Comparative Analysis of Photorhabdus luminescens Strains for Biological Control of Tetranychus truncatus: Novel Insights from Strain 2103-RUVI

The increasing resistance of agricultural pests to conventional pesticides necessitates the development of alternative biological control strategies. This study evaluated the acaricidal potential of two Photorhabdus luminescens strains (0805-P2R and the newly isolated 2103-RUVI) against the spider mite Tetranychus truncatus. Culture conditions were optimized using a Taguchi L9(34) design to maximize growth, protease activity, and acaricidal efficacy. The optimized medium for strain 2103-RUVI achieved 90% mortality against T. truncatus at 72 h, compared to 83% for strain 0805-P2R under equivalent conditions. Genomic analysis identified putative phosphoporin PhoE genes exclusively in 2103-RUVI, which may contribute to its enhanced virulence, although this association remains correlative and requires functional validation. Histopathological observations confirmed severe tissue disruption in treated mites. Comparative analysis demonstrated complex, strain-specific relationships among bacterial growth, enzyme activity, and acaricidal effects. These results highlight the potential of the P. luminescens strain 2103-RUVI as an effective biocontrol agent, providing insights for its application in sustainable integrated pest management programs.