Distribution of Healthy Propagules- NCRPIS program

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 $0.02

Student labor $1.98 (15 min.)

Tech. labor ~$1.25-1.65 (3-4 min.)

~Cost per accession $4.85 - 5.25

# Accessions tested:

1994 – 59

1995 – 82

1996 – 136

1997 – 134

1998 – 61

1999 – 141

2000 – 43

2001 – 152

2002 – 124

2003 – 182

2004 – 377

2005 – 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 $0.10

Latex gloves $0.42

Student labor at 8.00/hr $3.16

Tech labor at 25.00/hr $5.23

Avg. 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 Pathologist

USDA-ARS

North Central Regional Plant Introduction Station

Iowa State University, G212 Agronomy Hall

Ames, IA 50011-1170

Office: 515-294-4379

Fax: 515-294-4880

Email ccblock@iastate.edu