Registration of HA‐DM9, HA‐DM10, and HA‐DM11 oilseed sunflower germplasms with dual resistance to sunflower downy mildew

Downy mildew (DM), caused by the obligate pathogen Plasmopara halstedii(Farl.) Berl. & de Toni, is a worldwide yield‐limiting disease of sunflower (Helianthus annuusL.). To obtain durable DM resistance in sunflower hybrids, there is a need to stack new resistance genes into the best available germplasm. The DM resistance genes Pl8, Pl17, and Pl18were recently fine mapped to sunflower chromosomes 13, 4, and 2, respectively. The current study pyramided these genes into a single genotype by marker‐assisted selection. Three oilseed sunflower germplasms, HA‐DM9 (Reg. no. GP‐381, PI 700009), HA‐DM10 (Reg. no. GP‐379, PI 700004), and HA‐DM11 (Reg. no. GP‐380, PI 700005), are dual DM‐resistant germplasm lines developed and have been released by the USDA‐ARS, Sunflower and Plant Biology Research Unit in collaboration with the North Dakota Agricultural Experiment Station in 2021. The three lines, HA‐DM9 (Pl8Pl8/Pl17Pl17), HA‐DM10 (Pl8Pl8/Pl18Pl18), and HA‐DM11 (Pl17Pl17/Pl18Pl18), each stacked two different DM genes, providing broad resistance to all P. halstediiraces identified in North America and Europe so far, and can be used in sunflower breeding programs to enhance DM resistance. Three oilseed sunflower germplasms with dual resistance to downy mildew were developed using marker‐assisted selection.HA‐DM9, HA‐DM10, and HA‐DM11 each pyramided two different downy mildew R genes.All germplasms exhibit resistance to all known downy mildew races identified in North America and Europe.