Fungal endophytes inoculation improves soil nutrient availability, arbuscular mycorrhizal colonization and common bean growth

Some fungal isolates affect soil by solubilizing nutrients and promoting plant growth; however, little is known about the effects of applications of these isolates on soil biology and fertility. Thus, the aim of the present study was to identify the effect of five well-known fungal endophytes, namely, Beauveria bassiana, Trichoderma asperellum, Metarhizium anisopliae, Purpureocillium lilacinum and Pochonia chlamydosporia on plant growth and the biological and chemical properties of the rhizosphere soil under Phaseolus vulgaris L. Spore suspensions from each of the five fungal isolates and three consortia (T. asperellum/P. lilacinum; B. bassiana/M. anisopliae; and a consortium of all five species) were applied to seeds, soil and shoots of common bean plants in a greenhouse assay. All fungal treatments resulted in greater root colonization by arbuscular mycorrhizal fungi (53.6% of root length in control and 66.6%-77.0% in the remaining treatments), concentration of rhizosphere soil magnesium (10%- 33% higher than the control) and base saturation of cation exchange capacity (48.5% in control and 50.7%- 55.1% in all other treatments). Applications of B. bassiana/M. anisopliae and of the consortium of five fungal isolates increased fluorescein diacetate hydrolysis (FDA) by 63% and 72% respectively, relative to the control. beta-Glucosidase activity was lower in the applications of T. asperellum (20% lower), P. chlamydosporia (15% lower) and B. bassiana/M. anisopliae (18% lower) than in the control. Acid phosphatase was lower in the M. anisopliae (29%), P. chlamydosporia (22%) and T. asperellum/P. lilacinum (21%) and B. bassiana/M. anisopliae consortia (27%) treatments. Some fungal isolate applications stimulated shoot accumulations of N, P, B, Cu, Fe, Mn and Zn (mass). Applications of B. bassiana, T. asperellum, M. anisopliae, P. chlamydosporia and the consortium of five fungal isolates resulted in higher root dry mass relative to the control, while treatments of P. lilacinum, the B. bassiana/M. anisopliae consortium and the five fungal isolates resulted in higher dry shoot weight. Arylsulfatase activity and phosphate solubilizing fungi were not affected by the treatments. The values of the rhizosphere soil chemical and biological, accumulated nutrient mass and plant growth variables were highest in the (A) five fungi consortium, followed, in descending order, by (B) the B. bassiana/M. anisopliae consortium; (C) T. asperellum, B. bassiana and M. anisopliae; and (D) the T. asperellum/P. lilacinum consortium, P. lilacinum and P. chlamydosporia. These findings may benefit sustainable agricultural management systems that use fungal isolate treatments to eliminate or reduce the environmental impacts of mineral fertilizers and pesticides.

Automated summary

The study found that applications of fungal endophytes can promote plant growth, increase root colonization and improve some soil chemical and biological properties, highlighting the potential to reduce the environmental impact of mineral fertilizers and pesticides.