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Phloem sieve elements have shut-off mechanisms that prevent loss of nutrient-rich phloem sap when the phloem is damaged. Some phloem proteins such as the proteins that form forisomes in legume sieve elements are one such mechanism and in response to damage, they instantly form occlusions that stop the flow of sap. It has long been hypothesized that one function of phloem proteins is defence against phloem sap-feeding insects such as aphids. This study provides the first experimental evidence that aphid feeding can induce phloem protein occlusion and that the aphid-induced occlusions inhibit phloem sap ingestion. The great majority of phloem penetrations in Vicia faba by the generalist aphids Myzus persicae and Macrosiphum euphorbiae triggered forisome occlusion and the aphids eventually withdrew their stylets without ingesting phloem sap. This contrasts starkly with a previous study on the legume-specialist aphid, Acyrthosiphon pisum, where penetration of faba bean sieve elements did not trigger forisome occlusion and the aphids readily ingested phloem sap. Next, forisome occlusion was demonstrated to be the cause of failed phloem ingestion attempts by M. persicae: when occlusion was inhibited by the calcium channel blocker lanthanum, M. persicae readily ingested faba bean phloem sap.

Phloem sieve elements have shut-off mechanisms that prevent loss of nutrient-rich phloem sap when the phloem is damaged. Some phloem proteins such as the proteins that form forisomes in legume sieve elements are one such mechanism and in response to damage, they instantly form occlusions that stop the flow of sap. It has long been hypothesized that one function of phloem proteins is defence against phloem sap-feeding insects such as aphids. This study provides the first experimental evidence that aphid feeding can induce phloem protein occlusion and that the aphid-induced occlusions inhibit phloem sap ingestion. The great majority of phloem penetrations in Vicia faba by the generalist aphids Myzus persicae and Macrosiphum euphorbiae triggered forisome occlusion and the aphids eventually withdrew their stylets without ingesting phloem sap. This contrasts starkly with a previous study on the legume-specialist aphid, Acyrthosiphon pisum, where penetration of faba bean sieve elements did not trigger forisome occlusion and the aphids readily ingested phloem sap. Next, forisome occlusion was demonstrated to be the cause of failed phloem ingestion attempts by M. persicae: when occlusion was inhibited by the calcium channel blocker lanthanum, M. persicae readily ingested faba bean phloem sap.

ABSTRACT The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is an important rice pest which consumes leaf area during all phases of plant development. The objective of this study was to identify rice genotypes that provide antixenosis and antibiosis to fall armyworm. Antixenosis was investigated by measuring non-preference in free-choice and no-choice tests while antibiosis was determined by measuring biological parameters and nutritional indices of S. frugiperda in twelve rice genotypes. The genotype Miúdo Branco showed antixenosis to S. frugiperda, whereas the genotypes IR 64 and Bacaba Branco showed antibiosis to S. frugiperda by affecting insect development and prolonging insect life cycle. Insects that fed on Bacaba Branco genotype demonstrated the lowest nutritional indices. Since Miúdo Branco, IR 64 and Bacaba Branco showed moderate resistance, rice producers could use these genotypes as part of a control strategy for S. frugiperda.

Severe attacks of Brevicoryne brassicae (Hemiptera: Aphididae) on brassica crops may lead to a significant decrease in yield and can cause plant death. Host plant resistance is considered a valuable tool in integrated pest management and can assist in reducing the damage caused by aphids. This study evaluated the behavioral and biological parameters of B. brassicae in 37 Brassica oleracea (L.) var. acephala genotypes, and aimed to characterize the mechanisms of antixenosis and/or antibiosis. In antixenosis, plants were arranged in a circle inside an arena, releasing to the center one hundred adult aphids. The number of insects was evaluated at 1, 2, 3, 6, and 24 h after infestation. For antibiosis, 30 adults were confined inside each clip-cage on each genotype. The total number of nymphs; number of nymphs per adult per day; total nymphs until 10 d after the first nymph had been produced; duration of the pre-reproductive phase; duration of the reproductive phase; nymphal survival; adult longevity; nymph-adult period and nymphal mortality at 5, 7 and 10 d were evaluated. Several genotypes showed be less infested and more harmful to B. brassicae on collard greens. The genotypes 20T, 24X, 18R, 22V, 15O, 19S, 27VA, and 17Q were the least infested in the antixenosis 24 h free-choice test. 2B, 5E, 8H, 19S, 21U, 27VA, 30OP, PE, MGH, and TP genotypes prevented B. brassicae from completing nymphal period, indicating antibiosis and/or antixenosis expression. 4D, GAU, 20 T, 14 N, and MGI genotypes prevented the aphid from reaching the reproductive phase. These genotypes may be useful for breeding programs that focus on the resistance of collard greens to aphids. [ABSTRACT FROM AUTHOR]

Background: The impact of climate change on insect resistance genes is elusive. Hence, we investigated the responses of rice near-isogenic lines (NILs) that carry resistance genes against brown planthopper (BPH) under different environmental conditions. Results: We tested these NILs under three environmental settings (the atmospheric temperature with corresponding carbon dioxide at the ambient, year 2050 and year 2100) based on the Intergovernmental Panel on Climate Change prediction. Comparing between different environments, two of nine NILs that carried a single BPH-resistant gene maintained their resistance under the environmental changes, whereas two of three NILs showed gene pyramiding with two maintained BPH resistance genes despite the environmental changes. In addition, two NILs (NIL-BPH17 and NIL-BPH20) were examined in their antibiosis and antixenosis effects under these environmental changes. BPH showed different responses to these two NILs, where the inhibitory effect of NIL-BPH17 on the BPH growth and development was unaffected, while NIL-BPH20 may have lost its resistance during the environmental changes. Conclusion: Our results indicate that BPH resistance genes could be affected by climate change. NIL-BPH17 has a strong inhibitory effect on BPH feeding on phloem and would be unaffected by environmental changes, while NIL-BPH20 would lose its ability during the environmental changes. [ABSTRACT FROM AUTHOR]

