Bactericera Cockerelli Research Articles

Development of Action Thresholds for Management of Bactericera cockerelli and Zebra Chip Disease in Potatoes at Pukekohe, New Zealand

Bactericera cockerelli (tomato potato psyllid, TPP) is a serious pest of potato crops, causing feeding damage and also vectoring Candidatus Liberibacter solanacearum, the causal agent of the Zebra Chip (ZC) disease in potatoes. The results of 6 years of early and main crop potato trials at Pukekohe, New Zealand, are summarised and damage caused by TPP is reported. Results show that spring-sown (early) potato crops do not require insecticides. In main crop summer trials we tested action thresholds based on 10 and 20 TPP nymphs per 100 middle leaves but the incidence of ZC damage was commercially unacceptable, ranging from 4 to 9 %. Subsequently we tested an action threshold of >3 TPP adults per yellow sticky trap per week that led to ZC damage ranging from 0.9 to 1.6 %. We also compared monitoring of TPP using sticky trap catches with a degree day model started in mid winter (1 July) for forecasting generation times of TPP. On the basis of the field trial results, we recommend that from early summer onwards, the timing of the first foliar application of insecticide needs to be applied early enough to protect main crop potatoes from the first generation of TPP that occurs after potato tubers have emerged (at Pukekohe, this is the third TPP generation from 1 July when using degree day modelling). Three years of main crop trials indicate that an action threshold of >3 TPP per trap per week provides effective TPP/ZC management in the Pukekohe region when used in conjunction with natural enemies and an insecticide programme that features the use of selective insecticides.

Pathogenicity of the Hypocreales Fungi Beauveria Bassiana and Metarhizium Anisopliae Against Insect Pests of Tomato

Silverleaf whitefly, Bemisia tabaci Gennadius (Aleyrodidae), potato/ tomato psyllid, Bactericera cockerelli Sulc. (Triozidae), and western flower thrips, Frankliniella occidentalis (Pergande) (Thripidae), are insect pests of economic importance in tomato (Solanum lycopersicum L.) and other solanaceous vegetables in México. Soil is the main reservoir for many entomopathogenic fungi known as biological control agents important for IPM, but only a few strains obtained from soil have been used against insect pests. In this study, the biological activity of two native isolates of entomopathogenic fungi (from soil at Chihuahua, México), was evaluated against immatures of the three insect pests in a laboratory. Beauveria bassiana (Balsamo) Vuillemin (Hypocreales: Clavicipitaceae) (Bb-CIAD1) isolate was more virulent than the Metarhizium anisopliae (Metschnikoff) Socorin (Hypocreales: Clavicipitaceae) (Ma-CIAD1) isolate. Mortality based on mycosis varied significantly 8 days after inoculation. The number of immature insects infected by fungi was correlated with spore concentration. Beauveria bassiana (Bb-CIAD1) and M. anisopliae (Ma-CIAD1) had LT50 values of 5.6–6.4 and 5.3–6.5 days, respectively. The results indicated that psyllids, thrips, and whiteflies were susceptible to the native fungal isolates with potential as microbial control agents. Based on the results, we suggest the native isolates of entomopathogenic fungi from soil could be used as biological control agents of many other insect pests.

Synthesis and regulation of chlorogenic acid in potato: Rerouting phenylpropanoid flux in HQT-silenced lines.

