|
|
|
 |
Apple seeds from rare, wild trees in Central Asia offer a potential
genetic bonanza for breeders looking for better flavor, disease
resistance and other traits. ARS and university plant explorers,
who collected more than 60,000 seeds last summer, are now analyzing
traits of young plants grown from the seed. The trip was the third
in a series to Central Asia, where the modern domestic apple is
thought to have originated. The scientists collected seed and
cuttings from the wild species Malus sieversii. It's a
forerunner of the domestic apple, M. x domestica, which
includes Red and Golden Delicious, McIntosh, Granny Smith and
other popular varieties. One of the richest collecting sites was
in the Tarbagatai mountain range, not previously visited by the
American team. Tarbagatai, where winter temperatures dip to -40
degrees F, is the northernmost limit of M. sieversii. So,
the new germplasm could someday extend apple growing farther north
on this continent. The biggest apples the researchers collected--up
to three inches in diameter--were found in the Tarbagatai area.
Of the superior types collected, 84 percent had a pleasant, aromatic
flavor and 70 percent were free of scab, a fungal disease.
Plant Genetic Resources, Geneva, NY
Philip L. Forsline, (315) 787-2390
A protein found in stored Golden Delicious apples can protect
the fruit from storage rots. Also present in pears, tomatoes and
raspberries, the protein stops the rampage of an enzyme produced
by a pathogenic fungus, that attacks fruit after harvest. This
is the first time that the protein, called polygalacturonase-inhibiting
protein, has been purified from apples. Found in the apples by
ARS scientists, the protein decreases as the fruit matures. The
decrease occurs at a time when the fruit still needs protection
from organisms that cause decay. Growers have long protected fruit
from rots with fungicides, but many of the chemicals are no longer
available because of health and environmental concerns. Scientists
are cloning the gene responsible for producing the protein. They
plan to manipulate the gene to produce large amounts of the protein
as the fruit matures. It will be some time before they produce
transgenic apple trees with the new gene, but once it has been
inserted into tissue-cultured plants, they will be ready for field
testing.
Horticultural Crops Quality Laboratory,
Beltsville, MD
William S. Conway/Chenglin Yao, (301) 504-6128
A specific site on
Chromosome 23 in Holstein dairy cows may hold
a vital clue to whether a particular cow is more prone to mastitis
infection. Mastitis is a bacterial infection of dairy cows that
costs U.S. farmers more than $2 billion annually for treatment
and lost milk production. Researchers studied the DNA of "grandsires"
from seven different families of Holstein cattle, noting any genetic
differences at three locations on each chromosome of the bulls.
They discovered the lineup of genes at a specific site on Chromosome
23 differed between bulls whose daughters' milk contained high
numbers of somatic cells--indicating a greater rate of mastitis--and
bulls whose female offspring had lower somatic cell scores. Their
conclusion: One particular variation in the DNA appears to be
linked to lower somatic cell scores than in all other genetic
lineups at that spot on Chromosome 23. Next, the researchers will
check the DNA of Holsteins in a Maryland dairy herd, test those
animals to see how well they resist mastitis infection, and decide
whether the DNA predictors are accurate. If they can pinpoint
which DNA lineups suggest reduced mastitis susceptibility, prospective
breeding animals could be screened in advance for resistance to
the disease.
Gene Evaluation and Mapping Laboratory,
Beltsville, MD
Melissa S. Ashwell, (301) 504-8543
A map of the human genetic makeup is helping ARS scientists save
time and money as they sort out and map chickens' genes. An initial
genetic map for chickens has been developed. It will help breeders
in the future produce birds known to carry the best genes for
traits such as disease resistance and egg and meat production.
To help complete the process of breeding a better chicken, scientists
hope to find the exact genes by using information from the human
genetic map. While the genetic makeup of chickens and humans isn't
a particularly close match, researchers say there is enough similarity
that information already available on the human genetic map can
be used to search for specific genes in poultry. That's because
during evolution, certain "chunks" of genes may have
traveled together. So, a gene that's linked to arm length in humans
might occupy approximately the same chromosomal location as genes
related to wing growth in birds.
Avian Disease and Oncology Research, East Lansing, MI
Hans Cheng, (517) 337-6758
A variety of taro called Lila can triple the yield of this root
crop on tropical farms. Taro produces underground stems, called
corms, that are an excellent source of starch and minerals. The
stems can be boiled, baked or roasted. When cooked, a corm tastes
like a potato but has a softer texture. ARS scientists conducted
field studies of Lila and found that, if properly fertilized and
irrigated, it produces up to 17,770 pounds of commercial corms
per acre--a 230 percent increase over the worldwide average for
the crop. One reason for the yield increase: Lila was more efficient
than other varieties in using soil nutrients. In general, taro
is grown more widely in Pacific Island countries than in the Caribbean--partly
because little attention has been paid to its potential compared
to similar vegetables. In Puerto Rico, taro is grown on a small
scale, though scientists say the findings could help boost taro
production throughout the Caribbean and in other parts of the
world.
Tropical Agriculture Research Station,
Mayaguez, PR
Ricardo Goenaga, (787) 831-3435
Genes in a wild tobacco plant may give food and fiber crops a
new defense against silverleaf whiteflies and other pests. Those
genes could enable cotton, tomatoes and other crops to make the
same natural chemicals the wild plant makes to kill the leaf-feeding
insects. That's the objective of ARS scientists who have been
analyzing the genetics of Nicotiana gossei--a wild Australian
relative of commercial tobacco. N. gossei produces a number
of insecticidal chemicals including sucrose esters. In lab and
field tests, the esters have killed whiteflies, aphids, spider
mites, pear psyllas and tobacco hornworms. Now, the scientists
are pursuing genetic research, seeking to identify and isolate
the sucrose-ester genes. Ultimately, scientists would insert the
appropriate genes into crop species as a potential new form of
nature-based pest control.
Soybean and Alfalfa Research Lab,
Beltsville, MD
George Pittarelli, (301) 504-5723
Western Cotton Research Laboratory,
Phoenix, AZ
David Akey, (602) 379-3524
Medical researchers
may more quickly locate "jumping genes"--also known as
transposons--that could have potential use in gene therapies. That's
because ARS scientists and a software engineer at Silicon Graphics,
Mountain View, CA, devised a transposon-finding mathematical formula. The
team's intent is to design on-off switches for lab-built genes geared, for
example, to protect potatoes from bacteria. But the team first needs to
find more plant transposons. They then can devise new gene switches to
mimic the transposons' genetic architecture. The ARS-designed formula,
called an algorithm, instructs a supercomputer to search a gene database
for patterns associated with transposons. The scientists recently tested
the algorithm on the human gene data base. They knew this would be a
tougher challenge than the much smaller database of plant genes. But the
algorithm might also speed medical scientists' search for additional human
transposons. New transposons might prove valuable for moving potentially
beneficial genes into cells of patients suffering from AIDS, cancer or
gene-linked diseases. The ARS team found two human transposon genes--one
previously unknown, one only partially described before.
Crop
Improvement and Utilization Research Unit, Albany, CA
William R.
Belknap, (510)559-6072
For more information on Genetic Resources visit the National Germplasm
Resources Laboratory) ARS/USDA.
Last updated:
July 10, 1996
Return to: Quarterly
Report Table of Contents
|
|
|
|
Printable Version
E-mail this page
