Progress on Study of Resistance Mechanism of Strobilurin Fungicides

The main resistance mechanism of strobilurin fungicides was reviewed according to the documents of laboratory studies and field experiments and their characteristics of mode of action.Strobilurin fungicides mainly bind to Qo site of cytochrome b of the cytochrome bc1 complex in fungi .Since cytochrome b is coded by mitochondrial DNA with high mutant frequency,fungi are easily to express resistance to Qo inhibitors as a result of the DNA mutation.After 10 years of field application,at least 25 pathogens on 14 hosts have already developed resistance to strobilurin fungicides.The resistance mechanism of strobilurin fungicides is mainly amino acid residue single point substitution of the cytochrome b in fungi,and the substitution in the field resistance was G143A,F129L or G137R,respectively.However,in some non-target organism the amino acid residue 143 of the cytochrome b is alanine,and this is the reason of why they show resistance to strobilurin fungicides in all probability.Since the intron scissor position of rust pathogens (Puccinia spp.) tagged behind GGT encoding G143 in cytochrome b,and the substitution of G143A would cause the death of the pathogen,therefore,rust seldom develops resistance to strobilurin fungicides that caused by substitution of G143A in the field.Furthermore,if Qo inhibitors inhibit the electron transport in mitochondrial,the reactive oxygen species (ROS) will burst,which will induce cells to express alternative oxidase (AOX) and subsequently startup alternative pathway to cause resistance towards strobilurin fungicides.Therefore,amino acid residue single point substitution and expression of AOX are the main mechanisms of fungi resistance to strobilurins.