Effects of Rhizophagus intraradices on Plant Growth and the Composition of Microbial Communities in the Roots of Continuous Cropping Soybean at Maturity

Soybean is the major food and oil crop in the world. However, soybean continuous cropping can significantly reduce soybean yield. In this study, the effects of Rhizophagus intraradices on soybean growth and the composition of microbial communities in soybean roots under different continuous cropping regimes were investigated at maturity. The results showed that the mycorrhizal colonization rate was affected by R. intraradices and soybean continuous cropping. The mycorrhizal colonization rate was the highest in the inoculated soybean plants under 1 year of continuous cropping. Inoculation of R. intraradices significantly increased soybean plant growth. The greatest biomass parameters were obtained from the soybean plants inoculated with R. intraradices under 0 years of continuous cropping. Bacterial diversity was decreased by soybean continuous cropping, while the opposite result occurred for fungal diversity. Moreover, inoculation of R. intraradices could increase and decrease the diversity of bacteria and fungi in soybean roots, respectively. It also indicated that R. intraradices and soybean continuous cropping had significant effects on the composition of microbial communities in soybean roots. Proteobacteria and Ascomycota were the most dominant bacterial and fungal phylum in all samples, respectively. It would contribute to developing a biocontrol strategy to alleviate the soybean continuous cropping obstacles.