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Genetic and biochemical mechanisms of fungicidal action, selectivity and resistance

Reference	BBS/E/C/00813816
Principal Investigator / Supervisor	Dr Derek Hollomon
Co-Investigators / Co-Supervisors
Institution	Rothamsted Research
Department	Rothamsted Research Department
Funding type	Research
Value (£)	152,235
Status	Completed
Type	Institute Project
Start date	01/04/1997
End date	17/07/2000
Duration	39 months

Abstract

Details should only be considered in the context of PU information. The genetic and biochemical processes that underlie fungicide resistance problems are obscure in many cases, as are the roles of fitness, cultivar compatibility and pathogenicity. Detailedstudies of changes in these factors associated with loss of fungicide sensitivity are being pursued with major plant pathogens - currently barley powdery mildew, Rhynchosporium and eyespot in relation to DMI, morpholine anilinopyrimidine, and MBC fungicides. This includes assessment of likelihood of the risk of resistance developing to new fungicides. Isolation of putative resistance genes and transfer between fungal strains and species is proceeding. Possible exploitation of biochemical and genetical changes in identification of resistant forms will be explored, including the probing of changes to the nucleotide sequence of fungicide resistance genes. Mechanisms of fungitoxicity and of selectivity in modern fungicides may be unrelated, or they may be associated with the same biochemical process. Sterol biosynthesis inhibitors (SBIs) are an important class of fungicides but much remains to be learned about their mode of action and selectivity, and the cause of resistance in some pathogens. Potential new fungicides with novel modes of action are examined, together with work aimed at identifying new target sites and exploring the rational design of inhibitors. These questions are being investigated in a multidisciplinary approach involving chemists, biochemists and biologists. Biochemical effects of SBI fungicides on certain important pathogens are investigated in detail, and relationships between degree of sterol alteration and degree of inhibition of fungal growth are compared between major groups of fungal pathogens. Industrial companies contribute to this work at intervals. In Pseudocercosporella herpotrichoides (cereal eyespot) anilinopyrimidines inhibit excretion of hydrolytic enzymes, and their toxicity is reduced by addition of casamino acids to the culture medium. This new fungicide group may have more than one site of action and these may relate to different resistance mechanisms. At least one of these resistance mechanisms is controlled by a single gene, whilst molecular analysis has shown that another involves amplification of a DNA fragment. Sequence analysis of this fragment has not identified a possible function.

Summary

unavailable

Committee	Closed Committee - Plant & Microbial Sciences (PMS)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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