have been tested on focal organisms in the first instance, as reactions to non‐target lures are unpredictable and species specific.

Identification and Characterization of Potato Zebra Chip Resistance Among Wild Solanum Species

Potato zebra chip (ZC) disease, associated with the uncultured phloem-limited bacterium, Candidatus Liberibacter solanacearum (CLso), is transmitted by the potato psyllid Bactericera cockerelli. Potato ZC disease poses a significant threat to potato production worldwide. Current management practices mainly rely on the control of the psyllid to limit the spread of CLso. The present study investigated new sources of ZC resistance among wild Solanum species. A taxonomically diverse collection of tuber-bearing Solanum species was screened; one ZC-resistant accession and three ZC-tolerant accessions were identified among the 52 screened accessions. Further characterization of the resistant accession showed that the resistance was primarily associated with antibiosis effects due to differences in leaf trichome density and morphology of the wild accession, which could limit the psyllid feeding and oviposition. This germplasm offers a good resource for further understanding ZC and psyllid resistance mechanisms, contributing to potato breeding efforts to develop ZC resistance cultivars. Alternatively, it could be used as a potential trap crop to manage psyllid and control ZC disease.

Impacts of zebra chip disease and irrigation on leaf physiological traits in potato

Zebra chip disease (ZC) is caused by the fastidious, phloem-limited, bacterial pathogen ‘Candidatus Liberibacter solanacearum (Lso), which is transmitted from plant to plant by the potato psyllid (Bactericera cockerelli (Sulc)). Understanding how ZC impacts potato (Solanum tuberosum L.) physiology, could help growers in making more informed crop management decisions. Measurements of instantaneous leaf physiological responses, such as photosynthetic CO2 uptake and transpiration on the leaf surface, can be used not only for fast screening of affected plants in the field but also for optimizing irrigation management. Over the 2019 and 2020 field seasons, we characterized time-course photosynthetic physiological responses of potato plants infested by potato psyllids (B. cockerelli (Sulc)) carrying the Lso haplotypes A+B. Potato plants were subjected to different variable-rate irrigation (VRI) treatments (100%, 80%, and 60% of field capacity of the soil) through a center-pivot sprinkler system to examine the impact of the disease on key physiological parameters of photosynthesis and transpiration. Leaf and air temperatures, and hyperspectral profiles of the canopy were also measured and compared. The measurements were made during midday weekly from 25 to 50 days after plant infestation (DAI) with bacteriliferous psyllids. The results showed that many of the measured variables, including stomatal conductance, photosynthesis rate, transpiration rate, quantum yields, and normalized difference in vegetation index started to decrease beginning approximately 28–35 DAI, gradually worsening until 50 DAI, in both 2019 and 2020, as the infection proceeded. The decreases in stomatal conductance in infected plants led to decreases in photosynthesis and transpiration. In turn, reduced transpiration resulted in increased leaf temperature due to decrease in evaporative cooling on the leaf surface. Higher leaf temperatures under hot and dry conditions with high light intensity during the daytime would further reduce photosynthetic light harvesting, which is supported by our data, indicating the damage to the photosynthetic pigment formation and machinery. These findings support the previous report that increased leaf temperature in infected plants may have been derived from the closure of stomata in hypersensitive reactions to infection. These stomatal responses were detected within 28 DAI, a week earlier than the differences in hyperspectral profiles observed 35 DAI, and could be implemented in early disease detection strategiesusing measurements of leaf temperature.

Studies on seed transmission of “Candidatus Liberibacter solanacearum” in pepper and its impact on plant emergence

