DETECTION AND QUANTIFICATION OF INDIVIDUAL FUNGAL SPECIES IN FUSARIUMDISEASE COMPLEXES OF CEREALS BY POLYMERASE CHAIN-REACTION (PCR)

Until recently, no method was available to identify and quantify indiv idual Fusarium species present within plant tissue. Specific DNA marke rs have been identified for the Fusarium species which are predominant components of the 'Fusarium ear blight complex' (scab) and 'stem-base complex' of cereals. Assays based upon the polymerase chain reaction (PCR) have been developed for detection of several of these fungi in D NA extracts from plant tissue. These assays have been refined to enabl e quantification of each species, allowing the relative contribution o f each component to the disease of the plant to be estimated. Examples of the use of PCR techniques in host resistance and epidemiological s tudies involving F. poae, F. culmorum, Gibberella zeae (F. graminearum ), G. avenacea (F. avenaceum) and M. nivale varieties is presented. Th e role of trichothecene mycotoxins in the pathogenicity of Fusarium sp ecies towards cereals is also being investigated and visual disease sc oring and quantitative PCR are being used to investigate the effects o f Tri5 gene disruption of G. zeae on the infection of seedlings and ea rs of wheat.