Physalis virginiana as a Wild Field Host of Bactericera cockerelli (Hemiptera: Triozidae) and 'Candidatus Liberibacter solanacearum'.

The potato/tomato psyllid, Bactericera cockerelli (Sulc), is among the most important pests of solanaceous crops as a vector of the pathogen 'Candidatus Liberibacter solanacearum' (Lso). Lso-infected psyllids often arrive in crop fields from various wild species of Solanaceae and Convolvulaceae, especially those that provide early-season hosts for the vector. Physalis species are perennial plants within the family Solanaceae with often broad geographical distributions that overlap those of B. cockerelli, yet the status of many Physalis species as hosts for B. cockerelli or Lso remains unknown. Our objective was to determine whether wild Physalis species that occur in the potato-growing region of Galeana, Nuevo León, Mexico, host B. cockerelli populations and whether they also are susceptible to Lso. Sampling was carried out in the potato-growing zone of Galeana, Nuevo León, Mexico, where unidentified Physalis spp. are common. In March to October 2021, a wild plant identified as Physalis virginiana was observed; eggs, nymphs, and adults of B. cockerelli were observed on these plants throughout the growing season, and nymphs completed development on these plants under laboratory conditions. Lso also was detected in 22 of the 93 (23.7%) wild P. virginiana plants using conventional PCR, while 13.3% of B. cockerelli adults that emerged from P. virginiana cuttings harbored the pathogen. This is the first report that P. virginiana is a host for B. cockerelli and for Lso. These results suggest that P. virginiana is a likely source of Lso-infected psyllids colonizing solanaceous crops in northeastern Mexico. The importance of P. virginiana and other wild hosts on the population dynamics of the vector and pathogen should be investigated to assist in pest management decision-making.

High-throughput molecular gut content analysis of aphids identifies plants relevant for potato virus Y epidemiology.

Aphids are phloem-feeding insects that reduce crop productivity due to feeding and transmission of plant viruses. When aphids disperse across the landscape to colonize new host plants, they will often probe on a wide variety of nonhost plants before settling on a host suitable for feeding and reproduction. There is limited understanding of the diversity of plants that aphids probe on within a landscape, and characterizing this diversity can help us better understand host use patterns of aphids. Here, we used gut content analysis (GCA) to identify plant genera that were probed by aphid vectors of potato virus Y (PVY). Aphids were trapped weekly near potato fields during the growing seasons of 2020 and 2021 in San Luis Valley in Colorado. High-throughput sequencing of plant barcoding genes, trnF and ITS2, from 200 individual alate (i.e., winged) aphids representing nine vector species of PVY was performed using the PacBio sequencing platform, and sequences were identified to genus using NCBI BLASTn. We found that 34.7% of aphids probed upon presumed PVY host plants and that two of the most frequently detected plant genera, Solanum and Brassica, represent important crops and weeds within the study region. We found that 75% of aphids frequently probed upon PVY nonhosts including many species that are outside of their reported host ranges. Additionally, 19% of aphids probed upon more than one plant species. This study provides the first evidence from high-throughput molecular GCA of aphids and reveals host use patterns that are relevant for PVY epidemiology.

The functional decline of tomato plants infected by Candidatus Liberbacter solanacearum: an RNA-seq transcriptomic analysis.

Introduction: Candidatus Liberibacter solanacearum (CLso) is a regulated plant pathogen in European and some Asian countries, associated with severe diseases in economically important Apiaceous and Solanaceous crops, including potato, tomato, and carrot. Eleven haplotypes of CLso have been identified based on the difference in rRNA and conserved genes and host and pathogenicity. Although it is pathogenic to a wide range of plants, the mechanisms of plant response and functional decline of host plants are not well defined. This study aims to describe the underlying mechanism of the functional decline of tomato plants infected by CLso by analyzing the transcriptomic response of tomato plants to CLso haplotypes A and B. Methods: Next-generation sequencing (NGS) data were generated from total RNA of tomato plants infected by CLso haplotypes A and B, and uninfected tomato plants, while qPCR analysis was used to validate the in-silico expression analysis. Gene Ontology and KEGG pathways were enriched using differentially expressed genes. Results: Plants infected with CLso haplotype B saw 229 genes upregulated when compared to uninfected plants, while 1,135 were downregulated. Healthy tomato plants and plants infected by haplotype A had similar expression levels, which is consistent with the fact that CLso haplotype A does not show apparent symptoms in tomato plants. Photosynthesis and starch biosynthesis were impaired while starch amylolysis was promoted in plants infected by CLso haplotype B compared with uninfected plants. The changes in pathway gene expression suggest that carbohydrate consumption in infected plants was more extensive than accumulation. In addition, cell-wall-related genes, including steroid biosynthesis pathways, were downregulated in plants infected with CLso haplotype B suggesting a reduction in membrane fluidity, cell signaling, and defense against bacteria. In addition, genes in phenylpropanoid metabolism and DNA replication were generally suppressed by CLso infection, affecting plant growth and defense. Discussion: This study provides insights into plants' defense and functional decline due to pathogenic CLso using whole transcriptome sequencing and qPCR validation. Our results show how tomato plants react in metabolic pathways during the deterioration caused by pathogenic CLso. Understanding the underlying mechanisms can enhance disease control and create opportunities for breeding resistant or tolerant varieties.

