Résumé
The most economically important diseases of grapevine cultivation worldwide are caused by the fungal pathogen powdery mildew (
E
rysiphe necator
syn.
U
ncinula necator
) and the oomycete pathogen downy mildew (
P
lasmopara viticola
). Currently, grapegrowers rely heavily on the use of agrochemicals to minimize the potentially devastating impact of these pathogens on grape yield and quality. The wild
N
orth
A
merican grapevine species
M
uscadinia rotundifolia
was recognized as early as 1889 to be resistant to both powdery and downy mildew. We have now mapped resistance to these two mildew pathogens in
M
. rotundifolia
to a single locus on chromosome 12 that contains a family of seven
TIR
‐
NB
‐
LRR
genes. We further demonstrate that two highly homologous (86% amino acid identity) members of this gene family confer strong resistance to these unrelated pathogens following genetic transformation into susceptible
V
itis vinifera
winegrape cultivars. These two genes, designated
r
esistance to
U
ncinula
n
ecator
(
M
r
RUN
1
) and
r
esistance to
P
lasmopara
v
iticola
(
M
r
RPV
1
) are the first resistance genes to be cloned from a grapevine species. Both
M
r
RUN
1
and
M
r
RPV
1
were found to confer resistance to multiple powdery and downy mildew isolates from
F
rance,
N
orth
A
merica and
A
ustralia; however, a single powdery mildew isolate collected from the south‐eastern region of
N
orth
A
merica, to which
M
. rotundifolia
is native, was capable of breaking
M
r
RUN
1
‐mediated resistance. Comparisons of gene organization and coding sequences between
M
. rotundifolia
and the cultivated grapevine
V
. vinifera
at the
M
r
RUN
1
/
M
r
RPV
1
locus revealed a high level of synteny, suggesting that the
TIR
‐
NB
‐
LRR
genes at this locus share a common ancestor.