Ecology and function of grape-associated microorganisms with a special focus on biocontrol of Botrytis cinerea

Grapevine plants are affected by numerous pests, most of which are fungal pathogens. Significant yield losses are caused by fungal diseases and these thus represent an economic threat for grapevine production and for the wine industry. One of the most aggressive and destructive pathogens is Botrytis cinerea, an ascomycete fungus. It infects the plant through wounds inflicted, for example, by insects, and causes the bunch rot disease also known as grey mould (Elad et al., 2004). This pathogen can bypass disinfestation procedures as a result of its ability both to develop resistance (Elad et al., 1992) and to survive in a latent stage on non-host plants (Williamson et al., 2007). As the use of fungicides has been limited by international regulations owing to the environmental and health problems that they can cause (Spadoro and Gullino, 2005), new environmentally friendly alternatives are now required to control Botrytis and other pathogens. One promising technology is represented by the induction of systemic resistance in plants based on the addition of certain elicitors, such as oligogalacturonides (Aziz et al., 2003) and chitosan (Ait Barka et al., 2004; Trotel-Aziz et al., 2006). The most common alternative to chemical pesticides is biocontrol, a method that uses naturally occurring microorganisms as so-called biocontrol agents (BCAs) that specifically inhibit the growth of pathogens by various means. The major advantage of this approach is sustainability, ie the absence of environmental pollutants and chemical residues.
Most known modes of action of BCAs act through a combination of diverse mechanisms including competition for space and …