Development of a strain-specific real-time PCR assay for the detection and quantification of the biological control agent Fo47 in root tissues.

Being able to identify specifically a biological control agent at the strain level is not the only requirement set by regulations (EC)1107/2009, it is also necessary to study the interactions of the agent with the plant and the pathogen in the rhizosphere. Fo47 is a soil-borne strain of Fusarium oxysporum which has the capacity to protect several plant species against the pathogenic formae speciales of F. oxysporum inducing wilts. A strain-specific sequence-characterized amplified region marker has been designed which makes it possible to distinguish Fo47 from other strains of F. oxysporum. In addition, a real-time PCR assay has been developed to quantify Fo47 in root tissues. The proposed assay has been validated by following the dynamics of root colonization of tomato plants grown in soil infested with Fo47. Results showed that with the method it is possible to quantify Fo47 in roots in the absence or presence of the pathogen and in the absence or in presence of the native microbial communities.