steve marcroft – marcroft grains pathology, horsham phil salisbury, barb howlett – university of...
TRANSCRIPT
Steve Marcroft – Marcroft Grains Pathology, Horsham
Phil Salisbury, Barb Howlett – University of Melbourne
Trent Potter - SARDI
Unlike asexual rusts, blackleg is sexually reproducing
In contrast, all cereal rust spores are identical so cereal resistance genes will be effective against all rust spores until a mutation occurs or new introduction of a new strain (pathotype) from overseas.
Blackleg spores are all genetically different.
When you grow a new resistant canola variety there are already blackleg spores that can attack your variety.
When you grow the same variety year after year you select blackleg spores that can attack and therefore resistance can be overcome.
Varieties with a number of minor genes (polygenic) may lose resistance gradually.
Varieties with single major genes can go from resistant to susceptible very quickly.
Some varieties have lost resistance quickly others have never lost resistance.
The 2009 blackleg ratings have ‘Reduced Resistance’ warnings.
Effect of overcoming major gene verse polygenic resistance
01
23
45
67
89
Bla
ck
leg
ra
tin
g
Su
rpa
ss
40
0
Be
ac
on
Sa
pp
hir
e
Riv
ett
e
Kim
be
rle
y
To
rna
do
TT
Released 2004 2005 2006
Durability to blackleg differs between regions
NSW no issue in last 5 years
regional climate seasonal conditions canola intensity
Higher rainfall regions. Intensive canola production. Growing the same cultivar for the third year
or more in a row. Proximity to last year’s canola stubble.
Canola cultivars can regain blackleg resistance
-10
0
10
20
30
40
50
2004 2005 2006 2007 2008
% ex
tra di
seas
e in S
urpa
ss50
1TT
2007 2008
0
10
20
30
40
50
60
70
45Y77 ATR-Beacon AV-Garnet Dune
% b
lack
leg
infe
ction
2007 stubble type
45Y77
0
10
20
30
40
50
60
70
45Y77 ATR-Beacon AV-Garnet Dune
% b
lack
leg
infe
ction
2007 stubble type
ATR-Beacon
0
10
20
30
40
50
60
70
45Y77 ATR-Beacon AV-Garnet Dune
% b
lack
leg
infe
ction
2007 stubble type
AV-Garnet
010203040506070
45Y77 ATR-Beacon AV-Garnet Dune
% b
lack
leg
infe
ction
2007 stubble type
Hyola50
We can identify problems We can identify problems before they occur on a before they occur on a large scale large scale ◦– – but are sure to miss but are sure to miss some some
Hyola50 BravoTT
Blackleg is all speed but little puff
0
10
20
30
40
50
60
70
80
90
100
0 250 500 750 >850
Distance (m) from canola stubble
% S
ev
ere
inte
rna
l bla
ckl
eg in
fect
ion
6 Months
18 Months
30 Months
Isolation distance required
1. Annual rainfall (mm)2. Autumn rainfall total3. Month sown4. Canola intensity % on farm5. Cultivar Blackleg rating6. Jockey or Impact seed dressing7. Dist to 1 year old stubble8. Dist to 2 year old stubble9. Dist 1 yr old stubble of same cultivar10. Dist 2 yr old stubble of same cultivar11. Years of same cultivar sown in a row
Blackleg risk severity factor
Individual factor score
9 8 7 6 5 4 3 2 1 Your score
Rainfall <550 >500 >450 >400 >400 >350 >300 >250
Canola intensity
<20%
20% 15% 10% 5%
Blackleg rating
VS S-VS S MS-S MS MR-MS
MR R-MR R
Dist to stubble
0 100 250 500 >500
Years of same cultivar
<3 Years
3 years
Total score
Blackleg risk severity factor
Individual factor score
9 8 7 6 5 4 3 2 1 Your score
Rainfall <500 >500 >450 400 >400 >350 >300 >250
Canola intensity
<20%
20% 15% 10% 5%
Blackleg rating
VS S-VS S MS-S MS MR-MS
MR R-MR R
Dist to stubble
0 100 200 300 400 500 >500
Years of same cultivar
<3 Years
3 years
2 1 0
Total score 34
Resistance gene
Variety Rlm1 Rlm2 Rlm3 Rlm4 Rlm5 Rlm6 Rlm7 Rlm8 Rlm9 RlmS
Wesbrook - - - - - - - - - -
TAPAROO - - + - - - - - - -
Oscar - - + - - - - - - -
46C76 - - + - - - - - - -
Thunder TT - - - + - - - - - -
BLN3347 - - - + - - - - - or H -
Karoo - - - + - - - - - -
Dunkeld - - - + - - - - - -
Wesroona - - - H (75%) - - - - - -
Tl1Pinnacle - - + - - - - - + -
Tarcoola - - - + - - - - + -
Tornado TT - - - + - - - - + -
AV Garnet + - - - - - - - + -
Ripper - + - + - - - - + -
Surpass400 + - - - - - - - ? +
Rocket CL ? ? ? ? ? ? ? ? ? ?
Dune ? ? ? ? ? ? ? ? ? ?
Oasis CL ? ? ? ? ? ? ? ? ? ?
Sahara CL ? ? ? ? ? ? ? ? ? ?
Clear cut Genotypes
Numerical 1 - 9 has been replaced with alpha R to VS scale.
The alpha scale is consistent with other crop disease rating scales including cereals
BUT….
Cereals– R = immune
Canola– R = does not imply complete immunity
R May get leaf lesions May get some internal infection
MR Will get leaf lesions Will get some internal infection Some external canker Some plant death (high disease pressure situations)
MS Will get leaf lesions Will get internal infection Will get external canker Plant death (moderate to high disease pressure situations)
S If sown in moderate disease pressure situations plant death may be severe
VS If sown in moderate disease pressure situations plant death may be extremely severe