Predicting the potential geographical distribution of onion thrips, Thrips tabaci in India based on climate change projections using MaxEnt.

Onion thrips, Thrips tabaci Lindeman, an economically important onion pest in India, poses a severe threat to the domestic and export supply of onions. Therefore, it is important to study the distribution of this pest in order to assess the possible crop loss, which it may inflict if not managed in time. In this study, MaxEnt was used to analyze the potential distribution of T. tabaci in India and predict the changes in the suitable areas for onion thrips under two scenarios, SSP126 and SSP585. The area under the receiver operating characteristic curve values of 0.993 and 0.989 for training and testing demonstrated excellent model accuracy. The true skill statistic value of 0.944 and 0.921, and the continuous Boyce index of 0.964 and 0.889 for training and testing, also showed higher model accuracy. Annual Mean Temperature (bio1), Annual Precipitation (bio12) and Precipitation Seasonality (bio15) are the main variables that determined the potential distribution of T. tabaci, with the suitable range of 22-28 °C; 300-1000 mm and 70-160, respectively. T. tabaci is distributed mainly in India's central and southern states, with 1.17 × 106 km2, covering 36.4% of land area under the current scenario. Multimodal ensembles show that under a low emission scenario (SSP126), low, moderate and optimum suitable areas of T. tabaci is likely to increase, while highly suitable areas would decrease by 17.4% in 2050 20.9% in 2070. Whereas, under the high emission scenario (SSP585), the high suitability is likely to contract by 24.2% and 51.7% for 2050 and 2070, respectively. According to the prediction of the BCC-CSM2-MR, CanESM5, CNRM-CM6-1 and MIROC6 model, the highly suitable area for T. tabaci would likely contract under both SSP126 and SSP585. This study detailed the potential future habitable area for T. tabaci in India, which could help monitor and devise efficient management strategies for this destructive pest.

Chromosome-level genome assembly of bean flower thrips Megalurothrips usitatus (Thysanoptera: Thripidae).

Bean flower thrips Megalurothrips usitatus is a staple pest of cowpea and other legumes and causes dramatic economic losses. Its small size allows for easy concealment, and large reproductive capacity easily leads to infestations. Despite the importance of a genome in developing novel management strategies, genetic studies on M. usitatus remain limited. Thus, we generated a chromosome-level M. usitatus genome using a combination of PacBio long read and Hi-C technologies. The assembled genome was 238.14 Mb with a scaffold N50 of 13.85 Mb. The final genome was anchored into 16 pseudo-chromosomes containing 14,000 genes, of which 91.74% were functionally annotated. Comparative genomic analyses revealed that expanded gene families were enriched in fatty acid metabolism and detoxification metabolism (ABC transporters), and contracted gene families were strongly associated with chitin-based cuticle development and sensory perception of taste. In conclusion, this high-quality genome provides an invaluable resource for us to understand the thrips' ecology and genetics, contributing to pest management.

The effects of the E3 ubiquitin-protein ligase UBR7 of Frankliniella occidentalis on the ability of insects to acquire and transmit TSWV.

The interactions between plant viruses and insect vectors are very complex. In recent years, RNA sequencing data have been used to elucidate critical genes of Tomato spotted wilt ortho-tospovirus (TSWV) and Frankliniella occidentalis (F. occidentalis). However, very little is known about the essential genes involved in thrips acquisition and transmission of TSWV. Based on transcriptome data of F. occidentalis infected with TSWV, we verified the complete sequence of the E3 ubiquitin-protein ligase UBR7 gene (UBR7), which is closely related to virus transmission. Additionally, we found that UBR7 belongs to the E3 ubiquitin-protein ligase family that is highly expressed in adulthood in F. occidentalis. UBR7 could interfere with virus replication and thus affect the transmission efficiency of F. occidentalis. With low URB7 expression, TSWV transmission efficiency decreased, while TSWV acquisition efficiency was unaffected. Moreover, the direct interaction between UBR7 and the nucleocapsid (N) protein of TSWV was investigated through surface plasmon resonance and GST pull-down. In conclusion, we found that UBR7 is a crucial protein for TSWV transmission by F. occidentalis, as it directly interacts with TSWV N. This study provides a new direction for developing green pesticides targeting E3 ubiquitin to control TSWV and F. occidentalis.