Chlorogenic acid (CGA) is the major phenolic sink in potato tubers and can constitute over 90% of total phenylpropanoids. The regulation of CGA biosynthesis in potato and the role of the CGA biosynthetic gene hydroxycinnamoyl CoA:quinate hydroxycinnamoyl transferase (HQT) was characterized. A sucrose induced accumulation of CGA correlated with the increased expression of phenylalanine ammonia-lyase (PAL) rather than HQT. Transient expression of the potato MYB transcription factor StAN1 (anthocyanin 1) in tobacco increased CGA. RNAi suppression of HQT resulted in over a 90% reduction in CGA and resulted in early flowering. The reduction in total phenolics and antioxidant capacity was less than the reduction in CGA, suggesting flux was rerouted into other phenylpropanoids. Network analysis showed distinct patterns in different organs, with anthocyanins and phenolic acids showing negative correlations in leaves and flowers and positive in tubers. Some flavonols increased in flowers, but not in leaves or tubers. Anthocyanins increased in flowers and showed a trend to increase in leaves, but not tubers. HQT suppression increased biosynthesis of caffeoyl polyamines, some of which are not previously reported in potato. Decreased PAL expression and enzyme activity was observed in HQT suppressed lines, suggesting the existence of a regulatory loop between CGA and PAL. Electrophysiology detected no effect of CGA suppression on potato psyllid feeding. Collectively, this research showed that CGA in potatoes is synthesized through HQT and HQT suppression altered phenotype and redirected phenylpropanoid flux.

Translating Anatomical Structures and Functional Genomics of Candidatus Liberibacter asiaticus and solanacearum Into Circulative, Propagative Vector-Mediated Transmission Processes

Ca. Liberibacter asiaticus is the putative fastidious bacterial causal agent of citrus greening disease, also known as Huanglongbing (HLB), translated from Chinese as yellow dragon disease. The HLB bacterial pathogen is indigenous to Asia but has been introduced and dispersed to citrus throughout the Americas. A related bacterium that is indigenous to the Americas causes damage to potato (zebra chip) and tomato (vein-greening) and other solanaceous hosts. The causal agents are propagative and circulative in the psyllid vector, Diaphorina citri (Kuwayama) and Bactericera cockerelli (Sulc.), the Asian citrus and potato (or tomato) psyllid, respectively. The specific psyllid proteins that are indirectly or directly involved in the circulative, propagative transmission pathway are not known. However, if proteins were known that function at key points in the pathway e.g. post-ingestion, infection, biofilm formation, nutrition, circulation, and/or acquisition were known, such knowledge could be exploited to knock out their expression and abate pathogen transmission. To this end a combined approach involving functional genomics and anatomical localization of the bacterium is being implemented.  Results indicate that Ca. Liberibacter establishes biofilms on the outer surfaces of the alimentary canal and salivary glands of the Asian citrus psyllid (ACP) Diaphorina citri Kuwayama and the potato psyllid (PP) Bactericera cockerelli Sulc. In silico transcript profiling of infected and uninfected ACP and PP identified a number of mis-expressed, unique transcripts (unitrans). Functional predictions (gene ontology associations) implicate certain of these unitrans in Ca. Liberibacter infection of the psyllid host and/or in psyllid-mediated Ca. Liberibacter transmission processes.

A Comparative Transcriptomic Approach to Elucidate Psyllid-Ca. Liberibacter Interactions

Citrus greening is the most destructive disease of citrus crops worldwide. The introduced Asian citrus psyllid (ACP) Diaphorina citri Kuwayama transmits the (putative) causal bacterium, Candidatus Liberibacter asiaticus. A close relative, Ca. L. solanacearum, is the pathogen associated with Zebra chip disease of potato and vein-greening disease of tomato. It is both transmitted by and propagative in the endemic (western U.S) potato psyllid (PoP) Bactericerca cockerelli Sulc. The PoP occurs widely in the western U.S. and so has been used as a parallel study system for the quarantined ACP-greening complex. To identify proteins involved in global psyllid-Ca. Liberibacter interactions, the ACP and PoP transcriptomes were sequenced, yielding a total of 45,976 and 82,224 Illumina unique ACP and PoP transcripts, respectively. Cluster analysis revealed a high degree of sequence and transcript conservation suggestive of roles in core growth and developmental processes, providing the first molecular snapshot of the specific psyllid genes responsive to parasite invasion and circulation in the host. Evidence of inter-psyllid molecular conservation substantiates the suitability of PoP as a study system for ACP-Ca. L. asiatcus. Comparative in silico expression analysis within and between psyllid species revealed predicted functions involved in Ca. Liberibacter parasitism that were both unique and shared in common among adult and nymphal instars. In addition, functional characterization based on Gene Ontology analysis has revealed a number of genes associated with host-parasite interactions that could mediate Ca. Liberibacter infection, propagation, and circulation in the psyllid, as well as transmission processes.

