Registration of Oilseed Sunflower Germplasm HA‐BSR1 Highly Tolerant to Sclerotinia Basal Stalk Rot

Basal stalk rot (BSR) is a devastating disease that causes a significant damage to sunflower (Helianthus annuus L.) production worldwide by reducing seed yield and quality. The objective of this research was to develop highly BSR tolerant sunflower germplasm by incorporating genetic factors from various partially tolerant breeding lines. HA‐BSR1 (Reg. No. GP‐336, PI 678571) sunflower germplasm is an F7–derived oilseed maintainer developed from the cross HA 441/RHA 439, selected for tolerance to Sclerotinia BSR. HA‐BSR1 showed significantly higher tolerance to BSR disease than both of the parents and the checks when evaluated across seven environments in North Dakota and Minnesota from 2012 to 2015. A 4‐yr mean disease incidence of HA‐BSR1 was 1.6% compared with the parents HA 441 (20.0%) and RHA 439 (12.6%), the susceptible hybrid check ‘Cargill 270’ (32.8%), and the resistant hybrid check ‘Croplan 305’ (10.4%). Molecular genetic analysis of HA‐BSR1 indicated the presence of six alleles associated with quantitative trait loci (QTL) conferring resistance against BSR, three alleles derived from each parents. The release of HA‐BSR1 along with the information of single nucleotide polymorphism markers linked to QTL will be useful in marker‐assisted selection breeding to pyramid BSR resistance with other desirable agronomic traits in elite sunflower lines.