scholarly journals The influence of Western corn rootworm seed coating and granular insecticides on the seasonal fluctuations of soil nematode communities in a maize field

2013 ◽  
Vol 50 (3) ◽  
pp. 205-214 ◽  
Author(s):  
A. Čerevková ◽  
Ľ. Cagáň
Keyword(s):  
Diversity Index ◽  
Diabrotica Virgifera Virgifera ◽  
Western Corn Rootworm ◽  
Maturity Index ◽  
Soil Nematode ◽  
Corn Rootworm ◽  
Sample Collection ◽  
Species Diversity Index ◽  
Nematode Communities ◽  
Maize Field

Abstract Western corn rootworm, Diabrotica virgifera virgifera, is a pest that needs to be controlled with chemicals in the maize monoculture. The aim of this study was to examine the influence of insecticides on nematode communities in a maize field. Four soil treatments were used in this experiment: variant 1 — a granular application with tefluthrin (199.5 g a.i./ha); variant 2 — a granular application with clothianidin (110 g a.i./ha); variant 3 — a seed treatment with clothianidin (1.25 μg a.i/seed); and control — a maize field without insecticides. During the investigated period, a total of 19 117 soil nematode individuals were captured and 9 orders, 33 genera and 37 species were identified. Acrobeloides nanus, Cephalobus persegnis, Eucephalobus striatus and Basiria gracilis were the dominant species, accounting for 48 % of the total number of individuals. The mean abundance and species diversity index were significantly lower for variant 2. Bacterial feeders were the dominant trophic group for all 4 variants. The numbers of nematodes in particular trophic groups (i.e., bacterial feeders, fungal feeders and omnivores) were significantly different between variant 2 and the control. The Σ Maturity index, Maturity index and Plant parasitic index did not show significant differences among the variants. The higher values of the Enrichment and Structure indices were observed in the first month of the investigation in all 4 variants. A cluster analysis showed that nematode species population densities were strongly affected by the date of soil sample collection and by the variants used in the experiment.

Long-term effects of a wildfire on the soil nematode communities in the spruce forest ecosystem of High Tatra National Park

2015 ◽  
Vol 24 (5) ◽  
pp. 702 ◽  
Author(s):  
Marek Renčo ◽  
Andrea Čerevková
Keyword(s):  
Forest Ecosystem ◽  
Diversity Index ◽  
Control Plot ◽  
Parasitic Nematodes ◽  
Soil Nematode ◽  
Spruce Forest ◽  
Long Term Effects ◽  
Species Diversity Index ◽  
Nematode Communities ◽  
Soil Nematode Communities

This study evaluated the effect of a wildfire on soil nematode communities in the spruce forest ecosystem of the High Tatra Mountains 8 years after the fire. Two plots were established, an intact control plot (REF) and a fire-damaged plot after a windstorm (FIR). A total of 20 representative soil samples were collected; 10 from each site (five in June and five in October). A total of 64 species of nematodes were recorded. The mean number of species 8 years after the fire ranged from 24 to 36 and was always significantly higher in REF than in FIR (P < 0.05); with a significantly higher Shannon–Weaver diversity index in REF. Bacterivores were the most abundant trophic group at both sites. Omnivores were more abundant in FIR than in REF, and predators were more abundant in REF. The most abundant species at both sites were Acrobeloides nanus, Aglenchus agricola, Malenchus exiguus and Paratylenchus microdorus. Epidermal or root-hair feeders, mainly Malenchus exiguus, were the most abundant plant-parasitic nematodes at both sites, followed by the ectoparasitic P. microdorus. The migratory endoparasite, Pratylenchus pratensis, was found only in FIR in relatively high numbers, whereas the ectoparasitic species Criconemoides morgensis, Crossonema menzeli and Ogma cobbi occupied only REF. Nematode abundance and species diversity index differed significantly between the disturbed and undisturbed habitats, but ecological and functional indices and metabolic footprints indicate that the soil ecosystem 8 years after the fire had recovered, with moderate levels of nutrient enrichment comparable to those of the control plot.

scholarly journals Resistance to Bt Maize by Western Corn Rootworm: Effects of Pest Biology, the Pest–Crop Interaction and the Agricultural Landscape on Resistance

Insects ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 136
Author(s):  
Aaron Gassmann
Keyword(s):  
Agricultural Landscape ◽  
Continuous Cultivation ◽  
Diabrotica Virgifera Virgifera ◽  
The United States ◽  
Western Corn Rootworm ◽  
Corn Rootworm ◽  
Agricultural Crop ◽  
Bt Maize ◽  
Bt Toxin ◽  
Resistance Evolution

