Location: Crop Bioprotection Research
2024 Annual Report
Objectives
Objective 1: Develop effective entomopathogenic fungi for implementation as augmentative biological controls to support integrated pest management systems.
Objective 2: Expand fundamental knowledge of biological interactions between the beneficial pathogens(s), target host pest and crop environment to enhance the production, formulation, and application of beneficial microbial products for sustainable pest management.
Approach
The commercial use of microbial pathogens as biopesticides to manage crop pests continues to be constrained not only by expensive production methods, limited shelf-life, and variable pest control efficacy, but also by a lack of understanding of how basic fungal metabolism affects liquid-culture production in the factory and pest control efficacy in the field. This research project focuses on developing beneficial microbes (predominantly entomopathogenic fungi) as biopesticides and follows a vertical research path from understanding microbe metabolism during liquid culture production through practical formulation processing and integrative application into pest management systems. Although we have empirical data supporting efficient production of beneficial fungi, we still lack a basic understanding of the interaction between physical and nutritional conditions of liquid culture and the basic metabolisms of these organisms. To fill this void, effective microbial biopesticides will be developed by uncovering at the molecular level how entomopathogenic microbes interact with nutritional and environmental conditions present during the production, formulation, and application processes. Gaining this understanding is critical given that these processes likely affect fungal differentiation, biopesticide yield, product stability, and pest control efficacy. Post-production, research will evaluate specific processing and formulation technologies to create a usable product that retains physical characteristics suited for application against targeted pests and is expected to focus on product storage and handling characteristics for sprayable (yeast-like blastospores) and granular (microsclerotia-based) fungal biopesticides. Following application, the host plant environment will be studied to identify interactions among a variety of pest control practices (e.g. crop genetics providing host plant resistance to fungal pathogens) within specific cropping systems. Microbial biopesticides represent an additional tool for the management of crop pests. Non-chemical pest control tools such as these are particularly important for organic, chemically sensitive, and natural environments where few pest control measures are available, and to avoid the development of pesticide resistance to current chemical insecticides and transgenic crops used for pest control. The strategic development of microbial biocontrol agents will enhance the nation’s ability to effectively control pests and support increasingly sustainable crop production.
Progress Report
Objective 1
In support of Sub-objective 1.2, ARS researchers in Peoria, Illinois, completed resequencing of approximately 100 genomes of entomopathogenic fungi from our unit collection, to obtain results with improved accuracy. The respiration pathways of Metarhizium anisopliae, an important entomopathogenic fungus, were also evaluated to establish how this fungus converts fermentation components into energy for growth. The results confirmed specific metal ions and the oxidation state of the fungus are important in signaling changes in the morphology of these fungi during production. Understanding the role and function of these primary metabolic systems is key to the long-term development of entomopathogenic fungi for biological pest control. These experiments are specifically developed to help us understand how the morphology of the fungus is controlled, so we direct it towards preferred morphologies for improved control efficacy. Additionally, we collaborated with scientists from Auburn University to characterize the effects of duplicating a virulence related gene naturally found in this entomopathogenic fungus. The results showed the strain with the duplicated gene was more potent and killed wax moth larvae significantly faster. In another experiment, we used several methods to evaluate the genetic transformation efficiency of several strains of Bacillus velezensis bacteria. These bacterial strains are known to have antimicrobial, insecticidal and nematocidal activities. Understanding how to transform these strains will allow us to make genetic modifications to understand gene function and explore their mode of action.
Objective 2
Under Sub-objective 2.1, we completed an experiment with two strains of entomopathogenic fungi to determine the accessibility of genomic DNA under different production conditions. The goal is to understand how the accessibility of different regions of genomic DNA are used to regulate large changes in metabolism of entomopathogenic fungi. We are interested in understanding how these fungi regulate the morphology they adapt during production, so we can promote more desirable morphologies. We also collaborated with an ARS researcher in Fargo, North Dakota, to isolate and diagnose an entomopathogenic fungus naturally infecting the red sunflower seed weevil. These isolates will be evaluated as potential biopesticides for this damaging pest. Additionally, we isolated entomopathogenic fungi from local farms to create a record of the diversity of fungi present in these farming systems. This fungal inventory will be used in the future to determine how diverse entomopathogenic fungi adapt to farming systems.
In support of Sub-objective 2.2, a time course infection bioassay was conducted with the cabbage looper moth (Trichoplusia ni) and two distinct entomopathogenic fungi to evaluate the expression of fungal-derived secondary metabolites produced during infection and dissemination. This study indicated that some fungal secondary metabolites are not expressed continuously and that variability in expression of these metabolites exists even among individual insects from the same treatment. This information indicates that some other factors associated with the individual insect might play a role in stimulating fungal expression of some secondary metabolite genes. Ongoing studies are elucidating how these metabolites are affecting insect hemolymph, as this is a critical component of insect resistance to fungal infection. This study improves our understanding of the mechanisms and interactions of fungal-based microbial biopesticides with its target insect host.
