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The present study aims to evaluate the response of the three Mediterranean local grapevines 'Garnacha Blanca', 'Garnacha Tinta', and 'Macabeo' to treatments with biocontrol products, namely a botanical extract (Akivi

Biological control is an effective and sustainable alternative or complement to conventional pesticides for fungal and bacterial plant disease management. Some of the most intensively studied biological control agents are bacteria that can use multiple mechanisms implicated in the limitation of plant disease development, and several bacterial-based products have been already registered and marketed as biopesticides. However, efforts are still required to increase the commercially available microbial biopesticides. The inconsistency in the performance of bacterial biocontrol agents in the biological control has limited their extensive use in commercial agriculture. Pathosystem factors and environmental conditions have been shown to be key factors involved in the final levels of disease control achieved by bacteria. Several biotic and abiotic factors can influence the performance of the biocontrol agents, affecting their mechanisms of action or the multitrophic interaction between the plant, the pathogen, and the bacteria. This review shows some relevant examples of known bacterial biocontrol agents, with especial emphasis on research carried out by Spanish groups. In addition, the importance of the screening process and of the key steps in the development of bacterial biocontrol agents is highlighted. Besides, some improvement approaches and future trends are considered This research was funded by different grants from Spain Ministerio de Ciencia, Innovación y Universidades AGL2015-69876-C2-1-R, RTI2018–099410-B-C21, and from the European Union FP7-KBBE.2013.1.2-04 613678 DROPSA

The use of lactic acid bacteria (LAB) to control multiple pathogens that affect different crops was studied, namely, Pseudomonas syringae pv. actinidiae in kiwifruit, Xanthomonas arboricola pv. pruni in Prunus and Xanthomonas fragariae in strawberry. A screening procedure based on in vitro and in planta assays of the three bacterial pathogens was successful in selecting potential LAB strains as biological control agents. The antagonistic activity of 55 strains was first tested in vitro and the strains Lactobacillus plantarum CC100, PM411 and TC92, and Leuconostoc mesenteroides CM160 and CM209 were selected because of their broad-spectrum activity. The biocontrol efficacy of the selected strains was assessed using a multiple-pathosystem approach in greenhouse conditions. L. plantarum PM411 and TC92 prevented all three pathogens from infecting their corresponding plant hosts. In addition, the biocontrol performance of PM411 and TC92 was comparable to the reference products (Bacillus amyloliquefaciens D747, Bacillus subtilis QST713, chitosan, acibenzolar-S-methyl, copper and kasugamycin) in semi-field and field experiments. The in vitro inhibitory mechanism of PM411 and TC92 is based, at least in part, on a pH lowering effect and the production of lactic acid. Moreover, both strains showed similar survival rates on leaf surfaces. PM411 and TC92 can easily be distinguished because of their different multilocus sequence typing and random amplified polymorphic DNA profiles Funding was provided by AGL2015‐69876‐C2‐1‐R (Spain Ministerio de Economía y Competitividad and FEDER of the European Union), by FP7‐KBBE.2013.1.2‐04 613678 DROPSA of the European Union, and by the MPCUdG2016 grant (University of Girona). N. Daranas was recipient of the research grant 2015 FI_B00515 (Secretaria d'Universitats i Recerca, Departament d'Economia i Coneixement, Generalitat de Catalunya; ES, EU). The research group is accredited by SGR 2014‐697 and TECNIO net from the Department d'Economia i Coneixement‐ACCIÓ Catalonia

Lactobacillus plantarum strains PM411 and TC92 can efficiently control bacterial plant diseases, but their fitness on the plant surface is limited under unfavourable low relative humidity (RH) conditions. To increase tolerance of these strains to water stress, an adaptive strategy was used consisting of hyperosmotic and acidic conditions during growth. Adapted cells had higher survival rates under desiccation than non-adapted cells. Transcript levels and patterns of general stress-related genes increased immediately after the combined- stress adaptation treatment, and remained unaltered or repressed during the desiccation challenge. However, there were differences between strains in the transcription patterns that were in agreement with a better performance of adapted cells of PM411 than TC92 in plant surfaces under low RH environmental conditions. The combined-stress adaptation treatment increased the survival of PM411 cells consistently in different plant hosts in the greenhouse and under field conditions. Stress-adapted cells of PM411 had similar biocon- trol potential against bacterial plant pathogens than non-adapted cells, but with less variability within experiments Funding was provided by Spain MINECO (Ministerio de Economía y Competitividad) (AGL2012-39880-C02-01 and AGL2015-69876-C2-1-R) and FEDER of the European Union and in part by project FP7-KBBE.2013.1.2-04 613678 DROPSA of the European Union. N. Daranas was recipient of a research grant 2015 FI_B00515 (Secretaria d’Universitats i Recerca, Departament d’Economia i Coneixement, Generalitat de Catalunya; ESF, EU). The research group is accredited by SGR 2014-697 and TECNIO net from Catalonia