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ARS Home » Pacific West Area » Salinas, California » Crop Improvement and Protection Research » Research » Publications at this Location » Publication #380214

Research Project: Management of Pathogens for Strawberry and Vegetable Production Systems

Location: Crop Improvement and Protection Research

Title: Spontaneous changes in somatic compatibility in Fusarium circinatum

item GORDON, THOMAS - University Of California
item Henry, Peter
item JENNER, BRADLEY - University Of California
item SCOTT, JENESS - Oregon State University

Submitted to: Fungal Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/28/2021
Publication Date: 5/3/2021
Citation: Gordon, T.R., Henry, P.M., Jenner, B.N., Scott, J.C. 2021. Spontaneous changes in somatic compatibility in Fusarium circinatum. Fungal Biology. 12(9):725-732.

Interpretive Summary: Filamentous fungi grow by the extension of “hyphae,” which are thread-like cells that can absorb nutrients. These hyphae can also fuse together, which facilitates the exchange nutrients, but can also lead to viral transmission between cells. Fungi only fuse their hyphae with closely related strains that share the same genes governing fusion. Genetic barriers to fusion are thought to have evolved in response to selection pressures exerted by parasitism, because virus transmission is restricted when hyphae do not fuse. However, the mechanisms that generate diversity in the genes that restrict fusion are not well understood for asexual fungi. We hypothesized that somatic mutations in these genes could generate fusion incompatibility between strains. We found that by mutations in fusion incompatibility genes could occur at a rate of 5 and 8 per million spores.

Technical Abstract: Filamentous fungi grow by the elaboration of hyphae, which may fuse to form a network as a colony develops. Fusion of hyphae, also referred to as anastomosis, can occur between genetically different individuals, provided they share a common allele at loci affecting somatic compatibility. If not, anastomosis is restricted or prevented. Genetic barriers to anastomosis can reduce the risk of virus transmission; diversity among somatic compatibility phenotypes can therefore have a protective effect against parasitism. Meiosis can increase the diversity of somatic compatibility phenotypes by recombining the alleles governing compatibility, but it may not fully account for the diversity of this phenotype observed in nature. For example, previous work has documented multiple somatic compatibility groups of Fusarium circinatum to be associated with the same multi-locus haplotype, which implies they arose by mutation rather than recombination through sexual reproduction. We tested the hypothesis that changes in somatic compatibility could occur through somatic mutation and confirmed that spontaneous changes in somatic compatibility can occur at a frequency between 5 and 8 per million spores. Genomic analysis of strains with altered somatic compatibility revealed no consistent evidence of recombination and supported the hypothesis that spontaneous mutations generated the observed phenotypic changes. Genes known to be involved in somatic compatibility had no mutations, indicating that mutations occurred in a gene with an as-yet unexplored function in somatic compatibility.