Choice Assays Research Articles

Mechanisms of Carboxylic Acid Attraction in Drosophila melanogaster.

Sour is one of the fundamental taste modalities that enable taste perception in animals. Chemoreceptors embedded in taste organs are pivotal to discriminate between different chemicals to ensure survival. Animals generally prefer slightly acidic food and avoid highly acidic alternatives. We recently proposed that all acids are aversive at high concentrations, a response that is mediated by low pH as well as specific anions in Drosophila melanogaster. Particularly, some carboxylic acids such as glycolic acid, citric acid, and lactic acid are highly attractive to Drosophila compared with acetic acid. The present study determined that attractive carboxylic acids were mediated by broadly expressed Ir25a and Ir76b, as demonstrated by a candidate mutant library screen. The mutant deficits were completely recovered via wild-type cDNA expression in sweet-sensing gustatory receptor neurons. Furthermore, sweet gustatory receptors such as Gr5a, Gr61a, and Gr64a-f modulate attractive responses. These genetic defects were confirmed using binary food choice assays as well as electrophysiology in the labellum. Taken together, our findings demonstrate that at least two different kinds of receptors are required to discriminate attractive carboxylic acids from other acids.

Carnivorous Nepenthes x ventrata plants use a naphthoquinone as phytoanticipin against herbivory.

Carnivorous plants feed on animal prey, mainly insects, to get additional nutrients. This carnivorous syndrome is widely investigated and reported. In contrast, reports on herbivores feeding on carnivorous plants and related defenses of the plants under attack are rare. Here, we studied the interaction of a pitcher plant, Nepenthes x ventrata, with a generalist lepidopteran herbivore, Spodoptera littoralis, using a combination of LC/MS-based chemical analytics, choice and feeding assays. Chemical defenses in N. x ventrata leaves were analyzed upon S. littoralis feeding. A naphthoquinone, plumbagin, was identified in Nepenthes defense against herbivores and as the compound mainly responsible for the finding that S. littoralis larvae gained almost no weight when feeding on Nepenthes leaves. Plumbagin is constitutively present but further 3-fold increased upon long-term (> 1 day) feeding. Moreover, in parallel de novo induced trypsin protease inhibitor (TI) activity was identified. In contrast to TI activity, enhanced plumbagin levels were not phytohormone inducible, not even by defense-related jasmonates although upon herbivory their level increased more than 50-fold in the case of the bioactive jasmonic acid-isoleucine. We conclude that Nepenthes is efficiently protected against insect herbivores by naphthoquinones acting as phytoanticipins, which is supported by additional inducible defenses. The regulation of these defenses remains to be investigated.

Volatile chemical signals underlying the host plant preferences of Tuta absoluta

AbstractThe South American leaf miner, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), is a serious pest of tomato causing substantial annual economic losses at a global scale. Our study comprised choice and no‐choice bioassays, aimed at understanding the preference of this oligophagous pest for a few selected solanaceous hosts (tomato, potato, eggplant, ashwagandha, black nightshade, wild tomato, tobacco, and datura), and the identification of the volatile cues that influence its host selection process. In choice assays, T. absoluta females preferred tomato for oviposition over all the other plants, whereas ashwagandha, tobacco, and datura were the least preferred; on datura zero eggs were laid. A similar trend was observed in the subsequent number of larval mines formed. The moth’s preference for host plants of the genus Solanum was quite evident in both the choice and no‐choice assays. Tomato plant volatiles were found to be more attractive to the female moths in single‐ and dual‐choice olfactometer assays. In electroantennographic bioassays, the mean depolarization was significant for tomato, potato, ashwagandha, and eggplant compared to empty air and honey. In total 76 volatile compounds were identified in the GC‐MS analysis across the eight previously selected host–plant headspace samples. Principal component analysis revealed that 1‐fluorododecane and p‐quinone mainly contributed to the observed variation among the host plant volatiles. Of all the host plants, tomato, wild tomato, and tobacco were found to share similarities with respect to volatile cues, whereas ashwagandha, eggplant, and datura were found to be closely related. The other two hosts, potato and black nightshade, had fewer volatiles in common. Volatile cues, namely p‐quinone, 2‐carene, δ‐curcumene, and 1,2‐diethylbenzene, in tomato could serve as oviposition stimulants to T. absoluta, whereas the presence of 1‐fluorododecane in host plants such as datura, eggplant, ashwagandha, and black nightshade, might have deterred T. absoluta from ovipositing. 1‐Fluorododecane was found to be completely absent in tomato.

