June 1997
Disrupted by Karnal bunt, Off-Season Wheat Research Back on Track
by Stephanie Sorensen
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Prairie Grains is the
official publication of
the Minnesota
Association of
Wheat Growers,
North Dakota Grain
Growers Association,
South Dakota Wheat,
Inc., and the
Minnesota Barley
Growers Association.
Last year's discovery of Karnal bunt (Kb) disrupted the Arizona and southern California plant nurseries that northern crop researchers use for off-season winter crop breeding and varietal trials. The Kb issue had the potential to seriously set back development of new small grains varieties, as the off-season breeding programs allow geneticists and breeders to carry out two growing seasons in one year, hastening the development of promising crop lines.
As a result of federal restrictions in and around the southwest U.S. area where Kb was detected, some northern crop breeders moved their nurseries halfway across the globe last winter, while others remained at their sites in Arizona, at the risk of having their seed denied the trip home after harvest.
North Dakota State University wheat breeders Richard Frohberg and Elias Elias relocated their off-season nurseries from Arizona to New Zealand. Since our winter is summer Down Under, days in New Zealand were long and Frohberg and Elias were able to harvest seed from their off-season wheat and durum trials about a month earlier than they can in an Arizona winter.
Fred Townley-Smith, spring wheat breeder in Canada, also successfully conducted his winter research in New Zealand. Townley-Smith says, however, that the expense of a New Zealand nursery (about four times more than having one in the U.S.) is daunting, and he will probably return to the U.S. as soon as the Canadian government allows. It's likely to take a few years for Canada to lift its ban on wheat grown in the southern U.S., despite the U.S.'s eased restrictions, he says.
APHIS has revised its definition of Karnal bunt-afflicted grain to exclude kernels that have Kb spores only on the outside surface. Restrictions were lifted on some counties in Arizona and California. Whether Northern Plains breeders will return to these areas for the 1997-98 winter depends in large part on state regulations and the success of last winter's breeding locations.
Frohberg returned from his New Zealand site with such an abundance of seed that he says his primary concern is having enough time to sort through it. Frohberg emphasized the benefits of continuous progress in breeding programs, saying that NDSU breeding populations for spring wheat varietal development for eastern and north-central North Dakota all have a more developed source of germ-plasm for scab resistance. For now, Frohberg and Elias plan to continue their off-season plant breeding in New Zealand.
Bob Busch, USDA-ARS wheat geneticist at St. Paul, decided to keep his breeding program in Arizona last winter and follow required precautions on his seed wheat harvest. He obtained permits from the Arizona and Minnesota Ag Departments, and applied a bleach solution to seed before planting, to kill any present Karnal bunt spores.
Busch's winter nursery is in Yuma County, AZ, an area that is still under restriction despite the new APHIS Kb definition. Busch believes that the Arizona county is safe and intends to stay there in the future. "Yuma County is still under restriction because a farmer may have planted a seed infected with Karnal bunt a couple of years ago. No signs of Kb have been found since," said Busch.
Busch had a successful winter program in Yuma, returning to Minnesota with his target number of 480-500 promising wheat lines. In addition, his "preliminary yield" nurseries in Arizona have recently doubled in size, broadening the chances that some varieties will make it to advanced nurseries.
Two successful growing seasons per year has meant a speedier process for developing wheat varieties with higher scab tolerance, says Busch. In 1994, Busch estimates that 10-15% of his breeding material was rated scab-tolerant. Today, that percentage is over 60%.
Busch's colleague at the U of M, Don Rasmussen, conducted his barley breeding program in Yuma last winter as well. As barley is not a host of Kb, there was little fear of Kb having any effect on the barley breeding program, according to Rasmussen. He said his breeding material increased significantly after a productive winter in Yuma.
Jackie Rudd, South Dakota State University spring wheat breeder, split his off-season research between New Zealand and Arizona. He bleached his Arizona seed and was able to return breeding material to South Dakota and plant it into his summer breeding program.
As a precaution, Rudd planted his most promising lines in New Zealand. Although it harvested well, Rudd intends to breed 100% of his off-season crop in Arizona this winter because of the expense of maintaining a nursery in New Zealand. n