Changes of Phytophthora infestans isolates sensitivity to fungicides depending on mycelium age and contact with fungicides.

摘要

Five Phytophthora infestans isolates collected from potato and tomato were investigated on their response to modern fungicides, i.e., Shirlan [fluazinam], Amistar [azoxystrobin] (Quadris), and Ridomil [metalaxyl] according to age of mycelium and at sequential and crossed transferring of equal inocula (mycelial blocks) on oatmeal agar with sub-lethal fungicide concentration. These isolates were shown to demonstrate essential changes of sensitivity to fungicides without contact with them. During the incubation for 15, 30 or 60 days, the sensitivity to fungicides changed in different ways. Adaptive decrease of sensitivity (both sequential and crossed) was found only for some combinations of isolates and fungicides. The adaptation to fungicides was isolate-specific. The adaptive possibilities of one A2 isolate were much higher than in A1 isolates. Application of Shirlan, as a rule, suppressed the development of isolates. In some cases, crossed decrease of sensitivity to Amistar was observed. Ridomil in many cases was not efficient. The obtained data on efficiency of fungicides are in agreement with results of field trials. Application of different fungicides can lead to accumulation of isolates with adaptive possibilities in the field P. infestans populations, which may lead to a potential hazard for potato growers.