Registration of two confection sunflower germplasms, HA‐DM5 and HA‐DM6, resistant to sunflower downy mildew

Downy mildew (DM) is a primary biotic threat to sunflower (Helianthus annuusL.) production worldwide, negatively impacting yield. Germplasms HA‐DM5 (Reg. no. GP‐367, PI 687025) and HA‐DM6 (Reg. no. GP‐368, PI 691507) were developed and released through the collaboration of the USDA‐ARS and the North Dakota State University as new sources of resistance to downy mildew for confection sunflower. The backcross breeding method and DNA marker‐assisted selection were used to develop HA‐DM5 and HA‐DM6. HA‐DM5 is a BC2F3‐derived BC2F4maintainer selection from the cross of CONFSCLB1*2//CMS CONFSCLB1/ PI 435414 with the DM resistance transferred from a wild H. annuusPI 435414. Phenotypic/molecular characterizations confirmed the presence of the DM resistance gene Pl19located on sunflower chromosome 4 derived from PI 435414 in HA‐DM5. HA‐DM6 is a composite of seed from individual BC2F4plants from the cross of CONFSCLB1*2//CMS CONFSCLB1/ PI 494576. The DM resistance in HA‐DM6 is controlled by a single dominant gene Pl35located on chromosome 1 derived from wild H. argophyllusPI 494576. Both HA‐DM5 and HA‐DM6 confer resistance to several modern P. halstediiraces currently identified in the United States and Europe. They provide new genetic diversity in addition to the few currently used DM‐resistant inbred lines in confection sunflower ensuring protection from yield loss.