COMPARISON OF 3 MOLECULAR METHODS FOR THE CHARACTERIZATION OF FUSARIUM-OXYSPORUM STRAINS

Sixty strains of Fusarium oxysporum were characterized using three DNA -based methods: restriction fragment length polymorphism (RFLP) analys is of total DNA after hybridization with a random DNA probe, polymeras e chain reaction (PCR)-based fingerprinting with primers matching ente robacterial repetitive intergenic consensus (ERIC) sequences and repet itive extragenic palindromic (REP) elements, and restriction fragment analysis of PCR-amplified ribosomal intergenic spacers (IGS). All meth ods yielded intraspecific polymorphisms, but different levels of discr imination were obtained. Good correlation was found between the groupi ngs obtained by the three methods. RFLP analysis of total DNA was the most sensitive method, enabling the detection of 40 variants within th e sample of 60 strains. However, this technique is more time-consuming than the PCR-based methods. By ERIC- and REP-PCR fingerprinting and P CR/RFLP analysis of the IGS, the 60 strains were categorized into 27 a nd 11 genotypes, respectively. Though less discriminant, the PCR/RFLP method allowed estimation of the genetic relationships between the str ains. Discrimination of closely related strains within IGS genotypes c ould be achieved by ERIC- or REP-PCR fingerprinting, which is the most efficient procedure in terms of simplicity and rapidity. Therefore, t he two PCR-based procedures described in this paper appear to be rapid tools for the genetic characterization of large populations of F. oxy sporum.