Gnotobiotic system for selecting microorganisms with biocontrol potential against Fusarium oxysporum f. sp. physali

The cape gooseberry (Physalis peruviana) is a Solanaceae species with enormous economic importance in Colombia; it is the second most exported fruit, after bananas. Vascular wilt caused by Fusarium oxysporum f. sp. physali (Fox) is the most limiting factor of this crop, with losses of up to 80% of production. Biological control is a promising alternative for controlling this pathogen. Bacteria and fungi, originally isolated from potentially suppressive soils of cape gooseberry crops in Nariño, Colombia with different management (organic and conventional), were evaluated as biocontrol agents of Fox using a gnotobiotic model (seedlings cultured under axenic conditions with defined microbial strains). Of the 64 isolated microorganisms, 37.5% (15 bacteria and 9 fungi) were discarded because of toxicological risks and an unknow potential biological control. The remaining 62.5% of the microorganisms, 14 bacteria and 26 fungi, were evaluated to assess their potential as biological control agents against Fox. The gnotobiotic model system evaluated the protection and plant growth promotion characteristics. Response variables were used to group the microorganism using a principal component analysis (PCA), and five clusters were obtained. Cluster number four concentrated the 10 microorganisms (three bacteria and seven fungi) with the highest protection values against Fox, with a positive effect on growth. The isolates were identified as two Bacillus subtilis strains, Rhodococcus sp. , Podospora setosa, Debaryomyces vindobonensis, Plectosphaerella plurivora, Acinetobacter rhizosphaerae, Umbelopsis sp. and two strains of Trichoderma koningiopsis. The gnobiotic system offered clear advantages for evaluating and selecting microorganisms with a biological control potential against Fusarium oxysporum f. sp. physalis. 1 Universidad Nacional de Colombia, Facultad de Ciencias Agrarias, Bogota (Colombia). ORCID García, D. : 0000-0002-7843-6950; ORCID González, A. : 0000-0003-2261-8912 2 Corporación Colombiana de Investigación Agropecuaria (AGROSAVIA), Centro de Investigación Tibaitatá, Mosquera (Colombia). ORCID Dávila, L.L. : 0000-0002-3516-481X; ORCID Caro, A. : 0000-0001-8807-671X; ORCID Cotes, A.M.: 0000-0003-3649-5706 3 Corresponding author. dgarciav5@gmail.com Doi: https://doi.org/10.17584/rcch.2021v15i1. 11699 REVISTA COLOMBIANA DE CIENCIAS HORTÍCOLAS Vol. 15 No. 1, e11699, January-April 2021 e-ISSN: 2422-3719 · ISSN-L: 2011-2173 The cape gooseberry or golden berry (Physalis peruviana L.) is an herbaceous plant of the Solanaceae family (NRCS, 2020), with 1,311.8 ha planted in Colombia, mainly in the Boyaca, Cundinamarca and Nariño departments (Agronet, 2018), where it is grown commercially at altitudes between 1,800 and 2,800 m a.s. l. , with medium temperatures between 13 and 16°C, 1,500-2,000 h year-1 of direct sunshine, and 1,000-1,800 mm year-1 of rainfall (Fischer and Melgarejo, 2020). Its fruit is a sugary berry preferred in countries such as Germany, Canada, Brazil, the Netherlands and Belgium, which are the main consumers (Hassanien et al., 2011). However, this crop is severely affected by vascular wilt, caused by Fusarium oxysporum, Schltdl. , throughout Colombia (Galindo and Pardo, 2010; Enciso-Rodríguez et al., 2013; Villareal-Navarrete et al., 2017; Rodríguez, 2013; Giraldo-Betancourt et al., 2020), generating losses of up to 100% (Smith, 2012; Mayorga-Cubillos et al., 2019) and forcing the movement of crops to other producing areas (González and Barrero, 2011). Controlling this fungus is difficult because of the presence of inoculum in the soil, crop residues, infected plant debris and contaminated soils (McGovern, 2015). Plants can be infected by mycelium, conidia and chlamydospores (dormant propagules), which germinate when they come into contact with plant root exudates (Haglund and Kraft, 2001; Michielse and Rep, 2009; Zacky and Ting, 2013). In Colombia, the principal management strategy for this disease is treatment with flutriafol, propineb, iprodione and Additional key words: biological control; in vitro; vascular wilt; rhizosphere; suppressive soils; cape gooseberry; Fusarium oxysporum.