The western corn rootworm, Diabrotica virgifera virgifera LeConte, is among the most serious pests of maize in the United States. Since 2003, transgenic maize that produces insecticidal toxins from the bacterium Bacillus thuringiensis (Bt) has been used to manage western corn rootworm by killing rootworm larvae, which feed on maize roots. In 2009, the first cases of field-evolved resistance to Bt maize were documented. These cases occurred in Iowa and involved maize that produced Bt toxin Cry3Bb1. Since then, resistance has expanded to include other geographies and additional Bt toxins, with some rootworm populations displaying resistance to all commercially available Bt traits. Factors that contributed to field-evolved resistance likely included non-recessive inheritance of resistance, minimal fitness costs of resistance and limited adult dispersal. Additionally, because maize is the primary agricultural crop on which rootworm larvae can survive, continuous maize cultivation, in particular continuous cultivation of Bt maize, appears to be another key factor facilitating resistance evolution. More diversified management of rootworm larvae, including rotating fields out of maize production and using soil-applied insecticide with non-Bt maize, in addition to planting refuges of non-Bt maize, should help to delay the evolution of resistance to current and future transgenic traits.

scholarly journals Detection of alternative splicing in Diabrotica virgifera virgifera LeConte, in association with Bt resistance using RNA-seq and PacBio Iso-Seq

2020 ◽  
Author(s):  
Zixiao Zhao ◽  
Christine G. Elsik ◽  
Bruce E. Hibbard ◽  
Kent S. Shelby
Keyword(s):  
Alternative Splicing ◽  
Matrix Protein ◽  
Diabrotica Virgifera Virgifera ◽  
Western Corn Rootworm ◽  
Corn Rootworm ◽  
Diabrotica Virgifera ◽  
Rna Seq ◽  
Bt Resistance ◽  
Bt Toxins ◽  
Alternatively Spliced

AbstractBackgroundAlternative splicing is one of the major mechanisms that increases transcriptome diversity in eukaryotes, including insect species that have gained resistance to pesticides and Bt toxins. In western corn rootworm (Diabrotica virgifera virgifera LeConte), neither alternative splicing nor its role in resistance to Bt toxins has been studied.ResultsTo investigate the mechanisms of Bt resistance we carried out single-molecule real-time (SMRT) transcript sequencing and Iso-seq analysis on resistant, eCry3.1Ab-selected and susceptible, unselected, western corn rootworm neonate midguts which fed on seedling maize with and without eCry3.1Ab for 12 and 24 hours. We present transcriptome-wide alternative splicing patterns of western corn rootworm midgut in response to feeding on eCry3.1Ab-expressing corn using a comprehensive approach that combines both RNA-seq and SMRT transcript sequencing techniques. We found that 67.73% of multi-exon genes are alternatively spliced, which is consistent with the high transposable element content of the genome. One of the alternative splicing events we identified was a novel peritrophic matrix protein with two alternative splicing isoforms. Analysis of differential exon usage between resistant and susceptible colonies showed that in eCry3.1Ab-resistant western corn rootworm, expression of one isoform was significantly higher than in the susceptible colony, while no significant differences between colonies were observed with the other isoform.ConclusionOur results provide the first survey of alternative splicing in western corn rootworm and suggest that the observed alternatively spliced isoforms of peritrophic matrix protein may be associated with eCry3.1Ab resistance in western corn rootworm.

Soybean Foliage Consumption Reduces Adult Western Corn Rootworm (Diabrotica virgifera virgifera)(Coleoptera: Chrysomelidae) Survival and Stimulates Flight

2021 ◽  
Author(s):  
Joseph L Spencer ◽  
Timothy R Mabry ◽  
Eli Levine ◽  
Scott A Isard
Keyword(s):  
Wind Tunnel ◽  
Crop Rotation ◽  
Diabrotica Virgifera Virgifera ◽  
Western Corn Rootworm ◽  
Egg Laying ◽  
Corn Rootworm ◽  
Diabrotica Virgifera ◽  
Egg Maturation ◽  
Behavioral Resistance ◽  
Collection Sites

Abstract Western corn rootworm, Diabrotica virgifera virgifera LeConte, biology is tied to the continuous availability of its host (corn, Zea mays L.). Annual rotation of corn with a nonhost, like soybean (Glycine max (L.) Merrill) was a reliable tactic to manage western corn rootworm. Behavioral resistance to annual crop rotation (rotation resistance) allowed some eastern U.S. Corn Belt populations to circumvent rotation by laying eggs in soybean and in cornfields. When active in soybean, rotation-resistant adults commonly consume foliage, in spite of detrimental effects on beetle survival. Rotation-resistant beetle activity in soybean is enabled by the expression of certain proteinases and an adapted gut microbiota that provide limited protection from soybean antiherbivore defenses. We investigated the effects of corn and soybean herbivory on rotation-resistant female survival and initiation of flight using mortality assays and wind tunnel flight tests. Among field-collected females tested with mortality assays, beetles from collection sites in a cornfield survived longer than those from collection sites in a soybean field. However, reduced survival due to soybean herbivory could be restored by consuming corn tissues. Field-collected beetles that fed on a soybean tissue laboratory diet or only water were more likely to fly in a wind tunnel than corn-feeding beetles. Regardless of collection site and laboratory diet, 90.5% of beetles that flew oriented their flights upwind. Diet-related changes in the probability of flight provide a proximate mechanism for interfield movement that facilitates restorative feeding and the survival of females previously engaged in soybean herbivory. Rotation-resistant western corn rootworm females feeding on soybean tissues experience reduced survival in mortality assays and display increased flight probability (which may facilitate flight back to a cornfield where consumption of host tissues improves survival potential and facilitates maturation of eggs). The consequences of soybean herbivory provide a proximal mechanism for behavioral resistance to crop rotation. Increased egg-laying probability while feeding on soybean tissues, facilitation of egg maturation while feeding on corn tissues, and interfield movement are previously documented consequences.