Resistant rice cultivars are an alternative of insecticide control for one of the major rice pests: the brown planthopper, Nilaparvatalugens (Hemiptera: Delphacidae). However, N.lugens has obtained virulence to resistant rice cultivars as same as insecticide resistance. The monitoring of virulence to differential cultivars is important for detections of the breakdown of resistance genes 'BPH' owned by the cultivars. We conducted long-term virulence monitoring (2001–2019) of differential cultivars in N. lugens immigrant populations in Japan. The virulence to the cultivars IR26 (BPH1), Mudgo (BPH1), and ASD7 (BPH2) was higher than that to other differential cultivars. The virulence to Babawee (BPH4) was lower than that to IR26, Mudgo, and ASD7, but it fluctuated over the immigrant years. The virulence to Kanto-PL7 (BPH3), Rathu Heenati (BPH3, BPH17) and Balamawee (BPH27, Three QTLs) was lower than that to other differential cultivars. The immigrant populations have therefore not developed virulence to three differential cultivars. These results suggest that N. lugens continued to develop virulence to differential cultivars that possess BPH1 and BPH2 after the breakdown. However, our results indicate that N.lugens could not break through the efficacy of differential cultivars possessing multiple BPH resistance genes. [ABSTRACT FROM AUTHOR]

Plant structural traits can act as barriers for herbivore attachment, feeding, and oviposition. In particular, epicuticular waxes (EWs) on the aerial surfaces of many land plants offer protection from biotic and abiotic stresses. In rice (Oryza sativa L.), mutations that reduce EWs have been previously reported. However, whether such mutations affect rice water weevil (Lissorhoptrus oryzophilus Kuschel) and fall armyworm (Spodoptera frugiperda Smith) performance has not been investigated yet. These pests cause significant economic problems in important rice-producing areas of the United States. The aim of our study was to characterize the EWs of EW mutants and wild-type rice plants by gas chromatography–mass spectrometry and compare the resistance of mutant and wild-type plants against rice water weevil and fall armyworm. We hypothesized that mutants with reduced EWs would have weaker resistance to pests than wild-type plants. Three mutant lines (6-1A, 7-17A, and 11-39A) and their wild-type parent (cv. 'Sabine') were used to test this hypothesis. Levels of EWs were significantly lower in mutant lines than in the wild-type, and qualitative differences in EW composition were also observed. Reduction in EWs significantly affected performance of insects in experiments conducted under greenhouse conditions. Experiments with rice water weevils were conducted in arenas in which females were given a choice of the mutants and the wild-type for oviposition. Number of first instars emerging from the three EW mutants (an indication of oviposition preference) was higher on the three EW mutants than on wild-type plants with normal wax levels. Similarly, in no-choice experiments using whole plants or detached leaves, weight gains of armyworms on leaves were higher on the mutant lines than on the wild-type. These results indicate that EW traits are involved in rice resistance to weevils and armyworms. Understanding the plant traits that contribute to resistance to rice pests will be helpful for the development of resistant varieties for reducing pest insect damage. [ABSTRACT FROM AUTHOR]

Plants possess defense‐related traits that both reduce injury from herbivores (resistance) and the amount of yield loss per unit injury (tolerance). Plant resistance and tolerance can be utilized in pest management programs. The rice water weevil, Lissorhoptrus oryzophilus Kuschel (Coleoptera: Curculionidae), is the most destructive early‐season pest of rice (Oryza sativa L., Poaceae) in the USA. Additionally, lepidopteran stemborers, particularly the invasive Mexican rice borer, Eoreuma loftini (Dyar) (Lepidoptera: Crambidae), are increasing in economic importance as pests of rice in Louisiana, USA. This study was conducted to evaluate both the resistance and tolerance of commonly grown inbred rice cultivars in Louisiana to combined infestations of rice water weevils and stemborers. Field experiments were established at the Rice Research Station in Crowley, LA, USA from 2017 to 2019. Eight commonly grown inbred cultivars were selected and pest infestation levels were manipulated using insecticidal seed treatments. The rice cultivar 'Jupiter' supported the highest numbers of immature rice water weevils, whereas weevil densities on other cultivars were intermediate. Low levels of stemborer injury were observed in 'Cheniere' and 'Jazzman‐2', which suggests that these cultivars express some resistance to stemborers, whereas high stemborer injury was observed in 'Cocodrie, 'CL151', and 'Mermentau'. Together, rice water weevil and stemborer infestations negatively affected rice yields, with losses up to 18%. However, differences among cultivars in overall yield losses were minimal. Comparisons of slopes of yield × weevil density relationships among cultivars revealed a greater decline, that is, yield loss per weevil, for Cheniere relative to Cocodrie. Our data suggest that plant resistance can serve as a valuable component of an integrated pest management program, particularly for stemborers. [ABSTRACT FROM AUTHOR]

Antixenosis or non-preference mechanism of resistance to brown planthopper, Nilaparvata lugens (Stål) collected from Mahbubnagar district of Telangana state was studied in the selected rice gene differential entries along with susceptible resistant checks. Three gene differentials viz., RP 2068-18-3-5, RP BIO 4918-230S and PTB-33 were resistant with a damage score of 2.35, 2.7 and 1.7, respectively. Four genotypes viz., MTU 1010, IR 66, IR 72 and Ndiang marie were moderately resistant with a damage score of 3.1-5.0. On the resistant gene differentials, the brown planthopper probed more number of times and excreted less amount of honeydew and sucked more xylem sap. The results indicate the non-preference mechanism of resistance in terms of feeding in the brown planthopper on resistant gene differentials. The identified resistant gene differentials can be used as donors in breeding programmes. [ABSTRACT FROM AUTHOR]

Southeast Asian thrips (Thrips parvispinus Karny), poses a significant threat to chilli crop production causing severe economic losses. They feed heavily on leaves, flowers and young fruits causing severe damage to the crop. Exploring host plant resistance is the best ecofriendly management strategy to combat this pest. Large-scale field screening of 481 germplasm accessions, followed by further screening of selected accessions under polyhouse conditions led to identification of fourteen accessions that showed resistance against Southeast Asian thrips. Among the screened accessions, IIHR-B-HP-79 showed the highest level of Southeast Asian thrips resistance with significantly low leaf and fruit damage scores of 0.28 and 0.13, respectively. Further, screening of selected fourteen field resistant accessions was performed through whole plant bio-assay where in four accessions i.e., IIHR-B-HP-79 (C. frutescens), IIHR 4550, IIHR 4501 & IIHR 4410 (C. chinense) showed good level of resistance. Multi-choice leaf disc assay, demonstrated that IIHR-B-HP-79 exhibited a high level of resistance with the lowest percent of scraping damage during both the vegetative (10.98) and flowering stages (15.31). The identified resistant accession IIHR-B-HP-79 (C. frutescens), has the potential to be a valuable genetic resource as donor in breeding for Southeast Asian thrips resistance. [Display omitted] • Large set of 481 germplasm accessions were screened against Southeast Asian thrips resistance. • A score card has been developed to aid in the detection, monitoring and screening against Southeast Asian thrips. • Leaf disc assays are a reliable high-throughput method for screening for thrips resistance in chilli. • IIHR-B-HP-79 identified as a potential resistant source. [ABSTRACT FROM AUTHOR]