Drosophila melanogaster Stress Odorant (dSO) Displays the Characteristics of an Interspecific Alarm Cue.

Organisms depend on visual, auditory, and olfactory cues to signal the presence of danger that could impact survival and reproduction. Drosophila melanogaster emits an olfactory alarm signal, termed the Drosophila stress odorant (dSO), in response to mechanical agitation or electric shock. While it has been shown that conspecifics avoid areas previously occupied by stressed individuals, the contextual underpinnings of the emission of, and response to dSO, have received little attention. Using a binary choice assay, we determined that neither age and sex of emitters, nor the time of the day, affected the emission or avoidance of dSO. However, both sex and mating status affected the response to dSO. We also demonstrated that while D. melanogaster, D. simulans, and D. suzukii, have different dSO profiles, its avoidance was not species-specific. Thus, dSO should not be considered a pheromone but a general alarm signal for Drosophila. However, the response levels to both intra- and inter-specific cues differed between Drosophila species and possible reasons for these differences are discussed.

Long-Term Observation of Locomotion of Drosophila Larvae Facilitates Feasibility of Food-Choice Assays.

Animal behavior is reflected by locomotor patterns. To decipher the underlying neural circuitry locomotion has to be monitored over often longer time periods. Here a simple adaptation is described to constrain movement of third instar Drosophila larvae to a defined area and use Frustrated total internal reflection based imaging method (FIM) imaging to monitor larval movements up to 1 h. It is demonstrated that the combination of FIM imaging and long analysis periods facilitates the conduction of food choice assays and provides the means to easily quantify food preferences.

Methyl jasmonate‐induced resistance to Delia platura (Diptera: Anthomyiidae) in Lupinus mutabilis

Andean lupin (Lupinus mutabilis Sweet) is an important leguminous crop from South America with a high protein content. In Ecuador, lupin yields are severely affected by the infestation of Delia platura larvae on germinating seeds. The application of elicitor molecules with activity against herbivorous insects to control D. platura infestation constitutes an unexplored and promising alternative for chemical insecticides. In this study, methyl jasmonate (MeJA), hexanoic acid, menadione sodium bisulfite, and DL-β-aminobutyric acid were evaluated for their ability to induce resistance against D. platura in three commercial lupin cultivars. Only seeds pretreated with MeJA significantly impaired insect performance during choice and no-choice assays. Additionally, fitness indicators such as seed germination and growth were not affected by MeJA treatment. To investigate the molecular mechanisms behind the MeJA-mediated resistance, RT-qPCR assays were performed. First, RT-qPCR reference genes were validated, showing that LmUBC was the most stable reference gene. Next, expression analysis over time revealed that MeJA application up-regulated the activity of the jasmonic acid biosynthetic genes LmLOX2 and LmAOS, together with other jasmonate-related defense genes, such as LmTPS1, LmTPS4, LmPI2, LmMBL, LmL/ODC, LmCSD1, and LmPOD. This study indicates that MeJA can be used as an environmentally friendly elicitor molecule to protect Andean lupin from D. platura attack without fitness cost. MeJA application induces plant defense responses to insects in Andean lupin that may be modulated by the onset of terpenoid biosynthesis, proteinase inhibitors, lectins, polyamines, and antioxidative enzymes. © 2021 Society of Chemical Industry.

