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ABSTRACTDuring containerised production in forest nurseries, seedlings are often intensively fertilised to maximise seedling survival and growth. However, this practice can inadvertently harm the development of a robust root microbiome needed for plant resilience post-planting. In this controlled study using Pinus radiata, we combined reduced fertilisation and seedling inoculation with a diverse ectomycorrhizal (ECM) community as an alternative to intensive, industry-standard fertilisation. After 9 months, we investigated growth responses and changes to ECM and non-ECM root fungal communities. Reduced fertilisation improved the belowground growth and mycorrhizal root colonisation of inoculated seedlings. Isotopic nutrient tracing determined that, under moderate fertilisation, more photosynthetically fixed carbon was allocated belowground, and root-tip nitrogen (N) accumulation, a proxy for N uptake from the soil, also increased. Fertilisation level resulted in shifts in both ECM and non-ECM fungal community composition and substantial changes in the abundance of certain fungi. This study demonstrates that employing more-mycocentric fertilisation regimes may improve plantation nursery outcomes and that interactions between ECM and non-ECM fungi within inocula should be considered when studying the role of the soil microbiome in supporting P. radiatagrowth during containerised production.

ABSTRACTEarly detection of exotic pests is key to a timely response for enabling options for eradication and future management. It is widely recognised that engaging the public and industry in general surveillance significantly increases the chance of detecting newly arrived pests and pathogens. Once a new pest or pathogen is detected, Australia has guidelines to follow via the Emergency Plant Pest Response Deed and PLANTPLAN. This paper describes the detection of unusual symptoms in a Pinus radiataproduction nursery in New South Wales, Australia, and the subsequent response. The unusual symptoms were detected in early January 2021 by nursery staff and reported immediately to biosecurity authorities. The nursery was placed under quarantine as a precaution. Within five weeks, Fusarium communewas diagnosed from the samples, a known pathogen of conifers not previously recorded in Australia. Formal biosecurity processes were enacted immediately to determine whether the pathogen was an emergency plant pest and whether eradication was necessary and technically feasible. Quarantine and movement restrictions continued, such that no seedlings could leave the site other than for ongoing diagnosis and under biosecure protocols. Tracing was conducted to determine the distribution of the pathogen and a potential source, including ongoing sampling in production nurseries, diagnosis of planting media and seed, and diagnosis of root and soil eDNA samples collected in previous years. Fusarium communewas recovered at a very low frequency from two nurseries, primarily in association with healthy seedlings. Root and soil samples collected from nurseries and plantations between 2019 and 2020 tested negative for the presence of F. communeusing F. commune-specific primers. Pathogenicity tests revealed that F. communedid not cause wilting or significant disease on tested seedlings. Overall, evidence suggested that F. communedid not pose a serious threat to the P. radiataindustry. The Consultative Committee on Emergency Plant Pests determined that F. communewas not a significant pathogen and that no further action was warranted. The affected nursery was allowed to resume operations in mid-May 2021, in time for the winter planting season. Here we discuss the lessons from this response, including the benefits of a quick and timely response, cross-institutional collaboration, the potential threat to the forest industry, and the need to encourage greater general surveillance. These lessons can help in the event of an incursion of a serious pathogen such as F. circinatum(pine pitch canker).