Tricyclazole and azoxystrobin in rice blast management : a review of thier activity ad pathogen responses

Magnaporthe oryzae, the causal agent of the rice blast disease, is one of the most important pathogens of cultivated rice worldwide. It can cause serious epidemics resulting in substantial yield and economic losses. Rice blast management relies on the use of fungicides in many regions. At present, there are approximately thirty fungicides registered worldwide, most of which are being used in Asia. In Europe, azoxystrobin and tricyclazole were registered for application on rice at the beginning of 1990’s and in Italy are being extensively used since then. In this chapter, the main chemical classes of fungicides used in rice blast management will be characterized, with emphasis on azoxystrobin and tricyclazole, which will be described in more detail. The molecular basis of their modes of action and their activity on various stages of pathogen life cycle will be defined. Despite having an important role in rice disease management, only scarce information about responses of the M. oryzae isolated from rice to azoxystrobin and tricyclazole are available, therefore the baseline response of the pathogen, risks and possible emergence of resistance to both fungicides will be discussed.