# Rhizobium and Mycorrhizal Fungal Species Improved Soybean Yield Under Drought Stress Conditions

## TL;DR

This study shows that using Rhizobium and mycorrhizal fungi together can improve soybean growth and yield under drought conditions, offering a sustainable solution to food insecurity.

## Contribution

The study demonstrates the effectiveness of co-inoculation with Rhizobium and mycorrhizal fungi in enhancing soybean drought tolerance and productivity.

## Key findings

- Co-inoculation with Rhizobium spp. and mycorrhizal fungi significantly improved soybean leaf water content and reduced electrolyte leakage under drought stress.
- Plants inoculated with R1+R3MY showed the highest spore count and mycorrhization percentage across all water regimes.
- R1+R3MY treatment at 40% field capacity promoted soybean growth, pod number, seed number, and seed weight compared to non-inoculated plants.

## Abstract

Food insecurity is a serious threat due to the increasing human population particularly in developing countries and may be minimized by the use of microbial inoculants. Also, the problems of excessive use of chemical fertilizers including the fact that most of the fertilizers are relatively non-affordable and that they also contaminate underground and surface water, which can increase the risk of blue baby syndrome in infants and stomach cancer in adults. There is therefore the need to harness a more cost-effective, eco-friendly and beneficial biological agents to improve crops productivity especially under drought conditions. Thus, in this study, the ability of rhizobia species and arbuscular mycorrhizal fungi (AMF) to enhance soybean tolerance to drought stress under water regimens of 100, 70 and 40% field capacity (FC) was investigated. It was observed that co-inoculation of soybean with Rhizobium spp. (R1+R3) as well as with Rhizobium spp. and mycorrhizal consortium (R1+R3MY) had significant impacts (P < 0.05) on soybean leaf relative water content and electrolyte leakage, respectively. The levels of proline increased mainly in microbially amended soybean exposed to drought stress. Plants inoculated with R1+R3MY showed the highest number of spore and % mycorrhization in all the water regimes. At 40% FC, R1+R3MY treatment was found to promote soybean growth compared to the non-inoculated plants. Similarly, at 40% FC, R1+R3MY inoculum had the greatest impacts on soybean pod number, seed number, seed fresh weight, highest seed number per pod and seed dry weight while at 70% water stress, significant impacts of R1MY inoculation were observed on pod number, pod fresh weight and seed dry weight. These results revealed that co-inoculation of rhizobia and mycorrhizal fungi can be harnessed biotechnologically to proffer solution to food insecurity.