A Target-Based In Vivo Test System to Identify Novel Fungicides with Mode of Action in the HOG Pathway.

Resistance management plays a key role in modern plant protection. There is a growing need to identify new fungicide targets and new modes of action. In this context, it is also mandatory to find new compounds acting on successful target locations. For the latter, so-called target-site-specific test systems emerged to search for inhibitors. Most of them are based on in vitro assays, in which interaction between a compound and a purified target protein is demonstrated. Consequently, getting essential information about potentially toxic effects in the living cell or in the whole organism is not possible. Thus, we present a fluorescent-labelled mutant strain of the rice blast fungus Magnaporthe oryzae as a rapid tool for fluorescence-based identification and visualization of fungicides in vivo with the mode of action in the high osmolarity glycerol (HOG)-signaling pathway. The HOG pathway represents an excellent target for antifungal agents such as the phenylpyrrole fungicides, since almost no relevant resistances have occurred to date, despite 30 years of extensive usage of this fungicide class.