Identification of a wild carrot as carrot psylla (Bactericera trigonica) attractant and host plant chemistry

Carrot psylla is one of the devastating pests of carrot throughout northern Europe and the Mediterranean basin. Here we characterized the behavioral response of psylla females towards different carrot germplasm and identified the chemical cues involved in the host selection of psylla females by oviposition choice experiments and metabolic profiling of leaf volatiles. In choice assays, carrot psylla displayed differential responses to tested 14 germplasm. Among germplasm, wild accessions 21793 and 20465 were highly preferred by carrot psylla, while wild accessions 20465 and the orange cultivar Nairobi were less. In non-choice experiments conducted only with this four-germplasm revealed that the carrot psylla females gave higher preference to the Nairobi and wild accession 20465, indicating the vicinity to other host plants in the same area might affect female preference.Moreover, the nymph development and survival experiments showed the lowest nymphs survival rate on the wild accessions 21793 and 20497. Furthermore, the volatile emissions among different carrot cultivars infested with psylla showed qualitative and quantitative differences versus intact plants. Among these volatiles, apiol, β-asarone, myristicin, and sabinene showed a relationship with psyllas growth and survival. We also showed that myristicin and sabinene exogenous applications caused a dramatic reduction in the number of eggs laid by psylla and subsequent nymph survival. This is an initial study of the volatiles that mediate attraction and oviposition preference of carrot psylla in response to its host plant. The results from this study provide baseline information for the development of new control strategies against carrot psylla.

Exploring the neural mechanisms of aversion to bitter gourd phytochemicals in insects using Drosophila

• The mechanism by which bitter gourd repels insects is poorly known. • Drosophila – model to understand the neurophysiology of aversion to phyto-extracts. • Bitter gourd extract affects viability of developing flies, but not adults. • Bitter gourd extract – antifeedant sensed through bitter sensitive taste neurons. • Bitter gourd extract reinforces aversive memory (retained even after 24 h). Bitter gourd ( Momordica charantia L.) has compounds that repel insect pests. Unlike conventional pesticides, these compounds are eco-friendly and beneficial for human health. However the mechanisms by which these compounds repel insects and affect their physiology remains poorly known. Here we used Drosophila melanogaster (Meigen) to address these issues. We tested a wild strain, and a laboratory bred Canton S strain. Bitter gourd extract reduced the viability of developing flies, but did not affect survival in adults. Flies avoided bitter gourd extract in a food choice assay, and consumed a significantly low amount of food mixed with bitter gourd – indicating that it acts as an antifeedant. Transgenic flies with impaired aversive taste sensitive neurons showed a reduced aversion towards bitter gourd extract showing that these compounds act through the bitter sensitive gustatory neurons. Finally, flies also retained the memory of consuming bitter gourd extract for at least 24 hours, suggesting an additional cognitive mechanism for long term aversion. Our study provides the first evidence of bitter gourd compounds acting as antifeedants and also as potent reinforcers of aversive memory in drosophilids. We suggest that flies can be used to understand the physiological and neural mechanisms underlying the mode of action of other such phyto-extracts with the goal of developing potent but less harmful pest control formulations.

Evaluation of Wild Flora Surrounding Blueberry Fields as Viable Hosts of Drosophila suzukii (Matsumura, 1931) (Diptera: Drosophilidae) in Georgia.

Drosophila suzukii, an economically important pest of small and thin-skinned fruits, has caused annual crop losses up to 20% in the state of Georgia's multimillion-dollar blueberry industry. The known host range of D. suzukii is large, yet the breadth of uncultivated and wild plants that can serve as alternative hosts in the southeastern United States is still not fully understood. Establishing comprehensive lists of non-crop D. suzukii hosts in woodlands near blueberry production will assist in the creation of more sustainable integrated pest management (IPM) strategies. Objectives of this study were to determine viability of wild fruiting plant species to this pest based on survivorship to adulthood and assess D. suzukii short-range preference between cultivated blueberries and wild fruit. Laboratory choice and no-choice assays were performed to determine if D. suzukii could complete its development on wild fruits sampled from the field. Results from our no-choice assays indicated that multiple species of wild fruits surveyed in Georgia were viable D. suzukii hosts including blackberry species, deerberry, hillside blueberry, common pokeweed, beautyberry, elderberry, evergreen blueberry, and large gallberry. Yet, none of these hosts were preferred by adult female D. suzukii as ovipositional substrates when compared to cultivated blueberries. However, these uncultivated species have the potential to sustain D. suzukii populations pre- and post-harvest season. This information can help farmers do more targeted management of these viable alternative hosts from wooded areas surrounding blueberry fields in order to minimize D. suzukii populations.

