Distribution of Healthy Propagules - NCRPIS program NPGS Curator Workshop 2005 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 management This 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 $1.98 (15 min.) Tech. labor ~$ (3-4 min.) ~Cost per accession $ # Accessions tested: 1994 – – – – – – – – – – – – 442

Sunflower downy mildew disease management Objective: Ensure absence of downy mildew in the field. Starting in inspect all plots and remove infected seedlings 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 management Objective - prevent seed infection. 1. GH seedlings are tested prior to transplanting 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 Office: Fax: