Metalaxyl-resistant mutant strains of Phytophthora boehmeriae are as aggressive and fit as their metalaxyl-sensitive wild-type parents

Abstract Phytophthora boehmeriae Sawada is an important pathogenic oomycete, and causes blight of cotton ramie, which are main limiting factors to the production ramie in China. The aggressiveness fitness metalaxyl-resistant (MR) mutants P. obtained by inducing on LBA amended with sublethal dose (10 µg·mL −1 ) metalaxyl were studied this paper. results showed that there no significant differences between MR their metalaxyl-sensitive (MS) wild-type parents temperature for mycelial growth, zoosporangium production, sensitivity malachite green, pathogenicity seedlings. However, oospore productions much lower than those MS parents. growth rates colony morphology all displayed obvious variation or separation, inherited unsteadily single-zoospore single-oospore progenies. At same time, homothallic character could inherit steadily as well isolates did asexual sexual It was suggested possessed equal parental isolates, would develop population easily a short time long formed. Thereby, be high risk development resistance populations field, when continuously applied control diseases caused boehmeriae.