Do Bioinoculants Affect Resident Microbial Communities? A Meta-Analysis

Calvin Cornell,Christina Horst,Andrew Richards,Daniel Rosa,Jonathan A Bennett,Vasilis Kokkoris,Miranda M Hart

doi:10.3389/fagro.2021.753474

Abstract

There is a global industry built upon the production of “bioinoculants,” which include both bacteria and fungi. The recent increase in bioinoculant uptake by land users coincides with a drive for more sustainable land use practices. But are bioinoculants sustainable? These microbes are believed to improve plant performance, but knowledge of their effect on resident microbial communities is scant. Without a clear understanding of how they affect soil microbial communities (SMC), their utility is unclear. To assess how different inoculation practices may affect bioinoculant effects on SMC, we surveyed the existing literature. Our results show that bioinoculants significantly affect soil microbial diversity and that these effects are mediated by inoculant type, diversity, and disturbance regime. Further, these changes to soil microbes affect plant outcomes. Knowledge that these products may influence crop performance indirectly through changes to soil microbial diversity attests to the importance of considering the soil microbiome when assessing both bioinoculant efficacy and threats to soil ecosystems.

Highlights

Bioinoculants are soil additives composed primarily of fungal and/or bacterial isolates, and occasionally contain other abiotic additives (Figure 1)
When we looked at only the cases where diversity changes were detected (Figure 4B), inoculation increased bacterial diversity in 80 and 77% of the cases for no disturbance and chemical disturbance, but decreased bacterial diversity in 89% samples experiencing physical disturbance (F = 8.7935, P = 0.0002851)
Differences in reproduction may mean that fungi are not able to capitalize upon altered conditions as quickly as bacteria (Rousk and Bååth, 2011; Kirchman, 2012)

Summary

Introduction

Bioinoculants are soil additives composed primarily of fungal and/or bacterial isolates, and occasionally contain other abiotic additives (i.e., nutrients, or inorganic/organic carriers) (Figure 1). Inoculation with fungal inoculants can decrease (Koch et al, 2011; Symanczik et al, 2015; Islam et al, 2021), increase (Albertsen et al, 2006), or have no effect on resident fungal diversity (Antunes et al, 2009; Jin et al, 2013; Werner et al, 2014). This inconsistency exists for bacterial inoculants; for example, studies found no

Results

Discussion

Conclusion