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. 2005 Tornado TT 2004 Kimberley Released Rivette Sapphire Beacon Surpass 400 0 1 2 3 4 5 6 7 8 9 Blackleg rating Effect of overcoming major gene verse polygenic resistance 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 % extra disease in Surpass501TT 50 40 30 20 10 0 2004 -10 2005 2006 2007 2008 2007 2008 70 60 % blackleg infection 60 % blackleg infection ATR-Beacon 70 45Y77 50 40 30 20 50 40 30 20 10 10 0 0 45Y77 ATR-Beacon AV-Garnet 45Y77 Dune AV-Garnet % blackleg infection % blackleg infection 60 50 40 30 20 10 0 45Y77 ATR-Beacon AV-Garnet 2007 stubble type AV-Garnet Dune 2007 stubble type 2007 stubble type 70 ATR-Beacon Dune Hyola50 70 60 50 40 30 20 10 0 45Y77 ATR-Beacon AV-Garnet 2007 stubble type Dune We can identify problems before they occur on a large scale ◦– but are sure to miss some Hyola50 BravoTT Blackleg is all speed but little puff Isolation distance required % Severe internal blackleg infection 100 90 6 Months 80 18 Months 70 30 Months 60 50 40 30 20 10 0 0 250 500 750 Distance (m) from canola stubble >850 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. Annual rainfall (mm) Autumn rainfall total Month sown Canola intensity % on farm Cultivar Blackleg rating Jockey or Impact seed dressing Dist to 1 year old stubble Dist to 2 year old stubble Dist 1 yr old stubble of same cultivar Dist 2 yr old stubble of same cultivar Years of same cultivar sown in a row Individual factor score Blackleg risk severity factor Rainfall 9 8 7 6 5 4 3 <550 >500 >450 >400 >400 >350 >300 <20% 20% 15% 10% MS-S MS MRMS MR 500 >500 Canola intensity Blackleg rating Dist to stubble Years of same cultivar VS S-VS S 0 100 250 <3 Years 2 1 >250 5% R-MR R 3 years Total score Your score Individual factor score Blackleg risk severity factor Rainfall 9 8 7 6 5 4 3 <500 >500 >450 400 >400 >350 >300 <20% 20% 15% 10% Canola intensity Blackleg rating Dist to stubble Years of same cultivar S-VS S MS-S MS MRMS MR 0 100 200 300 400 500 >500 3 years 1 Your score >250 5% VS <3 Years 2 2 R-MR R 1 0 Total score 34 Clear cut Genotypes Resistance gene Variety Wesbrook TAPAROO Oscar 46C76 Thunder TT BLN3347 Karoo Dunkeld Rlm1 - Rlm2 - Rlm3 + + + - Rlm4 + + + + Rlm5 - Rlm6 - Rlm7 - Rlm8 - Rlm9 - or H - RlmS - Wesroona Tl1Pinnacle Tarcoola Tornado TT AV Garnet Ripper Surpass400 Rocket CL Dune Oasis CL Sahara CL + + ? ? ? ? + ? ? ? ? + ? ? ? ? H (75%) + + + ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? + + + + + ? ? ? ? ? + ? ? ? ? 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 May get leaf lesions May get some internal infection R MR Will get leaf lesions Will get some internal infection Some external canker Some plant death (high disease pressure situations) Will get leaf lesions Will get internal infection Will get external canker Plant death (moderate to high disease pressure situations) MS S VS If sown in moderate disease pressure situations plant death may be severe If sown in moderate disease pressure situations plant death may be extremely severe