Seven maize inbred lines were evaluated for resistance against fall armyworm, Spodoptera frugiperda (J.E. Smith). Non-preference for oviposition in no- and multi-choice tests and feeding non-preference of neonates in multi-choice test was observed in lines CML 338, CM 500 and CML 72. Antibiosis was observed in CML 338, CML 72 and CML 71, in terms of significantly prolonged larval period (18.22–19.56 days), lower larval (111.52–131.80 mg) and pupal weights (105.65–127.67 mg), shorter adult longevity and lower fecundity as compared to susceptible inbred lines, BML 6 and LM 24. Larvae fed on CML 338 and CML 71 had significantly higher mortality and lower nutritional indices. Significantly higher foliar damage rating was observed on younger plants (10 days old) in all test inbred lines, as compared to older plants (20 and 30 days old) during 2020 and 2021. The mean foliar damage rating by fall armyworm larvae varied significantly among the test inbred lines being significantly lower in CML 338 and CML 71 compared to BML 6 and CM 500 that had higher damage at all crop stages when recorded at 7, 14 and 21 days after release. Functional Plant Loss Index (FPLI) was significantly lower in CML 338 and CML 71 (12.18–18.58%) followed by CML 72 (24.87%). Regression of FPLI on fall armyworm larval dry weight indicated presence of antibiosis and tolerance in CML 338, CML 71 and CML 72 towards fall armyworm. Overall, maize inbred lines CML 338, CML 71 and CML 72 with moderate resistance may be used for resistance breeding programme against this insect pest. • Fall armyworm larvae fed on maize inbreds CML 338 and CML 71 had significantly higher mortality and lower nutritional indices. • Larvae fed on CML 338, CML 72 and CML 71 had significantly lower larval - pupal weights, fecundity and shorter adult longevity. • Foliar damage was significantly higher on younger plants, and it was significantly lower in CML 338 and CML 71. • CML 338, CML 71and CML 72 had moderate resistance towards fall armyworm categorized as antibiosis and tolerance. [ABSTRACT FROM AUTHOR]

Tomato leafminer, Tuta absoluta has invaded Iran in recent years and rapidly turned into an important pest of tomato crops in open fields and greenhouses. Tomato is the preferred host of the pest. However, preliminary observations have shown that it can feed and reproduce on the other Solanaceous crops like eggplant and potato. In his study, the fitness of tomato leafminer has been investigated on fifteen commonly cultivated eggplant genotypes including Ghasri Dezful, Paboland Yazd, Mahali Jahrom, Shendabad, Dastgerd Esfahan, Sarkhoun Bandarabas, Chahboland Neishabur, Ghalami Varamin, Black Beauty, Blacky, Yalda, Lady, Linda, Lima and Kime in a greenhouse with the mean daily temperature of 25 ± 2°C, 60 ± 5% Relative Humidity and a natural photoperiod during the May and June. The ovipositional preference of females and some biological parameters like development times and survival rates of egg, larva and pupa, pupal weight and sex ratio have been evaluated on the plant genotypes using free-choice and no-choice tests. Significant differences have been revealed in the number of daily oviposited eggs on both potted plants and excised leaves and in all biological parameters except pupal weight and sex ratio among the eggplant genotypes throughout the experiments. The ovipositional preference of the females was significantly correlated and negatively correlated respectively with chlorophyll content of the leaves of eggplant genotypes (P < 0.01) and with trichome density on the underside of the entire leaf surface (P < 0.05). The eggplant genotypes were clustered into three main categories of resistant (Kime), semi-resistant (Black Beauty and Blacky) and semi-susceptible (other genotypes) using Ward-1963 hierarchical clustering method. The observed differences among the examined genotypes can be used in cropping systems for designing of eggplant breeding and tomato leafminer management programs.

Abstract The microbiomes of phloem‐feeding insects include functional bacteria and yeasts essential for herbivore survival and development. Changes in microbiome composition are implicated in virulence adaptation by herbivores to host plant species or host populations (including crop varieties). We examined patterns in adaptation by the green leafhopper, Nephotettix virescens, to near‐isogenic rice lines (NILs) with one or two resistance genes and the recurrent parent T65, without resistance genes. Only the line with two resistance genes was effective in reducing leafhopper fitness. After 20 generations on the resistant line, selected leafhoppers attained similar survival, weight gain, and egg laying to leafhoppers that were continually reared on the susceptible recurrent parent, indicating that they had adapted to the resistant host. By sequencing the 16s rRNA gene, we described the microbiome of leafhoppers from colonies associated with five collection sites, and continually reared or switched between NILs. The microbiomes included 69–119 OTUs of which 44 occurred in ≥90% of samples. Of these, 14 OTUs were assigned to the obligate symbiont Candidatus sulcia clade. After 20 generations of selection, collection site had a greater effect than host plant on microbiome composition. Six bacteria genera, including C. sulcia, were associated with leafhopper virulence. However, there was significant within‐treatment, site‐related variability in the prevalence of these taxa such that the mechanisms underlying their association with virulence remain to be determined. Our results imply that these taxa are associated with leafhopper nutrition. Ours is the first study to describe microbiome diversity and composition in rice leafhoppers. We discuss our results in light of the multiple functions of herbivore microbiomes during virulence adaptation in insect herbivores.

ABSTRACT: Whitefly Bemisia tabaci (Gennadius) biotype B is the major pest of common bean (Phaseolus vulgaris L.) in Brazil and other countries. Host plant resistance is one of the cornerstones of Integrated Pest Management (IPM), and assessment of cultivars for insect resistance is fundamental to provide farmers options for pest control. This study evaluated common bean resistance to whitefly in the winter and rainy seasons in Jaboticabal, Brazil, and correlated the infestation with climatic factors. The plant part and development period of common bean that are more susceptible to whitefly infestation were also examined for potential use in IPM. Field experiments were carried out using 18 and 19 commercial cultivars in the winter and rainy seasons, respectively. Whitefly eggs, nymphs, and adults in the upper part and lower part of plants were sampled from 25 to 60 days after emergence (DAE). Cultivars IAC-Una and IAC-Eldorado had less oviposition and the former also showed lower adult infestation in the winter season. In the rainy season, cultivars IAPAR-81 and Guará had a smaller number of eggs, whereas IAC-Centauro was less infested by nymphs. The number of nymphs and adults was similar among cultivars in the winter and rainy seasons, respectively. The upper part of plants had a greater number of eggs and adults, while, the lower part harbored larger numbers of nymphs. Common bean was more susceptible to whitefly at 25-32 DAE in both seasons. These results add useful information to IPM of whitefly in common bean.

