Influence of plant diversity and perennial plant identity on <i>Fusarium</i> communities in soil

Abstract

<i>Fusarium</i> communities in soil are highly diverse and may play key functional roles in native and agricultural ecosystems. Despite the diversity and functional relevance of soil <i>Fusarium</i> communities, very little is known about what determines their diversity, structure, and function. This work tested the effects of perennial plant identity and plant community diversity on <i>Fusarium</i> communities in soil. Soil was collected from the rhizosphere of native perennial legumes and grasses growing in monoculture and polyculture at the Cedar Creek, Long Term Ecological Research site in Minnesota, USA. To characterize <i>Fusarium</i> communities, soil DNAs were used to create and pyrosequence amplicon libraries from a single copy protein-coding locus (RPB2). For functional characterization, individual isolates of <i>Fusarium</i> were cultured from the same soil. A portion of the RPB2 locus was sequenced for phylogenetic characterization of each isolate. Isolates were also tested for carbon use as measured by growth on 95 carbon substrates using Biolog phenotype arrays, and for the capacity to produce multiple secondary metabolites as measured using a PCR assay developed from genomic resources. <i>Fusarium</i> communities were influenced by plant diversity and perennial plant identity. <i>Fusarium</i> community structure was differentiated between monoculture and polyculture plant communities and by plant species in monoculture. Drivers of the richness within Fusarium communities were lineage specific; one lineage showed a positive response to soil edaphic characteristics and another a negative response. Cultured <i>Fusarium</i> isolates from the same soil showed isolates from rhizosphere soil of the legume <i>L. capitata</i> used more carbon substrates than isolates from the grass <i>A. gerardii</i>. Phylogenetic characterization showed that isolates within a given phylogenetic clade displayed more similar carbon use profiles than isolates between different clades, highlighting functional consequences of changes in the communities of the these fungi in response to plants. Screening for genes underlying the production of secondary metabolites in the <i>Fusarium</i> isolates showed the genetic potential to produce the plant hormones indoleacetic acid or gibberellic acid was correlated with reduced fungal growth.