Biocontrol activity in a nonpathogenic REMI mutant of Fusarium oxysporum f. sp conglutinans and characterization of its disrupted gene

A nonpathogenic mutant (REMI 10) of Fusarium oxysporum f. sp. conglutinans (FOC) was generated by restriction enzyme-mediated integration (REM 1). REM I 10 penetrated the cabbage root cortex much slower than, FOC and never invaded the xylem through the endodermis. Previous treatment of cabbage seedlings with REM] 10 reduced the disease incidence of yellows caused by FOC, suggesting that REMI 10 has biocontrol activity. FOC invasion into root tissues was restricted when the seedling was treated with REMI 10. The gene disrupted in REM I 10 genome by plasmid insertion was identified,and designated sapl, which encodes a putative secreted aspartic proteinase. The sal)l disruptants showed no reduction in virulence toward cabbage, Suggesting that SAPI is not essential for pathogenicity in FOC. (c) Pesticide Science Society of Japan