Chemosensory protein regulates the behavioural response of Frankliniella intonsa and Frankliniella occidentalis to tomato zonate spot virus-Infected pepper (Capsicum annuum).

Many herbivorous insects rely on plant volatiles to locate their host plants. Vector-borne viral infections induce changes in plant volatiles, which render infected plants more attractive to insect vectors. However, the detailed mechanisms underlying the olfactory responses of insect vectors induced by the volatiles produced by virus-infected plants are poorly understood. Here, we show that volatiles emitted by pepper (Capsicum annuum) plants infected with tomato zonate spot virus (TZSV), particularly the volatile cis-3-hexenal, which is recognized by chemosensory protein 1 of the thrips Frankliniella intonsa (FintCSP1), are more attractive to F. intonsa than the volatiles emitted by non-infected pepper plants. FintCSP1 is highly abundant in the antenna of F. intonsa. Silencing of FintCSP1 significantly decreased electroantennogram responses of F. intonsa antennae to cis-3-hexenal and impaired thrips' responses to TZSV-infected pepper plants and cis-3-hexenal, as assessed using a Y-tube olfactometer. Three-dimensional model predictions indicated that FintCSP1 consists of seven α-helixes and two disulfide bridges. Molecular docking analysis suggested that cis-3-hexenal is positioned deep inside the binding pocket of FintCSP1 and binds to residues of the protein. We combined site-directed mutagenesis and fluorescence binding assays and identified three hydrophilic residues, Lys26, Thr28, and Glu67, of FintCSP1 as being critical for cis-3-hexenal binding. Furthermore, CSP of F. occidentalis (FoccCSP) is also a key olfactory protein involved in modulating the behaviour of F. occidentalis to TZSV-infected pepper. This study revealed the specific binding characteristics of CSPs to cis-3-hexenal and confirmed the general hypothesis that virus infections induce changes in host volatiles, which can be recognized by the olfactory proteins of the insect vector to enhance vector attraction and this may facilitate viral spread and transmission.

HMG-like DSP1 is a damage signal to mediate the western flower thrips, Frankliniella occidentalis, immune responses to tomato spotted wilt virus infection.

Tomato spotted wilt virus (TSWV) causes a serious plant disease and is transmitted by specific thrips including the western flower thrips, Frankliniella occidentalis. The persistent and circulative virus transmission suggests an induction of immune defenses in the thrips. We investigated the immune responses of F. occidentalis to TSWV infection. Immunofluorescence assay demonstrated viral infection in the larval midguts at early stage and subsequent propagation to the salivary gland in adults. In the larval midgut, TSWV infection led to the release of DSP1, a damage-associated molecular pattern, from the gut epithelium into the hemolymph. DSP1 up-regulated PLA2 activity, which would lead to biosynthesis of eicosanoids that activate cellular and humoral immune responses. Phenoloxidase (PO) activity was enhanced following induction of PO and its activating protease gene expressions. Antimicrobial peptide genes and dual oxidase, which produces reactive oxygen species, were induced by the viral infection. Expression of four caspase genes increased and TUNEL assay confirmed apoptosis in the larval midgut after the virus infection. These immune responses to viral infection were significantly suppressed by the inhibition of DSP1 release. We infer that TSWV infection induces F. occidentalis immune responses, which are activated by the release of DSP1 from the infection foci within midguts.

Two new species of the genus Thrips Linnaeus (Thysanoptera, Thripidae) in Japan, with a revised key to Japanese species of Thrips.

Thrips coxalis sp. n. and T. spiranthicola sp. n. are described from Lespedeza buergeri and Spiranthes sinensis, respectively in Japan. Variation is discussed in campaniform sensilla on metascutum and abdominal tergite IX, also the distribution of microtrichia on hind coxae within Thripidae, and a revised key to Japanese species of Thrips is provided.