Development of a cortical delay discounting assay: a potential biomarker of externalizing disorders.

People who tend to impulsively choose smaller, sooner rewards over larger, later rewards are at increased risk for addiction and psychiatric disorders. A neurobiological measure of the tendency to overvalue immediate gratification could facilitate the study of individuals who are susceptible to these mental disorders. The objective of this research was to develop a cortical assay of impulsive choice for immediate rewards. A cortex-based assay of impulsive choice was developed using 1105 healthy adults from the Human Connectome Project, and then cross-validated in two independent samples of adults with elevated rates of psychiatric disorders. Study 1: Cortical delay discounting (C-DD) was developed using a multivariate additive model of gray matter thickness across both hemispheres. Higher C-DD corresponded to thinner cortex and greater impulsive choice for immediate rewards. It also predicted cannabis use beyond established risk factors for drug use, including familial substance use, childhood conduct problems, personality traits, and cognitive functioning. Study 2: C-DD replicated the association with delay discounting performance from study 1. Structural equation modeling showed C-DD covaried with symptoms of externalizing, but not internalizing disorders. Study 3: C-DD positively predicted future delay discounting behavior (6-34 months later). Across three studies, a cortical assay of impulsive choice evidenced consistent associations with drug use and delay discounting task performance. It was also uniquely associated with psychiatric disorders that share impulsivity as a core feature. Together, findings support the utility of C-DD as a neurobiological assay of impulsive decision-making and a possible biomarker of externalizing disorders.

Could Broccoli and Cauliflower Influence the Dispersal Dynamics of Western Flower Thrips (Thysanoptera: Thripidae) to Lettuce in the Salinas Valley of California?

The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is an important, worldwide vector of two tospoviruses (Family Bunyaviridae; Genus Tospovirus), Impatiens necrotic spot virus (INSV) and Tomato spotted wilt virus (TSWV). In the Salinas Valley of California, INSV causes severe necrosis, stunting, and crop losses to lettuce (Lactuca sativa L.). Because broccoli (Brassica oleracea var. italica L.) and cauliflower (Brassica oleracea var. botrytis L.) are major rotation crops with lettuce in the Salinas Valley, it is critical to understand if these Brassicas influence the dispersal dynamics of F. occidentalis. In 2013 and 2014, surveys were conducted evaluating yellow sticky cards and plant samples in lettuce, broccoli, and cauliflower fields in three regions of the Salinas Valley. F. occidentalis were collected on sticky cards from April to November and on foliage in all three regions. Two-choice oviposition assays as well as no-choice and two-choice feeding assays were conducted where F. occidentalis adults were exposed to leaves of lettuce, broccoli, and cauliflower. A significantly greater number of eggs was found on lettuce than on broccoli or cauliflower leaves in the choice assay, whereas for the broccoli and cauliflower choice assay, the number of eggs retrieved was low and not significantly different between hosts. The number of F. occidentalis feeding spots and leaf area injury ratings were similar on broccoli and lettuce leaves but were significantly lower on cauliflower than on lettuce and broccoli leaves. The implications of these results on thrips and plant virus management are discussed.

Histamine gustatory aversion in Drosophila melanogaster

Many foods and drinks contain histamine; however, the mechanisms that drive histamine taste perception have not yet been investigated. Here, we use a simple model organism, Drosophila melanogaster, to dissect the molecular sensors required to taste histamine. We first investigated histidine and histamine taste perception by performing a binary food choice assay and electrophysiology to identify essential sensilla for histamine sensing in the labellum. Histamine was found to activate S-type sensilla, which harbor bitter-sensing gustatory receptor neurons. Moreover, unbiased genetic screening for chemoreceptors revealed that a gustatory receptor, GR22e and an ionotropic receptor, IR76b are required for histamine sensing. Ectopic expression of GR22e was sufficient to induce a response in I-type sensilla, which normally do not respond to histamine. Taken together, our findings provide new insights into the mechanisms by which insects discriminate between the toxic histamine and beneficial histidine via their taste receptors.

