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Conditions for a testing requirement
1. Disease must cause a reduction in stand, etc.
2. Acceptable infection levels must be established
3. Restrictions may be imposed, if the disease can develop explosively
Preharvest Control
1. Planting disease-free seed
2. Seed treatment
3. Field spraying
4. Hand roguing
5. Resistant cultivars
6. Seed quality
7. Cultural practices
8. Isolate fields from potential innoculum sources
9. Control insect vectors
Post harvest control
1. Surface disinfectants
2. Separation of diseased seed and foreign material
3. Hot water treatment
4. Infusion of antibiotics
Fungi
1. Types
- Saprophytic
- Pathogenic
2. Potential dangers
- Reduce germination
- Provide innoculum for further spread
- Reduce yield and quality
Important fungal genera
1. Alternaria Alternar.gif
- Principally invade damaged or dead tissue
- Infects most crops
2. Ascochyta Ascochy.gif
-. Occurs chiefly as leaf spots on mature tissue
- Infects both monocots and dicots
3. Diaporthe Diapor.gif
- Causes premature death and reduced yield
- Important disease on soybeans
4. Fusarium Scab.gif
- Causes seedling blight, leaf spotting and seed blight or pod rot
- Infects most crops
5. Helminthosporium Helmin.gif
- Causes leaf spotting and seed blight
- Infects most cereals
6. Phoma Phoma.gif
- Similar to Ascochyta
7. Pyricularia Pyric.gif
- Important disease on rice
Methods of detection
1. Agar testing
2. Blotter tests
3. Virulence tests
4. Monocultural tests
Saprophytic fungi
- Are ubiquitous
- Commonly occur in storage
- Thrive @ 75% RH and 15 degrees C
1. Common ssp.
- Aspergillus
- Mucar
- Penicillium
- Rhizopus
Bacterial pathogens
- Common tests
1. Serological technique
2. Bacteriophage technique
3. Plant injection tests
4. Dome Test
Virus tests (seed-borne)
a. Biological tests
1. Grow-out tests
2. Direct seed tests
b. Serological tests
1. Double Diffusion Test
2. Radial Diffusion Test
3. Latex Flocculation Test
4. Enzyme-linked Immunosorbent Assay (ELISA)
5. Serologically Specific Electro Microscopy (SSEM)
References:
Principles of Seed Science and Technology. 3rd Ed. L.O. Copeland and M.B. McDonald. Chapman and Hill, New York, 1995
Principles of Seed Pathology. 2nd Ed. V.K. Agarwal and James B. Sinclair. Lewis Publishers, New York, 1997.
