Major Pest Of Soybean Research Articles

A conserved protein family in mirid bug Riptortus pedestris plays dual roles in regulating plant immunity.

The mirid bug (Riptortus pedestris), a major soybean pest, migrates into soybean fields during the pod filling stage and causes staygreen syndrome, which leads to substantial yield losses. The mechanism by which R. pedestris elicits soybean (Glycine max) defenses and counter-defenses remains largely unexplored. In this study, we characterized a protein family from R. pedestris, designated Riptortus pedestris HAMP 1 (RPH1) and its putative paralogs (RPH1L1, 2, 3, 4, and 5), whose members exhibit dual roles in triggering and inhibiting plant immunity. RPH1 and RPH1L1 function as herbivore-associated molecular patterns (HAMPs), activating pattern-triggered immunity (PTI) in tobacco (Nicotiana benthamiana) and G. max. Furthermore, RPH1 stimulates jasmonic acid and ethylene biosynthesis in G. max, thereby enhancing its resistance to R. pedestris feeding. Additionally, RPH1 homologs are universally conserved across various herbivorous species, with many homologs also acting as HAMPs that trigger plant immunity. Interestingly, the remaining RPH1 putative paralogs (RPH1L2-5) serve as effectors that counteract RPH1-induced PTI, likely by disrupting the extracellular perception of RPH1. This research uncovers a HAMP whose homologs are conserved in both chewing and piercing-sucking insects. Moreover, it unveils an extracellular evasion mechanism utilized by herbivores to circumvent plant immunity using functionally differentiated paralogs.

Genome scans for selection signatures identify candidate virulence genes for adaptation of the soybean cyst nematode to host resistance.

Plant pathogens are constantly under selection pressure for host resistance adaptation. Soybean cyst nematode (SCN, Heterodera glycines) is a major pest of soybean primarily managed through resistant cultivars; however, SCN populations have evolved virulence in response to selection pressures driven by repeated monoculture of the same genetic resistance. Resistance to SCN is mediated by multiple epistatic interactions between Rhg (for resistance to H. glycines) genes. However, the identity of SCN virulence genes that confer the ability to overcome resistance remains unknown. To identify candidate genomic regions showing signatures of selection for increased virulence, we conducted whole genome resequencing of pooled individuals (Pool-Seq) from two pairs of SCN populations adapted on soybeans with Peking-type (rhg1-a, rhg2, and Rhg4) resistance. Population differentiation and principal component analysis-based approaches identified approximately 0.72-0.79 million SNPs, the frequency of which showed potential selection signatures across multiple genomic regions. Chromosomes 3 and 6 between population pairs showed the greatest density of outlier SNPs with high population differentiation. Conducting multiple outlier detection tests to identify overlapping SNPs resulted in a total of 966 significantly differentiated SNPs, of which 285 exon SNPs were mapped to 97 genes. Of these, six genes encoded members of known stylet-secreted effector protein families potentially involved in host defence modulation including venom-allergen-like, annexin, glutathione synthetase, SPRYSEC, chitinase, and CLE effector proteins. Further functional analysis of identified candidate genes will provide new insights into the genetic mechanisms by which SCN overcomes soybean resistance and inform the development of molecular markers for rapidly screening the virulence profile of an SCN-infested field.

Buckwheat as a companion plant in soybean fields: Implications for management of major pests

Abstract Many studies have explored the potential of companion plants to manage pests through top–down or bottom–up effects in agricultural fields. Buckwheat is known as a good candidate for companion planting with various crops to enhance pest management, but rarely in soybeans. We investigated the impact of planting buckwheat as a new companion plant on the population dynamics of major soybean pests and their natural enemies in soybean fields in Andong, Republic of Korea. We recorded numbers of pests and natural enemies at 9–10‐day intervals from 20 soybean plants each in eight small experimental fields throughout the cropping season. Significant reduction in pests, such as Riptortus pedestris (F.) (Hemiptera: Alydidae) adults, and a significant increase in natural enemies, such as Orius species (Hemiptera: Anthocoridae) and crab spiders (Araneae: Thomisidae), were observed in the buckwheat treatment plots. However, there were significant increases in other pests, such as leafminers and leafhoppers, in the buckwheat treatment plots. While we observed effects on R. pedestris adult density, we did not find significant effects on other developmental stages of this pest or its parasitoids. Although there were some concerns in the buckwheat treatment plots, the positive effects of buckwheat in soybean fields appear to outweigh the drawbacks. Buckwheat is likely a suitable companion plant for use in soybeans to manage pests.

Attracting Scelionidae egg parasitoids to enhance stink bug egg parasitisation in soybean crops using methyl salicylate and (E,E)-α-farnesene.

Plant volatile organic compounds (VOCs) play a crucial role in mediating interactions between plants, herbivores and natural enemies. Among these VOCs, methyl salicylate and (E,E)-α-farnesene are emitted as herbivore-induced plant volatiles (HIPVs) by soybean plants in response to feeding by the brown stink bug Eushistus heros. These HIPVs function as synomones, influencing the foraging behaviour of the egg parasitoid, Telenomus podisi, the main natural enemy of E. heros, one of the major soybean pests in Brazil. Laboratory experiments showed that two soybean cultivars, BRS 7580 and BRS 7880, produced similar qualitative blends of HIPVs, with methyl salicylate, (E,E)-α-farnesene and (Z)-3-hexenyl acetate being produced by both cultivars. Soybean cultivar BRS 7580 produced a significant lower amount of HIPVs compared to BRS 7880 but this difference did not affect the attractiveness of the egg parasitoid Telenomus podisi. Field experiments using these two cultivars and synthetic applications of methyl salicylate and (E,E)-α-farnesene showed a substantial increase in egg parasitism in all treated areas. Parasitism rates ranged from 50% to 80% in areas where these HIPVs were deployed, compared to only 10% in untreated control areas. The egg parasitoid Telenomus podisi demonstrated an adept ability in recognising between HIPVs in soybean blends, even in the presence of significant quantitative differences. The results from the field experiment showed the potential of HIPVs in attracting natural enemies to specific target areas within fields. (E,E)-α-Farnesene showed an improved action during the later stages of soybean growth, notably at R6. In addition, this volatile attracted other families of natural enemies. © 2024 Society of Chemical Industry.

Pest categorisation of Popillia quadriguttata.

The EFSA Panel on Plant Health performed a pest categorisation of Popillia quadriguttata (Coleoptera: Scarabaeidae), following a commodity risk assessment of bonsai Pinus parviflora grafted onto P. thunbergii from China, in which P. quadriguttata was identified as a pest of possible concern for the territory of the European Union. This is a univoltine polyphagous pest that occurs in eastern Asia from Vietnam northwards through eastern China and Taiwan, South Korea and into Far East Russia. Hosts include species of fruit trees within the genera Malus and Prunus, trees of forestry and environmental importance such as Quercus and Ulmus, shrubs such as Wisteria, soft fruit such as Rubus, grasses, including amenity turf and field crops such as potatoes, maize and soybean. Adults feed on host leaves, tender stems, flower buds, flowers and fruits; larvae feed on host roots. In northern China P. quadriguttata is a major pest of soybean; in South Korea, P. quadriguttata is one of the most serious insect pests of golf course turf. P. quadriguttata could enter the EU on various pathways including infested soil and growing media accompanying host plants for planning. Biotic factors (host availability) and abiotic factors (climate suitability) suggest that large parts of the EU would be suitable for establishment. Local spread would be mainly via natural dispersal of adults. Long distance spread would be facilitated by the movement of eggs, larvae and pupae infesting soil especially with plants for planting; adults could spread on plants for planting without soil. Economic and or environmental impacts would be expected on a range of plants if P. quadriguttata were to establish in the EU. Phytosanitary measures are available to reduce the likelihood of its introduction. P. quadriguttata satisfies all of the criteria that are within the remit of EFSA to assess for it to be regarded as a potential Union quarantine pest.

