Distribution of mating type and metalaxyl-resistance of Phytophthora infestans in Fujian

The distribution of mating type and metalaxyl-resistance of Phytophthora infestansisolated during 1999-2002 in Fujian were investigated.The results showed that both A1 andA2 mating types existed in Fujian.Amongst 89 isolates tested,73 were A1 mating type,16were A2.The frequency of A1 and A2 were 82.1%,17.9%,respectively.The test for metal-axyl-resistance indicated that the proportion of resistant,intermediate and sensitive were36.0%、48.3%、15.7%,respectively.The metalaxyl-resistance of different isolates weremarkedly different,the systemic protection value of metalaxyl at 1.0 μg/mL to sensitive iso-lates was 68.7%,however,that of metalaxyl at 500 μg/mL to resistance isolates was 69.7%.Results strongly indicated that metalaxyl-resistance has seriously developed in Phytophthora in-festans.