Sap-sucking Insects Research Articles

Host-induced gene silencing of brown planthopper glutathione S-transferase gene enhances rice resistance to sap-sucking insect pests

Host-induced gene silencing (HIGS) of insect growth and development is a promising measure for pest control in practice; the feasibility of disarming insect detoxification of toxic phytochemicals via HIGS of insect detoxification enzymes remains largely unexplored. In this study, a HIGS system was applied to interfere with glutathione S-transferase (GST) gene expression in brown planthopper (BPH, Nilaparvata lugens), a key insect pest in rice of Asia, and regulate rice resistance to the insect. The recombination vector in transgenic plants was expressed in almost all organs, especially in vascular bundle tissues, mesophyll, epidermal cells and leaf sheath sap, but not in xylem. Target BPH NlGST1-1 was successfully integrated into rice genome, the resultant transgenic rice lines harbored a single-copy of BPH NlGST1-1 dsRNA, and expression of NlGST1-1 dsRNA was detected in leaves and leaf sheaths of transgenic lines. However, the content of phytochemical gramine, an inherent alkaloid in gramineous plants, did not change in these transgenic plants. BPH nymphs reared on the transgenic rice expressing NlGST1-1 dsRNA displayed significant reductions in NlGST1-1 transcript expression and GST activity. The transgenic plants significantly retarded relative growth rate of the nymphs and the insect female fecundity, the plants also showed enhanced resistance when attacked by BPH. Our study demonstrated the feasibility of reinforcing gramine-mediated plant defense via HIGS of GSTs in herbivorous insects. HIGS-mediated suppression of the herbivore adaptive mechanism has significant implications for efficiently managing BPH and other pests in rice.

Identification of Entomopathogenic Fungi as Naturally Occurring Enemies of the Invasive Oak Lace Bug, Corythucha arcuata (Say) (Hemiptera: Tingidae).

Simple SummaryThe oak lace bug (OLB), Corythucha arcuata, is a cell sap-sucking insect that is native to North America but has spread rapidly in European countries as an invasive pest. The main hosts are oaks, but it can develop on other forest species as well. Its occurrence is worrying in terms of the cumulative impacts that it could have on forests, as well as the molestation of imago in cities that have been frequently reported. Since the pest is still a new element of a biocoenosis, there is a lack of research on its natural enemies and competitors that could form a potential foundation for biological control strategies. Although there have been reports that lace bugs are quite susceptible to a fungal diseases amid more humid conditions, to date, none of the pathogenic fungi found on OLBs under natural conditions were identified in the literature. In this study, we provide evidence of four entomopathogenic fungi: Beauveria pseudobassiana, Lecanicillium pissodis, Akanthomyces attenuatus and Samsoniella alboaurantium that could present a potential as biological control agents against OLBs.The oak lace bug (OLB), Corythucha arcuata (Hemiptera: Tingidae), was first identified as an invasive pest in Europe in northern Italy in 2000 and since then it has spread rapidly, attacking large forested areas in European countries. The OLB is a cell sap-sucking insect that is native to North America, with Quercus spp. as its main host. Its rapid expansion, successful establishment in invaded countries, and observations of more damage to hosts compared to native areas are most likely due to a lack of natural enemies, pathogens and competitors. In its native area, various natural enemies of OLBs have been identified; however, little is known about the occurrence and impact of OLB pathogens. None of the pathogenic fungi found on OLBs in natural conditions have been identified until now. In this study, we provide evidence of four entomopathogenic fungi that are naturally occurring on invasive OLBs found in infested pedunculate oak forests in eastern Croatia. On the basis of their morphology and multilocus molecular phylogeny, the fungi were identified as Beauveria pseudobassiana, Lecanicillium pissodis, Akanthomyces attenuatus and Samsoniella alboaurantium. The sequences generated for this study are available from GenBank under the accession numbers MT004817-MT004820, MT004833-MT004835, MT027501-MT27510, and MT001936-MT0011943. These pathogenic species could facilitate biological control strategies against OLBs.

