21Soil-borne pathogen Setophoma terrestris is the causal agent of pink root of onion, one 22 of the most challenging diseases in onion production. Conventional approaches for 23 managing the disease like solarization, soil fumigation and crop rotation have not been 24 proven effective enough. In this work, we evaluated the biocontrol capacity of Bacillus 25 subtilis ALBA01 (BsA01) against S. terrestris, in a highly susceptible onion cultivar, both 26 under greenhouse and field conditions. Disease incidence and severity were evaluated 27 together with growth, photosynthesis among other physiological variables and yield 28 parameters. When compared with plants infected with the pathogen, those plants co-29 inoculated with BsA01 showed significantly less damage and levels of biocontrol above 30 50%. With regard to physiological parameters, plants challenged with S terrestris and 31 inoculated with BsA01 performed as well as the control non-infected plants revealing a 32 growth promotion effect of BsA01 on onion plants.33

13The soil-borne fungal plant pathogen Verticillium dahliae can infect more than 300 plant 14 species including important economic crops, causing great economic loses. V. dahliae 15 can persist and survive more than 14 years in the soil by resistance structures, known as 16 microsclerotia, which constitute the primary inoculum in the field. In vitro mass 17 production of microsclerotia is essential for performing many pathological assays. 18Nevertheless to harvest the microsclerotia is not an easy task and several protocols have 19 been described although none of them is completely satisfying for different reasons. here 20 we present a new protocol that is reproducible, robust, simple and fast allows to overcome 21 the difficulties for obtaining massive amounts of microsclerotia. In summary, we 22 developed a new culture medium that we called Pluronic Potato Medium (PPM) because 23 it is essentially potato dextrose media with the hydrogel, Pluronic F127 as a solidifying 24 agent. The microsclerotia collected in form PPM were infectious in tomato plants were 25 2 they were able to reproduce the disease and we recovered and quantitated V. dahliae in 26 infected plants. 27Keywords Verticillum dahliae, microsclerotia, inoculum, mass production, pluronic 28 29 This difficulty was absolutely overcomed by using a thermoreversible hydrogel as 175 Pluronic F-127 as a solidifying agent in PPM medium. 176 Poloxamer or Pluronics hydrogels are triblock copolymers (nonionic, polyoxyethylene-177 polyoxypropylene-polyoxyethylene (PEO-PPO-PEO)) that have multiple pharmaceutical 178 applications (Bohorquez et al., 1999). A widely explored member of this family is 179 Pluronic F127, which has 1200 kDa PPO units and 70% PEO content (Wang et al., 2019).180The most striking feature of this hydrogel is that, due to its composition, it shows 181 transformations as a function of temperature changes. This characteristic of 182 thermoreversible gel is useful in concentrations higher than or equal to 20%. Cold 183 temperatures cause the gel to go from solid to liquid state, while remaining solid at room 184 temperature (Akash & Rehman, 2015). These characteristics of appropriate hydrophilic / 185 lipophilic balance, high molecular weight, thermos-reversibility and lower mechanical 186 strength allow for a high extraction capacity in aqueous phase (Lv et al. 2007) by TIPS 187 (Qiu et al., 2008). Hydrogels such as Pluronic F127 have been used mainly as detergents, 188 stabilizers, foaming agents and emulsifiers in the field of biomedicine, in tissue 189 engineering and pharmacology (Bercea et al., 2011; Gwon et al., 2018; Wu et al., 2018). 190 Recently, they have been used in studies of interactions between plant parasitic nematodes 191 and plants (Li et al., 2019). 192 The main advantages of a massive production of V. dalihae MS using the PPM media and 193 the methodology here described are the short time elapsed from inoculating the mycelium 194 to the moment of collecting the MS, the minimal physical space needed for producing 195 MS an...