Resistance Breeding

Question 1

What are the advantages of resistant cul􀆟vars for the farmer?

Answer 1

Reducing the risk of yield reduc􀆟on due to the pathogens
Reduc􀆟on of pes􀆟cide use, thus reduced costs for pes􀆟cides and applica􀆟on
Reducing the risk for fungicide resistance
Essen􀆟al for diseases without chemical control
Slower spread of diseases => it’s possible to grow a culture more o􀅌en
Cheaper produc􀆟on for farmer

Question 2

If you are a plant breeder, which criteria you need to decide for star􀆟ng a program
for resistance breeding for a specific disease?-

Answer 2

Economic relevance of the disease  is the disease causing big losses in
yield? (e. g. BaYMV-complex/barley, Fusarium head blight/wheat)
-Availability of alterna􀆟ves (agronomy, fungicides,…) and would the advantages
of using a resistant cul􀆟var jus􀆟fy the higher price?  If I could save ten 􀆟mes
of spraying, the resistant cul􀆟var is more of interest as if I would save only 3
􀆟mes of spraying
-Availability of resistance sources (elite material, foreign cul􀆟vars, gene􀆟c
resource)
-Inheritance of the resistance (simple, complex): Important for predic􀆟ng the
workload and also the money input for breeding the resistant cul􀆟var
-Economic input (natural / ar􀆟ficial infec􀆟ons necessary, assessment)

Question 3

What is the disease triangle, name some of the effects, and what are the
consequences for resistance tes􀆟ng?

Answer 3

the disease triangle says that the environment effects both, the host and the
pathogen, while host and pathogen are also in interac􀆟on. These rela􀆟ons determine.
the severity of an infec􀆟on
Consequences for resistance tes􀆟ng:
-You need to know which pathogens are present in the environment
-A resistance tes􀆟ng needs to be done in different environments, with different
hosts and different pathogen races  huge workload; expensive
-As the genotype of the host should be determined during resistance tes􀆟ng as
exactly and reproducable as possible, all other factors should be standardized.
as far as possible. With sta􀆟s􀆟cal methods, it’s possible to separate the

interac􀆟ons (host x environment, pathogen x environment, host x pathogen, …

Question 4

Which differences between qualita􀆟ve and quan􀆟ta􀆟ve resistances do you know?Qualita􀆟ve resistance:
-Discon􀆟nuous distribu􀆟on Either plant is resistant (avirulent pathogen) or not
(virulent pathogen)
-Ver􀆟cal resistance (race-specific)  Plant can be resistant to certain races of
a type of pathogen, but resistant to other races of this type
-Resistance effect is differen􀆟al and full
-Monogenic inheritance  Simple type of inheritance, easy to work with
-In most cases low durability (adap􀆟on of the pathogen)
Quan􀆟ta􀆟ve resistance:
-Con􀆟nuous distribu􀆟on  Different levels of resistance/suscep􀆟bility (different
levels of aggressiveness of pathogen)
-Horizontal resistance (not race-specific)  Resistant to all races of a certain
type of pathogen
-Resistance effect is uniform, par􀆟al, field resistance, „background resistance“,
„slow rus􀆟ng“/ „slow mildewing“, durable
-Oligo-/ polygenic inheritance  Complicated (work intensive)
-High durability