title: [Environmental fitness of metalaxyl-resistant isolate of Phytophthora capsici].
abstract: OBJECTIVE
  The environmental fitness of metalaxyl-resistant isolate of Phytophthora capsici was studied for assessing the risk of metalaxyl-resistant P. capsici.
  
  
  METHODS
  We studied the main biological characteristics, competitive ability on plate, pathogenicity on pepper plant and adaptability in soil of the laboratory-induced metalaxyl-resistant isolate of P. capsici (Pc2-3 strain), with the metalaxyl-sensitive isolate (Pc2 strain, the wild-type) as the control.
  
  
  RESULTS
  The zoosporangia production, releasing rate of zoosporangia and germination rate of zoospores of Pc2-3 were less than that of Pc2. The temperature range, optimum temperature range and initial pH range for mycelia growth of Pc2-3 were consistent with that of Pc2, but mycelia growth rate of Pc2-3 was lower than that of Pc2. Pc2-3 exhibited significantly weak competitive ability compared with Pc2 on carrots plate. Disease incidence of pepper inoculated with Pc2-3 (14.3%) was significantly lower than that of Pc2 (88. 6% ). When pepper plant was inoculated by mixtures of zoospore suspension of Pc2-3 and Pc2 at same ratio, the disease incidence, closing to that by Pc2 strain, was 75.7% . And all the strains isolated from diseased plants in the treatment were metalaxyl-sensitive. The density of P. capsis Pc2-3 was 0.28 times of Pc2 after the soil inoculated with Pc2-3 and Pc2 respectively at same zoospores density was incubated for 20 days. Otherwise, the ratio of Pc2-3 to Pc2 was 0.42 if the metalaxyl concentration in the soil was 300 mg/kg dry soil. No matter the soil temperature and humidity were beneficial to survival of P. capsici or not, Pc2-3 showed lower soil adaptability than Pc2.
  
  
  CONCLUSIONS
  The environmental fitness of metalaxyl-resistant P. capsis Pc2-3 was weaker than the metalaxyl- sensitive strain Pc2 (the wild-type).
authors.forename: Guangfei
authors.initials: G
authors.lastname: Wang
authors.forename: Yan
authors.initials: Y
authors.lastname: Ma
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives* / Q000494:pharmacology; D002212:Capsicum / Q000382:microbiology*; D025141:Drug Resistance, Fungal; D017753:Ecosystem; D005659:Fungicides, Industrial / Q000494:pharmacology*; D010838:Phytophthora / Q000187:drug effects* / Q000502:physiology*; D010935:Plant Diseases / Q000382:microbiology; D012987:Soil / Q000737:chemistry
chemical_list: D005659:Fungicides, Industrial; D012987:Soil; C028175:metalaxyl; D000409:Alanine