Managing Plant-Microbe Interactions in Soil to Promote Sustainable Agriculture

Both plant host and plant diversity have significant effects on rhizosphere microbial composition and diversity, yet it is difficult to distinguish the effects of plant diversity from the effects of individual plant hosts on soil microbes.  To resolve this, we combined PCR with 454 sequencing targeting fungal communities, bacterial communities, and Actinobacterial communities associated with the same four host species grown in plots varying in plant species richness.  Pathogen suppressive activity was also evaluated for each plant host in each plant species richness treatment. 

Impacts of each host plant species all microbial communities varied consistently with plant community richness.  Pathogen suppressive activity of soil microbial communities associated with the same host also varied with plant community richness.  Variation among communities associated with different plant hosts was consistently greater for monocultures than for more diverse plant communities.  Significant relationships between plant community characteristics, soil edaphic characteristics, and microbial community composition and structure suggest that plant host and community effects on soil microbial communities may be mediated through soil nutrient and chemical characteristics.  Soil nutrients were also significantly correlated with inhibitory activities of indigenous Streptomyces.  Plant hosts, by providing distinct soil nutrient and chemical characteristics, play a significant role in selecting for antibiotic phenotypes and pathogen suppression in soil microbial communities.  Plant community diversity significantly influences the selective effects of the plant host on its rhizosphere microflora.