Abstract
This chapter discusses the evolutionary processes that give rise to and disperse the resistance alleles to quinone outside inhibitors (Qols). It is shown that the development of fungicide resistance often involves amino acid substitutions, caused mainly by spontaneous mutations at one or several positions in the target gene. The substitution of amino acid enables alteration in the protein structure, so the active substance of the fungicide cannot attach properly, leading to failure in efficacy. The substitutions are then selected for during fungicide application, and the population of less sensitive strains is increased. The mutations may also be forced to evolve by the use of fungicides or in laboratory experiments through radiation or gene transfer. Case studies in Europe are presented on Mycosphaerella graminicola, Phaeosphaeria nodorum, Alternaria solani and Rhynchosporium secalis, which disclose the evolutionary patterns underlying the emergence and spread of resistance allele to QoIs. Such studies represent the first step toward improved models to forecast the emergence and spread of fungicide resistance, and they might be helpful in understanding better the yet unpredictable spatial and temporal scales over which fungicide resistance develops.