OCCURRENCE OF A RETROTRANSPOSON-LIKE SEQUENCE AMONG DIFFERENT FORMAE SPECIALES AND RACES OF FUSARIUM-OXYSPORUM

Populations of the plant pathogen Fusarium oxysporum are differentiated into formae speciales and races based on specificity to the various hosts and differences in virulence to host cultivars. A DNA fragment from the reverse transcriptase gene of the LTR-retrotransposon CfT-1 from Cladosporium fulvum was used as a heterologous probe to investigate the existence of retroelements in five formae speciales of F. oxysporum. Polymorphism in the hybridization banding pattern using various restriction enzymes was detected between all formae speciales investigated but generally not between different races within a particular forma specialis. Results indicate that retrotransposon-like elements may be widespread in F. oxysporum, and that conservation of their genetic structure is correlated with classification of F. oxysporum into formae speciales.