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UD tissue culturalist uses coconut milk to clone native plants

Sherry Kitto (right) collects trillium with Jeanne Frett.
NEWARK, DE.--Dozens of coconuts — all with a couple of holes in their shells — sit outside Sherry Kitto’s office door at the University of Delaware. Kitto, professor of horticulture, has harvested quarts of coconut milk for her ongoing work in cloning trillium and other native plants. Now empty of their milk, the coconuts are free for the taking.

A plant tissue culturist, Kitto uses coconut milk as she works to develop cloning systems for plants native to the eastern temperate United States, thus preserving the heritage of the countryside. Because digging some wild flowers also is against the law, Kitto’s work may allow people to have more native flowers available for their home gardens.

"There are some special trillium that respond very slowly to conventional propagation systems. I am trying to establish Trillium grandiflorum ‘Quick Silver’ in vitro, and this is where the coconut milk comes in," she said.

Over a period of two to three weeks in early spring, Kitto collects her supply of trillium tissues (ovaries, leaves, stems), referred to as explants, from carefully selected cultivated plants.

"I have some really nice selections — some have double white flowers and others have pink," she said. "If I culture seed, I don’t know what the plant is going to look like. That’s because I know what the mother looks like, but I don’t know what the father looks like. When I collect tissues such as leaves or stems, however, I’m expecting that they will produce a plant exactly like the plant we collected it from."

Kitto explained that cloning is important because the appearance of the flower can be ensured only through this method of propagation.

Back in the lab, Kitto carefully cleans the plant tissues and places each into a baby food jar along with a medium she has created to encourage regeneration.

"There’s agar in there — that’s a gelling agent like pectin — table sugar, and all the macro and micro nutrients for fertilizer. There’s coconut milk and water, too, of course," she said.

"Coconut milk is something of a mystery. It’s so full of sugar, vitamins, trace elements and other nutrients that it encourages and sustains growth. It is considered a choice medium component for regenerating plant tissue," she explained, adding that the liquid is composed of endosperm, which is "sort of like amniotic fluid for plants."

Kitto harvests her coconut milk and then stores it in dozens of jars in the freezer, keeping the milk fresh until she needs it.

She explained that the first step in the process is to influence the stem to grow a callus, a thickening in the stem.

"If you bumped the lawn mower into a tree, for example, the tree would grow a callus in an attempt to heal the wounded cells," she says. "We can do this chemically, too, when we add a growth regulator such as 2,4-D to the medium. If it is done right, new growth will emerge from the callus."

At this point, shelves of baby food jars with the trillium explants are bathed in light for 16 hours a day and left to grow new tissue, a very slow process. Every two to four weeks the young plants are removed from the jars and placed in others with a fresh mixture of nutrients for the growing plant.

According to Kitto, regeneration of native plants such as trillium takes years and requires much patience.

"The most critical part of this experiment is harvesting the tissues because regeneration frequently requires very fast-growing, young cells for regeneration. I need to harvest the tissue before it has differentiated too far, because then cells can’t go backward in their development. Once they’ve matured beyond a certain point, they will no longer dedifferentiate and regenerate a new plant," she said.

"Next in importance is getting the culture clean and sterile and finding a medium that will allow the plant to thrive."

Kitto is one of only a few people in the United States cloning native trillium. She has been working with some very special cultivars for three years, and each year her plants stay healthy for a longer period of time. Three plants from her 1999 harvest are still alive and have developed calluses. This year she is planning an entirely new approach using multiple treatments to compare which treatment encourages the healthiest growth among her young plants.

While Kitto’s work with trillium is in its early stages, she also clones native ginger plants. More than 350 of these plants were sold at the University of Delaware Botanic Garden plant sale on Ag Day last spring.

Kitto’s motivation in cloning trillium and other native plants is to share them with others. "I want these plants to be in peoples’ gardens and freely available in the United States," she said.

Contact: Pat McAdams: (302) 831-1356

June 21, 2000