Kakothrips acanthus Berzosa (Thysanoptera: Thripidae) in Türkiye, with an illustrated key to the species of Kakothrips.

Kakothrips acanthus Berzosa, previously known only from Spain and Sicily, is newly reported from Türkiye, based on a single female. Diagnostic characters of the specimen are provided, also an illustrated key to the eight species of Kakothrips Williams, and available data on the plant associations of these species. Females of Kakothrips priesneri are considered remarkable among Thripinae in having sternal pore plates.

Endemism among Lord Howe Island Thysanoptera, with new species of Baenothrips (Phlaeothripidae) and Scirtothrips (Thripidae).

The Thysanoptera diversity of Lord Howe Island comprises 39 known species, of which 13 are considered likely to be endemic to this tiny remnant of an ancient submarine volcano. Three new species are described in Baenothrips, a small but widespread genus of wingless, fungus-feeding species in the Old World tropics. Two new species of Scirtothrips are described that are members of a species-group breeding on the youngest fronds of tree ferns.

Greenhouse test of spraying dsRNA to control the western flower thrips, Frankliniella occidentalis, infesting hot peppers.

BACKGROUND: The western flower thrips Frankliniella occidentalis is an insect pest that damages various crops, including hot peppers. It is a vector of a plant pathogen, tomato spotted wilt virus. To control this pest, chemical insecticides have been used in the past, but the control efficacy is unsatisfactory owing to rapid resistance development by F. occidentalis. METHODOLOGY: This study reports a novel control technology against this insect pest using RNA interference (RNAi) of the vacuolar-type ATPase (vATPase) expression. Eight subunit genes (vATPase-A ∼ vATPase-H) of vATPase were obtained from the F. occidentalis genome and confirmed for their expressions at all developmental stages. RESULTS: Double-stranded RNAs (dsRNAs) specific to the eight subunit genes were fed to larvae and adults, which significantly suppressed the corresponding gene expressions after 24-h feeding treatment. These RNAi treatments resulted in significant mortalities, in which the dsRNA treatments at ∼2,000 ppm specific to vATPase-A or vATPase-B allowed complete control efficacy near 100% mortality in 7 days after treatment. To prevent dsRNA degradation by the digestive proteases during oral feeding, dsRNAs were formulated in a liposome and led to an enhanced mortality of the larvae and adults of F. occidentalis. The dsRNAs were then sprayed at 2,000 ppm on F. occidentalis infesting hot peppers in a greenhouse, which resulted in 53.5-55.9% control efficacy in 7 days after treatment. Even though the vATPases are conserved in different organisms, the dsRNA treatment was relatively safe for non-target insects owing to the presence of mismatch sequences compared to the dsRNA region of F. occidentalis. CONCLUSION: These results demonstrate the practical feasibility of spraying dsRNA to control F. occidentalis infesting crops.

Preliminary Study on Insecticidal Potential and Chemical Composition of Five Rutaceae Essential Oils against Thrips flavus (Thysanoptera: Thripidae).

