ABSTRACT
This chapter discusses the various mechanisms of action of fungicides, the different mechanism of resistance in fungi, and the factors which govern the buildup of a resistant pathogen population in the field. Prior to the advance of the synthetic systemic fungicides, various antibiotics had been used for systemic disease control in the 1940s and 1950s. The sites of action appeared to be in protein synthesis, chitin synthesis, mitosis, and the functioning of the protoplast membrane. After the introduction of the chemically more simple synthetics, the use of the rather complicated antibiotics in practice has declined markedly. With specific-site inhibitors, resistance may be monogenic or polygenic. Genetic changes which result in fungicide resistance in an originally sensitive cell may also influence other characteristics of the cell. In order to keep antiresistance strategies possible in the future, it is essential that a varied arsenal of fungicides with different mechanisms of action remains available.
