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 annuus L.) 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 BC2F4 maintainer selection from the cross of CONFSCLB1*2//CMS CONFSCLB1/PI 435414 with the DM resistance transferred from a wild H. annuus PI 435414. Phenotypic/molecular characterizations confirmed the presence of the DM resistance gene Pl(19) located on sunflower chromosome 4 derived from PI 435414 in HA-DM5. HA-DM6 is a composite of seed from individual BC2F4 plants from the cross of CONFSCLB1*2//CMS CONFSCLB1/ PI 494576. The DM resistance in HA-DM6 is controlled by a single dominant gene Pl(35) located on chromosome 1 derived from wild H. argophyllus PI 494576. Both HA-DM5 and HA-DM6 confer resistance to severalmodern P. halstedii races 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.