Tea Green Leafhopper Research Articles

Effect of symbiotic microbiota and arginine on host plant selection by the tea green leafhopper in tea cultivation

The tea green leafhopper (TGLH), Empoasca (Matsumurasca) onukii Matsuda, poses a significant challenge to tea cultivation in East Asia because of its ability to infest specific tea plant cultivars. Here, we investigated the complex interactions between TGLHs, various tea cultivars, and their symbiotic microbiota, especially the effect of arginine on host selection. A detailed two-year field study involving 16 tea cultivars, coupled with controlled laboratory and field experiments, was conducted to establish a clear link between TGLH infestation and the arginine content of tea plants. Metagenomic analysis revealed a predominance of bacterial taxa in TGLHs, primarily from the phylum Proteobacteria, with significant contributions from orders such as Pseudomonadales, Enterobacterales, and Flavobacteriales, which are crucial for the biosynthesis of essential amino acids but lack the argF gene necessary for arginine synthesis. The absence of the argF gene indicates the potential presence of microbial-mediated dietary adaptation strategies in TGLHs. Additionally, our research examines microbial diversity within TGLH populations and confirms the critical role that symbiotic bacteria play in influencing dietary preferences. The results of our study provide insights into the dynamic interplay between pests, plants, and microorganisms. Our findings are preliminary, and further research is needed to explore the potential applications of symbiotic bacteria in sustainable tea cultivation and integrated pest management strategies.

Biocontrol potential of plant growth-promoting rhizobacteria against plant disease and insect pest.

Biological control is a promising approach to enhance pathogen and pest control to ensure high productivity in cash crop production. Therefore, PGPR biofertilizers are very suitable for application in the cultivation of tea plants (Camellia sinensis) and tobacco, but it is rarely reported so far. In this study, production of a consortium of three strains of PGPR were applied to tobacco and tea plants. The results demonstrated that plants treated with PGPR exhibited enhanced resistance against the bacterial pathogen Pseudomonas syringae (PstDC3000). The significant effect in improving the plant's ability to resist pathogen invasion was verified through measurements of oxygen activity, bacterial colony counts, and expression levels of resistance-related genes (NPR1, PR1, JAZ1, POD etc.). Moreover, the application of PGPR in the tea plantation showed significantly reduced population occurrences of tea green leafhoppers (Empoasca onukii Matsuda), tea thrips (Thysanoptera:Thripidae), Aleurocanthus spiniferus (Quaintanca) and alleviated anthracnose disease in tea seedlings. Therefore, PGPR biofertilizers may serve as a viable biological control method to improve tobacco and tea plant yield and quality. Our findings revealed part of the mechanism by which PGPR helped improve plant biostresses resistance, enabling better application in agricultural production.

Tea green leafhopper infestations affect tea plant growth by altering the synthesis of brassinolide.

Tea green leafhoppers are insects widely distributed in major tea-growing areas. At present, less attention has been paid to the study on effect of tea green leafhopper infestation on tea growth phenotype. In this study, tea green leafhoppers were used to treat tea branches in laboratory and co-treated with brassinolide (BL), the highest bioactivity of brassinosteroids (BRs), in tea garden. The results showed that the expression of genes related to BRs synthesis was inhibited and BL content was reduced in tea shoots after infestation by tea green leafhoppers. In addition, area of each leaf position, length and diameter of internodes, and the biomass of the tender shoots of tea plant were decreased after infestation by tea green leafhoppers. The number of trichomes, leaf thickness, palisade tissue thickness and cuticle thickness of tea shoots were increased after tea green leafhoppers infestation. BL spraying could partially recover the phenotypic changes of tea branches caused by tea green leafhoppers infestation. Further studies showed that tea green leafhoppers infestation may regulate the expression of CsDWF4 (a key gene for BL synthesis) through transcription factors CsFP1 and CsTCP1a, which finally affect the BL content. Moreover, BL was applied to inhibit the tea green leafhoppers infestation on tea shoots. In conclusion, our study revealed the effect of plant hormone BL-mediated tea green leafhoppers infestation on the growth phenotype of tea plants.

