Friday, May 26, 2017
University of Hawaii at Manoa
University of Hawaii System
College of Tropical Agriculture and Human Resources
 
A bioassy consists of exposing ginger plants growing in pots to field soils to see if bacterial wilt disease symptoms develop.

Bioassays are useful because they are:
  • Reliable diagnostic tests 
  • Very sensitive
  • Easy to set up
  • Symptoms develop rapidly, and
  • Results are simple for farmers to interpret 
Procedure:
  1. Collect samples of field soil from an area intended for ginger cultivation. Use appropriate soil sampling methods, as described in this CTAHR publication: AS-4.pdf
  2. Obtain young, tissue-cultured ginger plants. The advantage of using tissue-cultured plants is that they are pathogen-free and symptoms develop rapidly when they are exposed to R. solanacearum. Alternatively, one may use other non-tissue culture ginger plants if they are also pathogen-free. One can grow the tissue cultured plants at 70F if they are very small.
  3. Transplant the tissue-cultured ginger plants into pots containing the field soil.
  4. Raise the temperature to 80 F and keep the soil wet with frequent irrigation.
  5. Observe plants daily for the development of symptoms, which should occur in 1-2 weeks after transplant. If wilting develops, the test is positive for R. solanacearum. If desired, uproot the symptomatic plants and submit to the UH-CTAHR ADSC for pathogen confirmation.
Tissue-cultured (TC) ginger plants (above) growing in pots make excellent plants for bioassays for Ralstonia solanacearum.

Can TC ginger plants be used to start a farm directly? TC plants could be available to interested growers by CTAHR, but most TC plants will not produce high quality ginger rhizomes. One must go through a couple of selections to ensure that the rhizomes are of high quality. First, one selects the best yielding plants from the first batch of TC ginger plantlets after growing them in pots. These selected ginger plants are then planted under hydroponic culture, grown out and selections made again based on appearance, size, and quality of the ginger rhizomes produced.
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