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Objectives
To develop a rational approach to the use of fungicides to control diseases by:
Background
Many plant pathogenic fungi are not crop specific and consequently fungicide use on one crop can affect the development of fungicide resistance in diseases of other crops. It has become necessary to plan the use of fungicides to extend their effective life and this is aided by research on the mechanisms of resistance related to fungicide uptake, fungicide detoxification, alterations to the fungicide binding sites and altered membrane properties.
Research
The uptake of iprodione, lipid peroxide content and the activities of both catalase and superoxide dismutase enzymes in dicarboximide-sensitive and dicarboximide-resistant strains of Botrytis cinerea from grapevines were studied.
Outcome
B. cinerea resistant to
benzimidazoles and dicarboximides occurred in several grape growing
regions in Australia. A rapid resistance test for dicarboximides
using catalase as a biochemical marker has been developed. This
test can be validated using a wide range of fungal pathogens resistant
to dicarboximide fungicides.
An understanding of the mechanism of action of dicarboximides
obtained in this project suggests that dicarboximides may cause
the formation of reactive free radicals in the fungal cells. This
project has also demonstrated that dicarboximides caused lipid
peroxidation of fungal membranes.
This project shows similarities in the uptake of dicarboximides by resistant and susceptible strains of B. cinerea. The uptake of benomyl was found to be concentration-dependent. The importance of such work is efficient use of chemicals to reduce bunch rot of grapes, which starts with primary infection of the flower clusters by B. cinerea. The systemic action of a fungicide will lower the inoculum within the flowers. Benomyl would serve that purpose. The role of iprodione would be to protect the flowers from infection over a relatively longer period.
Implications
The occurrence of fungicide resistance in vineyard
populations of B. cinerea implies that an analytical approach
to resistance prediction is urgently required. One such approach
is resistance-monitoring, since it measures not only the existing
degree of resistance but also alerts to the possibility of a problem
arising in susceptible areas.
This project has developed a rapid test for dicarboximide
resistance using catalase as a biochemical marker. This will expedite
the screening of pathogen populations for resistance to dicarboximides.
An understanding of the mechanism of action of dicarboximides
obtained in this study suggests that dicarboximides may cause
the formation of reactive free radicals in the fungal cells. µ-Tocopherol
(Vitamin E) reversed the growth inhibition caused by dicarboximides
(iprodione). This study has also demonstrated that dicarboximides
caused lipid peroxidation of fungal membranes.
The results on uptake of benomyl and iprodione by
grapevine flowers showed the systemic nature of the former and
the relatively greater persistence of the latter chemical.
RIRDC Project No: DAN-38A
RESEARCHERS: Dr Tan Nair and Dr Chris Steel
ORGANISATION: NSW Dept of Agriculture
PMB 10
RYDALMERE NSW 2116
PHONE: 02 683 9777
FAX: 02 630 4475
Last updated: 10 October 1996
Copyright © RIRDC
Index of RIRDC Projects URL
http://www.rirdc.gov.au/pub/compendium/93-94/index-b.html