Effect of tea green leafhopper (Empoasca onukii Matsuda) sucking on the quality of Oriental Beauty

AbstractThis study aimed to investigate the effects of tea green leafhopper damage on the sensory quality and metabolite composition of Oriental Beauty by using tea leaves from different varieties of tea plants and processing factories. The results indicated that tea green leafhopper damage could reduce bitterness and increase the level of fruity aroma, which was related to the content changes of catechin components and alcohol substances. Furthermore, the tea green leafhopper salivary treatment experiment revealed that the decrease of catechin content and increase of theaflavin content were mainly influenced by the action of saliva and mechanical injury, and changes in volatile components such as linalool oxidation were responsible for the alteration in aroma. These findings provide a theoretical reference for the aroma formation and quality improvement of Oriental Beauty.

Proteomic Analysis of Salivary Secretions from the Tea Green Leafhopper, Empoasca flavescens Fabrecius.

Saliva plays a crucial role in shaping the compatibility of piercing-sucking insects with their host plants. Understanding the complex composition of leafhopper saliva is important for developing effective and eco-friendly control strategies for the tea green leafhopper, Empoasca flavescens Fabrecius, a major piercing-sucking pest in Chinese tea plantations. This study explored the saliva proteins of tea green leafhopper adults using a custom collection device, consisting of two layers of Parafilm stretched over a sucrose diet. A total of 152 proteins were identified using liquid chromatography-tandem mass spectrometry (LC-MS/MS) following the filter-aided sample preparation (FASP). These proteins were categorized into six groups based on their functions, including enzymes, transport proteins, regulatory proteins, cell structure proteins, other proteins, and unknown proteins. Bioinformatics analyses predicted 16 secreted proteins, which were successfully cloned and transcriptionally analyzed across various tissues and developmental stages. Genes encoding putative salivary secretory proteins, including Efmucin1, EfOBP1, EfOBP2, EfOBP3, Efmucin2, low-density lipoprotein receptor-related protein (EfLRP), EFVg1, and EFVg2, exhibited high expressions in salivary gland (SG) tissues and feeding-associated expressions at different developmental stages. These findings shed light on the potential elicitors or effectors mediating the leafhopper feeding and defense responses in tea plants, providing insights into the coevolution of tea plants and leafhoppers. The study's conclusions open avenues for the development of innovative leafhopper control technologies that reduce the reliance on pesticides in the tea industry.

Changes in volatile compounds in withering tea leaves after infestation with tea green leafhopper (Empoasca onukii Matsuda)

The effects of withering, cultivar yellowing, and Empoasca onukii infestation on tea leaf aroma have each been characterized, but variations in volatile compound (VC) contents as a result of co-occurrence of these factors remain unclear. In the present study, we analyzed VC contents in E. onukii-damaged leaves of Camellia sinensis (L.) cv. ‘Yinghong No. 9’ and the yellow bud variant ‘Yellowish Yinghong No. 9’ during the withering process. We found that glycoside-derived volatiles (GDVs) were the most abundant type of VCs, accounting for more than 83% of the total VC content. Linalool formed the main body of the tea aroma, contributing a floral, fruity scent. Differential accumulation of octanal and geranyl acetone in fresh leaves corresponded to differences in the aroma profiles between Yellowish Yinghong No. 9 and Yinghong No. 9. A higher degree of withering did not alter the pleasant aroma odors of Yellowish Yinghong No. 9, but rather maintained the floral, fruity flavors and reduced greenish odors and levels of defense-related compounds (e.g., benzeneacetaldehyde, benzyl nitrile) induced by E. onukii infestation. This study clearly establishes the effects of withering on the aroma profiles of E. onukii-infested leaves in both a standard and a yellow bud mutant tea variety, suggesting a method of maintaining the economic value of even insect-damaged tea leaves.

An Antennae-Enriched Odorant-Binding Protein EonuOBP43 Mediate the Behavioral Response of the Tea Green Leafhopper, Empoasca onukii Matsuda to the Host and Nonhost Volatiles.

Olfaction is crucial for Empoasca onukii Matsuda to recognize odors from the host and nonhost plants, and it has been proposed that odorant binding proteins are directly required for odorant discrimination and represent potential targets of interest for pest control. Here, we cloned EonuOBP43 and expressed the recombinant EonuOBP43 protein. Furthermore, competitive fluorescence binding assays with 19 ligands indicated that terpenoids and alkanes showed a relatively higher than for other classes of chemicals. Additionally, ligand docking and site-directed mutagenesis results revealed that seven hydrophobic residues, including Val-86, Met-89, Phe-90, Ile-104, Ile-105, Leu-130, and Val-134, played a key role in the binding of EonuOBP43 to plant volatiles. In olfactometer tests, E. onukii were significantly attracted to α-farnesene and repelled to β-caryophyllene, and dsOBP43 treated adult lost response to α-farnesene and β-caryophyllene. In summary, our results demonstrated that EonuOBP43 may function as a carrier in the process of sensing plant compounds of E. onukii.

