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By Sharon Durham
July 17, 2014
Two genes that protect sunflowers against rust disease have been discovered by U.S. Department of Agriculture (USDA) scientists.
Agricultural Research Service (ARS) molecular geneticist Lili Qi at the agency's Sunflower and Plant Biology Research Unit in Fargo, North Dakota, and her collaborators discovered that the genes, R13a and R13b, confer resistance against all rust strains tested to date. Her collaborators include Thomas Gulya and Brent Hulke at the ARS Fargo unit, and Li Gong and Samuel Markell with North Dakota State University. ARS is USDA's chief intramural scientific research agency, and this research supports the USDA priority of promoting international food security.
The R13a gene was found in the confection sunflower line called HA-R6, while the R13b gene was in the oilseed line RHA 397. The USDA inbred line HA-R6 is one of the few confection sunflower lines resistant to rust.
Rust is a serious fungal disease of sunflowers grown around the world. The disease can significantly reduce sunflower yields and has been increasing in severity in North America in recent years. In 2013, U.S. farmers produced more than 2 billion pounds of sunflowers, worth more than $757 million.
Sunflower seeds are predominantly grown as an oilseed crop, but some varieties are specifically grown as "confection" varieties, meaning their kernels are for eating, either raw or roasted.
An economic and environmentally friendly method to control rust is to use resistant cultivars and hybrids. Developing genetically resistant hybrids is the preferred approach for disease management, but few widely effective resistance sources to sunflower rust have been identified.
In an annual field survey conducted by the North Dakota State University Cooperative Extension Service and the U.S. National Sunflower Association, sunflower rust was found in 60 to 70 percent of surveyed fields. Kernels infected by rust can be damaged and discolored and are therefore unlikely to meet grading standards established by the industry for confection sunflower seeds.
The rust resistant lines should be very useful to breeders who want to develop rust-resistant commercial sunflower hybrids.
The research was published in Theoretical and Applied Genetics.
Read more about this research in the July 2014 issue of Agricultural Research magazine.