The control of soil-borne diseases in hops, such as Verticillium wilt remains challenging due to the limited effectiveness of fungicides, the perennial nature of hop cultivation, and the long-term persistence of the pathogens in the soil. Microbial biocontrol agents (mBCAs) with plant growth-promoting (PGP) and antagonistic effects offer a sustainable ecofriendly alternative for hops protection. Two Pseudomonas spp. strains from the UniMORE microbial collection were selected for this study based on their strong antagonistic activity against Verticillium spp. and multiple plant growth-promoting (PGP) traits. Rhizospheric and endophytic colonization capacities of the strains DLS1929 and DLS2318 were evaluated in hop plants (cv. Cascade) under controlled conditions at seven- and fourteen-days post-inoculation (DPI). Both bacterial strains were rhizosphere and endorhiza competent, with slight differences in their abundances. The highest cell density was observed at 7 DPI for the strain DLS2318, reaching log10 6.39 CFU g−1 root fresh weight in the rhizosphere and log10 4.75 CFU g−1 root fresh weight in the endorhiza; at 14 DPI, colonization results were in line with the previous assessment. Confocal laser scanning microscopy visualization of both eGFP-tagged Pseudomonas spp. strains confirmed their rhizosphere competence in hop. Additionally, root colonization by these bacteria enhanced the photosynthetic capacity in hop leaves, supporting their potential as a PGP agents observed in vitro. Successful root colonization and PGP effects are key prerequisites for an effective biocontrol of soilborne pathogens. Further studies are required to assess the consistent efficacy in the field of these beneficial mBCA candidates. This research was funded by the Italian Ministry of University and Research (MUR), 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”.
Root colonization pattern of Pseudomonas spp. strains: a key step in the biocontrol of soilborne pathogens in hops / Bellameche, F.; Modica, F.; Cortiello, M.; Costi, E.; Riccioni, C.; De Marchis, F.; Rubini, A.; Belfiori, B.; Bellucci, M.; Brilli, L.; Sberveglieri, V.; Lovino, M.; Núñez-Carmona, E.; Giovanardi, D.. - In: JOURNAL OF PLANT PATHOLOGY. - ISSN 2239-7264. - (2025), pp. 11-11. ( XXX Congress of the Italian Phytopathological Society (SIPaV) Monastero dei Benedettini - University of Catania, Catania, Italy September 15–17, 2025) [10.1007/s42161-025-02022-w].
Root colonization pattern of Pseudomonas spp. strains: a key step in the biocontrol of soilborne pathogens in hops.
Bellameche F.;Modica F.;Cortiello M.;Costi E.;Lovino M.;Giovanardi D.
2025
Abstract
The control of soil-borne diseases in hops, such as Verticillium wilt remains challenging due to the limited effectiveness of fungicides, the perennial nature of hop cultivation, and the long-term persistence of the pathogens in the soil. Microbial biocontrol agents (mBCAs) with plant growth-promoting (PGP) and antagonistic effects offer a sustainable ecofriendly alternative for hops protection. Two Pseudomonas spp. strains from the UniMORE microbial collection were selected for this study based on their strong antagonistic activity against Verticillium spp. and multiple plant growth-promoting (PGP) traits. Rhizospheric and endophytic colonization capacities of the strains DLS1929 and DLS2318 were evaluated in hop plants (cv. Cascade) under controlled conditions at seven- and fourteen-days post-inoculation (DPI). Both bacterial strains were rhizosphere and endorhiza competent, with slight differences in their abundances. The highest cell density was observed at 7 DPI for the strain DLS2318, reaching log10 6.39 CFU g−1 root fresh weight in the rhizosphere and log10 4.75 CFU g−1 root fresh weight in the endorhiza; at 14 DPI, colonization results were in line with the previous assessment. Confocal laser scanning microscopy visualization of both eGFP-tagged Pseudomonas spp. strains confirmed their rhizosphere competence in hop. Additionally, root colonization by these bacteria enhanced the photosynthetic capacity in hop leaves, supporting their potential as a PGP agents observed in vitro. Successful root colonization and PGP effects are key prerequisites for an effective biocontrol of soilborne pathogens. Further studies are required to assess the consistent efficacy in the field of these beneficial mBCA candidates. This research was funded by the Italian Ministry of University and Research (MUR), 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”.
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