Population dynamic of <i>Diclidophlebia irvingiae</i>, Burckhardt et al. (Hemiptera: Psylloidea), psyllid pest of <i>Irvingia gabonensis</i> Baill (Irvingiaceae, Rutales) in Bamenda, North-West region of Cameroon

Diclidophlebia irvingiae is a sap-sucking insect of Irvingia gabonensis inducing important damage to its host plant which has medicinal and nutritional importance in Africa particularly in Cameroon. The aim of the survey was to study numerical variation of the pest during the year and impact of biotic and abiotic factors on numerical variation. The study was carried in Bamenda from March 2018 to March 2019 where larvae and adults of D. irvingiae were collected monthly. The study permitted us to record 3290 individuals 1341 males, 1396 females and 553 larvae. Population fluctuation of the pest during the year showed five periods of individual outbreak corresponding to the generation number of the pest. As most tropical and sub-tropical psyllid species D. irvingiae is a multivoltine species with five annual generations. The outbreak periods depend principally on the phenology of host plant. The statistical test showed that the numerical individual variation of D. irvingiae is not directly related to climatic factors because they do not show significant probability.Keywords: Impact, Biotic, Abiotic, Factors, Insect, Faunistic.

Transmission of the Bean-Associated Cytorhabdovirus by the Whitefly Bemisia tabaci MEAM1.

The knowledge of genomic data of new plant viruses is increasing exponentially; however, some aspects of their biology, such as vectors and host range, remain mostly unknown. This information is crucial for the understanding of virus–plant interactions, control strategies, and mechanisms to prevent outbreaks. Typically, rhabdoviruses infect monocot and dicot plants and are vectored in nature by hemipteran sap-sucking insects, including aphids, leafhoppers, and planthoppers. However, several strains of a potentially whitefly-transmitted virus, papaya cytorhabdovirus, were recently described: (i) bean-associated cytorhabdovirus (BaCV) in Brazil, (ii) papaya virus E (PpVE) in Ecuador, and (iii) citrus-associated rhabdovirus (CiaRV) in China. Here, we examine the potential of the Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) to transmit BaCV, its morphological and cytopathological characteristics, and assess the incidence of BaCV across bean producing areas in Brazil. Our results show that BaCV is efficiently transmitted, in experimental conditions, by B. tabaci MEAM1 to bean cultivars, and with lower efficiency to cowpea and soybean. Moreover, we detected BaCV RNA in viruliferous whiteflies but we were unable to visualize viral particles or viroplasm in the whitefly tissues. BaCV could not be singly isolated for pathogenicity tests, identification of the induced symptoms, and the transmission assay. BaCV was detected in five out of the seven states in Brazil included in our study, suggesting that it is widely distributed throughout bean producing areas in the country. This is the first report of a whitefly-transmitted rhabdovirus.

Fitness costs in clothianidin-resistant population of the melon aphid, Aphis gossypii.

Clothianidin is a second-generation neonicotinoid insecticide, widely used against sap-sucking insect pest including melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae). This pest causes severe economic damage to Cucurbitaceae plants worldwide. In this study, we investigated clothianidin resistance development under continuous selection pressure. Moreover, the age-stage, two-sex life table approach was used to evaluate the impact of clothianidin resistance on the fitness of A. gossypii. A clothianidin resistant strain (CT-R) with a 23.17-fold resistance level was developed from a susceptible strain (CT-S) after continuous selection for 24 generations. Life table results showed a significant reduction in the relative fitness (0.847) of CT-R strain compared to the CT-S strain of A. gossypii. The developmental duration, oviposition days, total pre-oviposition period (TPOP), longevity, and fecundity of CT-R strain were found to be significantly lower when compared to CT-S strain. The demographic parameters, including the intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (R0), and mean generation time (T) were also significantly decreased in CT-R strain compared to the CT-S strain. Both the reproductive and survival rates were affected by clothianidin resistance in CT-R strain compared with the CT-S strain of A. gossypii. Overall, our results demonstrate that in-depth knowledge about the trade-off at play between resistance degree and fitness cost might be useful to design resistance management strategies against A. gossypii.

