Question

Discuss the common tests you would carry out for seedborne bacterial and viral diseases to a group of newly hired seed technicians in state seed laboratory where you are a director

Answer 1

Method for detecting seed borne bacteria:

First you examine how the seed look different from the normal one. The following test is done to detect bacteria:

'Growing on': Sow the test seed samples into seedlings under optimal condition for the disease development in glass house or closed environmental chambers. It is mainly used for large number of Xanthomonads and pseudomonads. Isolate the sample in agar media.

Indicator test: The seed sample is sterilized with 2.6% hypochlorite for 15 min and rinsed in sterile water. The sample is further incubated for 18-24h in sterile water. The water suspension is inoculated into the primary node of 10 day old bean seedlings. The appearance of lesions followed systemic necrosis is positive reaction.

Serology test: This method is used for detection of various phytobacteria. The washing of the working seed sample are cultured for 36h under sterile distilled water. The supernatent is tested with antiserum of suspected pathogen.

Detection of viruses:

Dry seed examination: Visual examination reveal abnormalities like disclouration, shriveling, reduced seed rice size, staining and seed coat necrosis.

Growing on test: Seeds are planted in blotter paper, sand, soil, vermiculture or in growth medium. Seedlings are examined at regular intervals for the viruses.

Indicator test: Extract different parts of seeds and seedlings raised from infected seeds on suitable indicator plants. This test has been used to detect BCMV in bean and urd bean, LMV in lettuce, TMV in tomato and tobacco ring spot virus in soybean.