Endophytes and pathogens both possessmany of the samevirulence factors: the endophytes studied thusfar produced the exoenzymes necessary to infect and colonise the host,even though only some of these endophytes are presumably.latent pathogens.The majority can produce phytotoxic metabolites.The host can respond with the same de-fence reactions as to a pathogen, i.e. with preformed and induced defence metabolites see Chaps. 3 , and 11 and general defence responses .As long as fungal virulence and plant defence are balanced, the interaction remains asymptomatic. In all of these interactions we are referring to a momentary status, an often fragile balance of antagonisms.