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Two new American elms with high levels of tolerance to the fungus
that causes Dutch elm disease could restore the American elm to
the Main Street USA of earlier days. Since the 1930s, an estimated
90 percent of American elms have died--victims of a fungus, Ophiostoma
ulmi, that wiped out 77 million American elms. For over 20
years, ARS scientists worked to develop "Valley Forge"
and "New Harmony" elms by screening thousands of American
elms and inoculating them with the culprit fungus, eventually
narrowing the selection to these final two trees. Compared to
other American elms, the two new trees have significantly lower
foliar symptoms and crown die-back, even after being intensively
inoculated with the Dutch elm fungus. Although neither tree is
completely immune to the disease, "Valley Forge" is
the most tolerant, while "New Harmony" is among the
three most tolerant of all the trees the researchers examined.
The two elm varieties will be the first commercially available,
Dutch elm-tolerant American elm trees. Over a hundred rooted cuttings
of "Valley Forge" and "New Harmony" were distributed
over the last two years to tree nurseries, experiment stations
and arboreta. Wholesale nurseries will propagate the trees for
sale by late 1997 or 1998; retail nurseries should have them in
1999.
U.S. National
Arboretum,
Glenn Dale Laboratory,
Washington, DC
Alden M. Townsend, (301) 344-4175
Four new watermelon lines that have genetic resistance to a viral
disease are now available to breeders. ARS scientists screened
670 germplasm accessions to find the four resistant lines, which
came from plants originally from the African countries of Zaire
and Nigeria. The new lines provide rare sources of resistance
to watermelon mosaic virus, which attacks watermelons and other
cucurbits around the world. To determine resistance, scientists
initially screened watermelon germplasm lines against a Florida
strain of the virus in the greenhouse and field studies. Then,
four of the most resistant lines were tested in the greenhouse
against strains from Florida, Arizona, California, New York, Israel
and Italy. Limited quantities of seed are available only to public
and private breeders who must cross the lines with commercial
types to develop new hybrids for public sale.
Plant Genetic Conservation Resources, Griffin, GA
A. Graves Gillaspie Jr., (770) 412-4777
Cotton breeders have 10 more ARS lines they can use to develop
new commercial varieties of top-quality Pima cotton. High yields
and long, strong fibers are among the agronomic benefits in the
new cotton lines. Breeders can use the new ARS lines to fine-tune
varieties for specific climates and soil types in the Southwest.
An additional two lines provide fiber length and strength, previously
unavailable in a heat-tolerant, early maturing cotton. Pima continues
to be popular with western growers because its superior fiber
brings higher prices than upland cotton. Upland cotton grows on
about 15 million acres; Pima, on 180,000 acres. ARS scientists
developed the new Pima lines in cooperation with the University
of Arizona at Tucson.
Western Cotton Research
Laboratory,
Phoenix, AZ
Richard G. Percy, (602) 379-4221
A new long-grain, semi-dwarf rice called Jefferson resists two
serious fungal diseases and offers high yield, excellent cooking
properties and other desirable traits to boot. A limited supply
of seed is available to rice farmers and breeders from the ARS
researchers who developed, tested and released the new variety.
Jefferson is a cross between Rosemont, a conventional long-grain
cultivar, and B 82-761, a germplasm breeding line. Three different
genes for fungus resistance protect Jefferson rice plants from
Pyricuylaria grisea, the fungus that causes blast, and
Rhizoctonia solani, which causes sheath blight. Both diseases
are prevalent in Texas, Arkansas and other rice-growing states
in the South. When challenged with the fungi in 1994-95 field
tests, Jefferson yielded 81 percent of the average 2,506-pound-per-acre
yield expected when the fungi are not present. Two commercial
varieties, Cypress and Lemont, retained only about 60 percent
of their yields. Jefferson matures in about 125 days. A sturdy
stem keeps the plant from toppling and spilling its grain onto
the ground where it can't be harvested. Long and thick, the rice
grains have an average 21 percent amylose, a starch component
that helps reduce stickiness and softness.
Rice Research Unit, Beaumont, TX
Anna M. McClung, (409) 752-5221
New, short rice plants now available to breeders can survive flooding
while delivering high grain yields. The new experimental rice
plants may turn out to be a boon to many Asian countries--and
to U.S. farmers, who grow rice mostly for export. Asian farmers
currently must grow lower-yielding tall rice varieties that survive
by keeping their grain heads above flood waters. But ARS scientists
crossbred tall and short varieties to combine their valuable traits
into one short, high-yielding variety and have located the gene
that confers submergence tolerance. Breeders can develop commercial
varieties from the new plants. In field tests in the Philippines,
the plants produced about five tons per acre--about 20 to 40 percent
more than tall Asian varieties. Another benefit of the new rice
might be weed control, because fields planted in short rice can
be flooded until the weeds drown. Annually, Asia produces about
90 percent of the 500 million tons of rough rice produced worldwide.
While this dwarfs the seven to nine million tons grown in this
country, the U.S. accounts for about 20 percent of all rice sold
in international markets.
Crops
Pathology and Genetics Research Unit,
Davis, CA
David J. Mackill, (916) 752-5966
A new test will help breeders find rice plants that have genes
for greater resistance to zinc deficiency--which costs farmers
millions of dollars in lost yields annually. Rice suffers from
zinc deficiency in this country and abroad--including China, India,
Japan and the Philippines--even though the soils contain adequate
zinc for other crops. The deficiency occurs because sulfides formed
in rice paddies make zinc unavailable. Yield loss to zinc deficiency
costs farmers millions of dollars each year. ARS scientists developed
the test in which rice seedlings grow in a special nutrient solution
that lowers zinc availability, while providing all other nutrients
needed for normal growth. By supplying all needed nutrients, except
the one being tested for, the solution avoids the risk of creating
a deficiency of another nutrient that could cause confusing results.