Indigenous Use of Lerps in Australia: So Much More than a Sweet Treat

We evaluate the cultural, ecological, and horticultural potential for a distinctively Australian sweet food to provide a means of Indigenous cultural revitalization. Among the world's Indigenous peoples, the Australian Aboriginal use of the sweet exudations (lerps and scales) of plant sap-sucking insects (Hemiptera) is exceptional in many respects. This food not only provides a sweet treat and a source of energy but can be stored as dry balls for hard times. Lerps feature in Aboriginal calendars, ceremonies, mythology, and cosmology, all of which have embedded biocultural knowledge about the time and place for optimal collection. These insects are central to Indigenous cultures, yet Western science knows surprisingly little about their taxonomy, biology, and ecology. Recently, there has been interest in using lerps in the restaurant industry as part of the commercialization of traditional Aboriginal foods. We highlight the numerous benefits of a collaborative approach to such enterprises and show that there is a wealth of Indigenous Biocultural Knowledge (IBK) that is invaluable for informing and guiding research, conservation, and commercialization of a guild of insects that remains poorly understood.

Sub-Lethal Effects of Partially Purified Protein Extracted from Beauveria bassiana (Balsamo) and Its Presumptive Role in Tomato (Lycopersicon esculentum L.) Defense against Whitefly (Bemisia tabaci Genn.).

Simple SummaryApart from their direct entomopathogenicity, many entomopathogenic fungi synthesize protein molecules that can trigger plant defense mechanisms against herbivore insect pests. This laboratory study determined the sub-lethal effects of a partially purified protein derived from Beauveria bassiana against whitefly Bemisia tabaci on tomato plants along with the subsequent gene expression analyses of key gens potentially linked to jasmonic acid (JA) and salicylic acid (SA) associated plant defense pathways. The exogenous foliar application of B. bassiana-derived protein significantly reduced the whitefly survival and fecundity parameters concomitantly with an up-regulation of all the plant defense associated genes, particularly of SA pathway genes. These findings demonstrate the putative role of this partially purified entomopathogenic fungal protein and suggest its further purification and characterization for using in future microbial pest control strategies against whiteflies and other sap-feeding insect pests.Plants rely on various physiological and molecular defense mechanisms against biotic stresses such as herbivore insects. Many entomopathogenic fungi synthesize protein molecules that can trigger these plant defenses. This laboratory study characterized the bioactivity of a partially purified protein derived from Beauveria bassiana (ARSEF 2860) against whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), which is an economically important pest of agricultural and horticultural crops worldwide. Different concentrations (i.e., 0.021, 0.042 and 0.063 μM) of fungal protein were bioassayed to determine their sub-lethal effect on the survival percentage and fecundity rate of B. tabaci on tomato (Lycopersicon esculentum) plants. In addition, the putative role of this partially purified B. bassiana protein in the defense mechanisms of plant was assessed through the expression analyses of important genes related to salicylic acid (SA)—and jasmonic acid (JA)—associated pathways using RT-qPCR. Results revealed a significant suppression of the survival percentage and fecundity rate of B. tabaci by the fungal protein. Lowest survival (41%) was recorded for the highest concentration of protein (0.063 μM), whereas mean survival for the other two protein concentrations (0.042 and 0.021 μM) were 62 and 71%, respectively. Likewise, the highest and lowest mean fecundity rates were observed for the control and the highest protein concentration (i.e., 3.3 and 1.8 eggs day−1 female−1, respectively). Furthermore, the exogenous application of B. bassiana-derived protein on tomato plants strongly up-regulated the SA-related genes (PAL, PR1, BGL2 and EDS1) and slightly up-regulated the JA-related genes (AOC, AOS, OPR3 and LOX) as compared to the control plants. These findings demonstrate the putative role of this partially purified B. bassiana protein fraction in inducing systemic resistance in the tomato plants against B. tabaci, suggesting its further purification and characterization to be used as novel biological pest control tool against B. tabaci and other sap-sucking insect pests.

