Location: Crop Bioprotection Research
2020 Annual Report
Objectives
Objective 1. Utilizing transcriptomics to link gene function to fungal morphogenesis, develop liquid culture methods for producing propagules of fungal biocontrol agents such as Metarhizium spp., Beauveria bassiana, and Mycoleptodiscus terrestris by optimizing nutritional and environmental conditions during fungal growth for optimal biocontrol efficacy and storage stability to control pests in agricultural, urban, and natural ecosystems.
Objective 2. Develop novel fungal formulation technologies through the selection and application of innovative processes and ingredients that lead to improved storage stability, product delivery, field stability, and efficacy of fungal pathogens for biocontrol of insects [Beauveria bassiana, Metarhizium spp., and Isaria fumosorosea] and weeds [Mycoleptodiscus terrestris].
Subobjective 2A: Evaluate the compatibility of improved entomopathogen formulations with representative corn pest resistance mechanisms for control of sweet corn pests.
Objective 3. Identify, chemically and behaviorally characterize, and deploy natural insect semiochemicals (pheromones/kairomones and plant volatiles) with microbial biocontrol agents for management of important agricultural insect pests such as brown marmorated stink bug and coffee berry borer.
Approach
Our approach to the development of production methods for fungal biocontrol agents will focus on the use of liquid fermentation techniques. We will identify defined or semi-defined media that support the growth of our fungal biocontrol agents. Propagule form yield, storage stability, and biocontrol efficacy are critical “fitness” factors that will be considered during medium optimization. Initially, we will focus on producing propagules of fungal biocontrol agents such as Metarhizium spp, Beauveria bassiana, and Mycoleptodiscus terrestris. We also will use transcriptomics to identify pathways that may impact these factors. We will evaluate the impact of culture harvest techniques, stabilization processes, and formulation ingredients on the physical characteristics, biological activity, storage stability, and field efficacy of selected biocontrol agents. Also, we will identify and chemically characterize insect attractants and deterrents and evaluate formulations for management of important agricultural insect pests such as the brown marmorated stink bug, coffee berry borer, polyphagous shot hole borer, and tea shot hole borer.
Progress Report
This is the final report for Project 5010-22410-017-00D. Under Objective 1 to utilize transcriptomics to link gene function to fungal morphogenesis and develop methods for producing propagules of fungal biocontrol agents, ARS scientist in Peoria, Illinois, in collaboration with Brazilian scientists investigated gene expression of the entompathogen Beauveria bassiana during liquid culture conditions that promote the formation of blastospores. The goal was to understand the genes involved in determining the morphology of the fungus during liquid culture production. The ability to manipulate the fungal morphology is critical in developing large scale production that would favor blastospores, which are desired for biopesticide products. This study provided novel insights into the metabolic status of the fungus during the liquid culture process and identified alternative oxidase pathways to be highly active during this process. Knowledge developed during this study of these pathways will be the subject of in-depth studies during the next project cycle to support the development of liquid culture fermentation technology to produce fungal entomopathogens.
ARS scientists from Peoria, Illinois and Byron, Georgia, along with University of Georgia scientists, developed liquid culture techniques to produce blastospores of a new strain of the insect pathogenic fungus Isaria javanica, which was collected from infected whiteflies in a Georgia cotton field during the summer of 2017. Studies showed the new strain produced spore numbers that were comparable with those produced by a commercial Isaria strain in liquid culture when using varied media. Insecticidal efficacy in laboratory and field experiments demonstrated the benefits of this strain and supported the submission of a patent application for this new strain of beneficial fungus.
In related research, a newly identified strain of bacteria was characterized for insecticidal efficacy as biological control agents of insects. In collaborative research between ARS researchers (Peoria, Illinois and Columbia, Missouri) and Johns Hopkins University, experiments assessed the insecticidal activity of a bacterium against important agricultural pests. ARS scientists discovered that this bacterium can significantly affect the longevity of the insecticide-resistant western corn rootworm. This discovery opens us the potential development of a new bioinsecticide in the fight against insecticide resistance in an important agricultural pest.
Though crickets are generally considered an agricultural pest, commercial rearing of crickets as a high protein food source for animal feed and human consumption is a growing industry in the United States. Thus, microbial pathogens that cause disease in cricket rearing facilities can impose substantial damage and reduce production. ARS scientists in Peoria, Illinois, collaborated with Illinois State University researchers to identify microbial pathogens affecting colony reared crickets. Several microbial isolations and molecular tests have identified several bacteria species with potential to infect crickets. Experiments to confirm the pathogenicity of these bacteria are underway. Identification of disease agents is needed to improve commercial production of crickets, but also offers potential for development as beneficial bacteria for control of cricket species that are agricultural pests.
