Scientists look to molecular markers to speed wheat breeding

Frances Gould, Blanchard, Tobie M.  |  10/28/2014 10:03:22 PM

AgCenter plant pathologist Trey Price talks about wheat diseases at the annual wheat and oat field day at the Macon Ridge Research Station. (Photo by Bruce Schultz)

Many wheat varieties developed by seed companies aren’t suited for Louisiana because the warm, humid Gulf South conditions encourage disease development. But LSU AgCenter wheat breeder Steve Harrison and his team are working to ensure that Southern farmers have varieties well-adapted to this region.

Harrison said wheat breeding is a long-term commitment taking up to 10 years from the time a cross is made until a new variety can be released.

"It involves screening tens of thousands of breeding lines in early generations, filtering out the best ones and genetically purifying them through self-pollination," Harrison said. "Then in six or seven years we conduct yield trials at multiple locations."

Harrison is working with AgCenter molecular biologist Niranjan Baisakh to speed up the wheat breeding process by developing and using molecular markers to identify desirable genes in potential wheat varieties.

"Molecular markers are like hundreds of milestones on the road," Baisakh said. "If we know a given molecular marker is linked to a gene for a particular trait of interest, then we can select lines containing the gene by using that particular marker."

Baisakh said this saves time, especially with traits difficult or expensive to screen for in the field.

"Without molecular markers, screening for disease resistance requires waiting for the disease to show up in the field," he said.

Harrison said screening for herbicide resistance requires growing a large number of breeding lines in the field and applying differential rates of herbicide to them. The markers are not reliant on environmental conditions to display resistance, and DNA can be extracted from a single plant a few days after it germinates in the lab or greenhouse

Baisakh is developing molecular markers associated with tolerance to the herbicide Sencor. This will allow breeding lines and varieties to be quickly screened for the presence of genes coding for Sencor tolerance. Harrison said Sencor is an inexpensive herbicide effective against weeds, but it can damage some wheat varieties.

"We can take leaf tissue, do a lab assay and see whether it has the gene or genes for resistance present in the variety," Harrison said. This method is also being used to determine which lines are resistant to the disease stripe rust.

AgCenter plant pathologist Trey Price evaluates experimental and commercial fungicides in field trials to see which ones work best.

"We rate plots several times to get an idea of disease severity and compare across treatments, then look at yields," Price said.

Price and Boyd Padgett, plant pathologist and director for the AgCenter’s Central Region, are working with the wheat team on a research project aimed at finding resistance to the disease, fusarium head blight, or scab. The AgCenter has several misted, inoculated scab nurseries each year to evaluate disease severity of breeding lines and varieties under high disease pressure. Price and Padgett help produce inoculum for the nurseries and evaluate lines in the field.

Price said scab is generally a problem in all wheat-growing areas in the country. It is more of a problem in Louisiana in areas that also grow rice.

Wheat specialist Josh Lofton coordinates educational and outreach programs for wheat producers. He is looking at the growth and development of wheat across different growing environments.

"Management decisions should be based on growth stage, not date," Lofton said. "Herbicide and fungicide applications should be set on growth stage."

The LSU AgCenter is part of the Southeastern University Grains (SUNGRAINS) consortium of six universities cooperating on wheat and oat research and variety development. The other five are the University of Georgia, North Carolina State University, Texas A&M University, the University of Arkansas and the University of Florida.

The AgCenter works with the Georgia Seed Development Commission, a nonprofit arm of the University of Georgia, to produce large seed increases. Tobie Blanchard

This article was published in the 2014 Louisiana Soybean & Grain Research & Promotion Board Report


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