RNAi‐mediated silencing of ferritin genes in the brown planthopper Nilaparvata lugens affects survival, growth and female fecundity

The brown planthopper (BPH), Nilaparvata lugens, is the most destructive rice insect pest. To exploit potential target genes for applications in transgenic rice to control this sap-sucking insect pest, three ferritin genes were functionally characterized in this study. In this study, three ferritin genes, that is, ferritin 1 Heavy Chain (NlFer1), ferritin 2 Light Chain (NlFer2) and soma ferritin (Nlsoma-Fer), were identified from BPH. Tissue-specific analyses showed that all three genes were highly expressed in the gut. Although double-stranded RNA injection-mediated RNA inference (RNAi) of Nlsoma-Fer expression resulted in only < 14% mortality in BPH, knockdown of NlFer1 or NlFer2 led to retarded growth and 100% mortality in young nymphs, and downregulation of NlFer1 and NlFer2 in newly emerged female adults caused undeveloped ovaries and severely inhibited oocyte growth, resulting in extremely low fecundity and a zero hatching rate. Knockdown of NlFer1 and NlFer2 caused similar phenotypes in BPH, indicating that they function together, as in many other animals. The results demonstrated that NlFer1 and NlFer2 were essential for BPH development and reproduction. BPHs showed high sensitivity to both dsNlFer1 and dsNlFer2, and injection of only 0.625 ng dsNlFer1 per BPH resulted in 100% mortality. Additionally, the effectiveness of feeding dsNlFer1 and dsNlFer2 to BPH nymphs was further proven. NlFer1 and NlFer2 are essential for BPH development and reproduction, and the insect is highly sensitive to their depletion, suggesting that the two gut-highly-expressed genes are promising candidates for application in RNAi-based control of this destructive pest.

Nutritional Relationship between Bemisia tabaci and Its Primary Endosymbiont, Portiera aleyrodidarum, during Host Plant Acclimation.

Simple SummaryPlant sap-sucking insects commonly have established mutualistic relationships with bacteria that live within their bodies and often provide nutrients that are lacking in the insect’s diet. The sweet potato whitefly (Bemisia tabaci) harbors one primary and up to seven secondary endosymbiotic bacteria. The primary endosymbiont of B. tabaci is already known to play a critical role in providing necessary nutrients for B. tabaci. Our objective was to study the relationship among B. tabaci, its primary endosymbiont, and the host plant through the effects of host plant shifting and acclimation, that is, physiological adjustments as an insect becomes accustomed to a new host plant over several generations. The results showed that host shifting from Chinese kale to cotton plants led to a decrease in the fecundity of B. tabaci in the first generation, which was restored after 10 generations of acclimation, and that its developmental time was also decreased by the tenth generation. Furthermore, essential amino acid biosynthesis genes of its primary endosymbiont were differentially regulated after B. tabaci had become acclimated to cotton plants. We speculate that the primary endosymbiont has a close nutritional relationship with B. tabaci during host plant acclimation.Plant sap-sucking insects commonly have established mutualistic relationships with endosymbiotic bacteria that can provide nutrients lacking in their diet. Bemisia tabaci harbors one primary endosymbiont, Portiera aleyrodidarum, and up to seven secondary endosymbionts, including Hamiltonella defensa and Rickettsia sp. Portiera aleyrodidarum is already known to play a critical role in providing necessary nutrients for B. tabaci. In the present study, the relationship among B. tabaci, its primary endosymbiont, and the host plant were examined through the effects of host plant shifting and acclimation. Bemisia tabaci was transferred from Chinese kale to four different host plants, and the effects on both its performance and the expression levels of nutrient-related genes of P. aleyrodidarum were analyzed. The results showed that host shifting from Chinese kale to cotton plants led to a decrease in the performance of B. tabaci in the first generation, which was restored after 10 generations of acclimation. Furthermore, the expression levels of essential amino acid biosynthesis genes of P. aleyrodidarum were found to be differentially regulated after B. tabaci had acclimated to the cotton plants. Host plant shifting and acclimation to cucumber, poinsettia, and tomato plants did not affect the fecundity of B. tabaci and the expression levels of most examined genes. We speculate that P. aleyrodidarum may help B. tabaci improve its performance and acclimate to new hosts and that P. aleyrodidarum has a close nutritional relationship with its host during host plant acclimation.