Improved methods for genome sequencing of Liberibacters by BAC library-based metagenomics approach

Liberibacters have not yet been successfully cultured; their minimal genomes carry multiple copies of several genes. Sequences identical to phage genomes have been found in many Liberibacters. Available evidences suggest that the Liberibacter genomes are adapting rapidly in different hosts and environments. Characterization of genomes of rapidly changing unculturable organisms can be challenging. We have used a model system based on Candidatus Liberibacter psyllaurous associated with tomato “psyllid yellows” (Hansen et al., 2008) to develop methodologies using alternate techniques for sequencing metagenomes. We have constructed a BAC library from infected tomato psyllids (Bactericera cockerelli). The library consists of 57,600 clones arrayed in 150 plates each with 384 wells. DNA from individual clones were pooled for screening purposes. Initial identification of clones with Liberibacter sequences were conducted based on 16s ribosomal sequences, and contiguous clones were characterized by end sequencing and identified as containing Liberibacter genome fragments. Screening of additional clones from the library was based on probes developed on such sequences. A total of 245 clones with Liberibacter genome fragments have been identified. A total of 63 bar-coded BAC clones were sequenced by using Roche 454 technology. BAC clones from this library contain large inserts (average size 70 kb). Similarities and differences with other well characterized genomes of Liberibacters (Duan et al., 2009, Lin et al., 2011) will be presented.

SEM- and TEM-informed anatomical observations of Ca. Liberibacter solanacearum (Lso) parasite localization in its psyllid host

With SEM, we studied external midgut surfaces of all potato psyllid instars, and, additionally with SEM and TEM, the anterior alimentary system of adults. The ontogenetically earliest point of Lso detection was in the 3rd instar, then in consecutively greater percentages of 4th and 5th instars, then in a lower percentage of teneral and mature adults. Two age-based patterns of proliferation were identified in the oral region of mature adults- streaming, in which Lso were confined to passageways, and diffuse, in which Lso occurred inside of, and around, cells of mouthpart components, muscles and epidermis.

Influence of the pathogen Candidatus Liberibacter solanacearum on tomato host plant volatiles and psyllid vector settlement.

Candidatus Liberibacter solanacearum (CLso) is an unculturable bacterium vectored by the tomato potato psyllid (TPP) Bactericera cockerelli and has been associated with Zebra chip disease in potato and with other economically relevant symptoms observed in solanaceous crops. By altering their host and vector's biological system, pathogens are able to induce changes that benefit them by increasing their transmission rate. Understanding these changes can enable better targeting of mechanisms to control pathogen outbreaks. Here, we explored how the CLso infectious status affects the volatile organic compounds (VOCs) of the tomato plant, and whether the CLso infectious status of TPP influences host plant settlement. These chemical and behavioral changes can ultimately affect the rate of encounter between the host and the vector. Results from headspace volatile collection of tomato plants showed that CLso infected tomato plants emitted a qualitatively and quantitatively different blend of VOCs compared to sham-infected plants. By a factorial experiment, we showed that CLso negative (CLso-) TPP preferred to settle 70 % more often on infected tomato plants, while CLso positive (CLso+) TPP were found 68 % more often on sham-infected tomato plants. These results provide new evidence in favor of both host and vector manipulation by CLso.