To meet the demand for novel pest management strategies to combat the development of insecticide resistance, plant essential oils may be a promising alternative source. This study investigated the insecticidal activity of five essential oils from the Rutaceae plant family against Thrips flavus Schrank (Thysanoptera: Thripidae) under laboratory conditions. The plant essential oils were citrus oil (Citrus reticulata Blanco), Chuan-shan pepper oil (Zanthoxylum piasezkii Maxim.), zanthoxylum oil (Zanthoxylum bungeanum Maxim.), pomelo peel oil (Citrus maxima (Burm.) Merr.) and orange leaf oil (Citrus sinensis (L.) Osbeck). Among the essential oils evaluated, orange leaf oil (LC50 = 0.26 g/L), zanthoxylum oil (LC50 = 0.27 g/L), and pomelo peel oil (LC50 = 0.44 g/L) resulted in a higher gastric toxicity under laboratory conditions. The results of the pot experiment also showed that orange leaf oil (93.06 ± 3.67% at 540.00 g a.i.·hm-2, 97.22 ± 1.39% at 720 g a.i.·hm-2, 100.00% at 900.00 g a.i.·hm-2) zanthoxylum oil (98.73 ± 1.27% at 900 g a.i.·hm-2), and pomelo peel oil (100.00% at 900 g a.i.·hm-2) exhibited a higher control efficacy, being the most effective against T. flavus after 7 days of treatment. The essential oil components were then identified by gas chromatography-mass spectrometry (GC-MS). The insecticidal activity of orange leaf oil, pomelo peel oil, and zanthoxylum oil could be attributed to their main constituents, such as methyl jasmonate (50.92%), D-limonene (76.96%), and linalool (52.32%), respectively. In the olfactory test, adult T. flavus were attracted by zanthoxylum oil and Chuan-shan pepper oil. We speculated that linalool might be the key signaling compound that attracts T. flavus. These results showed that orange leaf oil, zanthoxylum oil, and pomelo peel oil exhibited insecticidal activities under controlled conditions. They can be implemented as effective and low-toxicity botanical insecticides and synergistic agents against T. flavus.

Multigenerational variation in the nutrients and digestion of western flower thrips (Frankliniella occidentalis) depends on the nutritive quality of different foods.

Western flower thrips (WFTs), Frankliniella occidentalis (Thysanoptera, Thripidae), is one of the most serious pests that attack rose flowers. Little is known about the effect of different parts of the rose flower on nutritional contents and digestive enzyme activities in thrips. This study assessed variations in the nutritional contents and digestive enzyme activities in the second-instar larvae and adults WFTs fed on 3 food types (rose petals, rose flowers, and honey solution + kidney bean pods) for multiple generations. The highest contents of soluble sugar (in 10% honey solution + kidney bean pods), amino acid (in rose flowers), and protein (in rose flowers) were observed, respectively. Soluble sugar and protein contents in the second-instar larvae and adults fed on rose petals decreased in the F1 generation but increased in the F2 generation and remained at higher levels until the F7 generation. Feeding of thrips with 3 food types increased the lipid content in the F1 generation, which peaked in the F2 generation and remained high until the F7 generation. In most cases, α-amylase and trypsin activities significantly decreased in the F1 generation after feeding on rose petals and then prominently increased in the F2 generation. In contrast, chymotrypsin activity remarkably increased and peaked in the F1 generation after second-instar larvae thrips fed on rose petals. There were correlations among the contents of 3 nutrient related positively with the activities of α-amylase and trypsin in WFTs second-instar larvae and adults, respectively. Overall, variations in the nutrient properties of the 3 food types caused changes in nutrient contents and digestive enzyme activities in thrips.

Acylsugar-mediated resistance as part of a multilayered defense against thrips, orthotospoviruses, and beyond.

Resistant varieties are critical tools for crop production, and single-resistance genes providing strong protection against pests or pathogens are deployed in agriculture. Durability of these traits is threatened by emergence of resistance-breaking pests and pathogens. This review focuses on acylsugar-mediated resistance in tomato. Wild tomatoes have type-IV trichomes that exude chemically complex mixtures of acylsugars altering behavior and suppressing multiple pest species, and with thrips and whiteflies (WF), suppressing virus transmission, for example, Tomato spotted wilt orthotospovirus and Tomato yellow leaf curl virus, respectively. Marker-assisted selection and bioassays led to development of advanced cultivated tomato breeding lines rich in acylsugar variations, allowing acylsugar-mediated resistance to be combined with other resistance traits providing a layered defense system that reduces pest populations and virus disease prevalence. This strategy also holds promise for enhancing durability of virus resistance genes by reducing the intensity of selection for resistance-breaking variants.

Predicting the Potential Global Distribution of Scirtothrips dorsalis (Hood) (Thysanoptera: Thripidae) with Emphasis on the Americas Using an Ecological Niche Model.

