Effect of land use and soil organic matter quality on the structure and function of microbial communities in pastoral soils: Implications for disease suppression.

Marie-Joelle Virolle,Bryony E A Dignam,Joy D Van Nostrand,Maureen O’Callaghan,Leo M Condron,George A Kowalchuk,Jizhong Zhou,Steven A Wakelin

doi:10.1371/journal.pone.0196581

Abstract

Cropping soils vary in extent of natural suppression of soil-borne plant diseases. However, it is unknown whether similar variation occurs across pastoral agricultural systems. We examined soil microbial community properties known to be associated with disease suppression across 50 pastoral fields varying in management intensity. The composition and abundance of the disease-suppressive community were assessed from both taxonomic and functional perspectives. Pseudomonas bacteria were selected as a general taxonomic indicator of disease suppressive potential, while genes associated with the biosynthesis of a suite of secondary metabolites provided functional markers (GeoChip 5.0 microarray analysis). The composition of both the Pseudomonas communities and disease suppressive functional genes were responsive to land use. Underlying soil properties explained 37% of the variation in Pseudomonas community structure and up to 61% of the variation in the abundance of disease suppressive functional genes. Notably, measures of soil organic matter quality, C:P ratio, and aromaticity of the dissolved organic matter content (carbon recalcitrance), influenced both the taxonomic and functional disease suppressive potential of the pasture soils. Our results suggest that key components of the soil microbial community may be managed on-farm to enhance disease suppression and plant productivity.

Highlights

Agricultural grasslands are an extensive form of land use and are a key resource in terms of biodiversity and ecosystems services [1]
Across the 50 soils, total bacterial 16S rRNA gene abundance was 4.24 × 107 (± 3.78 × 105) per gram of soil, and the Pseudomonas community represented less than 1% of this total bacterial community
The results of PERMANOVA analyses that partitioned the influences of land use and soil type on bacterial and Pseudomonas community composition showed that land use impacted the structure of both the total bacterial (P = 0.035) and Pseudomonas communities (P = 0.084) (S4 Table)

Summary

Objectives

The aim of this work was not to determine variation within a field, farm, or catchment, but rather to assess changes across wider geographical ranges and with underlying soil properties

Methods

Results

Discussion

Conclusion