RESEARCH ARTICLE OPEN ACCESS Winter biodisinfestation with Brassica green manure is a promising management strategy for Phytophthora capsici control of protected pepper crops in humid temperate climate regions of northern Spain Maite Gandariasbeitia 1 , Mikel Ojinaga 1 , Estibaliz Orbegozo 1 , Amaia Ortiz-Barredo 1 , Mireia Núñez-Zofío 1 , Sorkunde Mendarte 2 and Santiago Larregla 1 1 NEIKER-Basque Institute for Agricultural Research and Development, Plant Production and Protection Dept. C/ Berreaga 1, 48160 Derio (Bizkaia), Spain. 2 NEIKER, Conservation of Natural Resources Dept. C/ Berreaga 1, 48160 Derio (Bizkaia), Spain. Spanish Journal of Agricultural Research 17 (1), e1005, 11 pages (2019) eISSN: 2171-9292 https://doi.org/10.5424/sjar/2019171-13808 Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, O.A, M.P. (INIA) Abstract Phytophthora capsici causes root and crown rot of protected pepper (Capsicum annuum L.) crops in the Basque Country (northern Spain), a humid temperate climate area. The objective was to determine the efect of winter biofumigation and plastic cover (biodisinfestation) with Sinapis alba L. (cultivar 'Ludique') fresh green manure on the survival of introduced P. capsici inoculum (oospores) in a greenhouse soil. After autumn-winter Brassica cover crop soil incorporation in February, oospores remained at 15 and 30 cm depth for four weeks´ time exposure in two consecutive years, 2009 and 2010. Oospores viability was estimated with a plasmolysis method and infectivity with a potted pepper bioassay. Viability was signifcantly higher in biodisinfestated oospores than in the non-treated control in both years (81% and 21% relative increase in 2009 and 2010, respectively) and signifcantly higher at 30 cm depth than at 15 cm in 2009 (24% relative increase). Conversely, biodisinfestation signifcantly delayed disease incidence progression until the frst half of infectivity bioassays in both years compared to the non-treated soils (83% and 75% relative decrease of dead plants in 2009 and 2010 respectively). The low soil temperatures could explain the low oospore survival reduction and suggest that the suppressiveness expressed in the infectivity bioassay was related with an increase of microbial activity in the biodisinfestation treatment. We conclude that winter biodisinfestation with fresh Brassica green manure is a promising management strategy for Phytophthora root rot control of protected peppers crops in regions of humid temperate climate such us northern Spain. Additional keywords: oospores; Capsicum annuum; biosolarization; biofumigation; Sinapis alba. Abbreviations used: AUDPC (area under the disease progress curve); DP (diseased plant); RAUDPC (relative area under the disease progress curve). Authors’ contributions: MNZ and SL participated in the conception and design of the research. MG, MO, EO, AOB and SM participated in the other stages of the work, including the performing of experiments, data analyzing, revision of the intellectual content and the drafting of the paper. Citation: Gandariasbeitia, M.; Ojinaga, M.; Orbegozo, E.; Ortiz-Barredo, A.; Núñez-Zofío, M.; Mendarte, S.; Larregla, S. (2019). Phytophthora capsici soil inoculum control through winter biodisinfestation with Brassica green manures application in protected pepper crops of northern Spain. Spanish Journal of Agricultural Research, Volume 17, Issue 1, e1005. https://doi.org/10.5424/ sjar/2019171-13808 Received: 08 Aug 2018. Accepted: 20 Mar 2019. Copyright © 2019 INIA. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International (CC-by 4.0) License. Funding: FEDER funds (projects INIA RTA 2011-00005-C03-03 and INIA RTA 2015-00060-C04-04); Basque Government, Dept. of Environment, Territorial Planning, Agriculture and Fisheries (projects BIOSOL and REVABIO). MG was the recipient of a predoctoral contract (INIA-2017-0043) of the State Training Subprogram of the Spanish Ministry of Economy, Industry and Competitiveness (MICINN); EO was the recipient of a technologist scholarship “Disease management in protected horticultural organic crops" (Order of October 18, 2017 of the Minister of Economic Development and Competitiveness of the Basque Government). Competing interests: The authors have declared that no competing interests exist. Correspondence should be addressed to S. Larregla: slarregla@neiker.us Introduction Phytophthora capsici is one of the main soil-borne pathogens that causes root and crown rot of protected pepper (Capsicum annuum L.) crops worldwide (Ristaino & Johnston, 1999) and in the Basque Country (northern Spain) (Riga et al., 2000; Larregla et al., 2015), an area characterized by a humid temperate climate. This pathogen species produces survival spores (oospores) that are capable to persist in the soil and act as the main initial inoculum that causes primary infec- tions in the next crop cycle (Erwin & Ribeiro, 1996). The presence of P. capsici is also reported in the southeast of Spain with a warm dried climate causing root and crown rot disease, not only in solanaceous plants (pepper, eggplant and tomato) but also in curcubitaceous like