0
Departement Biochemie ● Department of Biochemistry
Potato virus Y in South Africa:
Isolate characterization and
assessment...
Introduction
• Only PVYN and PVYO with classic symptoms
and yield losses occurred in South Africa
before 1995
• After 1995...
Changes in symptom development
Mild mosaic symptoms PTNRD
Project goals
• Characterize South African PVY isolates to
understand changed symptom expression
• Establish speed of spre...
Approach for strain characterization
• Use CP gene sequencing and differential
RT-PCR for strain identification - 2004 to
...
Results of CP gene sequencing and
differential RT-PCR
133 PVY isolates characterized:
• PVYO isolates (7.5%)
– 10 PVYO str...
Approach for strain characterization
• Use CP gene sequencing and differential
RT-PCR for strain identification - 2004 to
...
Whole genome sequencing results
4 PVYN
1 SASA-61
1 PVYNE-11
15 PVYNTN
4 PVYN-Wilga
2 PVYO
Diagram showing recombination pa...
Whole genome sequencing results
Phylogenetic analysis of the whole genome
sequence data indicates that some PVYNTN
and PVY...
Project goals
• Characterize South African PVY isolates to
understand changed symptom expression
• Establish speed of spre...
Biological characterization
• Small scale greenhouse trial
• 4 cultivars, 7 isolates
• Mechanical infection
• Viral spread...
Isolate
Cultivar
Z001 Z16 SS607 31 Z14 NTN OVS GP
Hermes
Sifra
Mondial
Fabula
0
1
2
1 2 3 4 5
0
1
2
1 2 3 4 5
0
1
2
1 2 3 ...
Z001
NTN-OVS
Z14
SS607(31) Z16 GP
0
0: No symptoms
observed
ND: Not done
Z001 Z16 SS607 31 Z14 NTN-OVS GP
Hermes 100.00 80...
Z001
NTN-OVS
Z14
SS607(31) Z16 GP
0
0: No symptoms
observed
ND: Not done
Z001 Z16 SS607 31 Z14 NTN-OVS GP
Sifra 33.33 40.6...
Z001
NTN-OVS
Z14
SS607(31) Z16 GP
0
0: No symptoms
observed
ND: Not done
Z001 Z16 SS607 31 Z14 NTN-OVS GP
Mondial 16.95 2....
Z001
NTN-OVS
Z14
SS607(31) Z16 GP
0
0
0
0: No symptoms
observed
ND: Not done
Z001 Z16 SS607 31 Z14 NTN-OVS GP
Fabula 0.00 ...
Conclusions
• PVYN and PVYO have been replaced with
PVYNTN and PVYN-Wilga strains
• Some virus isolates spread rapidly in ...
Future work
• Assess rate of viral spread and tuber
necrosis formation in 20 of the most
planted cultivars in South Africa...
Acknowledgements
• APA 2013 conference organizers
• Coral de Villiers, Wiets Roos, University of
Stellenbosch
• Anel Espac...
Thank you for your attention
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Sess10 3 chris visser and dirk bellstedt – potato virus y in south africa – isolate characterization and assessment of potato cultivar resistance

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Transcript of "Sess10 3 chris visser and dirk bellstedt – potato virus y in south africa – isolate characterization and assessment of potato cultivar resistance"

  1. 1. Departement Biochemie ● Department of Biochemistry Potato virus Y in South Africa: Isolate characterization and assessment of potato cultivar resistance Chris Visser and Dirk Bellstedt Department of Biochemistry University of Stellenbosch
  2. 2. Introduction • Only PVYN and PVYO with classic symptoms and yield losses occurred in South Africa before 1995 • After 1995 mosaic leaf symptoms became less prominent • Tuber necrosis (PTNRD) observed for the first time in 2005 - associated with severe yield and quality losses for the potato producer
  3. 3. Changes in symptom development Mild mosaic symptoms PTNRD
  4. 4. Project goals • Characterize South African PVY isolates to understand changed symptom expression • Establish speed of spread and PTNRD symptom development in local cultivars in order to assess cultivar resistance to PVY infection
  5. 5. Approach for strain characterization • Use CP gene sequencing and differential RT-PCR for strain identification - 2004 to 2008 • Use whole genome sequencing of representative PVY strains for full characterization - 2009 to 2011
  6. 6. Results of CP gene sequencing and differential RT-PCR 133 PVY isolates characterized: • PVYO isolates (7.5%) – 10 PVYO strains • PVYN isolates (20.3%) – 22 PVYN strains – 4 PVYNE-11 from China – 1 SASA-61 from Scotland • Recombinant strains (72.2%) – 34 PVYN-Wilga strain (25.6%)(1 PTNRD phenotype) – 62 PVYNTN strain (46.6%)(20 PTNRD phenotype)
