Induction of plant physiological responses and growth modulation upon inoculation with Beauveria bassiana (Bals.-Criv.) Vuill. and Metarhizium anisopliae (Metschn.) Sorokin as endophytes in arid and semi-arid zone tree species

• Inoculation with B. bassiana and M. anisopliae boosted root, shoot, biomass, and collar growth. • Endophytes raised phenolics, tannins, and antioxidants, strengthening defenses. • Antioxidant enzymes (CAT, AO, APX) increased, enhancing stress tolerance. • Pongamia pinnata showed highest phenolic and antioxidant boost with M. anisopliae. • EPF act as dual bioinoculants for sustainable forestry and better seedling vigor. Entomopathogenic fungi (EPF) such as Metarhizium anisopliae and Beauveria bassiana are recognized not only for their insect-pathogenic activity but also for their potential as plant growth-promoting endophytes. The present study evaluated their endophytic colonization efficiency, influence on seedling growth, secondary metabolite accumulation, and antioxidative enzyme activities in three arid-region forestry species Tectona grandis, Pongamia pinnata , and Tecomella undulata under two inoculation methods: foliar spray and soil incorporation. Endophytic colonization varied significantly between fungal species and methods, with M. anisopliae exhibiting the highest colonization rate (85.4 % in T. grandis foliar treatment) compared to B. bassiana (61.2 %). Significant improvements in growth performance were recorded, with increases in root length, shoot length, and total biomass over the control at 90 and 180 days after inoculation. Secondary metabolite contents, including total phenols, tannins, ferric reducing antioxidant power and total antioxidant activity increased by 53.9 %, 50.4 %, 45.5 % and 40.6 %, respectively, indicating enhanced metabolic activity. Similarly, antioxidative enzyme activities catalase, ascorbate oxidase, and ascorbate peroxidase showed marked enhancement by 58.6 %, 106.9 %, and 118.5 %, respectively, in M. anisopliae -treated plants relative to control, reflecting improved oxidative stress tolerance. Correlation analysis revealed a strong positive association ( r = 0.72–0.85, p < 0.001) between antioxidant enzyme activities and growth parameters, confirming that enhanced redox metabolism contributed to better growth. The results highlight that M. anisopliae , particularly when applied via foliar inoculation, serves as a superior multifunctional endophyte that enhances physiological vigor, biochemical resilience, and growth performance, demonstrating its potential as an eco-friendly bioinoculant for sustainable management of arid-zone forestry species.