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ARS Home » Southeast Area » Byron, Georgia » Fruit and Tree Nut Research » Research » Publications at this Location » Publication #411402
Research Project: Novel Approaches for Managing Key Pests of Peach and Pecan

Location: Fruit and Tree Nut Research

Title: Thiourea as a Polyphenoloxidase Inhibitor Enhances Host Infection by the Entomopathogenic Nematode, Heterorhabditis beicherriana

Author
item LI, XINGYUE - Sichuan Academy Of Agricultural Science
item Shapiro Ilan, David
item TARASCO, EUSTACHIO - University Of Bari
item QIZHI, LIU - China Agricultural University
item YANG, WUYUN - Sichuan Academy Of Agricultural Science
item YI, JUN - Sichuan Academy Of Agricultural Science
item CHENG, CHEN - Sichuan Academy Of Agricultural Science
item ZHANG, HONG - Sichuan Academy Of Agricultural Science
item FU, HUIJUAN - Sichuan Academy Of Agricultural Science

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/21/2024
Publication Date: 2/27/2024
Citation: Li, X., Shapiro Ilan, D.I., Tarasco, E., Qizhi, L., Yang, W., Yi, J., Cheng, C., Zhang, H., Fu, H. 2024. Thiourea as a Polyphenoloxidase Inhibitor Enhances Host Infection by the Entomopathogenic Nematode, Heterorhabditis beicherriana. Biological Control. 191/105474. https://doi.org/10.1016/j.biocontrol.2024.105474.
DOI: https://doi.org/10.1016/j.biocontrol.2024.105474

Interpretive Summary: Beneficial nematodes (also known as entomopathogenic nematodes) are small round worms that are used as natural biopesticides. Unlike many chemical insecticides that are toxic to humans, other nontarget organisms, and the environment, beneficial nematodes only kill insects and are considered safe to the environment. However, field efficacy when using beneficial nematodes is not always as high as needed to suppress the target pest. Therefore methods to improve efficacy of beneficial nematodes are needed. Once the beneficial nematodes enter the body of an insect, the insect mounts an immune response. Hence, one approach to improve beneficial nematode efficacy may be to thwart the insect immune system. We discovered that a chemical compound, thiourea, can be used in conjunction with the beneficial nematodes to suppress the insect immune system and thereby enhance biocontrol efficacy. This new approach of combining immune suppressant compounds and beneficial nematodes has great promise for increasing the efficacy of beneficial nematodes as natural biopesticides.

Technical Abstract: Entomopathogenic nematodes are potent microbial biocontrol agents that have been applied commercially against a wide array of economically important insect pests. However, in some cases, entomopathogenic nematode field efficacy is reduced relative to chemical insecticides partially due to the nematode’s sensitivity to environmental stress. Thus, research to develop mechanisms to enhance biocontrol efficacy in entomopathogenic nematodes is warranted. This study leveraged physiological mechanisms within the host-pathogen relationship to improve virulence. Specifically, we used thiourea as polyphenol oxidase inhibitors to improve entomopathogenic nematode efficacy. To investigate the effects of thiourea on polyphenol oxidase activity inhibition and entomopathogenic nematode pathogenesis, we studied the effects of thiourea on survival, infectivity, reproduction, and host searching ability of the entomopathogenic nematode, Heterorhabditis beicherriana, and monitored in vivo and in vitro polyphenol oxidase activity of the model insect host, Galleria mellonella. The survival of H. beicherriana infective juveniles was barely affected after exposure to 0.5mM and 1 mM thiourea solution, and reproductive output of H. beicherriana infective juveniles (after applying 50, 100 and 200 infective juveniles per host) in 0.5 mM and 1 mM thiourea was not different compared to the control. However, the LD50 of G. mellonella larvae caused by H. beicherriana without thiourea was significantly higher than H. beicherriana infective juveniles in thiourea. Moreover, thiourea inhibited in vivo and in vitro polyphenol oxidase activity of G. mellonella infected by entomopathogenic nematode at different concentration. Thus, thiourea can improve the biological control efficacy of entomopathogenic nematodes and the enhanced environmentally friendly approach may be applicable to diverse cropping systems.