Comparison of Potato and Asian Citrus Psyllid Adult and Nymph Transcriptomes Identified Vector Transcripts with Potential Involvement in Circulative, Propagative Liberibacter Transmission

The potato psyllid (PoP) Bactericera cockerelli (Sulc) and Asian citrus psyllid (ACP) Diaphorina citri Kuwayama are the insect vectors of the fastidious plant pathogen, Candidatus Liberibacter solanacearum (CLso) and Ca. L. asiaticus (CLas), respectively. CLso causes Zebra chip disease of potato and vein-greening in solanaceous species, whereas, CLas causes citrus greening disease. The reliance on insecticides for vector management to reduce pathogen transmission has increased interest in alternative approaches, including RNA interference to abate expression of genes essential for psyllid-mediated Ca. Liberibacter transmission. To identify genes with significantly altered expression at different life stages and conditions of CLso/CLas infection, cDNA libraries were constructed for CLso-infected and -uninfected PoP adults and nymphal instars. Illumina sequencing produced 199,081,451 reads that were assembled into 82,224 unique transcripts. PoP and the analogous transcripts from ACP adult and nymphs reported elsewhere were annotated, organized into functional gene groups using the Gene Ontology classification system, and analyzed for differential in silico expression. Expression profiles revealed vector life stage differences and differential gene expression associated with Liberibacter infection of the psyllid host, including invasion, immune system modulation, nutrition, and development.

Identification and expression analysis of aquaporins in the potato psyllid, Bactericera cockerelli.

Aquaporin (AQPs) proteins transport water and uncharged low molecular-weight solutes across biological membranes. Six to 8 AQP genes have been identified in many insect species, but presently only three aquaporins have been characterized in phloem feeding insects. The objective of this study was to identify candidate AQPs in the potato psyllid, Bactericera cockerelli. Herein, we identified four candidate aquaporin cDNAs in B. cockerelli transcriptome. Phylogenetic analysis showed that candidate BcAQP2-like had high similarity to PRIP aquaporins; while candidates BcAQP4-like, BcAQP5-like and BcAQP9-like clustered within clade B. In particular, candidates BcAQP4-like and BcAQP5-like clustered with functionally validated insect aquaglyceroporin proteins. Expression analyses using RT-qPCR showed that all candidates were expressed in all life stages and tissues. Candidates BcAQP4-like and BcAQP5-like were highly expressed in bacteriocytes, while BcAQP9-like appeared to be expressed at high levels in whole body but not in the assayed tissues. This study is the first global attempt to identify putative aquaporins in a phloem feeding insect.

The tomato potato psyllid,Bactericera cockerelli(Šulc, 1909) (Hemiptera: Triozidae): a review of the threat of the psyllid to Australian solanaceous crop industries and surveillance for incursions in potato crops

The tomato potato psyllid, Bactericera cockerelli (Sulc, 1909), is a major biosecurity threat to Australian solanaceous crop industries. Native to North and Central America, B. cockerelli was accidentally introduced into New Zealand in the mid-2000s. The psyllid is a vector of a phloem-limited, alpha-proteobacterium, ‘Candidatus Liberibacter solanacearum’ (= ‘Ca. L. psyllaurous’), which is associated with psyllid yellows disease in tomatoes, potatoes, capsicums, eggplants and tamarillos, and zebra chip disease in potatoes. Both the vector and pathogen have had a devastating impact on the solanaceous crop industries they affect, resulting in millions of dollars of losses annually through increased pest control and surveillance, reduced yields and disruption to commodity export markets. In April 2014, B. cockerelli and ‘Ca. L. solanacearum’ were reported on Norfolk Island, and it is feared that they could enter other Australian States or Territories either through the accidental importation of infested plant material or by the dispersal of psyllids on easterly airflows from New Zealand. In this paper, we give an overview of the threat of the vector and pathogen to Australian commodities. We report on an ongoing surveillance program, initiated in February 2011, designed to detect incursions of B. cockerelli in eastern Australian potato fields using yellow sticky traps. During the last 3 years, over 2300 traps were placed in the major potato growing regions of Tasmania, Victoria, South Australia and Queensland. No B. cockerelli were detected but over 9600 other Psylloidea were trapped, mainly Ctenarytaina spp. and Acizzia spp. (Psyllidae). Only 0.3% of all Psylloidea caught belonged to the Triozidae allowing the rapid differentiation of the majority of trapped psyllids from B. cockerelli based on wing venation. Recommendations are made for further research and to extend the surveillance program to include other Australian solanaceous crop industries.