Abstract“Candidatus Liberibacter solanacearum” (Lso), transmitted by the potato psyllid (Bactericera cockerelli), is the causal agent of potato zebra chip, but can also infect other solanaceous plants, including peppers. Studies were conducted to investigate whether Lso could be transmitted to the next generation of plants through seeds from infected pepper plants. In 2014, jalapeno pepper plants were infested with psyllids carrying a mixture of Lso A and B (AB) at the AgriLife Research Station at Bushland. The study was again conducted in 2019 and pepper plants were infested with psyllids carrying Lso B or Lso AB. In each of the studies, noninfested plants served as controls. At harvest, fruits were collected and tested for the presence of Lso using quantitative PCR. Seeds from infected fruits were then tested for Lso. Overall, the percentage of seeds that tested positive for Lso ranged from 33% to 70%. However, Lso detection in embryos ranged only from 0% to 8%. Seed samples from Lso‐positive fruits were planted in the greenhouse to determine the impact of Lso on emergence and the incidence of Lso in emerged plants. Although plant emergence differed between some of the seeds obtained from Lso‐positive and ‐negative fruits, the overall impact of Lso on plant emergence was not consistent. However, of the 182 plants that emerged from seeds collected from infected fruits, none was positive for Lso, suggesting that seeds are unlikely to serve as sources for new Lso infections and their impact on disease epidemiology is negligible.

Sustainable Potato Production in the Mountain Area of Ecuador, an Approach to Increase Productivity with Small Scale Farmers

Ecuador potato crop is family based production system. Potato production has two roles in their economy, the first is providing food for their families and the second is a source of income for the household. However small scale farmers have limited access to local markets and most of the sales are through intermediates’ who purchase directly in the field at the lowest price possible. Potato production challenges for the small-scale farmers are among others availability of quality potato seed, direct sales, purchase of agrochemical inputs to maintain their crops and lack of education. In 2021, only 4% of potato farmers used certified seed. Potato yield is still low around 16.1 t·ha-1, in the last 10 years the total potato cultivated area was reduced by at least 50%. The farmers produce “Bokashi” and other organic fertilizer and these are effective to improve soil fertility and plant health. Homemade bio-pesticides reduce agrochemical pesticides. The Decision Support System (DSS) is a handheld device to control late blight, minimizes fungicide applications and improve fungicide rotation. In 2018 Candidatus Liberibacter solanacearum (Lso), the causal agent of zebra chip, and its vector, the potato psyllid Bactericera cockerelli, together created havoc for farmers and researchers. Promotion of early potato varieties INIAP—Libertad is an alternative to lower the impact of this newest pest.

'Candidatus Liberibacter solanacearum' Infection of Physalis ixocarpa Brot. (Solanales: Solanaceae) in Saltillo, Mexico.

The potato psyllid Bactericera cockerelli (Šulc) (Hemiptera: Triozidae) is a pest of solanaceous crops (order Solanales), including potato (Solanum tuberosum L.) and tomato (S. lycopersicum L.). Feeding by high populations of nymphs causes psyllid yellows while adults and nymphs are vectors of the plant pathogen 'Candidatus Liberibacter solanacearum'. Foliar symptoms that were consistent with either 'Ca. L. solanacearum' infection or psyllid yellows were observed in 2019 on tomatillo (Physalis ixocarpa Brot.; family Solanaceae) grown within an experimental plot located near Saltillo, Mexico. This study had three primary objectives: 9i) determine whether the foliar symptoms observed on tomatillo were associated with 'Ca. L. solanacearum' infection, (ii) identify the haplotypes of 'Ca. L. solanacearum' and potato psyllids present in the symptomatic plot, and (iii) use gut content analysis to infer the plant sources of 'Ca. L. solanacearum'-infected psyllids. Results confirmed that 71% of symptomatic plants and 71% of psyllids collected from the plants were infected with 'Ca. L. solanacearum'. The detection of 'Ca. L. solanacearum' in plants and psyllids and the lack of nymphal populations associated with psyllid yellows strongly suggests that the observed foliar symptoms were caused by 'Ca. L. solanacearum' infection. All infected plants and insects harbored the more virulent 'Ca. L. solanacearum' haplotype B but one psyllid was also coinfected with haplotype A. The potato psyllids were predominantly of the central haplotype but one psyllid was identified as the western haplotype. Molecular gut content analysis of psyllids confirmed the movement of psyllids between noncrop habitats and tomatillo and indicated that 'Ca. L. solanacearum' infection of psyllids was associated with increased plant diversity in their diet.