Practical and Simple Systems for Food Intake Studies on Phloem-Sucking Insects.

Studies of insect feeding behavior are useful in different areas of entomology such as plant resistance, biology, and insecticide efficacy. For chewing insects, this kind of technique is well established, but for sap-sucking insects, especially tiny ones such as whiteflies, aphids, and psyllids, these tests can be laborious. Manipulation is difficult and can damage the plant, affecting the results. We describe here three types of cages for tests with small insects, one for seedlings in pots, a second for larger plants or plants in the field, and a third for caging insects on part of a leaf. These cages have been useful for different types of studies in addition to feeding behavior and can facilitate research with small phytophagous sucking insects.

Expression of Pinellia ternata leaf agglutinin under rolC promoter confers resistance against a phytophagous sap sucking aphid, Myzus persicae

Background: Piercing/sucking insect pests in the order Hemiptera causes substantial crop losses by removing photoassimilates and transmitting viruses to their host plants. Cloning and heterologous expression of plant-derived insect resistance genes is a promising approach to control aphids and other sap-sucking insect pests. While expression from the constitutive 35S promoter provides broad protection, the phloem-specific rolC promoter provides better defense against sap sucking insects. The selection of plant-derived insect resistance genes for expression in crop species will minimize bio-safety concerns. Results: Pinellia ternata leaf agglutinin gene ( pta ), encodes an insecticidal lectin, was isolated and cloned under the 35S and rolC promoters in the pGA482 plant transformation vector for Agrobacterium -mediated tobacco transformation. Integration and expression of the transgene was validated by Southern blotting and qRT-PCR, respectively. Insect bioassays data of transgenic tobacco plants showed that expression of pta under rolC promoter caused 100% aphid mortality and reduced aphid fecundity up to 70% in transgenic tobacco line LRP-9. These results highlight the better effectivity of pta under rolC promoter to control phloem feeders, aphids. Conclusions: These findings suggested the potential of PTA against aphids and other sap sucking insect pests. Evaluation of gene in tobacco under two different promoters; 35S constitutive promoter and rolC phloem-specific promoter could be successfully use for other crop plants particularly in cotton. Development of transgenic cotton plants using plant-derived insecticidal, PTA, would be key step towards commercialization of environmentally safe insect-resistant crops. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:Tabla normal; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-parent:; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:8.0pt; mso-para-margin-left:0cm; line-height:107%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:Calibri,sans-serif; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Times New Roman; mso-bidi-theme-font:minor-bidi;}

Characteristics of biochemical resistance mechanism of novel insecticides in Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae)

Phenacoccus solenopsis Tinsley is a major sap-sucking insect pest of many ornamental and agricultural crops in Pakistan. Insecticides are recommended to manage P. solenopsis but due to inappropriate use of insecticides, the resistance become the major concern. The study was conducted to investigate resistance against insecticides with different action modes (carbosulfan, clothianidin and chlorfenapyr) by selecting P. solenopsis populations successively for twelve generations with mentioned insecticides. Along with, possible biochemical mechanisms (acetylcholinesterase (AChE), acid and alkaline phosphatases (ACP and ALP), esterase (EST) and glutathione S-transferases (GST)) were assessed. The results described very high resistance (235-fold) to carbosulfan selected pop. (Carbo-SEL G12) and clothianidin selected pop. (Cloth-SEL G12) (112-fold) and high resistance to chlorfenapyr selected pop. (Chlor-SEL G12) (86-fold), relative to the unselected population. The activities of AChE, ACP, ALP, EST and GST enzymes gradually increased upon selection from G1 to G10. The enzymes contribute in resistance of tested insecticides were following: EST (15.61 μmol/min/mg of protein) in Carbo-SEL G12. Whereas, AChE activity (21.5 μmol/min/mg of protein) in Cloth-SEL G12 and the highest ALP enzymes activity 16.57 μmol/min/mg of protein in Chlor-SEL G12, as compared to the unselected population. Current research suggests that the detoxifying enzymes may contribute to resistance evolvement in P. solenopsis and this information may be used for the efficient management of insecticide resistance.

