Thursday, April 9, 2009

New American Chestnuts

Plainfield mayor Sharon Robinson-Briggs will honor the American chestnut at 946 Madison Avenue at the City's Arbor Day celebration Friday April 24.

The tree was planted by Bill Santoriello in 1992 and is now about 10 inches in diameter at breast height. The tree is currently owned by Vicki Blasucci. Lacking a nearby chestnut to pollinate it, the Madison Avenue chestnut has been sterile. But things are looking up for the tree. It will soon have neighbors. The American Chestnut Foundation provided germinated nuts for planting new trees nearby. Bill Santoriello, Vicki Blasucci, and Robin Gates planted four of the nuts this past weekend, two on Vicki's property and two on Bill's, which backs on Vicki's. The nuts are the progeny of a 19" diameter chestnut in Middletown (which was pictured in Plainfield Trees November 21, 2008.) One of the tree's nuts, with newly formed rootlet, is shown below.

The plantings were done with concern for chestnut blight at the forefront. The Madison Avenue chestnut is quite unusual in being absolutely untouched by blight. The last thing anyone wanted was to introduce blight to Madison Avenue with the planting of infected new trees.

Extraordinary measures were taken. First, nuts were planted instead of seedling trees. Why? Unlike seedlings, nuts are extremely unlikely to harbor blight. Second, plant protectors, needed to shelter the tender new trees from predatory deer, were virgin. Sterilizing previously used ones wasn't good enough for us worrywarts. Tony Rosati, a Chestnut Foundation volunteer from Monmouth County, drove out to Hightstown to acquire new ones for use in Plainfield. Third, the nuts were planted only in very close proximity to the Madison Avenue tree. Why? Blight fungi spread on the wind from tree to tree and can also be carried by birds and insects. Spreading chestnut trees around Plainfield could create blight "waystations" that would allow spread of the disease to the Madison Avenue tree.

With luck the new trees might begin flowering in five or six years and cross-pollinate the existing tree so that they can all produce chestnuts. Let's wish them luck.

Chestnut esoterica:
Crown gall, a disease that affects numerous plant species, is caused by Agrobacterium tumefaciens. The name of the bacterium is as ugly as the disease itself, which is pictured below.

I encountered this disease last fall when I bought some hollies to plant on Martha's Vineyard. When I took the hollies out of their pots and "roughed up" their roots for planting, I saw warty, tumor-like growths at the tree bases.

I sent a photograph to American Holly Society trustee Charles Wiley, owner of Vineyard Gardens(1) in West Tisbury MA, who diagnosed crown gall. The disease-causing bacteria enter the plant through a wound near the base of the trunk. The bacteria then engage in genetic engineering. They insert genes into the plant cells that cause the cells to grow rapidly, producing an ugly, tumor-like gall at the tree base. The cells of the gall generate unusual amino acids that are useless to the plant but nourish the bacteria.

What does all of this have to do with chestnut blight? The thuggish bacterial genetic engineers can be co-opted and turned into model citizens. Adopting a technique called Agrobacterium-mediated transformation, researchers at SUNY Syracuse modify the gall bacteria to make them helpful to chestnuts. The scientists replace the genes that direct gall production with genes that are known to be associated with fungus-resistance in some plant species. The modified gall bacteria are then mixed with chestnut embryos. When the modified bacteria inject the chestnut cells, the embryos acquire new genetic material that might help combat chestnut blight. A exciting line of research. See for more details. (2)

(1) For the record, Vineyard Gardens, a top-notch plant nursery on Martha's Vineyard owned by Charles and Chris Wiley, was not the seller of the infected plants. Having plants infected with crown gall in one's garden is to be avoided. The bacteria persist in the soil and can spread to other plants.

(2) Many thanks to Sara Fitzsimmons of The American Chestnut Foundation and Pennsylvania State University for educating me about Agrobacterium-mediated transformation research on chestnut blight.

Copyright Gregory Palermo

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