2014 ASHS Annual Conference

To insure a world class display of rare chrysanthemums which draws thousands of visitors each year, Longwood Gardens developed procedures to ensure virus-free chrysanthemum stock is preserved on site.  Specialty forms of Chrysanthemum x morifolium, such as spider forms and cascades, are not readily available in the trade, and laws prohibit the import of varieties from outside of the United States. Availability of specialty forms is very limited.  In some cases the stock is available from only one nursery or public garden.   Chrysanthemum Virus B is often wide spread in existing stock.  To maintain clean chrysanthemum stock Longwood Gardens created a preservation strategy.

Longwood maintains duplicate stock in greenhouses and tissue culture.  Each year greenhouse plants are tested for the presence of chrysanthemum virus B.  Clean stock is established in tissue culture where it acts as a bank of clean material.  If greenhouse stock becomes infected, the tissue culture stock can be rooted out for replacement of infected greenhouse stock.  If only infected plants are available a meristem isolation procedure is conducted to eliminate virus.  Stock in tissue culture is multiplied each year to supplement greenhouse cuttings for the display crop.  To reduce labor, cultures are grown at temperatures between 38 and 45 degrees Fahrenheit to slow growth rate and need for culture renewal. Cultures grown at room temperature are renewed approximately every six months.  Cultures grown under cool temperatures don’t need renewal for at least a year.   Each year a third of plants in tissue culture are grown to flowering to verify identity which could have altered from mutations or mislabeling.

Using this strategy, Longwood is able to maintain approximately 150 cultivars of rare chrysanthemum, create clean plants for their own use, and in some cases share rare stock with the community.