Altitude as a key environmental factor shaping microbial communities of tea green leafhoppers (Matsumurasca onukii).

The tea green leafhopper, Matsumurasca onukii Matsuda, is the most destructive insect pest of tea plantations in East Asia. While several microbes in M. onukii have been characterized, the microbial community compositions in wild M. onukii populations and the environmental factors that shape them are mostly unknown. In this study, M. onukii populations were collected from major tea growing regions in China. Following high-throughput sequencing of 16S rRNA gene fragments for bacteria and the internal transcribed spacer region for fungi, association analyses were performed within the microbial communities associated with M. onukii and their environmental drivers. We found that the bacterial community structures differed in various regions, and the abundance of dominant bacteria such as Wolbachia, Pseudomonas, Acinetobacter, Pantoea, Enterobacter, and Methylobacterium varied widely. Moreover, wild populations of M. onukii can be infected with facultative symbionts from six genera (Wolbachia, Rickettsia, Asaia, Serratia, Arsenophonus, and Cardinium) with divergent relative abundances. Correlation analysis indicated that altitude was a key environmental factor that shaped bacterial communities of M. onukii. Furthermore, longitude, temperature, and rainfall are also significantly correlated with the bacterial communities. The fungal communities of M. onukii populations were dominated by Ascomycota and Basidiomycota, of which most genera are considered to be plant endophytes or plant pathogens, such as Cladosporium, Fusarium, Alternaria, and Gibberella. We demonstrated that M. onukii carry a complex and variable microbial community, which is influenced by altitude as well as climate-related factors. Our results provide novel insights into the bacteria and fungi of M. onukii.IMPORTANCEHost-associated microbial communities play an important role in the fitness of insect hosts. However, the factors shaping microbial communities in wild populations, including environmental factors and interactions among microbial species, remain largely unknown. The tea green leafhopper has a wide geographical distribution and is highly adaptable, providing a suitable model for studying the effect of ecological drivers on microbiomes. This is the first large-scale culture-independent study investigating the microbial communities of M. onukii sampled from different locations. Altitude as a key environmental factor may have shaped microbial communities of M. onukii by affecting the relative abundance of endosymbionts, especially Wolbachia. The results of this study, therefore, offer not only an in-depth view of the microbial diversity of this species but also an insight into the influence of environmental factors.

Comparative Metabolomic Analysis Reveals the Differences in Nonvolatile and Volatile Metabolites and Their Quality Characteristics in Beauty Tea with Different Extents of Punctured Leaves by Tea Green Leafhopper.

The fresh leaves were processed into beauty tea from the Camellia sinensis "Jinxuan" cultivar, which were punctured by tea green leafhoppers to different extents. Low-puncturing dry tea (LPDT) exhibited a superior quality. Altogether, 101 and 129 differential metabolites, including tea polyphenols, lipids, and saccharides, were identified from the fresh leaves and dry beauty tea, respectively. Most metabolite levels increased in the fresh leaves punctured by leafhoppers, but the opposite was observed for the dry beauty tea. According to relative odor activity values (rOAVs) and partial least-squares discriminant analysis (PLS-DA), four characteristic volatiles, including linalool, geraniol, benzeneacetaldehyde, and dihydrolinalool, were selected. Mechanical injury to leaves caused by leafhoppers, watery saliva secreted by the leafhopper, and different water contents of the fresh leaves in different puncturing degrees are the possible reasons for the difference in the quality of the beauty tea with different levels of puncturing. Overall, this study identified a wide range of chemicals that are affected by the degrees of leafhopper puncturing.

Fumigant activity and transcriptomic analysis of two plant essential oils against the tea green leafhopper, Empoasca onukii Matsuda.

