WSU 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.