Endophytic colonization via Cordyceps cateniannulata induces a growth-enhancing effect and increases the resistance of tomato plants against Tetranychus urticae (Koch)

Tetranychus urticae represents an important global agricultural pest capable of inflicting severe damage on numerous fruits, vegetables, and ornamental plants. Cordyceps cateniannulata is traditionally used for direct arthropod control, but its role as an endophyte for indirect pest management is underexplored. Unlike surface applications, it has been suggested that endophytic colonization of entomopathogens protects fungal spores’ viability from environmental stress while combining pest control with plant growth promotion. Seed-soaking and root-drenching, simple and effective methods of microbial colonization, were used to inoculate tomato plants with C. cateniannulata at concentrations of 2 × 10⁶, 2 × 10⁷, and 2 × 10⁸ conidia/mL to assess their effects on seedling growth. Plant growth improved with higher concentrations, with 2 × 10⁸ conidia/mL being optimal for growth. At a concentration of 2 × 10⁸ conidia/mL, the effects of different inoculation methods on C. cateniannulata colonization and two-spotted spider mite growth were monitored. Correlation analysis showed that seed soaking effectively established C. cateniannulata on tomato plants, reducing mite damage. Leaf colonization rates positively correlated with the inhibition of spider mite populations. In C. cateniannulata-inoculated plants, which showed decreased populations of two-spotted spider mites, the activities of antioxidant enzymes, including peroxidase (POD), phenylalanine ammonia-lyase (PAL), superoxide dismutase (SOD), and polyphenol oxidase (PPO), were enhanced, suggesting improved defense responses against mite infestation.