Introduction: The tea green leafhopper, Empoasca (Matsumurasca) onukii Matsuda, R., 1952 (Hemiptera: Cicadellidae), is currently one of the most devastating pests in the Chinese tea industry. The long-term use of chemical pesticides has a negative impact on human health, impeding the healthy and sustainable development of the tea industry in this region. Therefore, there is a need for non-chemical insecticides to control E. onukii in tea plants. The essential oils from plants have been identified for their potential insecticidal ability; however, there is a lack of knowledge regarding the effect of plant essential oils on E. onukii and its gene expression. Methods: In order to address these knowledge gaps, the components of Pogostemon cablin and Cinnamomum camphora essential oils were analyzed in the present study using gas chromatography-mass spectrometry. The fumigation toxicity of two essential oils on E. onukii was tested using sealed conical flasks. In addition, We performed comparative transcriptome analyses of E. onukii treated with or without P. cablin essential oil. Results: The 36-h lethal concentration (LC50) values for E. onukii treated with P. cablin and C. camphora essential oils were 0.474 and 1.204μLmL-1 respectively. Both essential oils exhibited the potential to control E. onukii, but the fumigation activity of P. cablin essential oil was more effective. A total of 2,309 differentially expressed genes were obtained by transcriptome sequencing of E. onukii treated with P. cablin essential oil. Conclusion: Many of differentially expressed genes were found to contain detoxifification genes, indicating that these families may have played an important role when E. onukii was exposed to essential oil stress. We also found differential expression of genes related to redox-related gene families, suggesting the upregulation of genes associated with possible development of drug and stress resistance. This work offers new insights for the prevention and management of E. onukii in the future.

Diversity and Population Dynamics of Pest in Sambawa Tea Plantation, West Java

Tea plants are grown in monoculture on a large scale, so that can be a caused pest in the high population. This study aims to determine the diversity and dynamics of pest populations in Sambawa tea plantations in West Java. Tea pests are found in the crop and on the leaves picked at the plant. The dynamics of the pest population were noted by observing the area of attack, the intensity of the attack, and population density. Twenty-one pests on tea plants were identified based on their morphological characteristics and symptoms. Among them, seven species attack bud and young leaf, two species attack old leaf, twelve species attack young and old leaves, and one pest attacks tree trunk. Twelve pests were carried to the factory’s withering tub of leaves. Tea green leafhopper (Empoasca sp.), tea leaf roller (Caloptilia theivora), tea mosquito bug (Helopeltis bradyi), and tea tortrix (Adoxophyes sp. and Homona coffearia) were the main pests at the observation site. The population of tea green leafhoppers decreased after the second application of pesticides, post-picking, and heavy rains. The tea leaf roller was not found after the first and second pesticide applications. The population of tea leaf rollers began to increase during picking until the last observation. The highest population of tea mosquito bugs was found after the second pesticide application. The population of tea tortrix decreased after the second pesticide application.

Tea green leafhopper-induced synomone attracts the egg parasitoids, mymarids to suppress the leafhopper.

The tea green leafhopper, Empoasca flavescens is the most important pest of tea plants in China. Mymarid attractants based on herbivore-induced plant volatiles (HIPVs) from leafhopper feeding and oviposition-induced plant volatiles (OIPVs) were formulated and tested as a novel pest control agent against the leafhopper in tea plantations. Results showed that two mymarid species, Stethynium empoascae and Schizophragma parvula, had a reducing effect on leafhopper populations. The HIPVs and OIPVs were identified and bioassayed to screen the key synomones showing strong attraction to the mymarids. They were formulated into different blends, of which Field Attractant 1, comprising linalool, methyl salicylate, (E)-2-hexenal, perillen and α-farnesene at ratio of 1:2:3:58:146 (20 mg/lure), showed the strongest attraction to the mymarids. In field trials with the attractant, the average parasitism rate (60.46 ± 23.71%) of tea leafhoppers by the two mymarids in the attractant-baited area was significantly higher than that (42.85 ± 19.24%) in the CK area. Also, the average leafhopper density (46 ± 30 per 80 tea shoots) in the attractant-baited area was significantly lower than that (110 ± 70 per 80 tea shoots) in the CK area. This study showed that a synthetic blend of key volatiles from HIPVs and OIPVs at an optimal ratio can be formulated into an attractant with the potential to attract and retain wild mymarid populations to suppress leafhopper populations in infested tea plantations, so as to reduce or avoid the spraying of insecticides. © 2023 Society of Chemical Industry.

Intercropping Cover Crops for a Vital Ecosystem Service: A Review of the Biocontrol of Insect Pests in Tea Agroecosystems.

