The use of species‐specific DNA probes for the identification of Mycosphaerella fijiensis and M. musicola, the causal agents of Sigatoka disease of banana

The polymerase chain reaction (PCR)‐based technique of random amplification of polymorphic DNA (RAPD) was used to differentiate DNA from species of the genus Mycosphaerella. DNA from two pathogens which cause Sigatoka leafspot diseases of banana, M. fijiensis and M. musicola, and two other Mycosphaerella species which are commonly found on banana, M. musae and M. minima, gave distinct RAPD banding patterns with all PCR primers tested. PCR, using primer RC07, amplified a 1250bp RAPD fragment from all isolates of M. fijiensis obtained from 11 geographical origins. This fragment was absent from the other species of Mycosphaerella. In Southern blots of genomic DNA, this band hybridized exclusively to DNA from M. fijiensis, and the pattern of hybridization suggested that it was binding to repeated DNA. A RAPD band amplified with primer PM06 obtained from M. musicola was also found to be species‐specific. Southern analysis suggested that the fragment hybridized to a single‐copy sequence in the M. musicola genome. Total genomic DNA from M. musicola was found to be a species‐specific hybridization probe. Dot‐blots confirmed the specificity of these probes, and could be used to identify isolates of Mycosphaerella which cause Sigatoka disease of banana in south‐east Asia.