Amarillo, Texas
May 17, 2005
The only sugar beets growing in Texas are in the
laboratory. But those few plants are getting to the root of
problems throughout the sugar beet industry.
The sugar beet industry moved out of Texas in 1997 after the
close of the processing plant at Hereford. But the growing
research program within
Texas Agricultural Experiment Station's plant pathology lab
here didn't die.
Just the opposite, said Dr. Charlie Rush, professor and director
of the plant pathology labs in Bushland and Amarillo.
"We do all of our work in the greenhouse and laboratory," he
said. "Here, we have to have an understanding of everything,
from the crop growing in the field to the molecular aspects of
the pathogen. That makes our program totally unique."
Outside research dollars began pouring in and Rush's program was
reinvigorated in 2002 when a new strain of beet necrotic yellow
vein virus emerged.
The new strain threatened sugar beet production in California
and Minnesota. Getting answers was important because the
affected area in California holds records for production and
Minnesota boasts the most concentrated sugar beet growing region
in the world, Rush said.
Beet necrotic yellow vein virus, which causes the disease known
as rhizomania, was found near Hereford in 1986 by a California
researcher. A similar virus, beet soil borne mosaic virus, also
was found about the same time.
The two viruses are closely related, Rush said. But rhizomania
is devastating and found worldwide, while the mosaic virus is
not as destructive and is limited to the United States.
Growers, breeders and industry officials from Colorado,
Nebraska, Wyoming, Idaho, Minnesota, Michigan and North Dakota
began looking to Texas and Rush for help.
They would see rhizomania in isolated spots in a few fields, but
within a few years, it would spread across entire production
areas, Rush said. His team responded by studying the ecological
and epidemiological aspects of the pathogen and disease – what
could producers do to reduce the incidence and severity of the
disease.
"We started doing a lot of work with both of the viruses, and by
default, I ended up with more experience than anyone else," he
said.
Strong genetic resistance to rhizomania was bred into sugar beet
varieties and until 2002, that was effective, Rush said. But
with only one gene selected for resistance, the plant virus
mutated and overcame the resistant gene.
"We're going in now and looking at the molecular makeup of the
plant virus," he said.
Making trips to the Imperial Valley in California and the Red
River Valley growing region in Minnesota and North Dakota, Rush
said his team works with growers and sugar company
representatives at harvest time.
Soil samples and infected beets are brought back to the lab at
Bushland. Sugar beets are planted in the contaminated soil and
the virus is purified from the infected plants, he said. The
virus isolate is cultured in test tubes, and the plants are no
longer needed.
"We're trying to find out why this genetically mutated pathogen
is able to overcome the resistance in the plant," he said.
"We're looking at new crosses by seed companies and challenging
them with each of these two viruses, as well as a combination of
the two."
By measuring the effect of the disease on the plant, as well as
purifying the virus and quantifying how much is actually
present, they can determine if resistance is expressing itself,
Rush said.
Breeders have good indications they may have some resistance in
some wild relatives of sugar beets, he said. Advanced lines
identified with potentially high levels of resistance will be
planted in test plots in the sugar beet growing regions.
When these lines become available to producers and allow them to
grow beets at a profit, that's when the research has come full
circle, Rush said. |