Relationship Between Plant Vascular Architecture and Within-Plant Distribution of ‘Candidatus Liberibacter solanacearum’ in Potato

‘Candidatus Liberibacter solanacearum’ is an important pathogen of Solanaceous crops that causes zebra chip disease of potato. This pathogen is transmitted among plants by the potato psyllid Bactericera cockerelli. Within-plant spatial variability in Liberibacter infection impedes the ability to detect the bacterium before the onset of visible symptoms. The goal of our study was to test whether vascular architecture of potato explains the uneven distribution of Liberibacter after inoculation of leaves. The movement of rhodamine B among leaves was used to identify vascular connectivity among leaves. Three weeks after inoculating a single leaf with Liberibacter, the pathogen infected significantly more leaflets that had direct vascular connectivity with the inoculated leaf than leaflets with minimal connectivity. In a separate study, significantly more psyllids confined to whole leaves with direct vascular connectivity to a Liberibacter-infected leaf acquired the pathogen than did psyllids confined to leaves with indirect or partial connectivity to the infected leaf. Using fluorescence in situ hybridization, the pathogen was observed in the inner and outer phloem above and below the export leaf, respectively, corresponding with passive movement of Liberibacter in the phloem. Results of this study indicate that the distribution of Liberibacter in potato is at least partly limited by vascular architecture. This knowledge should improve the design of sampling methods to detect Liberibacter in asymptomatic plants.

Pore size criteria of mesh crop covers for the exclusion of tomato-potato psyllid (Bactericera cockerelli)

Control methods for tomato-potato psyllid (TPP; Bactericera cockerelli) are currently dominated by the use of synthetic biocides. A non-chemical alternative for TPP management is crop mesh, which forms a physical barrier between crop and pest. This study examined the ability of TPP adults to penetrate, or lay eggs through, 22 commercially available crop meshes using a laboratory bioassay. Adult TPP were prevented from moving through the mesh if the mesh complied with any one of the following criteria: shortest pore length <0.55 mm; longest pore length <0.60 mm; diagonal length <0.85 mm; area <0.3 mm2. Eggs were found on foliage only when TPP adults had penetrated the mesh, suggesting that eggs could not be laid through the mesh. The results indicate that crop meshes may provide non-chemical control for TPP that can be used by organic growers, and producers attempting to reduce chemical inputs as part of integrated pest management.

First Report of Natural Infection by 'Candidatus Liberibacter solanacearum' in Bittersweet Nightshade (Solanum dulcamara) in the Columbia Basin of Eastern Oregon.

Potatoes are a major crop in the Columbia Basin of Oregon and Washington, representing an annual farm gate value of almost $750 million. Zebra chip disease (ZC), a new and economically important disease of potato, was first reported in Oregon and Washington in 2011 (1). The disease is caused by the bacterium 'Candidatus Liberibacter solanacearum' (Lso, also referred to as 'Ca. L. psyllaurous'), which is vectored by the potato psyllid (Bactericera cockerelli Sulc) (1,2). Identifying alternative hosts for Lso may facilitate management of ZC disease, which has increased potato production costs in the region. The perennial weed, bittersweet nightshade (Solanum dulcamara L.), is a year-round host of the potato psyllid (3) and is also a suspected host of Lso. However, little is known about the role of this weed in ZC epidemiology. Naturally occurring bittersweet nightshade plants (n = 21) were sampled at six different locations near Hermiston, Oregon, between May and October in 2012. These plants exhibited several symptoms associated with Lso, ranging from asymptomatic to slight purpling, chlorosis, or scorching of the foliage. However, S. dulcamara exhibits similar symptoms under a variety of environmental conditions (drought stress, etc.); therefore, it was difficult to identify potentially infected plants based solely on symptomology. Leaf and stem tissue (n = 21) was analyzed with high-fidelity PCR using species-specific primers for the 16S rDNA gene, CLipoF, and OI2c (2,4). Approximately 27.3% of the plants tested positive for Lso using these primers, including plants from the following locations on 16 April, 16 May, and 24 May, respectively: Hat Rock, OR (45°55.033' N, 119°10.495' W), Irrigon, OR (45°54.560' N, 119°24.857' W), and Stanfield, OR (45°46.971' N, 119°13.203' W). Three plants were selected for further PCR analysis with primers for the outer membrane protein gene, 1482f and 2086r (1). Amplicons obtained with both sets of PCR primers were directly sequenced. A BLAST analysis showed that the 16S rDNA gene sequence (993 to 1,000 bp) shared 99 to 100% identity with several Lso accessions, including JN848751.1 (from Washington) and JN848753.1 (from Oregon). Likewise, the outer membrane protein gene sequence (600 to 601 bp) shared 99 to 100% identity with 'Ca. L. solanacearum' accession KC768330.1 (from Honduras). All six sequences were deposited in GenBank (Accession Nos. KJ854199 to KJ854204). According to these findings, bittersweet nightshade may be an important annual source of Lso in the region, particularly since it serves as a host for the potato psyllid. Potato psyllids were also detected at two of the locations with infected S. dulcamara: Irrigon, OR, and Stanfield, OR. A subsample of the psyllids collected in 2012 were analyzed with PCR and Lso was detected in a sample from Stanfield, OR (5). Identifying perennial hosts of Lso promotes a better understanding of both ZC disease epidemiology and management. To our knowledge, this is the first report of Lso causing natural infections in S. dulcamara in the United States.

