Biocontrol of fungal disease affecting hops: green and sustainable alternatives for the Italian cultivation.

The Italian craft beer market is supporting the demand for local hops. However, hop cultivation and pest management are still challenging. Verticillium spp. (VW), Podosphaera macularis (PM), and Botrytis cinerea (BC) are the main fungi affecting hops, whose current management relies on resistant cultivars and extensive use of fungicides. In 2023, hop roots and rhizomes were sampled and analysed to isolate root-associated bacteria (from the rhi-zosphere and the endosphere) and bacteria harboured on rhizomes. Plant samples were obtained from cultivated hop, cv. Cascade, and from wild accessions available in the Province of Modena (Italy). A total of 207 isolates were obtained and screened for their ability to trigger a Hyper¬sensitive Reaction (HR) on tobacco and tomato and, for further characterisation, only HR-negative isolates were considered. Such isolates were then tested in vitro for their ability to inhibit the growth of VW, BC, and PM. Twelve isolates showing significant antifungal activity were further evaluated for possible plant growth-promoting traits such as saline stress tolerance, phosphate solubilization, sidero¬phores, ammonia, and hydrogen cyanide production. The best-performing isolates were identified through partial sequencing and NCBI blast analysis of the 16S rRNA gene, revealing them as members of the genera Erwinia, Agrobac¬terium, and Pantoea. Additional experiments for assessing bacterial ability to colonize hop plants and their effective¬ness against fungal pathogens in planta are ongoing. Our study identified hop root and rhizome-associated bacteria that are potential candidates as biostimulant and biocontrol agents for “green” applications aimed to increase hop qual¬ity and productivity. This study was funded by the Italian Ministry of Educa¬tion, University and Research (MIUR), under the European Union funding– Next Generation EU - PRIN- 2022, (prot. 2022M3HR45) project: “IoHOP: Quality valorization of the Italian hop based on a multi-approach strategy”.