Cultivar resistance is an essential management strategy for the Mexican rice borer, Eoreuma loftini (Dyar), in sugarcane in the USA, but resistance mechanisms are poorly understood. Resistance was evaluated among Louisiana’s (USA) commercial sugarcane cultivars and experimental clones through field screenings, greenhouse trials, and a diet incorporation assay. Cultivars L 01-299 and HoCP 85-845 had the lowest borer injury levels, while HoCP 00-950 and L 12-201 were among the most heavily injured in field and greenhouse trials. The variability of results between the two field trials suggests that a genotype × environment interaction might affect the expression of resistance. Oviposition did not differ among evaluated cultivars in the greenhouse choice study. Results from the no-choice experiment showed that neonatal establishment differed among cultivars by up to 3-fold. In a diet incorporation assay, all cultivars reduced larval weight up to 86.5% and increased days to pupation by 1.8-fold relative to the diet-only control. Collectively, these results suggest that Louisiana’s sugarcane breeding germplasm contains various resistance levels to E. loftini, emphasizing the importance of screening cultivars before they are released to growers. Future studies should try to determine the influence of environmental factors on resistance expression.

Insect pests such as Spodoptera frugiperda cause significant losses to maize (Zea mays mays). Control of S. frugiperda is difficult, but the use of insect resistant cultivars, including tolerant cultivars, is a promising alternative, and landraces are a potential source of insect resistance. This study investigated tolerance to S. frugiperda in five Brazilian landraces, Amarelão, Aztequinha, Branco Antigo, Palha Roxa, and São Pedro, in relation to one conventional (non-Bt) hybrid, BM207, under field conditions. We assessed tolerance as the ratio of insecticide-free to insecticide-protected plants for plant height, stem diameter, and leaf chlorophyll content at two plant stages. Tolerance ratios varied across the maize genotypes, but inconsistently across plant variables, and cluster analysis revealed three groups based on tolerance ratios. A first group contained genotypes similarly tolerant to S. frugiperda, BM207, Palha Roxa, São Pedro, and Aztequinha, while the second and third groups each contained single genotypes, Amarelão, and Branco Antigo, which were considered not tolerant. Overall, the landraces Palha Roxa, São Pedro, and Aztequinha compared favorably to BM207 in terms of tolerance, and therefore may be valuable for management of this pest, and as germplasm sources to improve tolerance in other cultivars.

Spodoptera littoralis (Boisd) is a highly destructive pest that attacks a large number of economically important crops. We examined life table parameters as well as activity of major digestive enzymes of S. littoralis larvae in response to protein and starch contents across 11 legume cultivars to identify potential resistance traits. The results showed that S. littoralis reared on the common bean, Arabi, displayed the highest intrinsic rate of increase (r), while the lowest was recorded on the cowpea, Mashhad. Also, the highest net reproductive rate (R0) was obtained in those insects reared on the Arabi cultivar. Larvae displayed the highest and lowest proteolytic activities when fed on Mashhad and Arabi cultivars, respectively. The highest amylolytic activity was quantified in larvae that fed on the Arabi and 1057 cultivars, while the lowest occurred in larvae feeding on Yaghout and Mashhad cultivars. Developmental time of S. littoralis larvae was negatively correlated with protein content, while amylolytic activity was positively correlated with starch content of legumes. Our findings indicate that Arabi was a susceptible cultivar, while Mashhad exhibited tolerance traits against S. littoralis. These results should facilitate selection of legume cultivars for production or breeding efforts that involve S. littoralis management.

Sweetpotato weevil (SPW) pest management is challenging because the pest target is sub-terranean, so the application of pesticides is impractical and usually ineffective. Host plant resistance and the genetic transformation of sweetpotatoes to produce entomotoxic Bt proteins offer potential for environmentally benign pest control. Resistance can be conferred by naturally occurring hydroxycinnamic acids which protect against oviposition by adults, but these compounds are restricted to the root surface so do not protect against the cortex bound larvae where the greatest damage occurs. Resistance could be enhanced if combined with expression of Bt proteins in transformed plants, but interactions between hydroxycinnamic acids and Bt proteins remain unknown. Here the bioactivity of Cry7Aa1 protein and hydroxycinnamic acid esters was evaluated individually and in combination against SPW larvae and mortality determined. Low and high concentrations of hydroxycinnamic acid esters alone caused significantly higher mortality of both weevil species in all experiments compared to the control. SPW larval mortality was greater when tested as a combination of hydroxycinnamic acid esters and Bt protein, but this effect was additive not synergistic. Although we report no evidence of antagonistic interactions, the antifeedant effects of the plant compounds conferring host plant resistance could have reduced consumption of the Bt protein in our assays leading to a lower efficacy when combined. Further work is required to determine whether the toxic effects of Bt proteins function alongside host plant resistance in sweetpotato under field conditions. [ABSTRACT FROM AUTHOR]

Host plant resistance is an effective means of managing aphid pests in safflower but its genetic basis is not known. In this study, F1 and F6‐recombinant inbred lines (RILs) produced from the CO‐1 × EC‐523368‐2 cross were phenotyped for tolerance to the aphid, Uroleucon compositae based on days‐to‐wilt (DW) after infestation. The F1 plants showed the dominance effect and RILs exhibited quantitative variation. The RIL population was genotyped with 242 simple sequence repeat (SSR) markers, which included a set of 150 new SSRs designed through next‐generation sequencing and bioinformatics approaches. Two quantitative trait loci (QTLs), QUc‐Ct3.1 and QUc‐Ct5.1, putatively associated with DW after aphid infestation were detected. QUc‐Ct3.1 was a major QTL located on linkage group (LG) 3 with the closest marker SafM‐290 (LOD = 18.3), which explained 31.5% of the phenotypic variation. QUc‐Ct5.1 was a minor QTL located on LG‐5 with the closest marker CtDES‐237 (LOD = 7.0), which explained 9.1% of the phenotypic variation. This is the first report and a significant lead towards discovering genes for tolerance to aphids in safflower. [ABSTRACT FROM AUTHOR]

