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9 p.-3 fig.-2 tab. Proceedings of the 12th Meeting at Plovdiv (Bulgaria) 13-16 June (2022), Aerospores are one of the main components of aeromycobiota that can cause fungal diseases in fruits. Their presence in warehouses limits the storage time of apples and affects their organoleptic properties. Our study was based on previously identified airborne fungi collected from apple warehouses in Tunisia. Fifteen species: Penicillium allii, P. chrysogenum, P. citrinum, P. expansum, P. italicum, P. polonicum, P. solitum, P. steckii, P. sumatraense, P. viridicatum, Aspergillus europaeus, A. flavus, A. niger, A. pulverulentus and Alternaria alternata with different level of pathogenicity were tested for their carbon and nitrogen requirements. The tested compounds were selected for their abundance in apple cell wall: polygalacturonic acid, arabinan, arabinogalactan, fructose, galactose, arabinose, maltose, xylose, sucrose, sorbitol, xylan, cellulose microfibril and cutin. Assimilation tests proved that only P. expansum and P. polonicum, with the highest pathogenicity, were able to assimilate all types of carbohydrates and nitrogen sources present in the apple cell wall. This could be a mean to annotate virulence mechanisms of highly pathogenic fungi during apple colonization., This work was supported by funds from the VRR Project (no. 0310) and by the Ministry of Higher Education and Scientific Research of Tunisia (LR16ES05).

Additional file 1: Table S1. Localization and characteristics of the Tunisian orchards surveyed for blast and black pit disease in 2015, 2016 and 2017. Table S2. Other Pseudomonas strains characteristics isolated from symptomatic samples. Table S3. Detection of enzymatic activity of P. syringae and P. congelans strains of this study, using API ZYM system. Table S4. Resistance antibiotic patterns of the P. syringae and P. congelans strains used in this study. Table S5. Matrix of pairwise genetic similarity of rpoD gene sequences of strains of this study, strains from symptomatic citrus in Iran (FBF strains) and in Serbia (IZB strains). Fig. S1. Phylogenetic tree built with Neighbor joining method based on cts partial sequences of P. syringae strains isolated from Tunisian citrus orchards. Fig. S2. BOX fingerprints of representative strains of the P. syringae group isolated from citrus in symptomatic Tunisian orchards from different regions. Fig. S3. Phylogenetic tree based on the rpoD gene sequences of P. syringae strains of this study, together with other strains of P. syringae from Tunisia, (Abdellatif et al. 2017), Montenegro (Ivanović et al. 2017) and Iran (Beiki et al. 2016). Distance matrices were calculated by the Jukes-Cantor method (Jukes and Cantor 1969). Dendrograms were generated by the neighbour-joining method. P. aeruginosa ATCC 10145 T was used as the outgroup. The bar indicates sequence divergence. Percentage bootstrap values of more than 50% (from 1000 replicates) are indicated at the nodes. GenBank accession numbers are given in parentheses.

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International audience; Esca and Black Dead Arm (BDA) are two major actors of grapevine trunk decline diseases that affect worldwide. The knowledge about the symptoms of these diseases and the microflora associated with these wood pathologies is still incomplete in Tunisia, although they begin to cause considerable damage in our vineyards. In order to better characterize the microflora colonizing the trunk of vine, samples were collected from eight vineyards in the north of Tunisia. Symptoms were described and isolates taken at the level of sick and healthy vines. A halophilic bacterium J9 was used as antagonistic agent and has been tested against fungi isolated. Two symptoms were observed: rapid total or partial drying resulting in the death of the cep (apoplectic form of esca) and the presence, under the bark of the trunk of an orange to brown band, characteristic of the Black Dead Arm Disease (BDA). For the varieties studied, cultivated and diverse microflora are colonizing the vines. Many saprophytic fungi such as Aspergillus spp and Alternaria alternata were detected in the healthy wood and at the level of necrosis. The identification of fungi by molecular methods including by PCR and sequencing showed the presence of Phomopsis viticola and Diplodia seriata, two pathogens described in the literature as involved in diseases of wood. Next to these pathogens, the molecular analysis confirmed the presence of Alternaria alternata as majority saprophyte in healthy and diseased wood. The use of bacterial antagonist gave pretty promising results especially with Diplodia seriata. This is the first report of Phomopsis viticola and Diplodia seriata infections of grapevines in Tunisia.

Bacillus species are well known for their ability to control plant diseases through various mechanisms, including the production of secondary metabolites. Bacillus subtilis SR146 isolated from Tunisian salty soil showed in vitro activity against several species of Fusarium including Fusarium culmorum, Fusarium graminearum, Fusarium oxysporum, Fusarium melonis, Fusarium equiseti and Fusarium solani.Moreover, wheat seeds treated with SR146 strain was effective in controlling foot rot disease in wheat caused by F. culmorum under a glasshouse assay. The bacterial strain SR146 markedly increased the plant seedling emergence in comparison to the non-infested experimental series. Complete inhibition of F. culmorum spores germination by the strain SR146 was also observed. The highest levels of antifungal metabolites produced by B. subtilis SR146 were detected during bacterial stationary growth phase. The compounds which are responsible for antifungal activity were purified and characterized. Identification by mass spectrometry showed high similarity to fengycin, this result was confirmed by polymerase chain reaction (PCR) detection of the fenA gene of the fengycin operon. Key words: Bacillus subtilis, foot rot, Fusarium culmorum, fengycin, Matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS),polymerase chain reaction detection.