Utilizing Remote Sensing to Quantify the Performance of Soybean Insecticide Seed Treatments

Soybean (Glycine max) is one of the most important oilseed crops grown in North America and a key contributor to the global protein supply. Insect feeding by a major soybean pest, the bean leaf beetle (BLB; Cerotoma trifurcata), can result in economic yield loss if not controlled. The objective of this research was to use unmanned aerial vehicle (UAV) image analysis to compare the agronomic and efficacy traits of two soybean insecticide seed treatments (IST) in locations with BLB feeding. Across the 2018–2023 field trial locations, 29 had low BLB feeding pressure (less than 25% feeding damage to no IST plots) and 31 had high BLB feeding pressure (greater than 25% feeding damage to no IST plots). In low BLB pressure locations, cyantraniliprole and imidacloprid seed treatments had significantly higher BLB efficacy, significantly higher UAV greenness, and significantly higher final yield as compared to no IST. In high BLB pressure locations, cyantraniliprole and imidacloprid seed treatments were significantly better compared to no IST for BLB efficacy, UAV emergence, UAV vigor, UAV greenness, and final yield. In high BLB pressure locations, cyantraniliprole had significantly higher BLB efficacy, significantly better UAV emergence, and significantly higher yield compared to imidacloprid. The cyantraniliprole treatment had a +254.5 kg/ha increase compared to no IST in low BLB pressure locations and a +213.7 kg/ha increase in high BLB pressure locations. The imidacloprid treatment had a +163.4 kg/ha yield increase compared to no IST in low BLB pressure locations and a +121.4 kg/ha yield increase in high BLB pressure locations. The use of UAV image analysis enabled quantification of the effect of BLB feeding on early-season agronomic traits and, when combined with efficacy and final yield data, successfully differentiated the performance of two soybean ISTs in environments with low or high insect pressure.

Protection of soybean plants from phytophages under conditions of the Primorsky Territory

The effectiveness of pre-sowing treatment of soybean seeds and application of biorational insecticides in reducing the number of major pests of soybean in the conditions of the Primorsky Territory have been studied. The results of using insecticides and biopreparations to regulate the number of dominant pests of soybean have been presented. The studies were conducted in 2020 and 2021. The efficiency of insecticidal protectants Imidor Pro, SC (2 l/t) and Tabu, WSC (1.0 l/t), bioinsecticides Fitoverm, EC (0, 16 l/ha), Proclaim, WSG (0.3 kg/ha), Batsikol, L (15 l/ha), Biosleep BW, L (2 l/ha), Biosleep BT, P (2 kg/ha) against two-striped leaf beetle (Medythia nigrobilineatus Motsch.) and soybean pod borer (Leguminivora glycinivorella Mats.) were studied. Pre-sowing seed treatment with insecticides Imidor Pro and Tabu reduced damage of soybean plants in the sprouting phase by Medythia nigrobilineatus beetles compared to the control by 94.0–98.2%. Seed dressing with imidacloprid-based preparations provided effective protection of crops against the pest in the sprouting – branching phase. Biorational insecticides based on avermectin C and Bacillus thuringiensis showed high biological efficacy (71.1–98.8%) on the 5–10th day after treatment against the two-striped leaf beetle. Soybean seed damage when bioinsecticides were used against Leguminivora glycinivorella was 1.9–3.0% compared to 5.6% in the control. The conducted studies testify to the prospect of using the preparations of biological origin to control the number of dominant pests in soybean crops.

The Lethal and Sublethal Effects of Lambda-Cyhalothrin and Emamectin Benzoate on the Soybean Pest Riptortus pedestris (Fabricius).

