Post on 19-Jan-2018
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Distribution of Healthy Propagules- NCRPIS program
NPGS Curator Workshop2005 Chicago Charles C. Block, Ph.D.
Plant Pathologist
Three disease examples
• Stewart’s wilt of corn – Pantoea (Erwinia) stewartii
• Sunflower downy mildew – Plasmopara halstedii
• Squash mosaic virus of cucurbits
Stewart’s wilt disease managementThis is the top phytosanitary issue for corn seed exports
• Primary objective – to be able to certify seed as free of Erwinia stewartii. Field inspections document presence/absence of Stewart’s wilt.
• Absent in field – accession meets phytosanitary requirements for Stewart’s wilt.
• Present in field – most countries accept lab testing in lieu of field data. We do this testing in-house.
• About 90% of field positives are negative by ELISA.
Stewart’s wilt disease management
Approximate cost per accession for Stewart’s wilt lab testing
ELISA test kit $1.60 (4 wells/acc.)Buffers $0.02Student labor $1.98 (15 min.)
Tech. labor ~$1.25-1.65 (3-4 min.)~Cost per accession $4.85 - 5.25
# Accessions tested:1994 – 591995 – 821996 – 1361997 – 1341998 – 611999 – 1412000 – 432001 – 1522002 – 1242003 – 1822004 – 3772005 – 442
Sunflower downy mildew disease management
Objective: Ensure absence of downy mildew in the field.
Starting in 1990 - inspect all plots and remove infected seedlings.
1999 - present: Allegiance fungicide (metalaxyl) seed treatment – gives systemic protection.
Sunflower disease management
A minimum of two field inspections are made before flowering.
Infected plants are pulled and removed from field.
Curatorial staff observe plant health through season.
Downy mildew
Squash mosaic disease managementObjective - prevent seed infection.
1. GH seedlings are tested prior to transplanting.
2. 3-5 plants in each peat pot are tested as a group.
3. Plants in any positive pot are re-tested individually or the pot may be discarded.
4. Transplants are grown in screened cages to exclude cucumber beetles.
Cost per accession for SqMV testing
ELISA test kit $2.66 (0.38 x 7 wells)**
Sample grinding bags $1.33 (0.19 x 7 samp.)
Buffers $0.10Latex gloves $0.42Student labor at 8.00/hr $3.16 Tech labor at 25.00/hr $5.23Avg. cost per accession $12.90 **Average of 7 samples per accession and
~1500 samples per season (based on 2003 and 2004 data).
Questions?Contact: Charles C. Block, Ph.D.
Plant PathologistUSDA-ARSNorth Central Regional Plant Introduction StationIowa State University, G212 Agronomy HallAmes, IA 50011-1170Office: 515-294-4379Fax: 515-294-4880Email ccblock@iastate.edu