A study was performed to assess the preference of fourteen mango cultivars for fruit flies and their management by bagging. So the choice of Tephritid flies to mango cultivars during fruiting phase is crucial. Fourteen different cultivars of mango viz., 'Dusehri', 'Malda', 'Langra' early cultivars, 'Chaunsa', 'Fajri Klan', 'Sensation' medium whereas 'Sanglakhi', 'Retaul-12', 'Mehmood Khan', 'Tukhmi', 'Kala Chaunsa', 'Chitta Chaunsa', 'Dai Wala' and 'Sobey De Ting' late cultivars were assessed for their suitability for fruit flies. The results indicate that the population density of fruit flies was higher on late cultivars like 'Sanglakhi' (20.61 percent), 'Mehmood Khan' (20.22 percent) and 'Reutal-12' (19.92 percent) were proved to be highly susceptible to fruit flies. Among these the cultivar 'Reutal-12' was selected being commercial and future cultivar for the management of fruit flies through bagging. The results reported that the attack of tephritid fruit flies and other insect pests were zero in bagged fruits as compared with control. It was further recorded that the bagged fruits has maximum average fruit weight i.e. 203.50 and 197.83 g per fruit was noted in those treatments where butter paper bag and brown paper bag was wrapped with better coloration as compared with un-bagged fruit with 159.5 g per fruit. Similarly, on an average fruit length were more i.e. 90.17, 91.33 mm in bagged fruit and 85.33 in un-bagged fruits. Furthermore, bagged fruits have zero incidence of disease with reduced fruit crack, fruit sunburn, mechanical damage, bird damage, fruit blemished and agrochemical residues on the fruit. So, it is concluded that the special attention should be given on 'Reutal-12' for the management of fruit flies when devising an IPM program for the control of fruit flies. Further, bagging has proved to be the good agricultural practices for the production of quality mango. [ABSTRACT FROM AUTHOR]

The sugarcane aphid, Melanaphis sacchari (Zehntner), emerged as a severe pest of sorghum, Sorghum bicolor (L.), in Texas and Louisiana in 2013 and currently threatens nearly all sorghum production in the United States. Proper management of populations is critical as sugarcane aphid has a high reproductive potential and can rapidly damage plants, resulting in extensive yield losses. The overall objective of this work was to investigate sugarcane aphid population dynamics, and subsequent sorghum injury and grain yield on commercially available grain sorghum varieties in Alabama. This research includes three-site years of data that show variation in plant injury, physiological maturity, and yields among varieties tested. Although performance of each variety was variable among locations, potentially due to abiotic factors, four varieties including DKS 37-07, 1G588, 1G855, and 83P17 exhibited characteristics consistent with resistance and corroborates reports of resistance from other states. [ABSTRACT FROM AUTHOR]

Nutritional indices and biochemical profile of Helicoverpa armigera in response to feeding on different groundnut genotypes was studied. The moderately resistant genotypes were ICGV 86699, ICGV 86031, ICG 2271 and ICG 1697. JL 24 was used as the susceptible check. Consumption index (CI), approximate digestibility (AD), efficiency of conversion of ingested food (ECI) and efficiency of conversion of digested food (ECD) were recorded. In addition, the activities of digestive and defensive enzymes of H. armigera were studied. H. armigera larvae showed significantly lower CI, AD, ECI and EDI when fed on moderately resistant genotypes than the insects fed on JL 24. Serine protease and trypsin activities were low in insects fed on resistant genotypes than the ones fed on JL 24. Further, insects fed on resistant genotypes showed significantly greater glutathione-S-transferase activity than the insects fed on JL 24. A reverse trend was observed for esterase activity. Similar trend was observed for total protein content of the insects. Thus, nutritional quality of host plants affects insect’s physiology and could be used as an important indicator of host plant resistance against insect pests and to understand the adaptation of insect pests, if any, to various genotypes/host plants.

Soybean aphid (Aphis glycines) is a major soybean (Glycine max) herbivore pest in many soybean growing regions. High numbers of aphids on soybean can cause severe reductions in yield. The management of soybean aphids includes monitoring, insecticide applications when required, and the use of resistant cultivars. Soybean aphid-resistant soybean varieties are associated with genes that confer one or more categories of resistance to soybean aphids, including antibiosis (affects survival, growth, and fecundity), antixenosis (affects behaviour such as feeding), and tolerance (plant can withstand greater damage without economic loss). The genetic resistance of soybean to several herbivores has been associated with isoflavonoid phytoalexins; however, this correlation has not been observed in soybean varieties commonly grown in southern Ontario, Canada. Isoflavonoids in the leaves of 18 cultivars in the early growth stage were analyzed by HPLC and the concentration by fresh weight was used to rate the potential resistance to aphids. Greenhouse and growth cabinet trials determined that the cultivars with greater resistance to aphids were Harosoy 63 and OAC Avatar. The most susceptible cultivar was Maple Arrow, whereas Pagoda and Conrad were more tolerant to aphid feeding damage. Overall, there was a low correlation between the number of aphids per leaf, feeding damage, and leaf isoflavonoid levels. Metabolite profiling by high-resolution LC-MS determined that the most resistant cultivar had on average lower levels of certain free amino acids (Met, Tyr, and His) relative to the most susceptible cultivar. This suggests that within the tested cultivars, nutritional quality stimulates aphid feeding more than isoflavonoids negatively affect aphid feeding or growth. These findings provide a better understanding of soybean host plant resistance and suggest ways to improve soybean resistance to aphid feeding through the breeding or metabolic engineering of leaf metabolites.

Banana bunchy top disease (BBTD), caused by the banana bunchy top virus (BBTV, genus Babuvirus), is the most destructive viral disease of banana and plantain (Musa spp.). The virus is transmitted persistently by the banana aphid, Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae). While research efforts have focused on screening Musa genotypes for BBTD resistance, comparatively little work has been carried out to identify resistance to banana aphids. This study assessed 44 Musa germplasm of different A and B genome composition for the performance of banana aphids under semicontrolled environmental screenhouse conditions and in a field trial established in a BBTD endemic location. In the screenhouse, the AA diploid Calcutta 4 had the lowest apterous aphid density per plant (9.7 ± 4.6) compared with AAB triploid Waema, which had the highest aphid densities (395.6 ± 20.8). In the field, the highest apterous aphid density per plant (29.2 ± 6.7) occurred on the AAB triploid Batard and the lowest (0.4 ± 0.2) on the AA diploid Pisang Tongat. The AA diploid Tapo was highly susceptible to BBTD (100% infection) compared with the genotypes Balonkawe (ABB), PITA 21 (AAB), Calcutta 4 (AA), and Balbisiana Los Banos (BB), which remained uninfected. The Musa genotypes with apparent resistance to BBTD and least susceptibility to aphid population growth provide options for considering aphid and BBTD resistance in banana and plantain breeding programs.