Suitable reference genes for RT-qPCR analysis in Dichelops melacanthus (Hemiptera: Pentatomidae).

The relative quantification of gene expression is mainly realized through reverse transcription-quantitative PCR (RT-qPCR). However, the accuracy of this technique is deeply influenced by the expression stability of the reference genes used for data normalization. Therefore, the selection of suitable reference genes for a given experimental condition is a prerequisite in gene expression studies. Dichelops melacanthus (Hemiptera: Pentatomidae) is an important phloem sap-sucking insect pest of soybean, wheat, and maize in Brazil. Most of the genetic and molecular biology studies require gene expression analysis. Nevertheless, there are no reports about reference genes for RT-qPCR data normalization in D. melacanthus. In this study, we evaluated the expression stability of nine candidate reference genes (nadh, sdhb, gapdh, fau, ef1a, rpl9, ube4a, gus and rps23) in different developmental stages, body parts, sex, starvation-induced stress and dsRNA exposure by RefFinder software that integrates the statistical algorithms geNorm, NormFinder, BestKeeper, and ΔCt method. Our results showed that ef1a and nadh are the most stable reference genes for developmental stages, fau and rps23 for sex, ube4a and rps23 for body parts, rpl9 and fau for starvation stress, and nadh and sdhb for dsRNA exposure treatment. The reference genes selected in this work will be useful for further RT-qPCR analyses on D. melacanthus, facilitating future gene expression studies that can provide a better understanding of the developmental, physiological, and molecular processes of this important insect pest. Moreover, the knowledge gained from these studies can be helpful to design effective and sustainable pest management strategies.

Sequence Analysis of New Tuf Molecular Types of 'Candidatus Phytoplasma Solani' in Iranian Vineyards.

Grapevine Bois noir (BN) is caused by ‘Candidatus Phytoplasma solani’ (‘Ca. P. solani’) and is one of the most important phytoplasma diseases in the Euro-Mediterranean viticultural areas. The epidemiology of BN can include grapevine as a plant host and is usually transmitted via sap-sucking insects that inhabit herbaceous host plants. Tracking the spread of ‘Ca. P. solani’ strains is of great help for the identification of plant reservoirs and insect vectors involved in local BN outbreaks. The molecular epidemiology of ‘Ca. P. solani’ is primarily based on sequence analysis of the tuf housekeeping gene (which encodes elongation factor Tu). In this study, molecular typing of tuf, through restriction fragment length polymorphism and sequencing, was carried out on grapevine samples from Iranian vineyards. According to the molecular characterization, three molecular types—tuf b1, tuf b5 and tuf b6—were found, with tuf b1 being the most prominent. These data provide further knowledge of tuf gene diversity and question the ecological role of such “minor” tuf types in Iranian vineyards, which have been detected only in grapevines.

Chromosome-level assembly of the melon thrips genome yields insights into evolution of a sap-sucking lifestyle and pesticide resistance.