The intercropping of cover crops has been adopted in several agroecosystems, including tea agroecosystems, which promotes ecological intensification. Prior studies have shown that growing cover crops in tea plantations provided different ecological services, including the biocontrol of pests. Cover crops enrich soil nutrients, reduce soil erosion, suppress weeds and insect pests, and increase the abundance of natural enemies (predators and parasitoids). We have reviewed the potential cover crops that can be incorporated into the tea agroecosystem, particularly emphasizing the ecological services of cover crops in pest control. Cover crops were categorized into cereals (buckwheat, sorghum), legumes (guar, cowpea, tephrosia, hairy indigo, and sunn hemp), aromatic plants (lavender, marigold, basil, and semen cassiae), and others (maize, mountain pepper, white clover, round-leaf cassia, and creeping indigo). Legumes and aromatic plants are the most potent cover crop species that can be intercropped in monoculture tea plantations due to their exceptional benefits. These cover crop species improve crop diversity and help with atmospheric nitrogen fixation, including with the emission of functional plant volatiles, which enhances the diversity and abundance of natural enemies, thereby assisting in the biocontrol of tea insect pests. The vital ecological services rendered by cover crops to monoculture tea plantations, including regarding the prevalent natural enemies and their pivotal role in the biocontrol of insect pests in the tea plantation, have also been reviewed. Climate-resilient crops (sorghum, cowpea) and volatile blends emitting aromatic plants (semen cassiae, marigold, flemingia) are recommended as cover crops that can be intercropped in tea plantations. These recommended cover crop species attract diverse natural enemies and suppress major tea pests (tea green leaf hopper, white flies, tea aphids, and mirid bugs). It is presumed that the incorporation of cover crops within the rows of tea plantations will be a promising strategy for mitigating pest attacks via the conservation biological control, thereby increasing tea yield and conserving agrobiodiversity. Furthermore, a cropping system with intercropped cover crop species would be environmentally benign and offer the opportunity to increase natural enemy abundance, delaying pest colonization and/or preventing pest outbreaks for pest management sustainability.

Involvement of three chemosensory proteins in perception of host plant volatiles in the tea green leafhopper, Empoasca onukii.

Chemosensory proteins (CSPs) can bind and transport odorant molecules, which are believed to be involved in insect chemoreception. Here, we investigated three CSPs in perception of volatiles in Empoasca onukii. Expression profiles showed that although EonuCSP4, EonuCSP 6-1 and EonuCSP6-2 were ubiquitously expressed in heads, legs, thoraxes and abdomen, they were all highly expressed in the antennae of E. onukii. Further, fluorescence competitive binding assays revealed that EonuCSP4 and 6-1 had binding affinities for three plant volatiles, suggesting their possible involvement in the chemosensory process. Among them, EonuCSP6-1 showed relatively high binding affinities for benzaldehyde. Behavioral assays revealed that the adults of E. onukii showed a significant preference for two compounds including benzaldehyde. The predicted three-dimensional (3D) structures of these 3 CSP have the typical six α-helices, which form the hydrophobic ligand-binding pocket. We therefore suggest that Eoun6-1 might be involved in the chemoreception of the host-related volatiles for E. onukii. Our data may provide a chance of finding a suitable antagonist of alternative control strategies which block the perception of chemosensory signals in pest, preventing the food- orientation behaviors.

Transcriptome and co-expression network analysis uncover the key genes mediated by endogenous defense hormones in tea plant in response to the infestation of <i>Empoasca onukii</i> Matsuda

The tea green leafhopper [<italic>Empoasca</italic> (<italic>Matsumurasca</italic>) <italic>onukii</italic> Matsuda] is one of the most dominant pests in the tea production regions of China, greatly impacting tea yield and quality. Extensive studies have attributed the plant defense response to pest infestation to the activation of hormone signals, but the role of defense hormones in tea plants in response to the feeding of <italic>E. onukii</italic> is not clear. RNA-seq was performed on the leaf samples collected at different time points (6, 24 and 48 h) after feeding with <italic>E. onukii</italic> to explore the transcription characteristics of tea plant responses to feeding. The content variation characteristics of four phytohormones (JA, JA-Ile, ABA and SA) during this process were also determined. The results showed that feeding elevated the expression of key genes involved in phenylpropanoid biosynthesis, flavonoid biosynthesis, α-linolenic acid metabolism and terpenoids synthesis pathways, especially in the early stage after feeding. The contents of JA, JA-Ile, and ABA dramatically increased at different time points after feeding, but the absolute content decreased over time. The change in the absolute content of SA was opposite to that of the above three hormones. Two gene co-expression networks that were significantly positively associated with these hormonal changes were constructed based on WGCNA. The screened hub genes provide useful genetic resources for exploring the hormone-mediated defense responses of tea plants against <italic>E. onukii</italic>. Our results lay the foundation for the ecological control of <italic>E. onukii</italic> and breeding of resistant tea plant cultivars.