Riptortus pedestris (Fabricius, 1775) (Hemiptera: Alydidae) is a major soybean pest in East Asia that can cause soybean staygreen syndrome. To date, no insecticides have been registered for the control of R. pedestris in China, and these insects are primarily controlled in the field through the application of broad-spectrum insecticides including lambda-cyhalothrin (LCT) and emamectin benzoate (EMB). Here, the lethal and sublethal effects of LCT and EMB on R. pedestris were comprehensively evaluated. LCT and EMB were both found to exhibit high levels of toxicity and concentration-dependent repellent effects for R. pedestris. The exposure of third instar nymphs from the F0 generation to LC30 concentrations of LCT and EMB resulted in a significant increase in the duration of nymph development and adult pre-oviposition period (APOP), together with reductions in fifth instar nymph and adult body weight, longevity, oviposition days, fecundity, vitellarium length, lateral oviduct diameter, and vitellogenin (Vg) gene expression as compared to control treatment. Strikingly, these suppressive effects were transmitted to the F1 generation, which similarly experienced the prolongation of preadult development and the preoviposition period (TPOP). Relative to control-treated populations, the F1 generation for these insecticide-treated groups also exhibited significant decreases in population parameter values. Overall, these data offer new insight into the impact that LCT and EMB treatment can have on R. pedestris, providing a valuable foundation for the application of these pesticides in the context of integrated pest management strategies aimed at soybean crop preservation.

A push–pull strategy for controlling Riptortus pedestris (Hemiptera: Alydidae) using host plant semiochemicals

ABSTRACT Riptortus pedestris is a major pest of soybean in East Asia that feeds on maturing seeds, reducing nutritional quality and causing seed abortion. Aggregation pheromone of the bean bug has been conventionally used as a lure for mass-trapping, but the control practices, used by farmers and recommended by the manufacturer can increase infestation in soybean fields. Here we investigated the efficacy of soybean semiochemical blend as a repellent incorporated with an attractant blend to develop a push–pull strategy. The efficacy of potential repellents was tested in a soybean field by evaluating three control strategies: a potential repellent (push), an attractant based on the synergistic effect of synthetic host plant volatiles and the aggregation pheromone (pull), and a combination of the attractant and the potential repellent. We adopted two different monitoring systems, sticky traps and camera traps, to assess the spatial distribution of the bean bugs. The attractant and repellents were strategically deployed, by putting the repellent in the center of soybean plot while the attractants were placed at the edge of the plot. In soybean plots treated with only attractants at the edge, the number of bean bugs was significantly higher in both soybean and edge areas than those of control plots. In contrast, the number of attracted bean bugs to soybean area significantly decreased in the push–pull treated plot, verified by both sticky trap and camera trap methods. This strategy could prevent colonization and population establishment of the bean bugs in soybean fields as part of an integrated pest management.

Effects of the termination of LC30 imidacloprid stress on the multigeneration adaptive strategies of Aphis glycines population.

Aphis glycines Matsumura (Hemiptera: Aphididae) is a major soybean pest that often poses a serious threat to soybean production. Imidacloprid is one of the commonly used insecticides to control the soybean aphid. To investigate the effect of termination of imidacloprid stress on the adaptive strategies of soybean aphid populations, we studied the growth, development, and related metabolism changes when the stress was terminated after 24 generations of imidacloprid stress on A. glycines. The results show that the A. glycines population accelerated its recovery and expanded its population size across generations. The longevity of the adults of the recovering population in the F12, F18, and F24 generations, respectively, was 1.11, 1.15, and 1.11 times longer than the control, while the fecundity was 10.38%, 11.74%, and 11.61% higher than that of the control. The net reproductive rate (R 0) of the recovering population was always significantly higher than that of the control in the F1 to F24 generations. In addition, metabolisms related to the regulation of cell proliferation and oocyte meiosis were significantly upregulated in the recovering population. Even when the imidacloprid pressure disappeared, intergenerational stimuli still affected the adaptive strategies of soybean aphid populations. This effect was manifested as inhibiting the growth and development of the soybean aphid in the early generations and improving the fecundity of the soybean aphid in the later generations. Adaptive soybean aphid populations would surge in the absence of imidacloprid pressure. This study provides an important reference for exploring the adaptability of the A. glycines population under termination of stress from low lethal concentrations of imidacloprid across generations. It also provides important data for monitoring the population dynamics of A. glycines in the field and analyzing the degree of pharmacodynamic stress.