Biology and life history of Tamarixia triozae, a parasitoid of the potato psyllid Bactericera cockerelli

Tamarixia triozae (Burks) (Hymenoptera: Eulophidae) is an important parasitoid of the potato psyllid, Bactericera cockerelli Sulc (Hemiptera: Triozidae). We quantified the biology and life table parameters of T. triozae parasitizing B. cockerelli nymphs under laboratory conditions (26 ± 2 °C, 60 ± 10 % RH and 14:10 [L:D] h). Parasitoid developmental times were 1.5, 3.5, 5.7 days for eggs, larvae and pupae respectively, with an average of 12.0 days from egg to adult emergence. Female pupae took 0.4 day longer to develop than male pupae. Adult females lived 19.9 ± 4.5 days and had a 1.9 ± 0.8 days preoviposition period. Each female laid an average of 165.4 ± 45.2 eggs during her lifetime. The net reproductive rate (R0), generation time (T), intrinsic rate of increase (rm), doubling time (DT) and the finite rate of increase (λ) were 130.9, 18.72, 0.26, 2.7, and 1.3 respectively. The potential for the use of T. triozae as a biological control agent of B. cockerelli is discussed.

Management of Bactericera cockerelli (Sulc) (Hemiptera: Triozidae) in Greenhouses with Entomopathogenic Fungi (Hypocreales)

Research on entomopathogenic fungi has been conducted to control the potato psyllid, Bactericera cockerelli, to find new strategies and because of its mode of action, that, unlike other entomopathogenic microorganisms, does not require being ingested. Two Beauveria bassiana strains, a wild type (BB42) and a commercial (BB09), and two Metarhizium anisopliae strains (MA25 and MA28) were used at 1×107 spores ml-1, on B. cockerelli nymphs on chili peppers under greenhouse conditions. Three applications (at 1, 3, and 5 days) killed 36% (MA25) to 47% (BB09), achieving more control than imidacloprid.

Biology and epidemics of Candidatus Liberibacter species, psyllid‐transmitted plant‐pathogenic bacteria

