Multidrug Efflux Transporters

Fungicide resistance is an increasing problem in agriculture and threatens the performance of fungicides to protect plants against fungal diseases. The most common mechanism of resistance in plant pathogenic fungi is target site alteration, which usually confers medium or high levels of resistance against a specific group of fungicides. Resistance based on increased drug efflux mediated by membrane transporters, called MDR (multidrug resistance), has been discovered as a significant alternative resistance mechanism in Botrytis cinerea field populations and also in a few other fungi. MDR is caused by mutations leading to overexpression of ABC- or MFS-type multidrug transporters, resulting in low to medium resistance levels against different classes of fungicides. The main MDR type in B. cinerea, called MDR1, is of practical relevance because it significantly reduces the sensitivity against the phenylpyrrole fungicide fludioxonil and the anilinopyrimidines. In several countries, B. cinerea populations have been observed in recent years that have acquired both MDR1 and target site resistance against all site-specific fungicides registered against Botrytis, which make chemical control of grey mould increasingly difficult.