Investigating the Migratory Behavior of Soybean Looper, a Major Pest of Soybean, through Comparisons with the Corn Pest Fall Armyworm Using Mitochondrial Haplotypes and a Sex-Linked Marker.

The Noctuid moth soybean looper (SBL), Chrysodeixis includens (Walker), is an economically important pest of soybean (Glycine max (Linnaeus) Merrill). Because it is not known to survive freezing winters, permanent populations in the United States are believed to be limited to the southern regions of Texas and Florida, yet its geographical range of infestations annually extend to Canada. This indicates annual migrations of thousands of kilometers during the spring and summer growing season. This behavior is like that of the fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), also a Noctuid that is a major global pest of corn. SBL and FAW are projected to have very similar distributions of permanent populations in North America based on climate suitability modeling and the overlap in the distribution of their preferred host plants (corn and soybean). It therefore seems likely that the two species will display similar migratory behavior in the United States. This was tested by identifying genetic markers in SBL analogous to those successfully used to delineate FAW migratory pathways and comparing the distribution patterns of the markers from the two species. Contrary to expectations, the results indicate substantial differences in migratory behavior that appear to be related to differences in the timing of corn and soybean plantings. These findings underscore the importance of agricultural practices in influencing pest migration patterns, in particular the timing of host availability relative to mean seasonal air transport patterns.

Insecticidal Traits of Variants in a Genotypically Diverse Natural Isolate of Anticarsia Gemmatalis Multiple Nucleopolyhedrovirus (AgMNPV).

Outbreaks of Anticarsia gemmatalis (Hübner, 1818) (Lepidoptera: Erebidae), a major pest of soybean, can be controlled below economic thresholds with methods that do not involve the application of synthetic insecticides. Formulations based on natural isolates of the Anticarsia gemmatalis multiple nucleopolyhedrovirus (AgMNPV) (Baculoviridae: Alphabaculovirus) played a significant role in integrated pest management programs in the early 2000s, but a new generation of chemical insecticides and transgenic soybean have displaced AgMNPV-based products over the past decade. However, the marked genotypic variability present among and within alphabaculovirus isolates suggests that highly insecticidal genotypic variants can be isolated and used to reduce virus production costs or overcome isolate-dependent host resistance. This study aimed to select novel variants of AgMNPV with suitable insecticidal traits that could complement the existing AgMNPV active ingredients. Three distinct AgMNPV isolates were compared using their restriction endonuclease profile and in terms of their occlusion body (OB) pathogenicity. One isolate was selected (AgABB51) from which eighteen genotypic variants were plaque purified and characterized in terms of their insecticidal properties. The five most pathogenic variants varied in OB pathogenicity, although none of them was faster-killing or had higher OB production characteristics than the wild-type isolate. We conclude that the AgABB51 wild-type isolates appear to be genotypically structured for fast speed of kill and high OB production, both of which would favor horizontal transmission. Interactions among the component variants are likely to influence this insecticidal phenotype.

