Unlocking the Biocontrol Potential of Indigenous Soil Fungi: High-Performing Strains of Beauveria bassiana and Metarhizium robertsii Against the Tomato Leafminer Tuta absoluta

The invasive tomato leafminer, Tuta absoluta, poses a severe global threat to solanaceous crops, necessitating sustainable biocontrol solutions. Through systematic bioprospecting across several Moroccan soils, we constructed a novel library of indigenous fungal isolates using complementary Tenebrio molitor baiting and selective media methods. High-throughput phenotyping identified 49 highly pathogenic isolates, which were characterized for conidial production, thermotolerance, and virulence against T. absoluta. We discovered two lead isolates, Beauveria bassiana UCA-350 and Metarhizium robertsii UCA-329, that demonstrated superior virulence, reducing median survival time and achieving lower LC50 values than most commercial reference strains. Notably, virulence was positively correlated with in vitro conidial yield, revealing a key trait linkage for strain selection. Furthermore, genus-level divergence in thermotolerance was observed, with Beauveria isolates exhibiting significantly higher heat resilience. Our integrated multi-trait screening pipeline not only delivers two potent, regionally sourced biocontrol candidates but also establishes a phenotypic selection framework that prioritizes both efficacy and production scalability, advancing the rational development of next-generation mycoinsecticides.