Growing an apple or peach tree seems easy. You plant an apple or peach seed
from luscious fruit you just ate, and up springs a beautiful tree that will
someday bear the same, good-tasting apples and peachesright? Wrong!
Fruit trees are not grown from seed. "Varieties of peaches, pears, and
apples must be regrown from their own buds or twigs by grafting them onto
rootstock," says Agricultural Research
Service horticulturist Ralph Scorza.
The size and shape of fruit trees are vitally important to growers for ease
of tending and picking, as well as yield. In apples, special rootstocks are
commonly used to dwarf the varieties grafted onto them. That's why Scorza and
fellow ARS horticulturist Richard L. Bell are excited about their latest
development: the very first dwarf pear tree of an existing variety.
At the ARS Appalachian Fruit Research Station in Kearneysville, West
Virginia, they're also changing the shape of peach trees and releasing new
fruit varieties to give producers more of a choice.
Dwarfing Benefits Growers and Consumers
"We've actually been working with several genes that may dwarf pear
trees, and we've completed research on one of them," Scorza reports.
"We used this gene, originally isolated from a bacterium, to successfully
dwarf Bosc pear trees, which are growing in our greenhouse. These new dwarfs
should bear fruit in 2 to 3 years. We are anxious for the first harvest."
The research can go two ways: The gene may be used to dwarf scions, the tree
shoots grafted onto dwarfing rootstocks, or to impart dwarf-producing
properties to the rootstocks. Scorza and colleagues are already working with
other dwarfing genes for transfer into pear.
Why dwarf the pear trees? It would allow, for the first time, a high-density
production system for pears not dependent on quince rootstocks that dwarf
scions but aren't well adapted to major U.S. production districts, Scorza says.
"Our goal in this particular project is not to produce new varieties.
The pear industry is based on only a few major varieties, and there is a need
to improve those. Dwarfing will do that."
There are many advantages to dwarfing fruit trees. Primarily, they're more
productive than traditional-size trees. High-density plantings of smaller trees
can produce more fruit on the same land area than the larger, standard-size
trees. And they're also easier to prune, spray, and harvest. Fruit from a dwarf
tree is the same size as fruit from a normal tree.
Changing Tree Shapes
Not every fruit grower will use dwarf trees. "But all growers know that
the shape of a fruit tree is vitally important to the tree's production,"
Scorza says. "Right now, all commercial peach trees grow one way: large
Scorza and colleagues have developed a columnar peach tree shape. "This
new tree bears fruit of excellent quality. We expect to release it to home
gardeners within the next few years, because it takes up very little
room," Scorza reports. ARS scientists at Kearneysville have been working
on this project for about 15 years.
Home gardeners with little space will like the columnar peach tree because
the upright, narrow branches that grow close to its trunk won't shade other
vegetables that may be growing close by.
This research represents a totally new system for commercial peach growers.
With a tall and narrow shape, the columnar trees require much less management
and will allow high-density growing. This eliminates the large space between
trees that is necessary with traditional-size peaches. Chemicals and fertilizer
need be applied to only a very small area, saving the grower money and sparing
the environment chemical emissions.
At least three times as many of these columnar trees can be grown per unit
of land. With the cost of land available for agriculture at an all-time high,
this is an important factor. Since growers can plant more of these trees in an
orchard, they could increase production while cutting input costs. These
savings could be passed on to consumers.
In the fall of 1998 and spring of 1999, cooperators planted the columnar
peach trees in orchards in New Jersey, Virginia, West Virginia, South Carolina,
Arkansas, and Michigan. "We also have cooperators in California and
Washington who are considering our new tree and other shapes that we've
developed," says Scorza.
The Pear Is Plumb Delicious
In addition to dwarfing and changing the tree shape, Scorza and Bell are
working on new, improved varieties for fruit growers.
In 1998, Scorza released a new plum and Bell, in conjunction with
researchers at Ohio State University, introduced a fire-blight-resistant pear.
The most serious disease of apples and pears, fire blight is caused by the
Erwinia amylovora bacterium and has no cure.
Blake's Pride ... A tasty, high-quality, fire-blight-resistant pear.
Bluebyrd, the new plum, is named for Senator Robert C. Byrd, who dedicated
the Kearneysville research station in 1979. According to Scorza, it gives
growers a firm, excellent-quality plum that is 20 percent sugars. Bluebyrd is a
consistently high-producing European-type plum for the mid-Atlantic and other
fruit-growing regions of the United States. "And consumers get a
sweet-tasting plum," he says.
Blake's Pride, a new pear, resists fire blight, while most of the major pear
varieties are moderately to highly susceptible.
"Shoots of Blake's Pride are very resistant to fire blightand
blossoms, moderately so," says Bell. "If blooms do become infected,
the infection doesn't go deep into the wood. In addition, this high-quality
pear has excellent aromatic flavor, and the fruit is juicy and buttery."
Blake's Pride should be available in commercial nurseries in 2000, and
Bluebyrd is available for the first time this year.
"This research furthers our goal of giving U.S. fruit growers options
that maximize productivity and quality while reducing the amount of chemicals
needed," Scorza says. By Doris Stanley Lowe,
formerly with ARS.
This research is part of Plant Microbial and Insect Germplasm,
Conservation and Development, an ARS National Program described on the World
Wide Web at http://www.nps.ars.usda.gov/programs/cppvs.htm.
Ralph Scorza and
Richard L. Bell are at the
USDA-ARS Appalachian Fruit
Research Station, 45 Wiltshire Rd., Kearneysville, WV 25430-9425; phone
(304) 725-3451, fax (304) 728-2340.
"Shape of Things To
Come: Fruits of the Kearneysville Lab" was published in the
July 1999 issue of Agricultural
Kearneysville Releases at a Glance
- Blake's Pride 1998 A tasty, high-quality,
- Bluebyrd 1998 An excellent-tasting, high-yielding plum
for the mid-Atlantic and other U.S. fruit growing regions.
- Potomac 1993 A fresh-market pear for commercial
growers and homeowners that combines superior resistance to fire blight with
good-quality fruit. Ohio State University collaborated on the release.
- Bounty 1989 An important commercial peach variety,
released in conjunction with the Texas A&M; Agricultural Experiment
Station. Big and beautiful, this yellow freestone peach is one of the best for
midseason and is recommended as a replacement for Loring, the previous grower
- Earliscarlet 1985 A large, very high-quality,
midseason nectarine. The fruit skin is predominantly red over a golden-yellow
background, and the fruit is recommended for the packed or retail market.
- Sentry 1981 A tasty, firm, early-season, semifreestone
peach that grows on vigorous trees resistant to bacterial leaf spot.