Pengaruh Abu Sekam terhadap Populasi dan Serangan Lalat Kacang (Ophiomyia phaseoli) pada Tanaman Kedelai

<p>The bean fly (<em>Ophiomyia phaseoli)</em> is a major pest of soybean in Indonesia which causes the plants to die early in growth. Most farmers use insecticide synthetics to control this pest. Therefore the alternative control of bean flies is needed to reduce reliance on farmer's usage of chemical pesticides. One of the alternative control is with application of husk ash that has a high silica content. This study examined husk ash to know the effect of husk ash to population and proportion of bean flies attacks. This research conducted in Pengkok Village, Kedawung, Sragen from June - September 2019. The method used was field experiment with a Randomized Completely Block Design (RCBD) with one factor, namely the dose of husk ash five levels (0 tons ha-1, 1.25 tons ha-1, 2.5 tons ha-1, 3.75 tons ha-1, and 5 tons ha-1) and five replications. The results showed that the application of husk ash not affected significantly on the adults of the bean fly population, but affected significantly the percentage of attacks only in the cotyledons. The application of rice husk ash can reduce the percentage of attack on the cotyledons by 2.11-3.04% than without husk ash application. The number of plant deaths apparently followed the populations of bean flies. Furthermore, the height of soybean with application looked taller than without application.</p>

Re‐evaluation of the economic threshold for Crocidosema aporema injury to indeterminate Bt soybean cultivars

AbstractThe neotropical soybean budborer (Crocidosema aporema [Walsingham, 1914] [Lepidoptera: Tortricidae]) is classified as a major pest of soybean that is difficult to manage with insecticides because larvae cause leaf‐rolling and can bore into the stem. Genetically modified Bt (Bacillus thuringiensis) soybean has been effective in managing C. aporema populations until recently when resistance has emerged and high infestation rates have been observed in Brazilian Bt soybean fields expressing Cry1Ac. The economic threshold (ET) for C. aporema was previously studied only in conventional (non‐Bt) determinate varieties of soybean. The present work evaluated the potential of C. aporema to injure indeterminate Bt soybean cultivars in two independent field trials carried out in 2020–2021 and 2021–2022 growing seasons. One field trial compared the response of individual injured and noninjured plants in the same field. The number of pods per plant, number of seeds per plant, and seed mass per plant in 12 of 13 trials were similar. In the second field trial, areas with and without insecticide applications were compared. There was a reduction in C. aporema damage after three insecticide applications, but yields were similar between treatments. Based on these results, C. aporema had low potential to cause economic injury to indeterminant Bt soybean cultivars. Thus, the current ET for C. aporema of 25%–30% of infested plants can be increased to 50%.

The genome sequence of the Neotropical brown stink bug, Euschistus heros provides insights into population structure, demographic history and signatures of adaptation

The Neotropical brown stink bug, Euschistus heros, is a major pest of soybean in South America. The importance of E. heros as a pest has grown significantly in recent times due to increases in its abundance and range, and the evolution of insecticide resistance. Recent work has begun to examine the genetic diversity, population structure, and genetic mechanisms of insecticide resistance in E. heros. However, to date, investigation of these topics has been hampered by a lack of genomic resources for this species. Here we address this need by assembling a high-quality draft genome for E. heros. We used a combination of short and long read sequencing to assemble an E. heros genome of 1.4 Gb comprising 906 contigs with a contig N50 of 3.5 MB. We leveraged this new genomic resource, in combination with genotyping by sequencing, to explore genetic diversity in populations of this species in Brazil and identify genetic loci in the genome which are under selection. Our genome-wide analyses, confirm that there are two populations of E. heros co-occurring in different geographical regions in Brazil, and that, in certain regions of the country these populations are hybridizing. We identify several regions of the genome as under selection, including markers associated with putative insecticide resistance genes. Taken together, the new genomic resources generated in this study will accelerate research into fundamental aspects of stinkbug biology and applied aspects relating to the sustainable control of a highly damaging crop pest.

The effects of acetamiprid multigeneration stress on metabolism and physiology of Aphis glycines Matsumura (Hemiptera: Aphididae).

