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Isolation and Characterization of a Native Metarhizium rileyi Strain Mrpgbm2408 from Paralipsa gularis in Maize: First Data on Efficacy and Enzymatic Host Response Dynamics
by
, , ,
Yunhao Yao
1,
Kaiyu Fu
1,
Xiaoyu Wang
1,
Guangzu Du
1,
Yuejin Peng
1,
Guy Smagghe
2,3
,
Wenqian Wang
1,* and
Bin Chen
1,* 1
College of Plant Protection, Yunnan Agricultural University, Kunming 650201, China
2
Institute of Entomology, Guizhou University, Guiyang 550025, China
3
Department of Biology, Vrije Universiteit Brussel (VUB), 1050 Brussels, Belgium
*
Authors to whom correspondence should be addressed.
Insects 2025, 16(9), 872; https://doi.org/10.3390/insects16090872
Submission received: 24 July 2025
/
Revised: 13 August 2025
/
Accepted: 22 August 2025
/
Published: 22 August 2025
Simple Summary
In this study, we report, for the first time, the agricultural pest Paralipsa gularis naturally infected with the fungus Metarhizium sp. Molecular analysis using ITS and EF-1α sequences identified the strain as Metarhizium rileyi, which we named M. rileyi Mrpgbm2408. Laboratory tests showed that the strain grew best on SMAY medium under continuous light at 25 °C. It also displayed strong virulence against P. gularis. We found that protective and detoxifying enzymes in the pest played a role in defending against infection by M. rileyi Mrpgbm2408. These findings highlight the potential of this fungal strain as a biological control agent, offering promising implications for reducing crop losses, lowering economic damage, and supporting environmental sustainability.
Abstract
Paralipsa gularis (Zeller) has become an increasingly destructive pest in both storage and field ecosystems, particularly affecting maize crops across China. As chemical control methods face limitations due to resistance development and environmental concerns, biological control presents a promising alternative. In this study, we isolated and identified a novel strain of Metarhizium sp. from naturally infected P. gularis larvae collected in Yunnan Province, China. Morphological characterization, along with ITS-rDNA and EF-1α-rDNA sequencing, confirmed the fungus as Metarhizium rileyi. The optimal growth medium for this strain was SMAY, and the optimal conditions were 25 °C under continuous light (L:D = 24:0). Laboratory bioassays showed that the strain exhibited high virulence against P. gularis larvae, with cumulative mortality reaching 82% following infestation with 5 × 108 conidia/mL. Biochemical analyses revealed that fungal infection significantly inhibited the activity of the key antioxidant enzyme SOD in the host, while activities of POD, CAT, and detoxification enzymes (P450, CarE, AChE, and GSTs) were significantly increased. These results indicate that immune responses were triggered, and systemic colonization of the host was achieved. Overall, this native M. rileyi strain demonstrates strong potential as an effective biological control agent. Its ability to overcome insect defenses and induce high mortality supports its integration into pest management programs targeting P. gularis. This work advances the understanding of fungal–insect interactions and contributes to sustainable, environmentally safe strategies for managing a pest of economic importance in agricultural ecosystems.