Pharmacological Characterization of Synthetic Kratom Alkaloids for Improved Alcohol Use Disorder Therapeutics

Background Kratom is an opioid-containing plant and currently a federally unscheduled substance within the U.S. that is used to self-medicate chronic pain and opioid dependence, serving as a substitute for illicit and prescription opioids. Similarly, some individuals with Alcohol Use Disorder (AUD) find kratom helpful in reducing AUD dependence and withdrawal symptoms. We have previously shown that the kratom alkaloids can dose-dependently decrease alcohol consumption in mice, and that this activity is dependent on delta opioid receptor (DOR) expression. However, the most potent of the alkaloids 7-OH mitragynine, exhibited rewarding properties, presumably due to its mu opioid receptor (MOR) pharmacology. We hypothesized that reduction of MOR potency relative to potency at DOR would lead to an improved therapeutic window with respect to reward liability and alcohol consumption. Methods A series of kratom analogs were pharmacologically characterized for their ability to bind to opioid receptors and elicit G-protein and beta-arrestin signaling using radioligand binding and cellular signaling assays. Using the 2-bottle choice assay of 10% alcohol consumption, wildtype and DOR knockout (DOR KO) mice were used to assess to what degree the kratom alkaloids could reduce alcohol use, and whether any effects were DOR-mediated. Drug reward was also assessed through conditioned place preference experiments. Results Kratom analogs are G-protein-biased at the opioid receptors, similar to their parent compounds. Kratom analog #2 showed the most favorable pharmacology with similar DOR potency but greatly reduced MOR potency compared to 7-OH mitragynine, and was capable of significantly decreasing ethanol consumption in wildtype mice at a dose of 10 mg/kg. CPP experiments and experiments with DOR KO mice are currently being completed for kratom analog #2 and will be useful in confirming DOR-mediated effects and whether the improved pharmacological profile of the analogs confers therapeutic benefits. Discussion Our results indicate that the development of potent, DOR-selective opioids could provide a pathway to treat alcohol use without being significantly rewarding, and that the kratom alkaloids provide useful scaffolds to jumpstart these efforts.

Coeffects of diet and neonicotinoid exposure on honeybee mobility and food choice

Malnutrition and pesticide exposure are severe factors contributing to the current losses of honeybee colonies. As these stressors often occur combined, we studied the synergistic effects of different diets and pesticide exposure on food choice and mobility of Apis mellifera. We fed beehives with different food sources and exposed the bees to sublethal doses of thiacloprid. After that three different types of honey and pollen were offered in separate choice assays and behaviour towards food was recorded. Thiacloprid significantly affected the food choice in the honey assay, increasing the bees’ preference of polyfloral honey, while pre-pesticide diet had no influence. The pollen choice remained similar regardless of treatments, as bees always preferred polyfloral pollen. Interestingly, pesticide exposure affected bee mobility differently, depending on the previous diet. These results indicate that the diet is an important factor influencing the susceptibility to pesticides.

Domestication of Plants of Ugni molinae Turcz (Myrtaceae) Interferes in the Biology of Chilesia rudis (Lepidoptera: Erebidae) Larvae.

In terms of the domestication process in murtilla, studies have found changes in the concentration of phenolic compounds, with reduction of chemical defense of plants, depending on the change in the feeding behavior of insects. Thus, we hypothesized that the domestication of Ugni molinae decreases the content of phenolic compounds and modifies the feeding preference of Chilesia rudis larvae. Leaves of three parental ecotypes and four cultivated ecotypes were used in preference experiments to evaluate the mass gain and leaves consumption of larvae. Phenolic extracts from leaves of U. molinae were analyzed by HPLC. Identified compounds were incorporated in an artificial diet to assess their effect on mass gain, consumption, and survival of the larvae. The presence of phenolic compounds in bodies and feces was also evaluated. In terms of choice assays, larvae preferred parental ecotypes. Regarding compounds, vanillin was the most varied between the ecotypes in leaves. However, plant domestication did not show a reduction in phenolic compound concentration of the ecotypes studied. Furthermore, there was no clear relation between phenolic compounds and the performance of C. rudis larvae. Whether this was because of sequestration of some compounds by larvae is unknown. Finally, results of this study could also suggest that studied phenolic compounds have no role in the C. rudis larvae resistance in this stage of murtilla domestication process.