Bacterial Endosymbionts Identified From Leafhopper (Hemiptera: Cicadellidae) Vectors of Phytoplasmas.

Insects often harbor bacterial endosymbionts that provide them with nutritional benefit or with protection against natural enemies, plant defenses, insecticides, and abiotic stresses. Certain endosymbionts may also alter acquisition and transmission of plant pathogens by insect vectors. We identified bacterial endosymbionts from four leafhopper vectors (Hemiptera: Cicadellidae) of 'Candidatus Phytoplasma' species by direct sequencing 16S rDNA and confirmed endosymbiont presence and identity by species-specific conventional PCR. We examined three vectors of Ca. Phytoplasma pruni, causal agent of cherry X-disease [Colladonus geminatus (Van Duzee), Colladonus montanus reductus (Van Duzee), Euscelidius variegatus (Kirschbaum)] - and a vector of Ca. Phytoplasma trifolii, the causal agent of potato purple top disease [Circulifer tenellus (Baker)]. Direct sequencing of 16S identified the two obligate endosymbionts of leafhoppers, 'Ca. Sulcia' and 'Ca. Nasuia', which are known to produce essential amino acids lacking in the leafhoppers' phloem sap diet. About 57% of C. geminatus also harbored endosymbiotic Rickettsia. We identified 'Ca. Yamatotoia cicadellidicola' in Euscelidius variegatus, providing just the second host record for this endosymbiont. Circulifer tenellus harbored the facultative endosymbiont Wolbachia, although the average infection rate was only 13% and all males were Wolbachia-uninfected. A significantly greater percentage of Wolbachia-infected Ci. tenellus adults than uninfected adults carried Ca. P. trifolii, suggesting that Wolbachia may increase this insect's ability to tolerate or acquire this pathogen. Results of our study provide a foundation for continued work on interactions between leafhoppers, bacterial endosymbionts, and phytoplasma.

The Venom Compound N-(3-methylbutyl)acetamide Attracts Several Polistes (Fuscopolistes) Species (Hymenoptera: Vespidae).

Polistes paper wasps in the Fuscopolistes subgenus (Hymenoptera: Vespidae) can be serious pests when they swarm at tall man-made structures. Chemical attractants may be useful to trap such paper wasps when they achieve pest status. Polistes venom has been shown to elicit a variety of behavioral responses in congeneric wasps, making it a source for potential chemical attractants. The compound N-(3-methylbutyl)acetamide is a principal volatile component in the venom of many female vespid wasps, including numerous Polistes species. We report the presence of N-(3-methylbutyl)acetamide in autumn gynes of Polistes metricus Say, Polistes bellicosus Cresson, and Polistes dorsalis (F.), as well as workers of Polistes aurifer (Saussure), P. bellicosus, P. metricus, and P. dorsalis. In field tests conducted in Florida, Georgia, South Carolina, and Washington, N-(3-methylbutyl)acetamide attracted male and female P. aurifer and P. metricus, as well as male P. dorsalis and P. bellicosus. Thus, N-(3-methylbutyl)acetamide may be a useful lure for trapping these paper wasps in pest situations.

Survival and development of potato psyllid (Hemiptera: Triozidae) on Convolvulaceae: Effects of a plant-fungus symbiosis (Periglandula).

Plant species in the family Solanaceae are the usual hosts of potato psyllid, Bactericera cockerelli (Sulc) (Hemiptera: Psylloidea: Triozidae). However, the psyllid has also been shown to develop on some species of Convolvulaceae (bindweeds and morning glories). Developmental success on Convolvulaceae is surprising given the rarity of psyllid species worldwide associated with this plant family. We assayed 14 species of Convolvulaceae across four genera (Convolvulus, Calystegia, Ipomoea, Turbina) to identify species that allow development of potato psyllid. Two populations of psyllids were assayed (Texas, Washington). The Texas population overlaps extensively with native Convolvulaceae, whereas Washington State is noticeably lacking in Convolvulaceae. Results of assays were overlain on a phylogenetic analysis of plant species to examine whether Convolvulaceae distantly related to the typical host (potato) were less likely to allow development than species of Convolvulaceae more closely related. Survival was independent of psyllid population and location of the plant species on our phylogenetic tree. We then examined whether presence of a fungal symbiont of Convolvulaceae (Periglandula spp.) affected psyllid survival. These fungi associate with Convolvulaceae and produce a class of mycotoxins (ergot alkaloids) that may confer protection against plant-feeding arthropods. Periglandula was found in 11 of our 14 species, including in two genera (Convolvulus, Calystegia) not previously known to host the symbiont. Of these 11 species, leaf tissues from five contained large quantities of two classes of ergot alkaloids (clavines, amides of lysergic acid) when evaluated by LC-MS/MS. All five species also harbored Periglandula. No ergot alkaloids were detected in species free of the fungal symbiont. Potato psyllid rapidly died on the five species that harbored Periglandula and contained ergot alkaloids, but survived to adulthood on seven of the nine species in which ergot alkaloids were not detected. These results support the hypothesis that a plant-fungus symbiotic relationship affects the suitability of certain Convolvulaceae to potato psyllid.