Detection of Bacterial Endophytes in Vitis vinifera L. and Antibiotic Activity against Grapevine Fungal Pathogens

This chapter presents the results of studies conducted to (i) detect and localize endophytic bacteria in symptomless and symptomatic leaf tissues of grapevine (Vitis vinifera) using fluorescence in situ hybridization (FISH) in combination with confocal laser scanning microscopy (CLSM); and (ii) test the antagonistic activity of Bacillus amyloliquefaciens AG1, previously isolated from grape wood affected by the esca syndrome, against grapevine fungal pathogens: Alternaria alternata, obtained from grapevine leaves showing necrotic concentric spots; Aspergillus carbonarius, A. ochraceus and Penicillium verrucosum, isolated from grapes affected by secondary rot; Botrytis cinerea, isolated from grapes with grey mould; Cladosporium viticola, agent of grapevine leaf spots; Fomitiporia mediterranea, obtained from grapevines with white rot symptoms; Fusarium oxysporum, isolated from the grapevine rhizosphere; Lasiodiplodia theobromae, isolated from vine wood with cortical cankers; Phaeoacremonium aleophilum and Phaeomoniella chlamydospora, both isolated from grapevine showing esca symptoms; Phoma glomerata from grape leaves showing necrotic spots; and Verticillium dahliae, obtained from decaying vine. The FISH/CLSM approach was successfully applied to visualize endophytic bacteria in grapevine leaves, including also those that it is not possible to cultivate in sterilized medium. Also, B. amyloliquefaciens AG1 showed a potential role as a biological control agent against trunk fungal pathogens as well as other fungal phytopathogens.