Developing a non-destructive metabarcoding protocol for detection of pest insects in bulk trap catches

Metabarcoding has the potential to revolutionise insect surveillance by providing high-throughput and cost-effective species identification of all specimens within mixed trap catches. Nevertheless, incorporation of metabarcoding into insect diagnostic laboratories will first require the development and evaluation of protocols that adhere to the specialised regulatory requirements of invasive species surveillance. In this study, we develop a multi-locus non-destructive metabarcoding protocol that allows sensitive detection of agricultural pests, and subsequent confirmation using traditional diagnostic techniques. We validate this protocol for the detection of tomato potato psyllid (Bactericera cockerelli) and Russian wheat aphid (Diuraphis noxia) within mock communities and field survey traps. We find that metabarcoding can reliably detect target insects within mixed community samples, including specimens that morphological identification did not initially detect, but sensitivity appears inversely related to community size and is impacted by primer biases, target loci, and sample indexing strategy. While our multi-locus approach allowed independent validation of target detection, lack of reference sequences for 18S and 12S restricted its usefulness for estimating diversity in field samples. The non-destructive DNA extraction proved invaluable for resolving inconsistencies between morphological and metabarcoding identification results, and post-extraction specimens were suitable for both morphological re-examination and DNA re-extraction for confirmatory barcoding.

Impact of ‘Candidatus Liberibacter solanacearum’ haplotypes on sprout emergence and growth from infected seed tubers

‘Candidatus Liberibacter solanacearum’ (Lso), which is transmitted by the potato psyllid (Bactericera cockerelli), is the putative causal agent of potato zebra chip. Two haplotypes of the bacterial agent (A & B) are currently widely detected in US potato production regions. This study was aimed at determining the relative impacts of the two haplotypes on plant emergence and agronomic characteristics of emerged plants. Greenhouse experiments were conducted using tubers infected with known haplotypes (A, B or AB mix), collected from two separate locations. Collected tubers were planted in replicated pots and plant emergence was monitored daily. Thirty-five days after planting, emerged plants were harvested and individual plant biomass, height, stem diameter, and leaf area were determined. For both locations, tubers infected with Lso B had lower plant emergence compared to uninfected controls. However, there was no difference in plant emergence between tubers infected with Lso A and Lso B. Emergence of plants from tubers infected with Lso B was slower compared to that of uninfected tubers but there was no difference in time of plant emergence between tubers infected with Lso A and the uninfected controls. Biomass of plants which emerged from uninfected tubers was greater than that from all Lso-infected tubers, regardless of haplotype, and plants which emerged from tubers infected with Lso A had greater biomass than those from tubers infected with Lso B. Differences in height, stem diameter, and leaf area among emerged plants followed similar patterns for both locations (uninfected control the highest and Lso B the lowest) except those from tubers infected with AB, which were inconsistent.

Feeding behaviour of Bactericera cockerelli (\u0160ulc) (Hemiptera: Psylloidea: Triozidae) changes when infected with Candidatus Liberibacter solanacearum

Pathogens which need a vector for their transmission can alter the vectors’ behaviour to favour their spread. We used the electrical penetration graph technique to investigate this hypothesis by using the tomato potato psyllid Bactericera cockerelli infected or not with the plant pathogen Candidatus Liberibacter solanacearum (CLso) on African boxthorn and tomato. Probing was not affected by the host type but there was a significant effect on probing due to the infection status of the psyllid. More psyllids carried out probing activities in the sieve elements when infected with CLso, and more probing activities were observed from CLso-infected psyllids by comparison to the non-infected groups. Specifically, significant increases in salivation, phloem ingestion and number of probes, before and after reaching the sieve elements, were noticed in the infected groups. Furthermore, time elapsed to reach the sieve elements was significantly shortened by 2 h in the infected group. Remaining probing activities in xylem tissues were not different between all psyllid groups. The observed changes in feeding behaviour by pathogen-infected psyllids may well ensure further spread of the pathogen as greater salivation has the potential to increase transmission, highlighting at the same time the important role that crop and non-crop hosts play in disease epidemiology.

