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Summary: Plant‐derived volatiles mediate interactions among plants, pathogenic viruses, and viral vectors. These volatile‐dependent mechanisms have not been previously demonstrated belowground, despite their likely significant role in soil ecology and agricultural pest impacts. We investigated how the plant virus, tobacco rattle virus (TRV), attracts soil nematode vectors to infected plants.We infected Nicotiana benthamiana with TRV and compared root growth relative to that of uninfected plants. We tested whether TRV‐infected N. benthamiana was more attractive to nematodes 7 d post infection and identified a compound critical to attraction. We also infected N. benthamiana with mutated TRV strains to identify virus genes involved in vector nematode attraction.Virus titre and associated impacts on root morphology were greatest 7 d post infection. Tobacco rattle virus infection enhanced 2‐ethyl‐1‐hexanol production. Nematode chemotaxis and 2‐ethyl‐1‐hexanol production correlated strongly with viral load. Uninfected plants were more attractive to nematodes after the addition of 2‐ethyl‐1‐hexanol than were untreated plants. Mutation of TRV RNA2‐encoded genes reduced the production of 2‐ethyl‐1‐hexanol and nematode attraction.For the first time, this demonstrates that virus‐driven alterations in root volatile emissions lead to increased chemotaxis of the virus's nematode vector, a finding with implications for sustainable management of both nematodes and viral pathogens in agricultural systems. [ABSTRACT FROM AUTHOR]

Within soils there are microorganisms that act to break down complex substrates (saprophytes), microorganisms that actively aid nutrient delivery (mycorrhizal fungi and nitrogen-fixing bacteria), and others that hijack the system to their own benefit (parasitic bacteria and fungi). The complex interaction between plants, these microbes, and the soil determines how effectively nutrients will be recycled, with a significant impact on regional productivity and biodiversity. Each microbe plays a role in overall soil function but, despite the critical role they play, soil microbial communities and their functions remain challenging to accurately quantify. The functional behaviour of soils is difficult to quantify, in part due to the effects of disturbance when sampling. This suggests that noninvasive analytical tools are necessary to diagnose current soil function and to predict changes in soil behaviour with changing climate or land use. Microbial communities, the drivers of soil function, are diverse, and their individual metabolisms are often tightly coupled, such that the microbial community in aggregate may be considered to have a "net" metabolism. This net metabolism can be described by the volatile signatures that propagate from the soil into the atmosphere and, by proxy, allowing a noninvasive analysis of the microbial community active in the subsurface. Here, we detail the complexities of the soil volatile metabolism, propose a "fingerprint" strategy to describe this complex community that uses trace gas fluxes combined with environmental data, and describe the promising outcomes from an initial foray using this method. [ABSTRACT FROM AUTHOR]

Forest soils demonstrate in a microcosm the difficulties that are faced in quantifying methyl halide budgets. Carbon isotopic analyses have been proposed as a potential tool to address these concerns and in this study we have measured significant enrichment of the methyl chloride 13C/ 12C isotopic ratio (from −40.2 ± 0.8‰ to −33.4 ± 7.4‰) after 9 min chamber emplacement on local Irish forest soils. This enrichment occurred independent of direction of methyl chloride fluxes. Measurements from soil cores in a flow-through system ( FTS) are comparable with chamber-based isotopic measurements and indicate that methyl chloride produced abiotically from organic soil horizons has an isotopic 13C signature of −53 ± 49‰, significantly less depleted than previously reported. Average net methyl chloride, methyl bromide and methyl iodide fluxes from soils (77.8 ± 2.1, 1.25 ± 3.63 and 0.35 ± 2.00 μg Me X m−2 day−1, respectively) are in line with previously reported values; however, a better understanding of spatial and temporal variability is needed for budget quantification. Methyl halide fluxes from FTS soil cores demonstrate that, on a per gram basis, most consumption occurs through biologically driven processes in the O horizon, with progressively smaller contributions in deeper horizons. Sporadic biogenic production was observed in shallow soil horizons only. Abiotic production was at most one-tenth the net biological reaction rate in the O horizon and did not appear to be significantly different from zero in lower horizons. Modelled emissions based upon observed and reported rates for production, consumption and diffusion within the soil atmosphere system are unable to replicate all observed isotopic signatures from chamber fluxes. [ABSTRACT FROM AUTHOR]