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) analysis of total DNA after hybridization with a random DNA probe, polymerase chain reaction (PCR)-based fingerprinting with primers matching enterobacterial repetitive intergenic consensus (ERIC) sequences and repetitive extragenic palindromic (REP) elements, and restriction fragment analysis of PCR-amplified ribosomal intergenic spacers (IGS). All methods yielded intraspecific polymorphisms, but different levels of discrimination were obtained. Good correlation was found between the groupings obtained by the three methods. RFLP analysis of total DNA was the most sensitive method, enabling the detection of 40 variants within the sample of 60 strains. However, this technique is more time-consuming than the PCR-based methods. By ERIC- and REP-PCR fingerprinting and PCR/RFLP analysis of the IGS, the 60 strains were categorized into 27 and 11 genotypes, respectively. Though less discriminant, the PCR/RFLP method allowed estimation of the genetic relationships between the strains. Discrimination of closely related strains within IGS genotypes could be achieved by ERIC- or REP-PCR fingerprinting, which is the most efficient procedure in terms of simplicity and rapidity. Therefore, the two PCR-based procedures described in this paper appear to be rapid tools for the genetic characterization of large populations of F. oxysporum.