GENETIC-BASIS AND MONITORING OF RESISTANCE OF BOTRYOTINIA-FUCKELIANA TO ANILINOPYRIMIDINES

The anilinopyrimidines constitute a new class of mainly protective, br oad-spectrum fungicides with a high activity against Botryotinia fucke liana, the causal agent of gray mold an a wide range of host plants, T he present study was initiated to investigate the genetic basis of res istance to anilinopyrimidines in B. fuckeliana and to assess the frequ ency of resistant isolates in vineyards in Switzerland exposed to expe rimental applications of anilinopyrimidines. In mating experiments, tw o sensitive reference isolates were crossed with three anilinopyrimidi ne-resistant field isolates. The analysis of 72 sexual progeny from si x apothecia demonstrated that resistance to the anilinopyrimidine fung icide cyprodinil segregated in a 1:1 ratio and is therefore monogenic. The same segregation ratio was found for resistance to the dicarboxim ide fungicide vinclozolin. Resistance to cyprodinil segregated indepen dently from resistance to vinclozolin. From 1993 to 1995, isolates of B. fuckeliana were collected in Switzerland from five vineyards that d iffered in their anilinopyrimidine spray history. Of a total of 303 is olates tested in vitro. three anilinopyrimidine-resistant isolates wer e detected in two vineyards where the cumulative number of treatments was between two and nine. The results of the study are discussed with respect to the implementation of an antiresistance strategy in Switzer land.