AgAlerts From Griggs County
By John Swenson, Griggs County Extension Agent
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AgAlerts From Griggs County |
Issue # 9, August 16, 2000
In the August 2000 Agricultural Research magazine, they had an article on DNA profiling in scab research. The following is a summarization of this article.
One Disease - But Eight Causes
In the past, all scab epidemics worldwide were thought to
be caused by a single pathogen. But new evidence proves that's not
true. "To our surprise and dismay, our DNA data so far reveal at
least eight genetically distinct scab pathogens, all of which are being called Fusarium
graminearum," says Kerry O'Donnell, ARS Microbiologist at Peoria
Illinois.
"We recognize them as distinct species based on genealogical evidence
obtained from six different genes." Corby Kistler, ARS Molecular
Geneticist at St. Paul Minnesota, found that all eight pathogens caused the
devastating scab disease on wheat in greenhouse experiments. Six of the
eight species are know to infect corn. The Department of Veterinary and
Microbiological Sciences at NDSU found that all eight scab-causing Fusarium
species produce similar toxins on grain. They also found that the scab
species could not be distinguished from one another by the toxins they produced.
O'Donnell and Kistler made a disturbing discovery when they
examined strains isolated from moldy corn in Nepal. One strain had a
mixture of DNA from two F. gramineraurum family tree species thought to
be geographically isolated - one from Africa and one from Asia. "We
theorize that the African species was recently introduced to Asia on moldy corn
exported form Africa" says O'Donnell. The findings graphically
illustrate that international horticultural and agricultural trade in plants and
plant products can bring together closely rated species that have evolved in
isolation from one another. Could previously isolated species hybridize
and become a serious plant disease threat? Natural hybridization of two
fungal species, also called interspecific hybridization, may be rare, O'Donnell
says, but such incidences seem more likely when a fungus is introduced into a
new habitat occupied by a closely related species. One major lesson:
Scientists and government officials involved with quarantine regulations, plant
disease prevention and control, and plant breeding need to appreciate the
tremendous genetic diversity and global distribution of Fusarium species
that migh cause scab, says O'Donnell. For plant breeding breeding programs
to be fully effective, for example, breeders need to take into account all eight
Fusarium species. Now that Kistler realizes that the eight scab
species can infect wheat and knows that at least six can infect corn, the
scientists are concerned about the possibility of new pathogens evolving through
hybridization.
Looking at some HRSW fields I was finding several black heads. Sooty molds are a secondary invader. They normally appear on heads that were infected by some other disease. Most of the heads that I found sooty mold on were killed by common root rot. You see this mold every year, especially if the crop receives a rain fall event after swathing. When wet weather accompanies maturation and especially when harvest is delayed, green-black superficial molds often develop on wheat heads. Sometimes infections progress to seed and cause black point or smudge. Heads that are shaded, weakened, undersized or prematurely ripe for other reasons are prone to infection. Plants that are nutritionally deficient, lodged or damaged by diseases usually support 'sooty' molds . Thus, the molds often indicate damage form another cause, such as common root rot.
Sooty molds on HRSW (click on picture to enlarge)
Several sunflower fields around the county have uneven stand heights. This is caused by the presence of male lines that are used in the hybrid development. This can be caused by the seed grower not destroying the male lines prior to seed maturation. In the hybrid process, male plants are used to pollinate female plants to produce a hybrid. The male plants are then destroyed and the female plants are harvested. If male plants are allowed to go the seed and get mixed in to the seed lot, they do not exhibit the desired hybrid traits. The male plants usually have multiple heads that are small in size. They normally do not affect yields unless there is a high percentage of male plants. A one percent stand can look very bad but it will not affect yields.
Male sunflowers tower above (click on picture to enlarge). Notice multiple
heads.
The ND Agricultural Statistics Service has released the annual 2000 ND Wheat Varieties survey. Russ HRSW was the most popular spring wheat variety in 2000, moving up from second in 1999. It accounted for 19.4 percent of the spring wheat acres, 13,586,000 acres, compared to 14.4 percent last year. Russ was planted statewide and was the leading variety in the central district that includes Griggs County. Russ is a 1995 South Dakota release. Moving from fourth position to second was Gunner. Gunner accounted for 14.4 percent of the spring wheat acres, 10,061,000, compared to 6.2 percent in 1999. Dropping from first in 1999 to third in 2000 was 2375. It accounted for 13.7 percent of spring wheat acres compared to 25.5 percent in 1999. To see or get a copy of the whole publication click on the following link. 2000 ND Wheat Varieties.
The ND Agricultural Statistics Service has released the
annual 2000 ND Barley Varieties survey. Robust remained the most popular
barley variety in 2000 by a substantial margin over all other varieties in
ND. It accounted for 79.1 percent of the total barley acres. Stander
moved up to second place but continued its slide in popularity, representing 4.1
percent of the total acres. Foster ranked third among malting barley,
dropped down to the fourth position of all barley varieties with 2.4 percent of
the acres. Conlon was the leading feed variety for the second year in a
row, representing 2.5 percent of the total barley varieties and ranked third
over all in barley acres. To see or get a copy of the whole publication
click on the following link.
2000 ND Barley Varieties
Please Contact Our Office For Additional Information
E-mail: griggs@ndsuext.nodak.edu
Go to the 2000 AgAlert Index Page