Five rice accessions belonging to three wild species viz., IRGC99577 (Oryza punctata Kotschy ex Steud.), IRGC105270, IRGC105275 (O. australiensis Domin.), IRGC104646, CR100204 (O. nivara Sharma et Shastry) along with TN1 (susceptible check) and Ptb33 (resistant check) were used to study antixenosis and the role of biophysical factors in imparting resistance to brown planthopper (BPH), Nilaparvata lugens (Stål). The settling of BPH nymphs and adults was significantly less on IRGC99577, IRGC104646, and Ptb33 than on TN1. Oviposition and egg viability was less, while probing/feeding marks was more on IRGC99577 and IRGC105270 accessions. IRGC104646 showed longest trichomes while trichome density was greater in Ptb33. Largest silica cells were observed in IRGC99577 and TN1. Antixenosis resistance parameters did not show any significant association with biophysical factors. The accession IRGC99577 displayed a high level of antixenosis resistance for nymph settling, adult settling, feeding/probing marks and oviposition to BPH. This accession has emerged as a new source of resistance, which can be used for resistance breeding and to find gene/QTLs for antixenosis parameters. [ABSTRACT FROM AUTHOR]

This perspective presents a synopsis of the topics contained in the Phrtopathology Pathogen Spotlight on Botrytis spp. causing gray mold, including pathogen biology and systematics. genomic characterization of new species, perspectives on genome editing, and fungicide resistance. A timely breakthrough to engineer host plant resistance against the gray mold fungus has been demonstrated in planta and may augment chemical controls in the near future. While B. cinerea has garnered much of the research attention, other economically important Botrytis spp. have been identified and characterized via morphological and genome-based approaches. Gray mold control is achieved primarily through fungicide applications but resistance to various chemical classes is a major concern that threatens global plant health and food security. In this issue, new information on molecular mechanism (s) of fungicide resistance and ways to manage control failures are presented. Finally, a significant leap in fundamental pathogen biology has been achieved via development of CRISPR/Cas9 to assess gene function in the fungus which likely will spawn new control meclianisms and facilitate gene discovery studies. [ABSTRACT FROM AUTHOR]

Copyright of Gesunde Pflanzen is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Studying the intimate association of arthropods with their physical substrate is both important and challenging. It is important because substrate is a key determinant for organism fitness; challenging because the intricacies of this association are dynamic, and difficult to record and resolve. The advent of electropenetrography (EPG) and subsequent developments allowed researchers to overcome this challenge. Nonetheless, EPG research has been historically restricted to piercing–sucking hemipteran plant pests. Recently, its potential use has been greatly broadened for additional pests with instrument advances. Thus, blood‐feeding arthropods and chewing feeders, as well as non‐feeding behaviors like oviposition by both pests and parasitoids, are novel new targets for EPG research, with critical consequences for integrated pest management. EPG can explain mechanisms of crop damage, plant or animal pathogen transmission, and the effects of insecticides, antifeedants, repellents, or transgenic plants and animals, on specific behaviors of damage or transmission. This review broadly covers the principles and development of EPG technology, emphasizing controversies and challenges remaining with suggested research to overcome them. In addition, it summarizes 60+ years of basic and applied EPG research, and previews future directions for pest management. The goal is to stimulate new applications for this unique enabling technology. Published 2020. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Aphis gossypii Glover (Hemiptera: Aphididae) is a polyphagous species frequently associated with the presence of sooty mold and viruses lethal to plants. The purpose of this work was to characterize possible resistance categories of cotton genotypes against A. gossypii. Initially, a preliminary test was carried out with 78 genotypes, 15 of which were selected for infestation ability assays and the determination of the cumulative aphid-day rates. Posteriorly, these genotypes were also evaluated through antixenosis and antibiosis assays. The genotypes FM 910, FM 966 LL, Mocó, Gossypium hirsutum var. punctatum L. (Malvaceae), Variedade Reba = BTK-12, Deltapine, Hi-Bred, Acala 4–42, IAC PV010-1664, IAC 21, Reba B-50 PR and FMT 709 inhibited the aphid colonization. In the infestation ability assay, G. hirsutum punctatum, IAC PV010-1664 and Acala 4–42 were the least infested. In a multiple-choice assay, Deltapine Smooth Leaf and Variedade Reba = BTK-12 were significantly less infested, suggesting antixenosis. In the antibiosis assay, Gossypium arboreum L. (Malvaceae) 1 showed the lowest number of nymphs, number of nymphs per adult per day and, number of nymphs at 10 d after the birth of the first nymph in addition to reducing the reproductive period, nymphal survival, adult longevity and, developmental time. In the FM 910, the number of nymphs produced per day and, at 10 d after the birth of the first nymph decreased, which also indicated resistance. The results obtained here are unprecedented and can be explored in breeding programs to develop insect-resistant cotton cultivars. [ABSTRACT FROM AUTHOR]

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The sweetpotato whitefly, Bemisia tabaci (Gennadius) Middle East-Asia Minor 1 (MEAM1), causes significant losses to vegetable crops directly by sap-feeding, inducing plant physiological disorders, and elevating the build-up of sooty mold, and indirectly by transmitting plant viruses. In this study, we evaluated the susceptibility of 20 yellow squash and zucchini ( Cucurbita pepo ) cultivars to MEAM1, across three growing seasons in the southeastern United States. Weekly sampling of the numbers of MEAM1 adults, nymphs, and eggs were conducted from the fourth week after seed sowing and across 6 weeks during the summer and fall of 2021 and five weeks during the fall of 2022. In general, adult whitefly populations were high during the first week of sampling but decreased as the seasons progressed. The zucchini cultivar 'Black Beauty' harbored the most adults, while 'Green Eclipse Zucchini' was the least attractive zucchini cultivar to the adults in fall 2022. For yellow squash, 'Early Summer' (summer 2021) and 'Amberpic 8455' (summer 2021 and fall 2022) were the cultivars with the highest adult populations, while 'Lioness' (summer 2021) and 'Gourmet Gold Hybrid' (fall 2022) harbored the lowest adult counts. The whitefly egg counts across both vegetables trailed those of adults and peaked in the second week of sampling. The counts of nymphs increased as the seasons progressed, but there was a decline after the second week during fall 2021. For the yellow squash cultivars, 'Gourmet Gold Hybrid', (summer 2021 and fall 2022), 'Lioness', and 'Fortune' (summer 2021) recorded the highest yields. For zucchini, 'Golden Glory' (summer 2021) was the top performer. These results provide valuable information for whitefly management in yellow squash and zucchini based on host plant susceptibility and yield.

