Registration of Oilseed Sunflower Germplasms HA‐BSR2, HA‐BSR3, HA‐BSR4, and HA‐BSR5 with Resistance to Sclerotinia Basal Stalk Rot and Downy Mildew

Sclerotinia basal stalk rot (BSR) and downy mildew (DM) are two fungal diseases that are major yield limiting factors in global sunflower (Helianthus annuusL.) production. Four oilseed sunflower germplasm lines, HA‐BSR2 (Reg. No. GP‐346, PI 685015), HA‐BSR3 (Reg. No. GP‐347, PI 685016), HA‐BSR4 (Reg. No. GP‐348, PI 685017), and HA‐BSR5 (Reg. No. GP‐349, PI 685018), were developed to provide diversity for resistance to BSR and DM. The BSR resistance in HA‐BSR2 was derived from the wild annual H. petiolarisPI 435843, while BSR resistance in HA‐BSR3 to HA‐BSR5 was derived from wild annual H. argophyllusPI 494573. The four lines were tested for resistance to BSR in inoculated field nurseries from 2012 to 2015 and consistently showed high levels of BSR resistance across environments. A 4‐yr mean BSR disease incidence for HA‐BSR2, HA‐BSR3, HA‐BSR4 and HA‐BSR5 was 4.4, 3.0, 0.8, and 1.9%, respectively, compared with an average disease incidence of 36.1% for ‘Cargill 270’ (susceptible hybrid check), 31.0% for HA 89 (recurrent parent), 19.5% for HA 441 (resistant check), and 11.6% for ‘Croplan 305’ (resistant hybrid check). Genetic analysis detected the presence of wild sunflower species chromosome segments in all four germplasm lines, which are presumably associated with BSR resistance. HA‐BSR2, HA‐BSR3, and HA‐BSR4 are also resistant to DM, derived from the parental line HA 458. HA‐BSR2, HA‐BSR3, and HA‐BSR4 represent the first sunflower germplasm to combine resistance against both Sclerotinia BSR and DM.