Differential Gene Expression in the Heads of Behaviorally Divergent Culex pipiens Mosquitoes.

Simple SummaryHost preference has profound impacts on the epidemiology of mosquito-borne disease transmission, yet much is still unknown about the molecular basis for these preferences. Here, we examined host preference in the West Nile virus vector, Culex pipiens. We examined human and avian landing rates for eight populations: five originating from above- and three from below-ground breeding and overwintering habitats. While above-ground populations tended to be biased toward avian landing and below-ground populations tended toward human landing, a range of behaviors was observed, consistent with other mosquito species. Patterns of differential expression and splice site variation were measured for one avian- and one human-seeking population as a first step toward identifying genes involved in regulation of blood feeding behaviors as well as differences in host preference. We conclude with a discussion of specific differentially expressed genes and their potential to influence host seeking behaviors of Cx. pipiens females.Host preferences of Cx. pipiens, a bridge vector for West Nile virus to humans, have the potential to drive pathogen transmission dynamics. Yet much remains unknown about the extent of variation in these preferences and their molecular basis. We conducted host choice assays in a laboratory setting to quantify multi-day human and avian landing rates for Cx. pipiens females. Assayed populations originated from five above-ground and three below-ground breeding and overwintering habitats. All three below-ground populations were biased toward human landings, with rates of human landing ranging from 69–85%. Of the five above-ground populations, four had avian landing rates of >80%, while one landed on the avian host only 44% of the time. Overall response rates and willingness to alternate landing on the human and avian hosts across multiple days of testing also varied by population. For one human- and one avian-preferring population, we examined patterns of differential expression and splice site variation at genes expressed in female heads. We also compared gene expression and splice site variation within human-seeking females in either gravid or host-seeking physiological states to identify genes that may regulate blood feeding behaviors. Overall, we identified genes with metabolic and regulatory function that were differentially expressed in our comparison of gravid and host-seeking females. Differentially expressed genes in our comparison of avian- and human-seeking females were enriched for those involved in sensory perception. We conclude with a discussion of specific sensory genes and their potential influence on the divergent behaviors of avian- and human-seeking Cx. pipiens.

Polyphagous caterpillars of Spodoptera litura switch from a trap crop to the main crop, improve fitness, and shorten generation time

Trap crops are used for pulling the pest load from the main crops toward themselves. Here, we report a switching by a polyphagous pest, Spodoptera litura, from trap crop castor to main crop eggplant during its mid-larval development. In the eggplant–castor mixed field, adults oviposit exclusively on castor. However, 3rd and 4th instar castor-grown larvae migrate to eggplants. Host choice assays for adults and larvae conducted in the controlled environment and the nutritional indices of castor and eggplant-feeding larvae revealed that the natural enemies did not influence the host switch. The host switch was rather associated with larvae’s enhanced digestion and metabolism. It shortened the development time and increased the eclosion success on eggplant. Mother-selected castor is suitable for the early instars and eggplant is for the later instars, indicating that the host switching was not because of the mother’s erroneous host choice but has evolved as an advantageous behavior. S. litura’s ability to switch hosts in the same ontogenic phase and reduce the generation time can contribute to an additional generation within a cropping season and endanger the critical growth stage of fruiting. Our findings support the ‘mother knows the best’ concept and annex that the larvae can also possess the ability to know the best. Such ability in different ontogenic stages can be fundamental to the exceptional adaptability of species like S. litura.

