Brent Hulke, Jerry Miller and Thomas Gulya Jr.
Abstract: Sunflower rust (caused by Puccinia helianthi Schwein.) has become a more significant threat to U.S. sunflower (Helianthus annuus L.) production as a result of the multiplicity of races, increasing incidence, and lack of commercial hybrids with resistance. Thus, there is a need for new sources of effective rust resistance in the sunflower breeding community. At the same time, resistance to downy mildew [caused by Plasmopara halstedii (Farl.) Berl. & De Toni] is also critical to parental line development because of the major impact of this disease over years. Our objective was to produce a restorer sunflower germplasm with resistance to the most virulent race of sunflower rust, race 777, and combine with it the best currently available downy mildew resistance in a high-yielding genetic background. We achieved this objective by using the pedigree breeding method with early generation selection for rust and downy mildew resistance and late-generation testcross evaluation for yield. The resulting restorer oilseed sunflower (Helianthus annuus L.) germplasm, ‘RHA 464’ (Reg. No. GP-325; PI 655015; experimental ‘05 187’), which has resistance to the two pathogens of interest, was released by the USDA-ARS and the North Dakota Agricultural Experiment Station, Fargo, ND, to fill the urgent need in the sunflower industry for breeding lines with elite genetic background and disease resistance.
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