Registration of HA-DM15 and HA-DM16 oilseed sunflower germplasms with resistance to sunflower downy mildew

Sunflower (Helianthus L.) production ranked third in global oilseed production in 2021. Downy mildew (DM), caused by the oomycete pathogen Plasmopara halstedii (Farl.) Berl. et de Toni, is a major constraint for worldwide sunflower production, causing significant yield losses in susceptible hybrids. The search for new sources of resistance to DM is the primary objective of all sunflower breeding programs. Germplasms HA-DM15 (Reg. no. GP-385, PI 702359) and HA-DM16 (Reg. no. GP-386, PI 702360) were developed by introgressing two new DM resistance genes, Pl₃₇ and Pl₃₈, from the wild sunflower species H. annuus and H. praecox into oilseed sunflower, respectively. The BC₁F₃-derived HA-DM15 harboring the Pl₃₇ gene was selected from the cross of HA 89//NMS HA 89/wild H. annuus PI 435417. The germplasm line HA-DM16 carrying the Pl₃₈ gene is an improved oilseed derivative of Rf PRA-417 with DM resistance originally derived from the wild H. praecox PRA-417 from the cross of cytoplasmic male sterile (CMS) HA89*2/wild H. praecox PRA-417. HA-DM15/Pl₃₇ and HA-DM16/Pl₃₈ are immue to the most predominant and virulent DM races idenfied in North America and Europe. Pl₃₇ and Pl₃₈ have been genetically mapped to sunflower chromosomes 4 and 2, respectively, with single nucleotide polymorphism markers linked to the both genes facilitating their transfer to elite sunflower lines by marker-assisted selection, providing new and diverse sources for sunflower DM-resistance breeding.