Unraveling the hierarchical genetic structure of tea green leafhopper, Matsumurasca onukii, in East Asia based on SSRs and SNPs.

Matsumurasca onukii (Matsuda, R. (1952). Oyo‐Kontyu Tokyo, 8(1): 19–21), one of the dominant pests in major tea production areas in Asia, currently is known to occur in Japan, Vietnam, and China, and severely threatens tea production, quality, and international trade. To elucidate the population genetic structure of this species, 1633 single nucleotide polymorphisms (SNPs) and 18 microsatellite markers (SSRs) were used to genotype samples from 27 sites representing 18 geographical populations distributed throughout the known range of the species in East Asia. Analyses of both SNPs and SSRs showed that M. onukii populations in Yunnan exhibit high‐genetic differentiation and structure compared with the other populations. The Kagoshima (JJ) and Shizuoka (JS) populations from Japan were separated from populations from China by SNPs, but clustered with populations from Jinhua (JH), Yingde (YD), Guilin (GL), Fuzhou (FZ), Hainan (HQ), Leshan (CT), Chongqing (CY), and Zunyi (ZY) tea plantations in China and the Vietnamese Vinh Phuc (VN) population based on the SSR data. In contrast, CT, CY, ZY, and Shaanxi (SX) populations clustered together based on SNPs, but were separated by SSRs. Both marker datasets identified significant geographic differentiation among the 18 populations. Various environmental and anthropogenic factors, including geographical barriers to migration, human transport of hosts (Camellia sinesis [L.] O. Kuntze) and adaptation of M. onukii to various local climatic zones possibly account for the rapid spread of this pest in Asia. The results demonstrate that SNPs from high‐throughput genotyping data can be used to reveal subtle genetic substructure at broad scales in r‐strategist insects.

Chromosome-scale genome assembly of Camellia sinensis combined with multi-omics provides insights into its responses to infestation with green leafhoppers.

The tea plant (Camellia sinensis) is an important economic crop, which is becoming increasingly popular worldwide, and is now planted in more than 50 countries. Tea green leafhopper is one of the major pests in tea plantations, which can significantly reduce the yield and quality of tea during the growth of plant. In this study, we report a genome assembly for DuyunMaojian tea plants using a combination of Oxford Nanopore Technology PromethION™ with high-throughput chromosome conformation capture technology and used multi-omics to study how the tea plant responds to infestation with tea green leafhoppers. The final genome was 3.08 Gb. A total of 2.97 Gb of the genome was mapped to 15 pseudo-chromosomes, and 2.79 Gb of them could confirm the order and direction. The contig N50, scaffold N50 and GC content were 723.7 kb, 207.72 Mb and 38.54%, respectively. There were 2.67 Gb (86.77%) repetitive sequences, 34,896 protein-coding genes, 104 miRNAs, 261 rRNA, 669 tRNA, and 6,502 pseudogenes. A comparative genomics analysis showed that DuyunMaojian was the most closely related to Shuchazao and Yunkang 10, followed by DASZ and tea-oil tree. The multi-omics results indicated that phenylpropanoid biosynthesis, α-linolenic acid metabolism, flavonoid biosynthesis and 50 differentially expressed genes, particularly peroxidase, played important roles in response to infestation with tea green leafhoppers (Empoasca vitis Göthe). This study on the tea tree is highly significant for its role in illustrating the evolution of its genome and discovering how the tea plant responds to infestation with tea green leafhoppers will contribute to a theoretical foundation to breed tea plants resistant to insects that will ultimately result in an increase in the yield and quality of tea.