  7. 7. Approach for strain characterization • Use CP gene sequencing and differential RT-PCR for strain identification - 2004 to 2008 • Use whole genome sequencing of representative PVY strains for full characterization - 2009 to 2011
  8. 8. Whole genome sequencing results 4 PVYN 1 SASA-61 1 PVYNE-11 15 PVYNTN 4 PVYN-Wilga 2 PVYO Diagram showing recombination patterns No of isolates
  9. 9. Whole genome sequencing results Phylogenetic analysis of the whole genome sequence data indicates that some PVYNTN and PVYN-Wilga were imported via tissue culture material from Europe:
  10. 10. Project goals • Characterize South African PVY isolates to understand changed symptom expression • Establish speed of spread and PTNRD symptom development in local cultivars in order to assess cultivar resistance to PVY infection
  11. 11. Biological characterization • Small scale greenhouse trial • 4 cultivars, 7 isolates • Mechanical infection • Viral spread monitored by qRT-PCR • Tubers inspected for PTNRD Point of mechanical infection Monitored by qRT-PCR here
  12. 12. Isolate Cultivar Z001 Z16 SS607 31 Z14 NTN OVS GP Hermes Sifra Mondial Fabula 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 * * * Number of weeks Number of weeks Number of weeks Number of weeks Number of weeks Number of weeks Numberofplants Numberofplants Numberofplants Numberofplants Numberofplants Numberofplants 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 * * * Numberofplants Numberofplants Numberofplants Numberofplants Numberofplants Numberofplants Number of weeks Number of weeks Number of weeks Number of weeks Number of weeks Number of weeks 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5Number of weeks Number of weeks Number of weeks Number of weeks Number of weeks Number of weeks Numberofplants Numberofplants Numberofplants Numberofplants Numberofplants Numberofplants 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 0 1 2 1 2 3 4 5 * * 0 1 2 1 2 3 4 5 * * * * * Number of weeks Number of weeks Number of weeks Number of weeks Number of weeks Number of weeks Numberofplants Numberofplants Numberofplants Numberofplants Numberofplants Numberofplants Spread rate of PVYNTN isolates in 4 cultivars
  13. 13. Z001 NTN-OVS Z14 SS607(31) Z16 GP 0 0: No symptoms observed ND: Not done Z001 Z16 SS607 31 Z14 NTN-OVS GP Hermes 100.00 80.00 26.47 25.00 2.73 0.00 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 %TubersdisplayingPTNRD Hermes Tuber necrosis assessment
  14. 14. Z001 NTN-OVS Z14 SS607(31) Z16 GP 0 0: No symptoms observed ND: Not done Z001 Z16 SS607 31 Z14 NTN-OVS GP Sifra 33.33 40.63 5.56 13.64 0.00 5.66 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 %TubersdisplayingPTNRD Sifra Tuber necrosis assessment
  15. 15. Z001 NTN-OVS Z14 SS607(31) Z16 GP 0 0: No symptoms observed ND: Not done Z001 Z16 SS607 31 Z14 NTN-OVS GP Mondial 16.95 2.54 14.00 8.57 0.00 20.00 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 %TubersdisplayingPTNRD Mondial Tuber necrosis assessment
  16. 16. Z001 NTN-OVS Z14 SS607(31) Z16 GP 0 0 0 0: No symptoms observed ND: Not done Z001 Z16 SS607 31 Z14 NTN-OVS GP Fabula 0.00 4.88 6.58 0.00 0.00 9.68 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 %TubersdisplayingPTNRD Fabula Tuber necrosis assessment
  17. 17. Conclusions • PVYN and PVYO have been replaced with PVYNTN and PVYN-Wilga strains • Some virus isolates spread rapidly in the potato plant and induce tuber necrosis • Some potato cultivars only allow slower viral spread and exhibit less tuber necrosis • Together viral spread and ability to induce tuber necrosis give an indication of potato cultivar resistance
  18. 18. Future work • Assess rate of viral spread and tuber necrosis formation in 20 of the most planted cultivars in South Africa • Use rate of viral spread and PTNRD symptom development data to establish the levels of PVY resistance in cultivars planted in South Africa • Advise farmers to plant resistant cultivars to improve yields
  19. 19. Acknowledgements • APA 2013 conference organizers • Coral de Villiers, Wiets Roos, University of Stellenbosch • Anel Espach, Potato Certification Services • Dr Ben Pieterse, former research manager, Potatoes South Africa • Dr Fienie Niederwieser, research manager, Potatoes South Africa • Potatoes SA for funding
  20. 20. Thank you for your attention
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