Seasonal Population Dynamics of Potato Psyllid (Hemiptera: Triozidae) in the Columbia River Basin.

Understanding factors that affect the population dynamics of insect pest species is key for developing integrated pest management strategies in agroecosystems. Most insect pest populations are strongly regulated by abiotic factors such as temperature and precipitation, and assessing relationships between abiotic conditions and pest dynamics can aid decision-making. However, many pests are also managed with insecticides, which can confound relationships between abiotic factors and pest dynamics. Here we used data from a regional monitoring network in the Pacific Northwest United States to explore effects of abiotic factors on populations of an intensively managed potato pest, the potato psyllid (Bactericera cockerelli Šulc), which can vector Candidatus Liberibacter psyllaurus, a bacterial pathogen of potatoes. We assessed effects of temperature on psyllid populations, and show psyllid population growth followed predictable patterns within each year, but there was considerable variation across years in psyllid abundance. Examination of seasonal weather patterns suggested that in 2017, when psyllid populations were less abundant by several orders of magnitude than other years, a particularly long and cold period of winter weather may have harmed overwintering populations and limited population growth. The rate of degree-day accumulation over time, as well as total degree-day accumulation also affected trap catch abundance, likely by mediating the number of psyllid generations per season. Our findings indicate that growers can reliably infer the potential magnitude of risk from potato psyllids using monitoring data, date of first detection, seasonal weather patterns, and population size early in the growing season.

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.

Potato psyllid (Bactericera cockerelli Sulc)-transmitted “Candidatus Liberibacter solanacearum” (Lso) has been negatively impacting the potato industry in the United States as well as other potato-producing countries. Lso has been linked to a condition known as zebra chip (ZC) that affects yield and quality of potato tubers. Efforts to find sources of resistance to ZC have primarily focused on greenhouse evaluations based on a single inoculation time prior to harvest. Plant response to infection, however, could be influenced by the developmental stage of the host plant, and ZC may continue to develop after harvest. The objectives of this study were to quantify Lso inoculation success, Lso titer, ZC severity and Lso development during storage in eight potato genotypes. These evaluations were conducted on plants infested with Lso-positive psyllids at 77, 12, and 4 days before vine removal (DBVR). The evaluated genotypes were categorized according to their relative resistance to Lso and tolerance to ZC symptoms. Lso inoculation success in the genotype family A07781, derived from Solanum chacoense, was lower than that of the susceptible control (‘Russet Burbank’). A07781-4LB and A07781-3LB genotypes were characterized relatively resistant to the pathogen and highly tolerant to ZC symptoms, while A07781-10LB was categorized as susceptible to Lso but relatively tolerant to symptom expression. In stored potatoes, increase in Lso concentrations was observed for all infestation times. However, significantly higher Lso titer was detected in tubers infested 12 DBVR and the effect was similar across genotypes. Overall, the A07781 family can be considered as a promising source of resistance or tolerance to ZC.

Concanavalin A Toxicity Towards Potato Psyllid and Apoptosis Induction in Midgut Cells.

Concanavalin A (ConA), a legume lectin, has been drawing increasing attention in recent years concerning its toxicity against insects and its potential application in pest management. In an attempt to evaluate the effect of ConA on potato psyllid (Bactericera cockerelli), an economically important pest of solanaceous crops, the effect of ConA on potato psyllid survival, psyllid gut nuclear morphology, and expression of psyllid caspase genes were evaluated. Our results determined that artificial diet-feeding assays using ConA had deleterious effects on potato psyllids, resulting in significant psyllid mortality following ingestion. We also found that an apoptotic response was induced by ConA in psyllid midgut cells, which was demonstrated by the DNA fragmentation and abnormal nuclear architecture in the midgut cells. Following ConA ingestion, there was also upregulation of caspase genes in the psyllid midguts. Therefore, a key mechanism behind ConA toxicity towards potato psyllid probably involves the induction of apoptosis in midgut cells. This study could provide a better understanding of the mechanisms underlying ConA toxicity in insects and be a stepping stone towards the development of new psyllid control strategies based on plant lectins.