Adaptation of fungi to fungitoxic compounds

Some fungitoxic chemicals often fail to protect crops because the target fungi develop resistance. Depending on its mechanism of action, the fungicide may lose its effectiveness completely after a limited number of applications, it may show a gradually less satisfactory performance or it may retain its effectiveness unchanged despite extensive use. In all cases investigated, resistance to agricultural fungicides has been shown to result from mutations of chromosomal genes. Biochemical mechanisms of adaptation have been recognized mainly as alterations of the cellular component with which the fungicide interacts, as reduced uptake or increased efflux, and as decreased conversion into a more toxic compound. However, most studies on biochemical genetics have utilized laboratory mutants and it is not always certain that similar mechanisms are responsible for adaptation in nature.