Thrips are tiny insects from the order Thysanoptera (Hexapoda: Condylognatha), including many sap-sucking pests that are causing increasing damage to crops worldwide. In contrast to their closest relatives of Hemiptera (Hexapoda: Condylognatha), including numerous sap-sucking species, there are few genomic resources available for thrips. In this study, we assembled the first thrips genome at the chromosomal level from the melon thrips, Thrips palmi, a notorious pest in agriculture, using PacBio long-read and Illumina short-read sequences. The assembled genome was 237.85Mb in size, with 1,324 contigs and a contig N50 of 567kb. All contigs were assembled into 16 linkage groups assisted by the Hi-C technique. In total, 16,333 protein-coding genes were predicted, of which 88.13% were functionally annotated. Among sap-sucking insects, polyphagous species (e.g., T. palmi and Bemisia tabaci) usually possess more detoxification genes than oligophagous species (e.g., Diaphorina citri). The polyphagous thrips genomes characterized so far have relatively more detoxification genes in the GST and CCE families than polyphagous aphids, but they have fewer UGTs. HSP genes, especially from the Hsp70s group, have expanded in thrips compared to other hemipterans. These differences point to different genetic mechanisms associated with detoxification and stress responses in these two groups of sap-sucking insects. The expansion of these gene families may contribute to the rapid development of pesticide resistance in thrips, as supported by a transcriptome comparison of resistant and sensitive populations of T. palmi. The high-quality genome developed here provides an invaluable resource for understanding the ecology, genetics, and evolution of thrips as well as their relatives more generally.

The potential and efficacy of Allium sativum leaf lectin (ASAL) against sap-sucking insect pests of transgenic maize

The gene sequence encoding the mannose-binding homodimeric protein Allium sativum leaf agglutinin (ASAL) was introduced into maize inbred lines to achieve resistance against sap-sucking corn leaf aphids in transgenic lines. Maize transformants were generated after the co-cultivation of immature maize embryos with the Agrobacterium strain LB4404 harbouring a recombinant Ti-binary ASAL construct driven by the polyubiquitin promoter. The preliminary screening of maize transformants was performed via GUS histochemical analysis, and PCR and Southern blotting confirmed the insertion of the transgene and its stable integration in five transgenic maize lines. Transcript abundance was quantified by a quantitative real-time PCR assay, which revealed variable expression of the ASAL transgene among five transgenic maize lines. The highest mRNA expression of the ASAL gene was found in the A23 transgenic maize line, while the lowest expression was found in the AU1 transgenic maize line. In planta bioassays in the T1 progeny of the transgenic maize lines revealed high resistance against corn leaf aphids compared to the control non-transgenic line. The mortality of the infesting aphids (Rhopalosiphum maidi) was found to vary from 40 to 71% compared to that of the non-transgenic control maize line.

Potential distribution and population dynamics of Pulvinariella mesembryanthemi, a promising biocontrol agent of the invasive plant species Carpobrotus edulis and C. aff. acinaciformis

The geographic distribution of the invasive plant Carpobrotus spp. and its potential biocontrol, the scale insect Pulvinariella mesembryanthemi (Vallot), was predicted in NW Spain using the maximum entropy algorithm (MaxEnt). Since both species are mainly present along the coast the potential distribution of the species overlapped. Plant distribution was influenced by soil thermal regime (51%) and continentality index (22%), while insect distribution was determined by the continental index (39%) and the soil thermic regimen (38%). The population dynamics of P. mesembryanthemi was examined through a 2-year field study in four localities invaded by Carpobrotus taking into account climatic factors and biotic interactions. In the studied localities, this scale was bivoltine, reaching its highest densities in the warmer and drier months of summer and sharply decreasing in winter. Only in a specially sheltered locality (Mera) did the insect densities stay high throughout the year. Pulvinariella mesembryanthemi infestation increased necromass proportion of its host plant. However, Chalcidoidea parasites and Coccinellidae predators limited P. mesembryanthemi density, and therefore may restrict its efficiency as a biocontrol agent. Chalcidoidea parasitism affected predominately the largest scales (particularly when P. mesembryanthemi reached high densities), slowing down the development of scales in summer. The excretion of honeydew by these scales attracted ants, and exceptionally, led to mould fouling. Carpobrotus plants were also attacked by fruit predators (facilitating seed dissemination and germination), other sap-sucking insects (i.e. aphids, mealybugs, spittlebugs), and viruses. There were no severe consequences. The utilization of the scale-insect as biological control due to complex interactions between both invaders and a set of generalist enemies and mutualists, as well as its implications, are discussed.

