Submitted to: Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2015
Publication Date: 3/4/2015
Citation: Kepler, R.M., Maul, J.E., Ugine, T.A., Cavigelli, M.A., Rehner, S.A. 2015. Community composition and population genetics of insect pathogenic fungi in the genus Metarhizium from soils of a long-term agricultural research system. Environmental Microbiology. DOI:10.1111/1462-2920.12778.
Interpretive Summary: Fungi in the genus Metarhizium are insect pathogens. These fungi may also benefit plant health through plant-fungal interactions occurring in the plant root zone. Genetic diversity of Metarhizium species was evaluated in a long-term agricultural research system established to contrast conventional, no-till and organic cropping management strategies. Four species of Metarhizium were determined by DNA sequences with M. robertsii and M. brunneum predominating. Low genetic diversity was indicated for all species except M. robertsii. Fields under soybean cultivation had statistically greater numbers of Metarhizium than either corn or alfalfa. Plots under chisel-till and organic farming practices rboredstatistically significant greater numbers of Metarhizium, with lower numbers in no-till plots. This information will be useful to plant pathologists and extension personnel researching and applying integrated pest management strategies.
Technical Abstract: Fungi in the genus Metarhizium are facultative pathogens of insects with the capacity to function in other niches, including soil and plant rhizosphere habitats. In agroecosystems, cropping and tillage practices heavily influence soil fungal communities with unknown effects on the distribution of Metarhizium species, whose presence can reduce populations of crop pests. We report results from a cultivation-based survey of Metarhizium in soils within a long-term farming project in the Mid-Atlantic region. Fields under soybean cultivation had higher numbers of Metarhizium colony forming units (CFUs) than corn or alfalfa. Plots under chisel-till and organic farming practices harbored higher numbers of Metarhizium CFUs, with lower numbers in no-till plots. Sequence typing of Metarhizium isolates revealed five species, largely dominated by M. brunneum and M. robertsii. Isolates of M. brunneum were dominated by a single clone when examined with microsatellite markers. In contrast, M. robertsii was found to contain significant diversity, with the majority of isolates belonging to one of two clades. Evidence for sexual recombination was observed in the most abundant clade. These findings illuminate the full breadth of Metarhizium diversity that can inform strategies by which soil Metarhizium populations may be manipulated to exert downward pressure on pest insects and promote plant health.