A new doubled haploid sugar beet line developed by the USDA's Agricultural Research Service in Kimberly, Idaho, as a breeding cultivar has the best resistance to curly top virus ever tested.
Courtesy of USDA
A sugar beet plant shows symptoms of curly top virus. A doubled-haploid line developed in Kimberly, Idaho, has demonstrated the best curly top tolerance ever in testing.
Courtesy of USDA
Scientists and industry representatives walk through a curly top screening nursery at USDA's Agricultural Research Service in Kimberly, Idaho. A doubled-haploid line developed in Kimberly has demonstrated the best curly top tolerance ever in the testing.
KIMBERLY, Idaho — Scientists say a new USDA sugar beet line developed for breeding programs to use as a parent in crosses has demonstrated the best curly top virus resistance ever recorded in repeated trials.
Molecular biologist Imad Eulayi, who developed the breeding line, KDHL13, at USDA's Agricultural Research Service in Kimberly, said it has also provided researchers a better understanding of the genetics behind curly top resistance.
Eulayi said scientists compiled a "gene expression library" by studying KDHL13's genetic response to curly top infection. He anticipates his station will publish on curly top resistance molecular markers — which help crop breeders quickly screen progeny for desirable traits — from the broader "library" by October.
Carl Strausbaugh, a local USDA plant pathologist who tested KDHL13 in screening nurseries, said curly top can be especially bad when high heat forces the sugar beet leaf hoppers that harbor the virus to abandon desert plants early for new beet growth, sometimes causing yield losses above 30 percent. During the past decade, however, he said new seed treatments and resistant varieties have helped producers better control curly top.
"From a historical perspective, curly top has been one of the primary yield-limiting diseases sugar beet growers have had to deal with since sugar beets were grown in Idaho," Strausbaugh said.
Eulayi said KDHL13 was USDA's first sugar beet cultivar developed with doubled-haploid technology — an advanced breeding method, though it's not classified as genetic modification, yielding plants with two identical sets of chromosomes, thereby eliminating variability in progeny so crosses fully retain desirable traits. His process exposes unfertilized plant ovules to a growth medium in a petri dish. As a plant develops, its cells spontaneously duplicate the single set of chromosomes. Any mutations are removed.
"This (method) is now becoming the bread and butter for us," Eulayi said.
The lack of variability also makes doubled-haploids ideal for genetic analysis. Since KDHL13 was first released for breeding programs to evaluate in 2012, Eulayi said his facility has developed 140 doubled-haploid sugar beet lines, with a host of different desirable traits. None are ready for release yet, but he anticipates at least a dozen more doubled-haploids will come out of his program by 2019.
Based on three years of testing, KDHL13 was accepted by the Journal of Plant Registrations as the top performing sugar beet line for curly top resistance in January, and it was featured in this month's edition of the USDA-ARS publication.
Cody Bingham, chairman of the Snake River Sugarbeet Research and Seed Alliance, said Amalgamated Sugar will allow no new sugar beet varieties to be planted in 2016, but during the next few years, the company intends to slightly relax its resistance standards for curly top in order to introduce additional options capable of yielding slightly higher sugar levels.
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