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Problems to test if you understand avr/R gene
interactions
1) Group the following strains into “races”?
Strain
Race 1
A
G
J
Race 2
B
H
Race 3
C
E
Race 4
D
Race 5
F
I
Cultivar 1
Species
Cultivar 2 Cultivar 3
Cultivar 4
HR
HR
HR
S
S
S
HR
HR
HR
S
S
S
S
S
S
S
HR
HR
S
S
HR
HR
S
S
HR
HR
HR
HR
HR
S
S
S
S
S
S
S
S
S
S
S
HR = Hypersensitive response S = susceptible
If you have called the race something different that doesn’t matter – it the
grouping of the strains that is important.
2)What would you predict the outcome of the following
interactions.
S
S
S
S
S
HR
S
HR
S
S
HR
HR
S
HR HR HR
3) If you assume that any race only has a single avirulence gene,
how many avirulence genes and resistance genes are needed
to explain the interactions in question 1? And what would the
cultivar genotypes be?
Four avirulence and resistance genes – (remember S = no
avr/R genes).
Cultivar 1 = 1, 3, 4
Cultivar 2 = none
Cultivar 3 = 1,2,3,
Cultivar 4 = 3
Remember, you may have called the genes something
different – that’s OK- it’s the grouping that is important.
4) On the diagram below, annotate





Hrp proteins = 1
A resistance gene product = 2
A hrp-dependent virulence gene = 3
A hrp-dependent avirulence gene = 4
A hrp-independent virulence gene = 5
5
4
3
3
3
1
2
5) You have generated a range of mutants in a bacteria
pathogen. Individual mutants have yielded the following
results when inoculated across a range of plant cultivars.
Based on these results decide whether you have mutated and
pathogenicity gene, a virulence gene, a hrp gene or an
avirulence gene.
Key. HR = Hypersensitive Response, Figures refer to a score
for disease severity. 5 = most severe, 0 = no response.
Wild type
Mutant 1
Mutant 2
Mutant 3
Mutant 4
Mutant 5
Cultivar 1
Cultivar 2
Cultivar 3
Cultivar 4
HR
0
HR
4
HR
HR
5
0
3
5
1
0
5
0
1
5
2
0
HR
0
HR
4
HR
HR
Mutant 1 = hrp mutant
Mutant 2 = virulence mutant
Mutant 3 = avirulence mutant
Mutant 4 = virulence mutant
Mutant 5 = pathogenicity mutant
6) The following schematics represent the Pto, Xa21, RPM1, N
and Cf9 resistance genes. Based on the colour coded motifs ,
identify which is which.
Cf9
N
RPM1
2
Xa21
Pto