Resistance risk assessment of Phytophthora capsici to metalaxyl in Anhui province

Resistance of Phytophthora capsici isolates from Anhui province to metalaxyl was investigated. The results showed that the metalaxyl sensitive isolates,metalaxyl tolerant and metalaxyl resistant isolated were 63.2%,30.4% and 6.4%,respectively. It indicated that most of Phytophthora capsici isolates from Anhui were sensitive to metalaxyl,but the EC50 value showed that the sensitivity to metalaxyl has a diverse differentiation among these isolates. Metalaxyl resistant isolates were induced in vitro. It showed that resistant mutants are easy obtained from metalaxyl amended media,and the resistant level was about 1 000 times of that of the sensitive wild-type. These studies indicate that there might be resistance risk to metalaxyl in the isolates of Phytophthora capsici. The strategy of the resistant risk management is discussed in the paper.