Field tests have borne out the lab results.
Environmental
Chemistry Laboratory,
Beltsville, MD
Rufus Chaney, (301) 504-8324
New oat varieties could someday make it possible to grow winter
oats in cold weather states--and in less frigid states where a
hard freeze won't spoil a farmer's crop. ARS and cooperating
researchers
are testing domestic and foreign varieties to discover which ones
hold up well in a broad range of winter weather, especially as
a livestock feed. Some current domestic varieties, for example,
do well with wet winter conditions, but die out in dry cold. A
wild blue-green oat, found in Algeria and Turkey, is showing promise
of winter hardiness. Still to be answered: whether acceptable
yields can be produced from crossing this oat with domestic varieties.
Raleigh Research Unit, Raleigh, NC
David Livingston, (919) 515-5834
Orange trees growing in air with 75 percent more carbon dioxide
(CO2) than today's level have produced nearly two and one half
times more fruit and slightly more vitamin C in the juice. Researchers
want to learn how rising CO2 levels in the future could affect
crop productivity. For the experiment, the sour orange trees grow
in outdoor open-topped chambers having a CO2 concentration most
scientists agree will occur about the middle of the 21st century.
The CO2-enriched trees have nearly twice the trunk and branch
volumes compared to trees in chambers that don't get extra CO2.
The experiment, now in its ninth year, is the world's longest
of its kind.
U.S. Water Conservation
Laboratory,
Phoenix, AZ
Sherwood B. Idso, (602) 379-4356
A soybean strain that overcomes the inverse relationship between
seed yield and seed protein content has been developed--a first
in soybean breeding. Until now, developing soybean varieties with
both high yields and high protein has been difficult, because
as seed yield increases, protein tends to decrease. Using conventional
breeding techniques, ARS scientists incorporated the exceptionally
high seed protein (49.8 percent) of the low-yielding variety Pando
into a plant similar to Cutler 71. Cutler 71 has 40.8 percent
protein and yielded about 36 bushels per acre (bu/a) in performance
tests. The new strain combines Cutler's yield with Pando's high
seed protein. The new soybean strain, evaluated for maturity date,
seed protein, oil content and other traits, had an average protein
content of 47.2 percent and had significantly higher yields (42
bu/a) than Cutler. This strain also had 17.4 percent oil content
in the seed--significantly more than the 14.8 percent in Pando
but less than the 20.4 percent in Cutler 71. Soybeans are grown
for seed oil and for the high-protein meal that is left after
the oil is extracted.
Crop Production and Pathology Research, West Lafayette, IN
Jim Wilcox, (317) 494-8074
An improved bacteria for inoculating soybeans could bring farmers
an additional $500 million annually if used on all U.S. soybean
acreage. The new strain of Bradyrhizobium japonicum increases
production by 3.4 percent, according to 28 university yield tests.
Urbana Laboratories, St. Joseph, MO, sold enough of the patented
strain in 1995 to treat 227,000 acres, and sold one-third more
in 1996. Some 10 to 12 million acres of soybeans are inoculated
each year. The new inoculant, a product of conventional bacterial
genetics by ARS scientists, resulted in plants that develop 25
percent more root nodules. Inside these nodules, bacteria live
and convert nitrogen from the air into a form the plants can use.
Soybean and Alfalfa
Research Laboratory,
Beltsville, MD
L. David Kuykendall, (301) 504-5736
Soil, Plant and Nutrient Research Unit, Fort Collins, CO
William J. Hunter, (970) 498-4208
Electrical changes in soybean roots seem to protect the plant
from stress, such as excess oxygen. As a result, bacteria living
in nodules on the roots are still able to fix nitrogen. Nodules
have to maintain just the right amount of oxygen. Too much or
too little harms the bacteria's ability to supply nitrogen from
the air to the plant. No one is sure how nodules regulate their
oxygen supply, but ARS researchers used microelectrodes to discover
that electrical changes are linked to changes in oxygen supply
in soybean, alfalfa, clover and birdsfoot trefoil nodules under
oxygen stress. This discovery could eventually lead to improvements
in stress tolerance of root nodules, allowing them to continue
supplying the crop with nitrogen even under moderate drought or
after cattle grazing. The electrical response to stress was discovered
after excess oxygen was pumped around the nodules. To the researchers'
surprise, the negative electrical charge on the inside walls of
the nodules' cells dropped. That caused the nodules to counteract
the oxygen stress by letting in less oxygen. Future tests may
determine whether the change in electrical charge accompanies
stresses other than excess oxygen.
Appalachian Soil and Water
Conservation Research Lab,
Beckley, WV
Thomas B. Kinraide, (304) 252-6426
R. Ford Denison (formerly with ARS), (916) 752-9688
Peanut breeders can choose between four varieties to get the best
flavor to go along with peanut size, based on a 12-year study
by ARS scientists. Over 200 varieties and breeding lines were
analyzed for flavor traits. Results: Dixie Giant, Spanish 18-38
and Small Spanish White varieties 3x-1 and 3x-2, were consistent
in contributing to enhanced flavor traits. A trained taste panel
at North Carolina State University evaluated peanut flavor for
the various varieties and their offspring. Plant samples came
from Florida, Georgia, Oklahoma, Texas and Virginia.
Market Quality and Handling Research, Raleigh, NC
Harold E. Pattee, (919) 515-6745
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