Hybrid rice results from crossing a male-sterile line (the A line) with a pollen doner (the restorer or R line). In 3-line hybrid breeding systems, a fertile B line is also required to maintain A line populations. Heterosis is defined as a condition of traits whereby the hybrid exceeds the average of the parental lines. Heterobeltiosis is where the hybrid exceeds both parents. Hybrid rice may display heterosis/heterobeltiosis for growth, yield and resistance to herbivores, among other traits. In a greenhouse experiment, we assessed the frequency of heterosis for resistance to the brown planthopper ( Nilaparvata lugans (BPH)), whitebacked planthopper ( Sogatella furcifera (WBPH)) and yellow stemborer ( Scirpophaga incertulas (YSB)) in eight hybrids under varying soil nitrogen conditions. We also assessed plant biomass losses due to herbivore feeding as an approximation of tolerance (the plant's capacity to compensate for damage). Nitrogen reduced resistance to all three herbivores but was also associated with tolerance to WBPH and YSB based on improved plant survival, growth and/or yields. Plant biomass losses per unit weight of WBPH also declined under high nitrogen conditions for a number of hybrids, and there were several cases of overcompensation in rice for attacks by this herbivore. There was one case of nitrogen-related tolerance to BPH (increased grain yield) for a hybrid line with relatively high resistance, likely due to quantitative traits. Heterosis and heterobeltiosis were not essential to produce relatively high herbivore resistance or tolerance across hybrids.

Background: The wheat stem sawfly (WSS, Cephus cinctus) is a major pest of wheat (Triticum aestivum) and can cause significant yield losses. WSS damage results from stem boring and/or cutting, leading to the lodging of wheat plants. Although solid-stem wheat genotypes can effectively reduce larval survival, they may have lower yields than hollow-stem genotypes and show inconsistent solidness expression. Because of limited resistance sources to WSS, evaluating diverse wheat germplasm for novel resistance genes is crucial. We evaluated 91 accessions across five wild wheat species (Triticum monococcum, T. urartu, T. turgidum, T. timopheevii, and Aegilops tauschii) and common wheat cultivars (T. aestivum) for antixenosis (host selection) and antibiosis (host suitability) to WSS. Host selection was measured as the number of eggs after adult oviposition, and host suitability was determined by examining the presence or absence of larval infestation within the stem. The plants were grown in the greenhouse and brought to the field for WSS infestation. In addition, a phylogenetic analysis was performed to determine the relationship between the WSS traits and phylogenetic clustering., Results: Overall, Ae. tauschii, T. turgidum and T. urartu had lower egg counts and larval infestation than T. monococcum, and T. timopheevii. T. monococcum, T. timopheevii, T. turgidum, and T. urartu had lower larval weights compared with T. aestivum., Conclusion: This study shows that wild relatives of wheat could be a valuable source of alleles for enhancing resistance to WSS and identifies specific germplasm resources that may be useful for breeding. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry., (© 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.)

Aphid genomic resources enable the study of complex life history traits and provide information on vector biology, host adaption and speciation. The currant-lettuce aphid (Nasonovia ribisnigri (Hemiptera: Aphididae) (Mosley)) is a cosmopolitan pest of outdoor lettuce (Lactuca sativa (Asterales: Asteraceae) (Linnaeus)). Until recently, the use of resistant cultivars was an effective method for managing N. ribisnigri. A resistant cultivar containing a single gene (Nr-locus), introduced in the 1980s, conferred complete resistance to feeding. Overreliance of this Nr-locus in lettuce resulted in N. ribisnigri's ability to break resistance mechanism, with first reports during 2003. Our work attempts to understand which candidate gene(s) are associated with this resistance-breaking mechanism. We present two de novo draft assembles for N. ribisnigri genomes, corresponding to both avirulent (Nr-locus susceptible) and virulent (Nr-locus resistant) biotypes. Changes in gene expression of the two N. ribisnigri biotypes were investigated using transcriptomic analyses of RNA-sequencing (RNA-seq) data to understand the potential mechanisms of resistance to the Nr-locus in lettuce. The draft genome assemblies were 94.2% and 91.4% complete for the avirulent and virulent biotypes, respectively. Out of the 18,872 differentially expressed genes, a single gene/locus was identified in N. ribisnigri that was shared between two resistant-breaking biotypes. This locus was further explored and validated in Real-Time Quantitative Reverse Transcription PCR (qRT-PCR) experiments and has predicted localisations in both the cytoplasm and nucleus. This is the first study to provide evidence that a single gene/locus is likely responsible for the ability of N. ribisnigri to overcome the Nr-locus resistance in the lettuce host., (© 2024 The Authors. Insect Molecular Biology published by John Wiley & Sons Ltd on behalf of Royal Entomological Society.)

Background: The sweet potato whitefly (Bemisia tabaci) is a globally important insect pest that damages crops through direct feeding and by transmitting viruses. Current B. tabaci management revolves around the use of insecticides, which are economically and environmentally costly. Host plant resistance is a sustainable option to reduce the impact of whiteflies, but progress in deploying resistance in crops has been slow. A major obstacle is the high cost and low throughput of screening plants for B. tabaci resistance. Oviposition rate is a popular metric for host plant resistance to B. tabaci because it does not require tracking insect development through the entire life cycle, but accurate quantification is still limited by difficulties in observing B. tabaci eggs, which are microscopic and translucent. The goal of our study was to improve quantification of B. tabaci eggs on several important crop species: cassava, cowpea, melon, sweet potato and tomato., Results: We tested a selective staining process originally developed for leafhopper eggs: submerging the leaves in McBryde's stain (acetic acid, ethanol, 0.2% aqueous acid Fuchsin, water; 20:19:2:1) for three days, followed by clearing under heat and pressure for 15 min in clearing solution (LGW; lactic acid, glycerol, water; 17:20:23). With a less experienced individual counting the eggs, B. tabaci egg counts increased after staining across all five crops. With a more experienced counter, egg counts increased after staining on melons, tomatoes, and cowpeas. For all five crops, there was significantly greater agreement on egg counts across the two counting individuals after the staining process. The staining method worked particularly well on melon, where egg counts universally increased after staining for both counting individuals., Conclusions: Selective staining aids visualization of B. tabaci eggs across multiple crop plants, particularly species where leaf morphological features obscure eggs, such as melons and tomatoes. This method is broadly applicable to research questions requiring accurate quantification of B. tabaci eggs, including phenotyping for B. tabaci resistance., (© 2024. The Author(s).)