Genomic Variations in the Tea Leafhopper Reveal the Basis of Its Adaptive Evolution

Tea green leafhopper (TGL), Empoasca onukii, is of biological and economic interest. Despite numerous studies, the mechanisms underlying its adaptation and evolution remain enigmatic. Here, we use previously untapped genome and population genetics approaches to examine how the pest adapted to different environmental variables and thus has expanded geographically. We complete a chromosome-level assembly and annotation of the E. onukii genome, showing notable expansions of gene families associated with adaptation to chemoreception and detoxification. Genomic signals indicating balancing selection highlight metabolic pathways involved in adaptation to a wide range of tea varieties grown across ecologically diverse regions. Patterns of genetic variations among 54 E. onukii samples unveil the population structure and evolutionary history across different tea-growing regions in China. Our results demonstrate that the genomic changes in key pathways, including those linked to metabolism, circadian rhythms, and immune system functions, may underlie the successful spread and adaptation of E. onukii. This work highlights the genetic and molecular basis underlying the evolutionary success of a species with broad economic impacts, and provides insights into insect adaptation to host plants, which will ultimately facilitate more sustainable pest management.

The Relative Preference of Empoasca onukii (Hemiptera: Cicadellidae) for Oviposition on Twenty-Four Tea Cultivars.

The tea green leafhopper, Empoasca onukii Matsuda (Hemiptera: Cicadellidae) is currently one of the most threatening pests of tea production in China. Several approaches have been used to identify the resistance of different tea cultivars to this important tea pest. However, relatively limited information has been documented about its oviposition preferences. This study aimed to elucidate the preferential oviposition of E. onukii among 24 tea cultivars. Towards this objective, a multi-selective test for E. onukii oviposition was conducted in the laboratory, and the egg densities of E. onukii on 24 varieties were also surveyed in plantations at different time periods during the tea plant growing season in 2019. There was a significant difference in E. onukii egg densities among the 24 cultivars studied in both laboratory tests and the field investigations. Moreover, there was a positive correlation between the laboratory and field data for the number of eggs laid per cultivar. According to the laboratory and field evaluations, 2 cultivars were identified as very-susceptible for E. onukii oviposition, while another 5 cultivars were assigned as susceptible, 9 cultivars were classified as resistant and 2 cultivars were identified as very-resistant, respectively. This information on the oviposition preference for E. onukii on different cultivars could be used as a selection parameter for further breeding of leafhopper-resistant tea cultivars.

A Temperature-Dependent Model for Tritrophic Interactions Involving Tea Plants, Tea Green Leafhoppers and Natural Enemies.

Simple SummaryTritrophic interactions have achieved much attention in research on ecology. The tea plant Camellia sinensis (L.) O. Kuntze is a major economic crop in Asian countries, especially in China. Tea plants suffer infestations from herbivory attack during their lifetime. The tea green leafhopper (Empoasca onukii Matsuda) is a major pest for tea plants. The parasitic or predatory natural enemies of tea green leafhoppers (TGLs) can feed on their eggs, nymphs, or adults. However, a detailed mathematical model for tea plants–TGLs–natural enemies is still lacking. In the current work, we established a novel model based on laboratory measurements or field observations with temperature-dependent effects on tritrophic interactions for tea ecosystems. As expected, cyclic behaviors are identified. Stochastic simulations further showed two TGL outbreaks, the timing of which is consistent with field observations. Effective accumulated temperature (EAT) is possibly an important predictor of TGL outbreak. Applying slow-releasing semiochemicals as either repellents or attractants may be highly efficacious for pest biocontrol. An optimal treatment time of semiochemicals can also be determined. Our detailed model identifies key features of tritrophic interactions involving tea plants and can be extended to other ecosystems.The tea green leaf hopper, Empoasca onukii Matsuda, is a severe pest of tea plants. Volatile emissions from tea shoots infested by the tea green leafhopper may directly repel insect feeding or attract natural enemies. Many studies have been conducted on various aspects of the tritrophic relationship involving tea plants, tea green leafhoppers and natural enemies. However, mathematic models which could explain the dynamic mechanisms of this tritrophic interaction are still lacking. In the current work, we constructed a realistic and stochastic model with temperature-dependent features to characterize the tritrophic interactions in the tea agroecosystem. Model outputs showed that two leafhopper outbreaks occur in a year, with their features being consistent with field observations. Simulations showed that daily average effective accumulated temperature (EAT) might be an important metric for outbreak prediction. We also showed that application of slow-releasing semiochemicals, as either repellents or attractants, may be highly efficacious for pest biocontrol and can significantly increase tea yields. Furthermore, the start date of applying semiochemicals can be optimized to effectively increase tea yields. The current model qualitatively characterizes key features of the tritrophic interactions and provides critical insight into pest control in tea ecosystems.