Scirtothrips dorsalis Hood (Thysanoptera: Thripidae) is an invasive pest that is popularly known as chilli thrips. This insect pest has a wide range of hosts distributed across 72 plant families, causing damage to numerous crops of great economic importance. In the Americas, it is present in the USA, Mexico, Suriname, Venezuela, Colombia, and some Caribbean Islands. Knowing the regions which have environmentally suitable conditions for the survival of this pest is important for phytosanitary monitoring and inspection. Thus, our objective was to forecast the distribution potential of S. dorsalis with a focus on the Americas. Models were produced to design this distribution, in which the environmental variables used were made available in Wordclim version 2.1. The algorithms used for the modeling were the generalized additive model (GAM), generalized linear model (GLM), maximum entropy (MAXENT), random forest (RF), and Bioclim, in addition to the ensemble, which consisted of the grouping of the algorithms used. The metrics used to evaluate the models were area over the curve (AUC), true ability statistics (TSS), and Sorensen score. All models had satisfactory results (> 0.8) for all metrics used. In North America, the model showed favorable regions on the west coast of the USA and east coast near New York. In South America, the potential distribution of the pest is significant, encompassing regions in all countries. It is concluded that S. dorsalis has suitable areas for the occurrence in the three American subcontinents and, in particular, a large part of South America.

Responses of Thrips hawaiiensis and Thrips flavus populations to elevated CO2 concentrations.

Increased atmospheric CO2 concentrations may directly affect insect behavior. Thrips hawaiiensis Morgan and T. flavus Schrank are economically important thrips pests native to China. We studied the development, survival, and oviposition of these two thrips under elevated CO2 concentrations (800 µl liter-1) and ambient CO2 (400 µl liter-1; control) conditions. Both thrips species developed faster but had lower survival rates under elevated CO2 levels compared with control conditions (developmental time: 13.25 days vs. 12.53 days in T. hawaiiensis, 12.18 days vs. 11.61 days in T. flavus; adult survival rate: 70.00% vs. 64.00% in T. hawaiiensis, 65.00% vs. 57.00% in T. flavus under control vs. 800 µl liter-1 CO2 conditions, respectively). The fecundity, net reproductive rate (R0), and intrinsic rate of increase (rm) of the two species were also lower under elevated CO2 concentrations (fecundity: 47.96 vs. 35.44 in T. hawaiiensis, 36.68 vs. 27.88 in T. flavus; R0: 19.83 vs. 13.62 in T. hawaiiensis, 14.02 vs. 9.86 in T. flavus; and rm: 0.131 vs. 0.121 in T. hawaiiensis, 0.113 vs. 0.104 in T. flavus under control and 800 µl liter-1 CO2 conditions, respectively). T. hawaiiensis developed slower but had a higher survival rate, fecundity, R0, and rm compared with T. flavus at each CO2 concentration. In summary, elevated CO2 concentrations negatively affected T. hawaiiensis and T. flavus populations. In a world with higher CO2 concentrations, T. hawaiiensis might be competitively superior to T. flavus where they co-occur.

Antennal Transcriptome Analysis of Olfactory Genes and Characterization of Odorant Binding Proteins in Odontothrips loti (Thysanoptera: Thripidae).

To identify odors in complex environments accurately, insects have evolved multiple olfactory proteins. In our study, various olfactory proteins of Odontothrips loti Haliday, an oligophagous pest that primarily affects Medicago sativa (alfalfa), were explored. Specifically, 47 putative olfactory candidate genes were identified in the antennae transcriptome of O. loti, including seven odorant-binding proteins (OBPs), nine chemosensory proteins (CSPs), seven sensory neuron membrane proteins (SNMPs), eight odorant receptors (ORs), and sixteen ionotropic receptors (IRs). PCR analysis further confirmed that 43 out of 47 genes existed in O. loti adults, and O.lotOBP1, O.lotOBP4, and O.lotOBP6 were specifically expressed in the antennae with a male-biased expression pattern. In addition, both the fluorescence competitive binding assay and molecular docking showed that p-Menth-8-en-2-one, a component of the volatiles of the host, had strong binding ability to the O.lotOBP6 protein. Behavioral experiments showed that this component has a significant attraction to both female and male adults, indicating that O.lotOBP6 plays a role in host location. Furthermore, molecular docking reveals potential active sites in O.lotOBP6 that interact with most of the tested volatiles. Our results provide insights into the mechanism of O. loti odor-evoked behavior and the development of a highly specific and sustainable approach for thrip management.