AbstractCandidatus Liberibacter species are Gram‐negative bacteria that live as phloem‐limited obligate parasites in plants, and are associated with several plant diseases. These bacteria are transmitted by insects called psyllids, or jumping plant lice, which feed on plant phloem sap. Citrus huanglongbing (yellow shoot) or citrus greening disease is associated with three different species of Ca. Liberibacter – Ca. L. asiaticus, Ca. L. africanus and Ca. L. americanus – all originally found on different continents. Ca. L. asiaticus is the most severe pathogen, spread by Asian citrus psyllid Diaphorina citri and causing devastating epidemics in several countries. Ca. L. africanus occurs in Africa where it is spread by the African citrus psyllid Trioza erytreae. Ca. Liberibacter solanacearum is associated with diseases in several solanaceous plants, and transmitted by potato psyllid Bactericera cockerelli. Zebra chip disease is causing large damage in potato crops in North America. In Europe Ca. Liberibacter solanacearum is associated with diseases of the Apiaceae family of plants, carrot and celery, and transmitted by psyllids Trioza apicalis and Bactericera trigonica. When Ca. Liberibacter is suspected as the disease agent, the diagnosis is confirmed by DNA‐based detection methods. Ca. Liberibacter‐associated plant diseases can be controlled by using healthy plant propagation material, eradicating symptomatic plants, and by controlling the psyllid populations spreading the disease.

Transcriptome analysis of "Candidatus Liberibacter solanacearum" in its psyllid vector, Bactericera cockerelli.

“Candidatus Liberibacter solanacearum” (Lso) is an emergent pathogen of carrots in Europe and solanaceous plants in North and Central America and New Zealand. This bacterium is closely related to other pathogenic Candidatus Liberibacter spp., all vectored by psyllids. In order to understand the molecular interaction of this pathogen and its psyllid vector, Bactericera cockerelli, Illumina sequencing of psyllid harboring Lso was performed to determine if this approach could be used to assess the bacterial transcriptome in this association. Prior to sequencing, psyllid RNA was purified and insect and bacterial rRNA were removed. Mapping of reads to Lso genome revealed that over 92% of the bacterial genes were expressed in the vector, and that the COG categories Translation and Post-translational modification, protein turnover, chaperone functions were the most expressed functional categories. Expression levels of selected Lso genes were confirmed by RT-qPCR. The transcriptomic analysis also helped correct Lso genome annotation by identifying the expression of genes that were not predicted in the genome sequencing effort.

Solanum habrochaites, a potential source of resistance against Bactericera cockerelli (Hemiptera: Triozidae) and "Candidatus Liberibacter solanacearum".

The potato psyllid, Bactericera cockerelli Sulc, also known as tomato psyllid, is a serious pest of solanaceous plants. Its host selection criteria are poorly understood. In this study, we tested whether the Solanum habrochaites (PI127826), a wild solanaceous plant known for its property to repel whiteflies, was repellent to potato psyllids. Using a combination of nonchoice assays and choice assays on different psyllid stages, we demonstrated that S. habrochaites is both repelling and toxic to potato psyllids compared with Solanum lycopersicum. However, those properties were not sufficient to avoid. transmission of the plant bacterial pathogen "Candidatus Liberibacter solanacearum" vectored by potato psyllids, the causative agent of potato zebra chip disease. However, a lower bacterial transmission rate to S. habrochaites was observed compared with S. lycopersicum.

Efficacy of Entomopathogenic Fungi (Hypocreales) forBactericera cockerelli(Sulc.) (Hemiptera: Triozidae) Control in the Laboratory and Field

Abstract. The potato psyllid, Bactericera cockerelli (Sulc.) is one of the most economically important insect pests affecting solanaceous crops. Current research on entomopathogenic fungi for control of the pest has shown potential as biological insecticides. We evaluated four Mexican entomopathogenic fungus isolates (three B. bassiana s.l. and one M. anisopliae s.l.) and one commercial isolate (GHA) for control of the potato psyllid. All isolates at a single concentration of 1×108 conidia ml-1 were evaluated under laboratory conditions and were observed to kill more than 80% of psyllids. In addition, one Mexican isolate (Bb42) and the GHA B. bassiana strain were evaluated on ‘ancho’ pepper, Capsicum annuum L., under field conditions. Results showed that control of potato psyllid by Bb42 applied at 1 ×1013 conidia ha-1 was comparable with that by the GHA strain at 2 × 1013 and 4 × 1013 conidia ha-1. Field experiments resulted in significant (P < 0.001) differences in mortality (69.5%) of B. cockerelli by ...