Guido Marchi, holds the position of Associate Professor at the Department of Agriculture, Food, Environment and Forestry (DAGRI) - University of Florence (Italy), were he currently instructs Plant Pathology course and  Phytosanitary Management of Alien Parasites courses. The research activity carried out by Guido Marchi deals with plant pathology as well as microbial ecology. The main activity of his research have included: the epidemiology and the diagnosis of the phytopathogenic bacteria Pseudomonas savastanoi and Rhizobium vitis and of the phytoplasma "Ca. Phytoplasma solani "; the interactions between P. savastanoi and Pantoea agglomerans during the process of pathogenesis on olive; the study of the exopolysaccharides produced by phytopathogenic bacteria; the associations existing in planta between fungi that cause grapevine decline and the characterization of some of their pathogenic factors; the study of the symptomatology and epidemiology of Esca disease of grapevine. More recently he has started to study the bacterium  Xylella fastidiosa working on aspects related to the molecular, phylogenetic and biochemical characterization of the causative agent and its interactions with Olea europea, Spartium junceum and Rhamnus alaternus hosts. As a visiting scientist, he cooperated to a research program funded by the Cooperative Research Center for Viticulture (CRCV) of Australia. With a C.I.B. scholarship (Inter-university Biotechnology Consortium) he participated to a research program on interactions between Ageratum conyzoides and Agrobacterium tumefaciens at the University of Washington in Seattle (USA). He has been head of the research program (“Analyses and regulation of enzymatic aggression factors produced by Phaeoacremonium spp. causal agents Esca disease of grapevine, to develop sustainable defense strategies”) supported by the C.N.R. (National Research Council) and participated to Regional (SIDIO), Inter-regional (MESVIT) and EU (MYCORRAY) funded projects.