Sugar Producer

16 Sugar Producer AUGUST/SEPTEMBER 2016 The sugarbeet curly top virus could meet its match in new sugarbeet varieties derived from KDH13, a germplasm breeding line developed by Agricultural Research Service (ARS) researchers for resistance to the disease-causing pathogen. Transmitted by small insects called beet leafhoppers, the curly top virus courses through the phloem of susceptible beet plants, wreaking cellular havoc that can manifest as yellow, inwardly curled leaves; stunted growth; and other telltale symptoms. Severe outbreaks of curly top disease can reduce sugarbeet yields 30 percent or more. Spraying insecticides can prevent leafhoppers from transmitting the virus to plants while feeding, but the preferred approach is to plant sugarbeet varieties that naturally resist the pathogen, notes Imad Eujayl, a molecular biologist with ARS's Northwest Irrigation and Soils Research Lab in Kimberly, Idaho. Fortunately, a new germplasm line is now being used by beet breeders and seed companies as a source of resistance genes that can be bred into the commercial varieties now grown, shoring up the low levels of tolerance to the virus in existing germplasm. Disease Resistance | By Jan Suszkiw, Photos by Imad Eujayl Breeding Beets for Better Resistance to Curly Top Virus Beet leafhoppers can transmit curly top virus as they feed on plant leaves. Plant pathologist Carl Strausbaugh rates a sugarbeet plant for the viral disease known as curly top. Eujayl, together with ARS plant pathologist Carl Strausbaugh and members of the Beet Sugar Development Foundation, developed, tested and released the new genetic stock line— KDH13—as part of an ongoing sugarbeet improvement program at the Kimberly lab. A cornerstone of that program involves the use of molecular markers and genetic mapping techniques to identify resistance genes and other economically important traits, including improved storage quality, better tolerance to drought and frost, and increased sugar content. KDH13 was derived from the use of "gynogenesis," a tissue-culture technique in which the new sugarbeet line got its start from the regenerated egg-cell tissue of a single, unfertilized female parent plant known to be resistant to the virus. In greenhouse and nursery tests, mature plants of KDH13 outperformed Hilleshog PM90, a top resistant cultivar used for comparison. Technical details about KDH13, including its growth characteristics and availability as seed, were published in the January 2016 issue of the Journal of Plant Registrations. "Ultimately, the new genetic and pathogen knowledge that's generated will allow our stakeholders to reduce losses by improved disease management," the researchers say. "New Sugarbeet Resists Curly Top Virus" was published in the March 2016 issue of AgResearch Magazine. n

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