scholarly journals Inheritance and Fitness Costs of Cry3Bb1 Resistance in Diapausing Field Strains of Western Corn Rootworm (Coleoptera: Chrysomelidae)

2020 ◽  
Vol 113 (6) ◽  
pp. 2873-2882
Author(s):  
Ram B Shrestha ◽  
Aaron J Gassmann
Keyword(s):  
Developmental Rate ◽  
Diabrotica Virgifera Virgifera ◽  
Dry Mass ◽  
Western Corn Rootworm ◽  
Corn Rootworm ◽  
Adult Size ◽  
Inheritance Of Resistance ◽  
Diabrotica Virgifera ◽  
Fitness Costs ◽  
Diabrotica Virgifera Virgifera Leconte

Abstract Field-evolved resistance to Cry3Bb1 corn by western corn rootworm, Diabrotica virgifera virgifera LeConte (Colleoptera: Chrysomellidae), has been reported in field populations in Iowa, Illinois, Nebraska, and Minnesota. Inheritance and fitness costs associated with Cry3Bb1 resistance have been determined for non-diapausing laboratory strains of western corn rootworm with either laboratory-selected resistance or field-derived resistance. However, information on inheritance and fitness costs of Cry3Bb1 resistance in the diapausing field populations is lacking. In this study, we determined the inheritance of Cry3Bb1 resistance for four diapausing field strains of western corn rootworm using plant-based bioassays. We also determined the fitness costs for eight diapausing field populations in a greenhouse experiment. We found that Cry3Bb1 resistance was an autosomal trait and that the inheritance of resistance was mostly non-recessive; however, there was some variation in the dominance of Cry3Bb1 resistance. We did not find evidence of fitness costs affecting survival to adulthood, developmental rate, or adult dry mass. However, we did detect a fitness cost affecting adult size. The results of this study will add to the current understanding of field-evolved resistance to Cry3Bb1 corn by western corn rootworm and help in developing better strategies to manage resistance.

scholarly journals Functional validation of DvABCB1 as a receptor of Cry3 toxins in western corn rootworm, Diabrotica virgifera virgifera

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Xiping Niu ◽  
Adane Kassa ◽  
James Hasler ◽  
Samantha Griffin ◽  
Claudia Perez-Ortega ◽  
...  
Keyword(s):  
Resistant Strain ◽  
Insect Pest ◽  
Amino Acid Level ◽  
Diabrotica Virgifera Virgifera ◽  
Western Corn Rootworm ◽  
Hek293 Cells ◽  
Corn Rootworm ◽  
Diabrotica Virgifera ◽  
Functional Validation ◽  
Bt Toxins

Abstract Western corn rootworm (WCR), Diabrotica virgifera virgifera (Coleoptera: Chrysomelidae), is a serious insect pest in the major corn growing areas of North America and in parts of Europe. WCR populations with resistance to Bacillus thuringiensis (Bt) toxins utilized in commercial transgenic traits have been reported, raising concerns over their continued efficacy in WCR management. Understanding the modes of action of Bt toxins is important for WCR control and resistance management. Although different classes of proteins have been identified as Bt receptors for lepidopteran insects, identification of receptors in WCR has been limited with no reports of functional validation. Our results demonstrate that heterologous expression of DvABCB1 in Sf9 and HEK293 cells conferred sensitivity to the cytotoxic effects of Cry3A toxins. The result was further validated using knockdown of DvABCB1 by RNAi which rendered WCR larvae insensitive to a Cry3A toxin. However, silencing of DvABCB2 which is highly homologous to DvABCB1 at the amino acid level, did not reduce the sensitivity of WCR larvae to a Cry3A toxin. Furthermore, our functional studies corroborate different mode-of-actions for other insecticidal proteins including Cry34Ab1/35Ab1, Cry6Aa1, and IPD072Aa against WCR. Finally, reduced expression and alternatively spliced transcripts of DvABCB1 were identified in a mCry3A-resistant strain of WCR. Our results provide the first clear demonstration of a functional receptor in the molecular mechanism of Cry3A toxicity in WCR and confirmed its role in the mechanism of resistance in a mCry3A resistant strain of WCR.

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