Pullman, Washington
October 2, 2007
Washington State University is seeking international patent
protection on Scarlet Rz1, a new spring wheat genotype believed
to be the first to have resistance to Rhizoctonia root rot, a
yield-limiting root disease found world-wide.
“This is the first wheat genotype that we know of that has
tolerance to this disease,” said Kim Kidwell, interim spring
wheat breeder and associate dean of academic programs for WSU’s
College of Agricultural, Human, and Natural Resource Sciences.
“It’s a major problem in direct seeded spring wheat production.
We’ve just started to present data publically, and people are
interested in it because the disease is a serious yield-limiting
factor in Australia as well as here, and we don’t have any means
of controlling the disease aside from tillage.”
The soil-borne fungal disease can cut wheat yields by as much as
30 percent when conditions favor it.
“In the lower rainfall areas of the state, it’s a real problem
in drought years,” said John Burns, WSU Extension agronomist.
“If you want to do any sort of crop rotation with a spring crop,
it’s a real limiting factor.
“Direct seeding into the residue of previous crops is one of the
best options for planting spring wheat in low rainfall regions
of the state. The practice helps prevent soil wind erosion and
conserves soil moisture,” Burns continued. “Unfortunately,
Rhizoctonia persists in undisturbed soil and serves as annual
reservoir of this fungus which is most pronounced in undisturbed
direct-seeded fields.”
The new wheat gentoype is a mutation of the variety Scarlet
developed and released by Kidwell in 1998. Scarlet-Rz1 was
created by a chemical mutation, and is not considered to be a
genetically modified organism.
Camille Steber, a USDA-ARS geneticist, and Kidwell treated
Scarlet wheat seeds with a chemical mutagen, which causes
mistakes to occur in DNA sequences. The mistakes can sometimes
lead to creation of valuable new genes.
Victor DeMacon, a senior scientific assistant in Kidwell’s lab,
tested the mutant seedlings for resistance to Rhizoctonia root
rot in the greenhouse. One exhibited tolerance.
The team of researchers in collaboration with Patricia Okubura,
a USDA-ARS research geneticist, confirmed that resistance was
conferred by a single gene.
“Probability would say that the possibility of identifying a
novel gene this way is rare,” Kidwell said. “Vic found the one
we now call Scarlet-Rz1 in the first 200. We’ve screened half a
million since and have found others that have pretty good levels
of tolerance, but this is the one we like the best.”
The utility of the gene has not been fully determined but in the
future researchers hope to clone the gene and transfer disease
resistance to other wheat varieties. Eventually the gene may be
adapted for use in other crops where Rhizoctonia root rot is a
problem, including ornamental plants as a means for preventing
damping off disease.
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