Diseases and Management of Crops under Protected Cultivation

(Diseases and Management of Crops under Protected Cultivation)
all the seed health testing methods were validated and accepted according to the ISTA rules and
published as “Hand book of method validation” 2002.In 2005 ISTA–SHC emphasized the validity
of a test protocol and characterization of new seed borne pathogens .
Non destructive seed health test
Indexing the seed for health through non destructive seed health test is carried out by
methods like:
• Ultra sound
• Optical and infrared analyses, and Biopsis
Advances in Indexing Seed for Pathogen
Several advances in seed health testing have been made such as:
• Liquid plating assay (seed-borne bacteria)
• Enzyme-Linked Immunosorbent Assay (seed-borne viruses)
• Serology and
• Polymerase Chain Reaction (PCR)/ molecular biology based techniques
Serological Methods
These methods are generally simple to perform, rapid and accurate when used, generally
to detect a number of bacterial and viral pathogens even if present in low level. These methods
are being applied for many seed borne pathogens successfully, for example
Indexing seed for lettuce mosaic virus was started as grow-out assay on several thousand
seedlings (30,000) Later the test was changed to indicator host plant Chenopodium quinoa test.
Further ,since 1983, ELISA (enzyme-linked immunosorbent assay), has been used which not only
proved to be more efficient but very sensitive in detecting low levels of infections that could
potentially threaten lettuce production.The lack of sensitivity and ambiguity in results and inability
to detect all strains of the pathogen sometimes limits their use.
Indirect Immuno-fluorescence Colony Staining Method
Used for detection of seed-borne bacterial pathogens. The test is especially suitable for
seed companies, and quarantine stations which have no facilities for conjugation of primary
antiserum. The assay is easy to perform and quick to be assessed. Choosing the right secondary
conjugate is however, necessary to get best results in the assay.
Nucleic acid based detection methods
Highly sensitive BIO-PCR methods have been developed for several bacterial pathogens
from seeds, including Pseudomonas syringae pv. Phaseolicola, Acidovorax avenae ssp. Avenae,
Xanthomonas oryzae pv. oryzae and X. campestris pv.campestris .
A DNA-based polymerase chain reaction (PCR) has been developed as an alternative or
supportive method to a costly and time consuming grow-out test (10,000 seedlings) for detecting (
Acidovorax avenae sub sp. citrulli ), the cause of watermelon fruit blotch .
Molecular Methods
Certain laboratories are testing the D-Genos ready-to-use kits to detect certain seed borne
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