Hyphal Growth and Conidia Germination Are Induced by Phytohormones in the Root Colonizing and Plant Growth Promoting Fungus Metarhizium guizhouense

Beneficial associations are very important for plants and soil-dwelling microorganisms in different ecological niches, where communication by chemical signals is relevant. Among the chemical signals, the release of phytohormones by plants is important to establish beneficial associations with fungi, and a recently described association is that of the entomopathogenic ascomycete fungus Metarhizium with plants. Here, we evaluated the effect of four different phytohormones, synthetic strigolactone (GR24), sorgolactone (SorL), 3-indolacetic acid (IAA) and gibberellic acid (GA(3)), on the fungus Metarhizium guizhouense strain HA11-2, where the germination rate and hyphal elongation were determined at three different times. All phytohormones had a positive effect on germination, with GA(3) showing the greatest effect, and for hyphal length, on average, the group treated with synthetic strigolactone GR24 showed greater average hyphal length at 10 h of induction. This work expands the knowledge of the effect of phytohormones on the fungus M. guizhouense, as possible chemical signals for the rapid establishment of the fungus–plant association.