Under Objective 2 to develop novel formulation technologies for fungal control of insects, an ARS scientist at Peoria, Illinois, tested representative compounds for benefits as formulation ingredients with fungal bio-insecticides when applied to crop with resistance to plant pathogen. Host plant resistance provides crop plants with defenses intended to combat plant fungal diseases, but these defenses have been shown to also interfere with the beneficial fungal biopesticides applied to control insect pests. Ingredients that are generally regarded as safe were evaluated for their ability to specifically counteract these plant defenses. One compound significantly increased the efficacy of the beneficial Beauveria bassiana fungus by increasing mortality of Lepidoptera larvae feeding on treated leaves from a corn line with plant pathogen resistance. Another compound significantly increased the ability of the Beauveria fungus to grow on the damaged leaf surface, providing a potential source for secondary infection of insect pests. The addition of these types of compounds could potentially enhance the efficacy and duration of insect diseases used for pest control.
In research on control of plant disease, two genes were identified in corn that are associated with resistance to plant fungal disease. ARS scientist discovered that when the two genes were expressed together in transgenic corn, the plants expressed increased resistance to diseases when leaves inoculated with the corn diseases pathogens. If successfully applied to commercial corn hybrids, these genes could reduce diseases caused by these fungi and accumulation of their toxins, resulting in better quality and safer corn for commercial users and consumers.
Accomplishments
1. Fungal bioinsecticide for control of soil insects. The corn rootworm is an important pest of corn that feeds on roots, costing an estimated $1 billion annually in damage and control costs in the United States. ARS scientists in Peoria, Illinois, previously developed a liquid culture technique to produce specialized fungal structures known as microsclerotia, which are naturally suited for the soil environment. This patented production technology for the insect killing Metarhizium fungus was then licensed for commercial production and is now being developed by an international seed producer to control rootworms. Metarhizium microsclerotia liquid culture production techniques were applied to new fungal isolates identified by the seed company. ARS scientists continue to consult with the industrial partners to develop these isolates as an environmentally friendly pest control that is needed to prevent insect resistance to current control practices.
2. Corn varieties affect biocontrol efficacy of insect pathogens. Insect pathogens have potential for safe insect control, but factors that limit their efficacy or consistency are not well understood. Several corn inbred lines with varying resistance to plant disease fungi were evaluated by ARS scientists in Peoria, Illinois, for their effect on the efficacy of two different commercial strains of an insect fungal pathogen on two major insect pests of corn. Great differences were noted between the rate of efficacy of both fungal biocontrol strains on both pests for some corn inbreds versus others, which also impacted the amount of damage that occurred by the insect pests. This information indicates the importance of considering the plant aspect when developing integrated pest management strategies that involve insect diseases, which suggests insect disease efficacy should be considered as a factor when developing new crop varieties.
3. Discovery of new entomopathogens for control of agricultural pests. The current rise of insecticide resistance in several agricultural pests only heightens our need for alternative methods of pest control. Microbial control offers an environmentally friendly alternative by using microbes that are lethal to those pests, including those that have already developed resistance to insecticides. ARS scientists in Peoria, Illinois, in collaboration with Johns Hopkins University scientist have tested a recently isolated bacteria for its ability to kill a range of agricultural pests. Laboratory tests have confirmed the ability of this bacterium to kill the most important insect pest of corn, the western corn rootworm, and affect the longevity of several others. Proper development of this bacteria as a pest control technology will provide a new biocontrol product for crop protection, supporting both the biopesticide industry and producers in need of non-chemical crop protection.
Review Publications
Dowd, P.F., Naumann, T.A., Johnson, E.T., Price, N.P.J. 2020. A maize hydrolase with activity against maize insect and fungal pests. Plant Gene. 21:100214. https://doi.org/10.1016/j.plgene.2019.100214.
Sayed, A.M.M., Dunlap, C.A. 2019. Virulence of some entomopathogenic fungi isolates of Beauveria bassiana (Hypocreales:Cordycipitaceae) and Metarhizium anisopliae (Hypocreales:Clavicipitaceae) to Aulacaspis tubercularis (Hemiptera:Diaspididae) and Icerya seychellarum (Hemiptera:Monophlebidae) on mango crop. Journal of Economic Entomology. 112(6):2584-2596. https://doi.org/10.1093/jee/toz187.
Dowd, P.F., Johnson, E.T. 2020. Transgenic expression of a previously uncharacterized maize AIL1 gene in maize callus increases resistance to multiple maize fungal and insect pests. Plant Gene. 23:100235. https://doi.org/10.1016/j.plgene.2020.100235.
Burkett-Cadena, M., Sastoque, L., Cadena, J., Dunlap, C.A. 2019. Lysinibacillus capsici sp. nov, isolated from the rhizosphere of a pepper plant. Antonie van Leeuwenhoek. 112:1161-1167. https://doi.org/10.1007/s10482-019-01248-w.
Dunlap, C.A. 2019. Lysinibacillus mangiferihumi, Lysinibacillus tabacifolii and Lysinibacillus varians are later heterotypic synonyms of Lysinibacillus sphaericus. International Journal of Systematic and Evolutionary Microbiology. 69(9):2958-2962. https://doi.org/10.1099/ijsem.0.003577.
Price, N.J.P., Jackson, M.A., Singh, V., Hartman, T.M., Dowd, P.F., Blackburn, J.A. 2019. Synergistic enhancement of beta-lactam antibiotics by modified tunicamycin analogs TunR1 and TunR2. Journal of Antibiotics. 72(11):807-815. https://doi.org/10.1038/s41429-019-0220-x.