Aphis glycines Matsumura (Hemiptera: Aphididae) is a major soybean pest that often poses a serious threat to soybean production. In this study, we checked the effects of acetamiprid on redox, energy metabolism, and hormone expression in A. glycines. The LC50 and LC30 of acetamiprid were used to treat the fourth instar nymphs in each generation from F0 to F4 to measure the activity of peroxidase, pyruvate kinase, and trehalase using a microassays approach. The peroxidase activity was significantly higher than control when treated with the LC30 of acetamiprid in F2-F5 generations. The activity of pyruvate kinase was significantly higher, while trehalase activity was substantially lower than control in each generation. Besides, we monitored molting and juvenile hormone expression in soybean aphids using enzyme-linked immunosorbent assay. The juvenile hormone titer of third instar nymphs was significantly higher in the treatment group (F1, F2, F4, and F5), while no effects were noted in the F3 generation. Taken together, the activity of peroxidase and pyruvate kinase in soybean aphid first increased to the peak and then decreased, while the trehalase activity continuously decreased in all generations following exposure to acetamiprid. The juvenile hormone titer was significantly higher, while the molting hormone titer was significantly lower in LC50 -treated aphids than in control. Moreover, the LC30 of acetamiprid increased the molting hormone expression in soybean aphids. These findings indicated a baseline for the effective use of acetamiprid in controlling soybean aphids.

Validation of Reference Genes Across Populations of Aphis glycines (Hemiptera: Aphididae) for RT-qPCR Analysis of Gene Expression Related to Pyrethroid Detoxification

Metabolic detoxification is a common mechanism of insecticide resistance, in which detoxifying enzyme genes are overexpressed. Aphis glycines Matsumura (Hemiptera: Aphididae) is one of the major soybean pests in the United States and has developed resistance to pyrethroid insecticides after almost two decades of use. To date, there are no validated reference genes to normalize expression of detoxification genes for pyrethroid resistance in A. glycines. From a literature review, a list was compiled of genes from 36 gene families (68 sequences) frequently used as reference genes in gene expression analysis in Hemiptera. Exon–exon junction primers were designed for the best alignment matches to a draft A. glycines genome and were assayed in a three-phase screening. The first screen eliminated nonamplifying primers. The second screen used nine A. glycines populations varying in resistance to pyrethroids and eliminated primers with inconsistent amplification or low amplification efficiency, and quantitatively assessed the stability of expression in the 14 remaining candidates using NormFinder and a generalization of BestKeeper. The third screen quantitatively validated these results on the best candidates. Six genes were identified with the greatest stability across technical and biological replication and the nine populations. The genes identified as the most suitable reference genes for the study of detoxifying enzymes related to pyrethroid resistance in soybean aphid were: actin, RPL9 (ribosomal protein L9), RPS9 (ribosomal protein S9), AK (arginine kinase), RNAPol2 (RNA polymerase II), and RPL17 (ribosomal protein L17). Our findings will support studies related to insecticide resistance in A. glycines.

RESPONSE OF (Glycine max (L.) Merr.,) GENOTYPES AGAINST Spodoptera littoralis BASED ON AGRO-MORPHOLOGICAL AND MOLECULAR MARKERS

Defoliating insects can cause significant damage to soybean plants in Egypt. The cotton leaf worm (Spodoptera littoralis) is a major pest of soybean and important economic insect pests in Egypt than other insect pests. Susceptibility of 15 soybean genotypes to infestation of cotton leaf worm Spodoptera littoralis were studied under natural field conditions. The relationship between agro-morphological and molecular DNA in relation to leaves defoliation were also studied. Defoliation of tested plants by the cotton leaf worm, in the field screenings system showed the genotypes L105 and L153 recorded the highest values of insect resistant and recorded defoliation ranking from zero to 0.1 respectively, followed by genotypes named H10L10A, L162, and H1L1. Whereas, AGS-129 genotype showed a maximum insect susceptible had defoliation score (4.0) indicating heavy insect feeding, over both seasons. Moreover, highest values of seed yield/fed recorded by L 153, H10L10A and H1L1, this attributed to the considerable increasing in number of branches/plant, 100-seed weight and number of pods/plant over both seasons, representing those genotypes are promising and could be suggested for release, also; these genotypes revealed to high insect resistance to cotton leaf worm. In total 13 SSR primers amplify 45 bands. The polymorphic SSRs were successfully used to distinguish cotton leaf worm resistance among soybean genotypes. In general, it could be supposed that the some soybean genotypes, H153, H105, L162 H1L1 and H10 L10 are promising genotypes that can be used in cultivation to expand soybean resistance to cotton leaf worm.