Predacious Natural Enemies Associated With Suppression of Onion Thrips, Thrips tabaci (Thysanoptera: Thripidae), in Intercropped Onion-Barley Agroecosystems.

The effects of two possible factors, prevention of pest immigration and enhancement of natural enemies, in suppressing onion thrips, Thrips tabaci L., were estimated in a small-scale experimental system of spring-planted onions intercropped with barley. The population dynamics of the thrips and their potential predatory natural enemies were investigated in four treatments: control (bare ground), insect net barrier, and onion-barley intercropping with or without trimming. We found that intercropping significantly suppressed onion thrips. It is unlikely that this effect was due to the prevention of thrip immigration because they seemed to move over the camouflage and/or physical barriers of the barley and the net barrier surrounding the onions easily. Intercropping with barley significantly increased hoverfly (Syrphidae) larvae numbers on onion leaves, and that of some groups of ground-dwelling predators such as large carnivorous ground beetles (Carabidae), ants (Formicidae), and wolf spiders (Lycosidae). We conclude that the suppression of thrips in this system was associated with the enhancement of hoverfly larvae abundance, mainly Sphaerophoria macrogaster (Thomson) (Syrphidae: Diptera) because they were observed together with thrips on onions and have been reported to predate thrips as well as aphids. Some hoverfly larvae on barley might move to nearby onions to search for new food sources and attack thrips.

A push-pull strategy to control the western flower thrips, Frankliniella occidentalis, using alarm and aggregation pheromones.

Since the first report in 1993 in Korea, the western flower thrips, Frankliniella occidentalis, has been found in various crops throughout the country. Although more than 20 different chemical insecticides are registered to control this insect pest, its outbreaks seriously damage crop yields, especially in greenhouses. This study developed a non-chemical technique to control F. occidentalis infesting hot peppers cultivated in greenhouses. The method was based on behavioral control using an alarm pheromone ("Push") to prevent the entry of the thrips into greenhouses and an aggregation pheromone ("Pull") for mass trapping inside the greenhouses. The greenhouse fences were treated with a wax formulation of the alarm pheromone and a yellow CAN trap covered with sticky material containing the aggregation pheromone was constructed and deployed inside the greenhouses. Field assay demonstrated the efficacy of the push-pull tactics by reducing thrips density in flowers of the hot peppers as well as in the monitoring traps. Especially, the enhanced mass trapping to the CAN trap compared to the conventional yellow sticky trap led to significant reduction in the thrips population. This novel push-pull technique would be applicable to effectively control F. occidentalis in field conditions.

Sequential Sampling Plans for Thrips (Thysanoptera: Thripidae) in Soybean Crops With Insecticide Applications Using Tractor or Airplane.

Sampling plans are an essential part of integrated pest management programs. Sequential sampling plans enable rapid and low-cost assessment of pest densities. Thrips are emerging pests in soybean crops, and the main method used in pest control is chemical. In soybean crops, insecticides are applied mainly using tractors or airplanes. Thus, this work aimed to determine sequential sampling plans for thrips in soybean crops with insecticide applications using a tractor or airplane. Data were collected in 56 soybean fields, and each field was 20 ha. Sampling plans were determined and validated. The lower (m0) and upper (m1) limits of the sequential sampling plans were: m0 = 1.72 and m1 = 3.43 (by tractor applications) and, m0 = 2.27 and m1 = 4.53 thrips. sample-1 (by airplane applications). The slope (S) and the lower (h0) and upper (h1) intercepts of the sequential sampling plans were: S = 2.42, h0 = -5.79, and h1 = 5.79 (by tractor applications) and, S = 3.19, h0 = -6.83, and h1 = 6.83 (by airplane applications). Sequential sampling plans allowed for correct decisions to be made in all situations using a maximum of 10 samples. The sequential plan reduced the sampling effort by over 87% compared to conventional sampling plans. Therefore, these control decision-making systems have proven feasible and advantageous for implementing integrated pest management programs for controlling thrips species in soybean crops.

