Fungicide Resistance Dynamics: Knowledge from Downy Mildew Management in Japanese Vineyards

This review summarizes the mechanisms and historical development of fungicides registered for grape downy mildew control in Japan, with a particular focus on their diverse molecular targets, including cell division and mitochondrial respiration. Grapevine downy mildew is one of the most important pathogens in Japanese grapevine cultivation. Grapevine downy mildew tends to be fungicide-resistant, and in recent years, a quinone outside inhibitor (QoI) fungicide-resistant strain of downy mildew has caused extensive damage in Yamanashi Prefecture, making headlines in newspapers. Although approximately 60 fungicides have been registered for downy mildew management in Japan, many have been withdrawn due to the emergence of resistant pathogen populations. Recent challenges with resistance to quinone outside inhibitors, carboxylic acid amides, and oxysterol-binding protein inhibitors underscore the ongoing importance of resistance management in Japanese viticulture and grape downy mildew control strategies.