Endophytic Metarhizium brunneum mitigates nutrient deficits in potato and improves plant productivity and vitality

There is growing evidence that entomopathogenic fungi play a role in plant growth promotion as colonizers of internal plant tissues. However, little is known about their potential to mitigate plant abiotic stress. Here, we investigated the influence of soil fertility on Metarhizium brunneum strain CB15 endophytism levels in potato plants linked to plant productivity and vitality. By application of encapsulated M. brunneum, the endophytism level, i.e. % presence of fungus in plant tissue, increased significantly under nutrient poor conditions. This correlated with significantly improved quantum yields of photosystem II. In addition, water use efficiency was increased with higher levels of M. brunneum endophytism. Furthermore, biomass, leaf area, nitrogen and phosphorus contents were enhanced indicating fungal nutrient mobilization and transfer. Our results provide first evidence for the role of entomopathogenic fungi in mitigating nutrient deficits in soil by improving plant productivity and vitality which may increase their use in plant protection strategies.