Cadmium contamination triggers negative bottom-up effects on the growth and reproduction of Frankliniella occidentalis (Thysanoptera: Thripidae) without disrupting the foraging behavior of its predator, Orius sauteri (Heteroptera: Anthocoridae).

Heavy metal contaminants may influence tri-trophic interactions among plants, herbivores, and their natural enemies and affect the results of pest management practices. We examined how the widely distributed heavy metal cadmium (Cd) could modify interactions between kidney bean, Phaseolus vulgaris L., western flower thrips, Frankliniella occidentalis Pergande, and a predator, Orius sauteri (Poppius) by examining Cd effects on the feeding damage on leaves, the growth and reproduction of the thrips, and the feeding and plant location selection behaviors of predators. Leaf feeding damage was significantly reduced only at the highest Cd treatment (625 mg L-1). Survival, reproduction, and population growth of thrips decreased with the increase of Cd treatment concentration (0, 25, and 625 mg L-1). The reproduction rate of thrips from the highest Cd treatment group was reduced to less than 30% of the controls. Predator choice of plants was not impacted at the lowest level of Cd treatment (25 mg L-1) when prey were excluded, but the predators were deterred from plants treated at the high level of Cd (625 mg L-1). However, the predators responded strongly to the presence of prey, and the Cd-based deterrence was effectively eliminated when prey were added. Thus, the presence of Cd can cause a bottom-up effect on the fitness of pests without disrupting the foraging behavior of its predator. Our results provide baseline data on the toxic impacts on the pest and predator, and indicate that the ecology of the system and the biological control efficiency would be potentially impacted by high levels of Cd (625 mg L-1).

KASP genotyping and semi-quantitation of G275E mutation in the α6 subunit of Thrips palmi nAChR gene conferring spinetoram resistance.

BACKGROUND: Pesticide resistance is a long-standing and growing problem in the chemical control of invertebrate pests. Molecular diagnostic methods can facilitate pesticide resistance management by accurately and efficiently detecting resistant mutations and their frequency. In this study, the kompetitive allele specific PCR (KASP) approach, a technology for high-throughput single nucleotide polymorphism (SNP) genotyping, is validated as a useful method for characterizing genotypes at a pesticide-resistance locus for the first time. We focus on the spinetoram resistance mutation of G275E in the nicotinic acetylcholine receptor alpha 6 (nAChR α6) subunit gene of Thrips palmi. RESULTS: Of the 341 individuals of Thrips palmi tested, 98.24% were successfully genotyped, with 100% concordance with Sanger sequencing results. We then quantitatively mixed genomic DNA of known genotypes to establish 21 DNA mixtures with a resistant allele frequency ranging from 0 to 100% at steps of 5%. The linear discriminant analysis (LDA) showed that 75.8% of original grouped cases were correctly classified; six groups had no overlap in membership (resistant allele frequency: 0%, 5%, 10-75%, 80-85%, 90-95%, and 100%). When we chose 11 pooled samples with 10% steps for LDA, 84.4% of original grouped cases were correctly classified; seven groups had no overlap in membership (0%, 10%, 20-30%, 40-70%, 80%, 90%, 100%). The results indicated that KASP applied to pooled samples may provide a semi-quantitative estimate of resistance. CONCLUSIONS: Our study points to the suitability of KASP for high-throughput genotyping of genotypes affecting pesticide resistance and semi-quantitative assessments of resistance allele frequencies in populations. © 2023 Society of Chemical Industry.