Mayetiola destructor (Diptera: Cecidomyiidae) host preference and survival on small grains with respect to leaf reflectance and phytohormone concentrations

The Hessian fly Mayetiola destructor (Diptera: Cecidomyiidae) is a major pest of wheat, globally. We conducted a series of laboratory choice and no-choice assays to quantify Hessian fly host preference for barley (cv. Champion), oat (cv. Cayuse), susceptible (cv. Alturas), and resistant (cv. Hollis) wheat. In addition, larval survivorship and adult emergence were compared among the evaluated host plants. We then examined whether insect preference for a host can be explained by differences in plant spectral reflectance. Further, larval survivorship and adult emergence were compared among host plants in relation to phytohormone concentrations. Hessian flies laid more eggs on wheat compared to either oat or barley. Spectral reflectance measurements of leaves were similar between susceptible and resistant wheat cultivars but different from those of barley and oat. Our results suggested that higher reflectance in the near-infrared range and lower reflectance in the visible range may be used by females for host selection. Hessian fly larvae were unable to develop into the pupal stage on resistant wheat and oat. No significant difference in larval survivorship was detected between the susceptible wheat and barley. However, adult emergence was significantly higher on barley than the susceptible wheat. Phytohormonal evaluations revealed that salicylic acid (SA) may be an important contributor to plant defense response to larval feeding as relatively higher concentrations of SA were present in oat and resistant wheat. While resistance in the resistant wheat is achieved only through antibiosis, both antibiosis and antixenosis were in effect rendering oat as a non-host for Hessian flies.

Oviposition responses of Bactrocera dorsalis and Ceratitis cosyra to Dufour’s and poison gland extracts of Oecophylla longinoda (Hymenoptera: Formicidae)

The predatory African weaver ant, Oecophylla longinoda (Hymenoptera: Formicidae) effectively control pests by predation as well as by semiochemicals which influence the behaviour of certain species. Here, we investigated and compared the role of O. longinoda semiochemicals on the oviposition responses of two major fruit fly (Diptera: Tephritidae) species of mango; the invasive species, Bactrocera dorsalis, endemic to Southeast Asia and the African native species, Ceratitis cosyra. We carried oviposition choice assays with ant-exposed and unexposed mangoes, using extracts of ant whole body and body parts. Our results show that the flies avoided and laid fewer eggs on weaver ant-exposed than unexposed mango peel discs. Subsequent assays with mango discs treated with whole body extracts in hexane, ethyl acetate, methanol and water reduced oviposition responses in C. cosyra. Moreover, discs treated with abdominal extracts in hexane and water reduced egg laying in B. dorsalis. whereas hexane, methanol and water extracts of the abdomen reduced oviposition in C. cosyra. Additionally, mango discs treated with extracts of exercised Dufour’s and poison gland in hexane elicited stronger oviposition reduction responses in C. cosyra than in B. dorsalis. These results suggest that ant gland compounds play a role in the oviposition avoidance behaviour of both fruit fly species. Moreover, both African fruit fly species and invasive Asian species, are repelled by Oecophylla longinoda semiochemicals implying that B. dorsalis experienced similar evolutionary pressures, and reacting to similar cues, from Oecophylla smaragdina in Asia as did C. cosyra from Oecophylla longinoda in Africa.

Nanopore Flongle Sequencing as a Rapid, Single-Specimen Clinical Test for Fusion Detection

The identification of gene fusions is a cornerstone of diagnosis and treatment decision making for tumors of many forms and primary sites. Diverse molecular approaches are currently used for the molecular diagnosis of fusions, but few permit broad, partner agnostic detection of fusions over multiple potential targets. We previously described the combination of nanopore sequencing with the anchored multiplex PCR technique to permit a rapid testing paradigm. Recently, a new platform for nanopore sequencing has become publicly available, the Flongle flow cell from Oxford Nanopore Technologies, which offers lower throughput, but lower price testing. Here, we describe the results of retesting of 15 specimens previously tested with both Illumina and Oxford Nanopore Technologies MinION sequencing. Furthermore, we additionally blindly tested 13 specimens that had undergone clinical Illumina-based sequencing. The Flongle sequencing pipeline removed key complexities of a multiplexed nanopore sequencing protocol, reduced sequencing turnaround time, and showed excellent concordance with Illumina results. It was particularly strong in identifying notoriously difficult to detect CIC-DUX4 translocations. The Flongle sequencing pipeline may be the assay of choice for deployment in small- to medium-sized molecular laboratories.