Impact of Plant-Beneficial Bacterial Inocula on the Resident Bacteriome: Current Knowledge and Future Perspectives

Abstract

The inoculation of plant growth-promoting bacteria (PGPB) as biofertilizers is one of the most efficient and sustainable strategies of rhizosphere manipulation leading to increased plant biomass and yield and improved plant health, as well as the ameliorated nutritional value of fruits and edible seeds. During the last decades, exciting, but heterogeneous, results have been obtained growing PGPB inoculated plants under controlled, stressful, and open field conditions. On the other hand, the possible impact of the PGPB deliberate release on the resident microbiota has been less explored and the little available information is contradictory. This review aims at filling this gap: after a brief description of the main mechanisms used by PGPB, we focus our attention on the process of PGPB selection and formulation and we provide some information on the EU regulation for microbial inocula. Then, the concept of PGPB inocula as a tool for rhizosphere engineering is introduced and the possible impact of bacterial inoculant on native bacterial communities is discussed, focusing on those bacterial species that are included in the EU regulation and on other promising bacterial species that are not yet included in the EU regulation.

Survival of a microbial inoculant in soil after recurrent inoculations

“…Numerous studies have assessed the impact of single microbial inoculation on the resident soil community 24 but less is known about the impact of recurrent inoculations. Despite the fact that the recurrent inoculation also increased the number of invaders, we did not observe any significant effect of the recurrent inoculation sequences on either the composition or the diversity of the resident soil bacterial community.…”

“…While diversity and composition of the resident community modulate invasion success, invaders generally affect this resident community in return 23 , 24 , with both compositional and functional changes, including shifts in nitrogen cycling 25 – 27 . In addition, the impact of microbial inoculations on the resident soil microbial communities has often been overlooked despite calls for a more comprehensive assessment of the consequence of microbial inoculation 28 , 29 .…”

Improving Grapevine Heat Stress Resilience with Marine Plant Growth-Promoting Rhizobacteria Consortia

“…Bacteria selection and consortia design is a key determinant of the effectiveness of the bacterial inoculant and the finished product itself. Thus, a knowledge-based solution for this formulation or an experience repository is being debated to maximize research efficacy [95]. Furthermore, long-term ecological implications for the use of allochthonous bacteria as agro-inoculants have not been reported.…”

Microalgal and Nitrogen-Fixing Bacterial Consortia: From Interaction to Biotechnological Potential

“…The free-living diazotrophs belonging to the Azospirillum genus are a group of plant rhizosphere bacteria that have been widely recognized as model PGPB due to their positive impact on plant growth, crop yields, and nitrogen content [53]. Bacteria belonging to this genus synthesize one polar flagellum during growth in liquid medium, primarily used for swimming towards optimal oxygen concentrations, a behavior known as aerotaxis [54].…”