Beyond Biocontrol: Species‐Dependent Growth Promotion of Forage Grasses by Metarhizium anisopliae Isolates

ABSTRACT

Research on the interaction between entomopathogenic fungi used in biological control programs and forage grass species remains limited. This study evaluated the effects of inoculating seedlings of the forage grass species Axonopus catharinensis cv. SCS315 Catarina Gigante, Hemarthria altissima cv. Florida, and Cynodon dactylon cv. Tifton 85 with five native and two commercial isolates of Metarhizium anisopliae . Plant growth responses varied according to both fungal isolate and forage species. In C. dactylon and A. catharinensis , specific isolates significantly increased leaf and root fresh and dry biomass, leaf number, and plant height. In contrast, similar positive effects were generally not observed in H. altissima , in which some isolates even reduced certain growth parameters. Considering overall plant performance (shoot and root traits combined), isolates CEPAF_ENT25, CEPAF_ENT27, and IBCB425 were particularly effective in promoting growth of A. catharinensis and C. dactylon . Root inoculation successfully established a fungal‐plant interaction, as Metarhizium spp. were recovered from all evaluated plant tissues (roots, stems, and leaves), with higher colonization frequencies in roots. Although all isolates were reisolated from the substrate, recovery rates decreased over time. These findings demonstrate substantial variability in plant growth‐promoting effects among M. anisopliae isolates and differential responsiveness among forage species. The results highlight the potential of selected isolates as multifunctional biological agents for sustainable pasture systems.