This document discusses fungicide resistance in agriculture. It begins by explaining that fungicides are commonly used to control fungal diseases but can have negative impacts if used improperly. Repeated and improper use can lead to fungicide resistance in fungal pathogens. There are two main types of fungicide resistance: qualitative, which results in complete loss of disease control, and quantitative, which develops more gradually. The document then covers various mechanisms that can cause fungicide resistance, such as altered target sites or efflux pumps. It concludes by emphasizing the importance of integrated pest management and diversifying fungicide use to delay further development of resistance.

1. PRESENTED BY:
Yangki Kiirong Taki
M-894/15
MSc (Ag) 2nd yr.
Department of Plant Pathology

2.  Fungicides are widely used in agriculture for
for control of fungal disease and crop yield.
 Their intensive and faulty use can have
adverse impacts on crops, useful antagonistic
organism and environment. Its use may even
lead development of fungicide resistance
strain.
 Fungicide resistance not only threatens the
usefulness of individual of fungicides, but
also the farm economy because of potential
yield losses from poor disease control

3. Fungicide resitance : Defined as stable,
inheritable adjustment by a pathogen to a
fungicide, resulting in reduced sensitivity of
the pathogen to fungicide.

4.  Improper use of fungicides leads to
development of fungicide resistance
 Genetic mutation occurs in the pathogen.
 Repeated used of particular fungicides exerts
selection pressure in the fungal population.
 Results in selection of resistant strain and
failure in disease control.

6.  QUALITATIVE RESISTANCE:
 Complete loss of disease control.
 It is associated with site specific fungicide.
 QUANTITATIVE RESISTANCE:
 Develops over time, a continuous variation in
sensitivity to a fungicide within a pathogen
population .
 Ocuurs in fungicideshaving multi site action.

7.  CROSS RESISTANCE
 Pathogen population that is resistant to one
fungicide within a group, develops resistant
over other members of that same group.
 MULTIPLE RESISTANCE:
 Pathogen populations have been shown to
develop resistance to fungicides from more
than one chemical group

8.  ALERTED TARGET SITE:
o A fungicide has a
specific target site
where it acts to disrupt
a particular
biochemical process
o If this site altered
fungicide no longer
binds to site of action
and unable to exert its
toxic effect

9.  DETOXIFICATION OF THE FUNGICIDE:
. This metabolic machinery may be able
to modify the fungicide to a non-toxic form.
 OVEREXPRESSION OF THE TARGET:
The production of additional target site
enzyme may increase the likelihood that enough
of the fungal substrate will be able to bind with
the target site enzyme such that cellular
processes such as respiration can occur to some
degree.

11.  Exclusion or expulsion from the target site:
 Efflux pumps exist within the cell to exclude
or expel foreign substances or to export
endogenous substances.
 In fungi, the most common efflux pumps are
ABC and MFS transporters.

12. Fungicide of Fungicide Class Mechanism of resistance
Aromatic hydrocarbons Unknown, but show cross-resistance with dicarboximides and
phenylpyrroles
Organo-mercurial *Detoxification by binding substances
Dodine Unknown
Benzimidazoles Altered target site (B-tubulin)
2-Amino-pyrimidines Unknown
Kasugamycin Altered target site (ribosomes)
Phosphorothiolates Metabolic detoxification
Phenylamides Possibly altered target site (RNA polymerase)
Dicarboximides and Phenylpyrroles *Altered target site ( protein kinase involved in
osmoregulation)
DMIs Increased efflux; altered target site; decreased demand for
target-site product; target-site over-production
Carboxanilides Altered target site (succinate-ubiquinone oxidoreductase
QoIs (strobilurins) Altered target site (ubiquinol-cytochrome c reductase)
Melanin Biosynthesis Inhibitors (Dehydratase) MBI-D Altered target site (scytalone dehydratase)
*Some doubt regarding occurrence in field isolates

13.  Do not use the product exclusively
 Apply it as a mixture with one
 More fungicides of a different type
 As one component in a rotation or
alternation of different fungicide treatments

14.  Restrict the number of treatments applied
per season, and apply only when strictly
necessary
 Maintain manufacturers’ recommended
dose
 Avoid eradicant use
 Integrated disease management
 Chemical diversity

15.  Fungicide resistance has created challenges
for both the agrochemical industry to
discover and commercialise novel modes of
action, and for growers to successfully
incorporate new products into effective
disease control strategies without reducing
productivity.
 By integrating fungicide use with other
disease control approaches, along with
growers have a key role to play in delaying
resistance by reducing the need for
fungicides.

16. THANK YOU