Metabolomics has become an important tool in elucidating the complex relationship between a plant genotype and phenotype. For over 20 years, nuclear magnetic resonance (NMR) spectroscopy has been known for its robustness, quantitative capabilities, simplicity, and cost-efficiency. 1 H NMR is the method of choice for analyzing a broad range of relatively abundant metabolites, which can be used for both capturing the plant chemical profile at one point in time and understanding the pathways that underpin plant defense. This systematic Review explores how 1 H NMR-based plant metabolomics has contributed to understanding the role of various compounds in plant responses to biotic stress, focusing on both primary and secondary metabolites. It clarifies the challenges and advantages of using 1 H NMR in plant metabolomics, interprets common trends observed, and suggests guidelines for method development and establishing standard procedures.

Sesame, an oilseed plant with multiple applications, is susceptible to infestations by the stink bug Nezara viridula (Linnaeus, 1758) (Hemiptera: Pentatomidae). This pest suctions the seeds of this plant and injects toxins into them. Possible sources of resistance on sesame cultivars are important to manage this bug. The objective of this study was to evaluate the biological aspects of N. viridula fed on three sesame cultivars aiming to select possible resistance sources for integrated pest management (IPM) programs of this stinkbug. The experimental design used randomized blocks with three treatments and four replications, each with newly emerged N. viridula nymphs fed with sesame capsules of the cultivars BRS Anahí (T1), BRS Morena (T2) and BRS Seda (T3). Two to three green sesame capsules were supplied every two days per group of ten N. viridula nymphs as one replication until the beginning of the adult stage. Adults of this stinkbug were fed in the same manner as its nymphs but with mature sesame capsules until the end of the observations. Survival during each of the five instars and of the nymph stage of N. viridula with green sesame capsules was similar between cultivars, but the duration of the nymph stage was shorter with green capsules of the BRS Morena than with those of the BRS Anahí. The oviposition period, number of egg masses and eggs per female, and the percentage of nymphs hatched were higher with mature capsules of the sesame cultivar BRS Anahí and lower with the others. Nymphs did not hatch from eggs deposited by females fed mature seed capsules of the sesame cultivar BRS Morena, which may indicate a source of resistance against this stinkbug in this cultivar. The worldwide importance of N. viridula to sesame cultivation makes these results useful for breeding programs of this plant aiming to develop genotypes resistant to this bug. In addition, the BRS Morena is a cultivar already commercially available and can be recommended in places where there is a history of incidence of N. viridula , aiming to manage the populations of this pest.

Soybean aphids (Aphis glycines Matsumura) are invasive insect pests of soybean, and they cause significant yield losses. Resistance to soybean aphids is conferred by Resistance to Aphis glycines (Rag) genes. Since the first discovery of aphid-resistant soybean genotypes in 2004, several studies have attempted to characterize Rag genes from aphid-resistant soybean genotypes. To date, 12 Rag genes and four quantitative trait loci for aphid resistance have been reported on soybean chromosomes 07, 08, 13, 16, and 17. Although candidate genes have been proposed for several discovered Rag loci, additional studies are needed to pinpoint, validate, and further explain the potential mechanisms of Rag gene action. A major challenge to utilizing host plant resistance is the discovery of virulent aphid biotypes that can colonize aphid-resistant soybean. This occurrence suggests the need for additional studies to devise strategies to enhance the effectiveness of aphid-resistant soybean. In this mini review, we discuss current knowledge on the resistant soybean-Aphis glycines interaction, potential mechanisms of Rag gene action, opportunities to discover new Rag genes, and prospects for utilization of host plant resistance to manage soybean aphids. A clearer understanding of host plant resistance to soybean aphids will guide researchers on strategies for developing soybean varieties with more durable aphid resistance, reducing the present challenge of virulent aphid biotypes.

Abstract The aim of the present study was to identify Aleurodicus cocois resistant genotypes among five dwarf cashew clones available in the germplasm bank of Embrapa/Centro Nacional de Pesquisa Agroindústria Tropical. Free-choice and no-choice tests were applied in order to evaluate the relative attractiveness of the clones and the oviposition preferences, egg-to-adult development times and adult emergence rates of the pest. In comparison with other clones, PRO143/7 exhibited the lowest attraction to the whitefly and was least preferred for oviposition in the free-choice test. Conversely, CCP76 attracted the highest number of A. cocois and was preferred for oviposition. In the no-choice test, the rates of emergence of adults from clones BRS274, CCP76 and PRO143/7 varied between 53.0 and 56.8%, values that were significantly lower (p < 0.05) than those of clones BRS226 and EMBRAPA51, which were 72.34 and 75.16%, respectively. Some of the cashew clones tested showed antibiotic (CCP76, PRO143/7 and BRS274) and antixenotic (PRO143/7 and BRS226) resistance to A. cocois. These clones are good candidates for use in breeding programs of cashew.

Abstract Insecticides can cause secondary pest outbreaks that weaken the benefit of chemical pest control. These detrimental nontarget effects motivate the use of alternative pest management strategies such as host plant resistance and intercropping. However, when alternative pest management strategies effectively suppress primary pests, they also have the potential to promote secondary pest populations via competitive release. The potato leafhopper (Empoasca fabae) is a key pest of alfalfa, and leafhopper‐resistant cultivars are being widely adopted by growers in the Midwest and Northeast United States. We conducted a field experiment comparing leafhopper‐susceptible alfalfa, leafhopper‐resistant alfalfa, and leafhopper‐resistant alfalfa intercropped with orchardgrass. Leafhopper‐resistant alfalfa reduced potato leafhopper abundance and protected the crop from protein loss, but there was no benefit of intercropping leafhopper‐resistant alfalfa with orchardgrass. Importantly, the abundance of a secondary pest, the pea aphid (Acyrthosiphon pisum), was twice as high in the leafhopper‐resistant plant treatments compared to the leafhopper‐susceptible treatment. Field sampling and microcosm experiments confirmed that the increase in pea aphids was caused, at least in part, by release from competition with leafhoppers. These results suggest that, when host plant resistance against insects is employed, efforts to monitor and manage secondary pest populations are warranted.