Performed the first experiment assessing the impact of repeated liquid culture methods on growth and efficacy of entomopathogenic fungi. Continuous production of effective entomopathogenic fungi is critical for economic viability; however, repeated culturing or subculturing methods to grow fungus may reduce its production levels and efficacy. We subjected six fungal isolates to 60 cycles of subculturing and evaluated the effect of continuous subculturing on production and efficacy. Continuous subculturing enhanced the growth and performance of some fungal isolates and negatively impacted the growth and performance of other isolates. These results could guide efforts to cost-effective production of entomopathogenic fungi effective against destructive agricultural pests.
Led collaborative studies to improve the health and yield of mass-reared insects (e.g., black soldier flies, mealworms, and crickets) used for sustainably produced food, feed, fertilizer, and other products. Using robust molecular analyses, we are working to discover novel microbial pathogens causing disease in a population of reared black soldier flies that are used for organic waste upcycling. In addition, we sequenced the genome of the economically important banded cricket Gryllodes sigillatus. This information provides a critical resource for further research into the biology and genetics of this economically important mass-reared insect. These efforts are essential to maintain insects as economically viable sustainable commodities and organic waste management solutions.
In support of Sub-objective 2.3, gene expression was examined in corn hybrids with favorable versus unfavorable combinations of fungal pathogen resistance and fungal insect biocontrol efficacy to determine favorable gene combinations. Once identified and validated, this information could be used to develop new corn hybrids that can be effectively integrated with biocontrol fungi, especially in organic production.
Accomplishments
1. New weapons to fight insect pests. Farmers require a pipeline of new pesticidal compounds to manage insecticide resistance that occurs from the repeated use of a single insecticide. ARS researchers in Peoria, Illinois, analyzed approximately 5,000 microbial genomes from our in-house collection and identified thousands of putative proteins with insecticidal and nematocidal activities. This research has identified putative pesticidal proteins in microbial species not previously known to possess pesticidal activities. Utilization of this research will provide a new resource of biobased pesticides that farmers can use to sustainably manage pests and increase yields and food quality.
2. Discovered a key component of how cabbage loopers defend themselves against fungal infections. Cabbage looper infestations can result in substantial economic losses to farmers due to reduced yields, lower crop quality, and costs associated with pest control. Insect-killing fungi offer an alternative eco-friendly solution to control cabbage loopers. Nevertheless, insects have strong immune systems that can reduce the effectiveness of these fungi. Understanding how insects defend themselves against these fungi can help scientists choose and improve fungi for pest control. ARS researchers in Peoria, Illinois, found that cabbage loopers, a major agricultural pest, boost their immune response by increasing the production of the molecule phenoloxidase when infected by fungi. Future research will focus on weakening this immune response to make fungal pest control more effective
3. Sequenced the banded cricket genome. Insect genome information is critical for future research and efforts to improve the breeding of important insect species, like those raised in large numbers for food, animal feed, and fertilizer. Mass-reared insects provide a sustainable source of nutrients (e.g., protein, fats, vitamins, and minerals) that are increasingly essential to meet the demands for expanding livestock production. Working with universities in the United Kingdom, Australia, and Illinois, ARS researchers in Peoria, Illinois, have sequenced the genome of the banded cricket. This genetic information will help mass-reared insect farms develop better breeding programs and explore possible genetic changes to enhance desirable traits. This also provides an important resource for studying key biological processes, such as immunity and reproduction at a greater detail.
4. Bad corn genes found. Sustainable production of corn is of great importance to the United States economy, producers, end users, and consumers. Insects and diseases cause great losses to corn, so increased resistance to these pests is highly desirable. ARS researchers in Peoria, Illinois, demonstrated that defective genes, which would not produce effective resistance proteins, were widespread in many lines of corn used for breeding. This information will help breeders and seed companies develop commercial varieties with greater insect and disease resistance leading to higher yields and quality.
Review Publications
Dowd, P.F., Johnson, E.T. 2024. Appropriate selection of organic hybrid sweet corn varieties can positively influence both the effectiveness of the insect biological control agent Beauveria bassiana and fungal disease resistance. Organic Agriculture. https://doi.org/10.1007/s13165-024-00453-w.
Duffield, K.R., Rosales, A., Muturi, E.J., Behle, R.W., Ramirez, J.L. 2023. Increased phenoloxidase activity constitutes the main defense strategy of Trichoplusia ni larvae against fungal entomopathogenic infections. Insects. 14(8). Article 667. https://doi.org/10.3390/insects14080667.
Lyon, R.M., Johnson, E.T., Dowd, P.F. 2024. Undesirable protein sequence variations in maize genes that confer resistance to fungal pathogens and insect pests. Plant Gene. 37. Article 100441. https://doi.org/10.1016/j.plgene.2023.100441.