P finder: genomic and metagenomic annotation of RNase P RNA gene (rnpB)

BackgroundThe rnpB gene encodes for an essential catalytic RNA (RNase P). Like other essential RNAs, RNase P’s sequence is highly variable. However, unlike other essential RNAs (i.e. tRNA, 16 S, 6 S,...) its structure is also variable with at least 5 distinct structure types observed in prokaryotes. This structural variability makes it labor intensive and challenging to create and maintain covariance models for the detection of RNase P RNA in genomic and metagenomic sequences. The lack of a facile and rapid annotation algorithm has led to the rnpB gene being the most grossly under annotated essential gene in completed prokaryotic genomes with only a 24% annotation rate. Here we describe the coupling of the largest RNase P RNA database with the local alignment scoring algorithm to create the most sensitive and rapid prokaryote rnpB gene identification and annotation algorithm to date.ResultsOf the 2772 completed microbial genomes downloaded from GenBank only 665 genomes had an annotated rnpB gene. We applied P Finder to these genomes and were able to identify 2733 or nearly 99% of the 2772 microbial genomes examined. From these results four new rnpB genes that encode the minimal T-type P RNase P RNAs were identified computationally for the first time. In addition, only the second C-type RNase P RNA was identified in Sphaerobacter thermophilus. Of special note, no RNase P RNAs were detected in several obligate endosymbionts of sap sucking insects suggesting a novel evolutionary adaptation.ConclusionsThe coupling of the largest RNase P RNA database and associated structure class identification with the P Finder algorithm is both sensitive and rapid, yielding high quality results to aid researchers annotating either genomic or metagenomic data. It is the only algorithm to date that can identify challenging RNAse P classes such as C-type and the minimal T-type RNase P RNAs. P Finder is written in C# and has a user-friendly GUI that can run on multiple 64-bit windows platforms (Windows Vista/7/8/10). P Finder is free available for download at https://github.com/JChristopherEllis/P-Finder as well as a small sample RNase P RNA file for testing.

Impact of sap-sucking insect pests (Blastopsylla occidentalis Taylor and Glycaspis brimblecombei Moore, Hemiptera: Psyllidae) on unifloral eucalyptus honey

Eucalyptus species are important worldwide as melliferous plants, as a source of nectar and pollen, and contribute to the production of large quantities of honey, especially in summer when E. Camaldulensis Dhnh., the most common eucalyptus species in the Mediterranean area, flowers. Its honey yield potential exceeds 200 kg/ha, sometimes accounting for more than 50% of total apiary production. In Italy, eucalyptus plantations cover at least 50,000 hectares, corresponding to a potential production of 10,000 tons of honey per year. Since 2000 several invasive eucalyptus pests have spread and settled in the Mediterranean. Of these, psyllids Blastopsylla occidentalis Taylor and Glycaspis brimblecombei Moore have become major threats to eucalyptus plantations. The main objective of this study was to verify the impact of sap-sucking insects unifloral eucalyptus honey production and quality in Northern Sardinia (Italy). Our results show that a pronounced decrease in honey production occurred after 2011, with no production at all in 2012 and 2013, partial recovery in 2014-2016 and a further increase in 2017 and 2018. Moreover, the incidence of honeydew produced by psyllids has led to modifications in the chemical-physical characteristics and pollen spectrum of unifloral eucalyptus honey.

Prospects for classical biological control of Marchalina hellenica in Australia

The giant pine scale, Marchalina hellenica Gennadius (Hemiptera: Marchalinidae), is a sap-sucking insect native to South-East Europe that was recently introduced in Australia where it threatens the pine forestry industry. To initiate a classical biological control programme, a literature review and field surveys were carried out in Greece to investigate the natural enemy complex of the scale. While no parasitoids were found, M. hellenica was attacked by several predators, most notably Neoleucopis kartliana Tanasijtshuk (Diptera: Chamaemyiidae). N. kartliana was present at all sites investigated and is presumably specific to Marchalina. This highlights its potential as a biological control agent for M. hellenica. This predatory fly has already been used to control M. hellenica on the Italian island of Ischia. Interestingly, molecular analyses of Greek samples revealed other Chamaemyiidae predatory flies that can be potentially included in the Australian classical biological control programme of M. hellenica.