The fungus Gnomoniopsis castaneae is the causal agent of the “brown rot” of sweet chestnut fruits. These days, this pathogen represents one of the main limiting factors for the sustainability of fruit production worldwide. Although heat treatment post-harvest is efficient in completely inactivating the pathogen, the application of appropriate protocols to control “brown rot” in chestnut orchards is required to help in reducing the latent population of the fungus in fruit tissues, and the consequent development of “brown rot” symptoms in the field before the post-harvest handling process. The present study aims to evaluate and compare the efficiency of products at a minimum environmental impact in experimental trials conducted in chestnut orchards in Central Italy for two consecutive years in 2019 and 2020. Phosphonate-based salts and, specifically, Zn-phosphonate were efficient in reducing the impact of the disease and the pathogen inoculum in fruits with an efficacy comparable to the fungicide Tebuconazole. A unique treatment at the blooming time produced the best results for both Zn-phosphonate and Tebuconazole, also giving indirect evidence of female flowers as a main site of infection. Phosphonate salts, and at first Zn-phosphonate, are highly effective to protect chestnut fruits from the ‘brown rot’ fungus G. castaneae. Its use in orchard management may complement the post-harvest heat treatment during the processing of fruits. Although a still ongoing debate on phosphonate salts use and efficacy in agriculture, they can be considered an optimal fungicide in chestnut orchards because of the low environmental impact when used at the recommended doses, the high translocability and stability, and the multiple mechanisms of action.

The first genome assemblies of Gnomoniopsis castaneae (syn. G. smithogilvyi), the causal agent of chestnut brown rot of kernels, shoot blight and cankers, are provided here. Specifically, the complete genome of the Italian ex-type MUT401 isolate was compared to the draft genome of a second Italian isolate (GN01) and to the ICMP 14040 isolate from New Zealand. The three genome sequences were obtained through a hybrid assembly using both short Illumina reads and long Nanopore reads, their coding sequences were annotated and compared with each other and with other Diaporthales. The information offered by the genome assembly of the three isolates represents the base of data for further application related to -omics strategies of the fungus and to develop markers for population studies at a local and global scale.

The large production of biowaste can cause environmental risks if not managed properly. Composting is considered a sustainable solution for the disposal of this material, but generating high-quality compost requires proper design of feedstock composition and operational procedures. Microorganisms mediate the degradation of organic matter into a nutrient-rich substrate yet their response to different compost recipes is still poorly understood. In this study, fruit and vegetable biowaste was co-composted with woodchips or a perlite + cardboard mix in four different recipes (two representing optimal composting conditions and the other two were unideal composting conditions). Then, using Illumina high throughput sequencing, was defined the core fungal community shared by all treatments, mapped fungal succession through all composting phases and treatments, and identified indicator taxa associated to compost's specific recipes or phases. Our results confirm the presence of a core microbiome common to all compost piles dominated by Aspergillus but also reveal that every recipe has a degree of uniqueness in its fungal community and that the type of bulking agent used can significantly affect the composition of the fungal community during the latest stages of composting. At least one biomarker was associated with every recipe, with some reflecting the environmental conditions occurring such as the yeast P. kudriavzevii when more biowaste was present or T. lanuginosus when higher temperatures were reached during the thermophilic phase. These findings will contribute to increasing the knowledge of microbial dynamics during composting and provide useful information for the future use of biological parameters to assess compost quality.