Effects of Acetamiprid at Low and Median Lethal Concentrations on the Development and Reproduction of the Soybean Aphid Aphis glycines.

Simple SummaryWe conducted a study on the effects of LC50 and LC30 acetamiprid on the growth and development of the soybean aphid Aphis glycines Matsumura (Hemiptera: Aphididae). We found that exposure to acetamiprid at LC50 significantly extended the mean generation time, adult pre-ovipositional period, and total pre-reproduction period compared to the control, whereas exposure to acetamiprid at LC30 significantly shortened these periods. Acetamiprid at LC50 treatment significantly decreased the growth rate compared with the LC30 treatment. In addition, this study also found that low lethal concentration of acetamiprid could advance the occurrence of a reproductive peak, which could help us understand the major occurrence period of soybean aphids under acetamiprid stress. The present study provides reference data that could facilitate the exploration of the effects of acetamiprid on A. glycines in the field.The soybean aphid Aphis glycines Matsumura (Hemiptera: Aphididae) is a major pest of soybean and poses a serious threat to soybean production. Studies on the effect of acetamiprid on the life table parameters of A. glycines, provide important information for the effective management of this pest. We found that exposure to acetamiprid at LC50 significantly extended the mean generation time, adult pre-reproductive period, and total pre-reproduction period compared with the control, whereas exposure to acetamiprid at LC30 significantly shortened these periods. Exposure to acetamiprid at both LC30 and LC50 significantly decreased the fecundity of the female adult, net reproductive rate, intrinsic rate of increase, and finite rate of increase compared with the control. The probability of attaining the adult stage was 0.51, 0.38, and 0.86 for a newly born nymph from the LC30 acetamiprid treatment group, LC50 acetamiprid treatment group, and control group, respectively. Acetamiprid at both LC50 and LC30 exerted stress effects on A. glycines, with the LC50 treatment significantly decreased the growth rate compared with the LC30 treatment. The present study provides reference data that could facilitate the exploration of the effects of acetamiprid on A. glycines in the field.

Evaluation of linear and nonlinear models for temperature driven development of Spodoptera litura (Fabricius) on soybean crop


 The tobacco caterpillar, Spodoptera litura, a major pest of soybean in India is under surveillance in all soybean growing areas in Maharashtra in order to issue alerts to farmers and prevent economic losses. In this context, two linear models were fitted to developmental data of S. litura life stages reared on soybean at five constant temperatures viz. 15, 20, 25, 30 and 35°C through laboratory experiments. Optimum temperature for development (Topt) and upper temperature threshold (Tmax) were estimated from three nonlinear models by additionally including developmental response at >35°C. Topt estimates for the total immature development were 34.5°C (Lactin-2), 33.7°C (Briere-1) and 33.2°C (Simplified Beta type function) while Tmax estimates were in the range of 38 to 40°C. Application of a thermodynamic non-linear model (Optim SSI) gave estimate ofintrinsic optimum temperature (Tφ) for development of egg (28.3°C), larva (27.5°C) and pupal stage (30.3°C). The phenology model of S. litura on soybean based on estimated developmental threshold temperatures and thermal constants was validated using available field surveillance data to facilitate informed pest management decisions.