Barley (Hordeum vulgare L.) ranks fourth in importance among cereals, after wheat, maize and rice. This crop represents two thirds of the forage grains demanded worldwide and most of it is destined for livestock feeding, with industrial consumption remaining practically stable. The main barley producers around the world are the European Union, Russia, Canada, Ukraine, Australia, USA and Argentina (MAGyP, 2023). Although globally most barley grains are destined for forage, feed and food, the best quality barley is used for malt production, and as a fermentable material for the production of beer and distilled beverages such as whisky (Pernica et al., 2019; Drakopoulos et al., 2019). In Argentina, barley grains are mostly associated with the brewing industry (SISA, 2023). Around 75 % of barley production in Argentina is exported, and the remaining 25 % is used in the domestic market for malt production in beer manufacture (MAGyP, 2023). During 2022 Argentina exported >1.1 MT of barley mainly to China, and 275,000 T of malt, whose main buyer was Brazil (Agrositio, 2023). Nevertheless, different factors such as diseases, agricultural practices, and climatic conditions may affect barley production, decreasing quality and yield of this crop, and producing at the same time economical losses and health risks.

Resilient crops are needed to cope up fungal diseases in a global climate change scenario. In this sense, globalisation and market trade are pressured by emergent plant pathogens that threaten our agro-ecosystems (Corredor-Moreno and Saunders, 2020). In the context of global warming, Fusarium Head Blight (FHB) is of particular concern as it is considered an increasing problem for cereal crops (Juroszek and Von Tiedemann, 2013). FHB causes significant losses in yield since the affected grains are small, shrunken, or have low mass and quality (Alisaac and Mahlein, 2023). This disease is highly fluctuating and causing species within genera Fusarium can respond differently to the changing climate (Zhang et al., 2014; Valverde-Bogantes et al., 2020). Within Fusarium graminearum species complex, F. graminearum sensu stricto (ss) is worldwide distributed while the others are endemic to certain regions (Wang et al., 2023). Fusarium graminearum has a very dynamic strategy to infect barley due to its sexual reproduction ability and the regular production of sexual ascospores to enhance its ability to generate more variability for adaptation and virulence (Zheng et al., 2015; Yerkovich et al., 2020). As F. graminearum plays an important role in the FHB disease, it is also responsible for the accumulation of mycotoxins such as trichothecenes type B, including deoxynivalenol (DON) that is also a virulence factor on FHB. Not only F. graminearum ss but also F. poae are the most frequent species isolated from barley in several countries including Argentina (Castañares et al., 2016; Logrieco et al., 2002; Gunst et al., 2005; Rohácik and Hudec, 2005; Xu et al., 2005; González et al., 2008; Stenglein, 2009). Fusarium poae produce mainly nivalenol that also act as a virulence factor during FHB infection and disease progression (Huang et al., 2020).

An excessive dietary intake of food contaminated with high levels of DON may produce gastroenteritis in humans, and chronic consumption may lead to developmental problems and infertility. Because of its detrimental effects, international organisations, including the World Health Organization and the Scientific Committee for Food (SCF), have set a daily limit of 1 μg/kg body weight for this mycotoxin (Ganesan et al., 2022). Additionally, the European Commission set legislative limits for the main mycotoxins produced by Fusarium species in grain-based foodstuffs intended for human consumption being the limit for DON between 200 and 750 μg/kg (European Commission n1881/2006). Regarding NIV, due to its potent cytotoxicity, this mycotoxin constitutes a serious health risk to both humans and animals. It can cause inhibition of cell proliferation, induction of CXCL8/interleukin (IL) -8 secretions, and the involvement of stress-activated mitogenactivated protein kinases. Regarding the general toxicity of NIV, the Scientific Committee on Food (SCF) has set a temporary tolerated daily intake up to 0.7 g/kg body weight per day (Kumar et al., 2022).

Different strategies have been proposed to reduce the impact of FHB, including crop rotation, tillage practices, fungicide application (chemical control), planting of resistant cultivars, and biological control (Mesterházy et al., 2003, Mesterházy et al., 2018; Torres et al., 2019). The best approach to control FHB is the implementation of an integrated management, combining two or more of such alternatives (McMullen et al., 2012; Wegulo et al., 2015). Chemical control is an available tool to reduce the risk of the disease, and selection, rate, coverage and timing of application are important factors (Mesterházy et al., 2011). However, to reach a lower environmental impact and to reduce the population's exposure to chemical compounds, active work is being done on the search for eco-friendly strategies. In this context, biological control is an important alternative based on the use of microorganisms and their metabolites. Several biocontrol strategies have been developed and used in both pre- and post-harvest stages (Magan, 2020; Alaniz Zanon et al., 2023). Among the use of microorganisms, bacteria of the Bacillus genus have shown good activity as biocontrol agents, due to their ability to produce a wide variety of molecules with the potential to inhibit phytopathogenic fungal species growth (Dunlap et al., 2013). The biofungicidal effect of Bacillus velezensis RC218 on F. graminearum ss growth and the reduction in DON accumulation in wheat, both under greenhouse conditions and field trials was demonstrated (Palazzini et al., 2016a, Palazzini et al., 2009). Bacillus velezensis RC218 produces the lantibiotic ericin and several lipopeptides from the iturin, surfactin and fengycin family, with fungicidal and bactericidal potential (Palazzini et al., 2016b). Strains of B. inaquosorum can produce very different and unique secondary metabolites compared to B. velezensis species that have been described (Steinke et al., 2021). Moreover, it has been marketed for the control of fungal pathogens of turfgrass and ornamental plants as well as a probiotic such that its use for application in products intended for food production would not be questionable and could be beneficial (Knight et al., 2018; Dunlap et al., 2019). Another related potential biocontrol agent is Lactobacillus plantarum. Strains of this species are capable to produce different antimicrobial compounds, such as hydrogen peroxide, organic acids (primarily lactic and acetic acid), antiaflatoxigenic compounds, and bacteriocins (Guimarães et al., 2018; Evanovich et al., 2019). In this context, the objectives of the present study were to evaluate the in vitro effect of Bacillus velezensis, B. inaquosorum, B. nakamurai and Lactobacillus plantarum as potential biocontrol agents for F. graminearum ss and F. poae growth and their mycotoxin production, and to select, among the evaluated strains, the most effective one to test it under greenhouse and field trials. The development of a biocontrol strategy and its implementation into an integrated pest management would contribute to increase both barley yields and food safety.