Inoculating plant growth-promoting bacteria and arbuscular mycorrhiza fungi modulates rhizosphere acid phosphatase and nodulation activities and enhance the productivity of soybean (Glycine max)

Christopher Ngosong; Blaise Nangsingnyuy Tatah; Marie Noela Enyoe Olougou; Christopher Suh; Raymond Ndip Nkongho; Mercy Abwe Ngone; Denis Tange Achiri; Gylaine Vanissa Tchuisseu Tchakounté; Silke Ruppel

doi:10.3389/fpls.2022.934339

Inoculating plant growth-promoting bacteria and arbuscular mycorrhiza fungi modulates rhizosphere acid phosphatase and nodulation activities and enhance the productivity of soybean (Glycine max)

Front Plant Sci. 2022 Sep 26:13:934339. doi: 10.3389/fpls.2022.934339. eCollection 2022.

Authors

Christopher Ngosong¹, Blaise Nangsingnyuy Tatah¹, Marie Noela Enyoe Olougou^{1

2}, Christopher Suh³, Raymond Ndip Nkongho¹, Mercy Abwe Ngone¹, Denis Tange Achiri¹, Gylaine Vanissa Tchuisseu Tchakounté², Silke Ruppel²

Affiliations

¹ Rhizobiology Group, Department of Agronomic and Applied Molecular Sciences, Faculty of Agriculture and Veterinary Medicine, University of Buea, Buea, Cameroon.
² Research Group on Beneficial Microorganisms and Plant Interactions, Leibniz Institute of Vegetable and Ornamental Crops, Großbeeren, Germany.
³ Institute of Agricultural Research for Development (IRAD), Yaoundé, Cameroon.

Abstract

Soybean [Glycine max (L.) Merrill] cultivation is important for its dual role as rich source of dietary protein and soil fertility enhancer, but production is constrained by soil nutrient deficiencies. This is often resolved using chemical fertilizers that exert deleterious effects on the environment when applied in excess. This field study was conducted at Nkolbisson-Yaoundé in the agro-ecological zone V of Cameroon to assess the performance of soybean when inoculated with plant growth-promoting bacteria (PGPB) and arbuscular mycorrhiza fungi (AMF), with or without NPK fertilizer addition. Ten treatments (Control, PGPB, AMF, PGPB+AMF, PGPB+N, PGPB+PK, PGPB+N+PK, PGPB+AMF+N, PGPB+AMF+PK, and PGPB+AMF+N+PK) were established in a randomized complete block design with three replicates. Mycorrhizal colonization was only observed in AMF-inoculated soybean roots. In comparison to control, sole inoculation of PGPB and AMF increased the number of root nodules by 67.2% and 57%, respectively. Co-application of PGPB and AMF increased the number of root nodules by 68.4%, while the addition of NPK fertilizers significantly increased the number of root nodules by 66.9-68.6% compared to control. Acid phosphatase activity in soybean rhizosphere ranged from 46.1 to 85.1 mg h^-1 kg^-1 and differed significantly across treatments (p < 0.001). When compared to control, PGPB or AMF or their co-inoculation, and the addition of NPK fertilizers increased the acid phosphatase activity by 45.8%, 27%, 37.6%, and 26.2-37.2%, respectively. Sole inoculation of PGPB or AMF and their integration with NPK fertilizer increased soybean yield and grain contents (e.g., carbohydrate, protein, zinc, and iron) compared to the control (p < 0.001). Soil phosphorus correlated significantly (p < 0.05) with soybean grain protein (r = 0.46) and carbohydrate (r = 0.41) contents. The effective root nodules correlated significantly (p < 0.001) with acid phosphatase (r = 0.67) and soybean yield (r = 0.66). Acid phosphatase correlated significantly (p < 0.001) with soybean grain yield (r = 0.63) and carbohydrate (r = 0.61) content. Effective root nodules correlated significantly with carbohydrate (r = 0.87, p < 0.001), protein (r = 0.46, p < 0.01), zinc (r = 0.59, p < 0.001), and iron (r = 0.77, p < 0.01) contents in soybean grains. Overall, these findings indicate strong relationships between farm management practices, microbial activities in the rhizosphere, and soybean performance.

Keywords: N2-fixation; P-solubilization; fertilizer; phosphatase; rhizosphere.