Validation of broomrape resistance QTLs in sunflower line HA-267

Abstract

Broomrape (Orobanche cumana) is a parasitic weed that causes substantial yield losses in sunflower. While chemical options for suppressing sunflower broomrape are available, breeding for resistance has both economic and environmental advantages. In a previous study, we reported on the mapping of polygenic broomrape resistance in the HA-267xOD-DI-82 mapping population. We identified 2 major quantitative trait loci (QTL), or7.1 and or12.1, as well as numerous small effect QTLs that were dispersed across the genome. While these results provided valuable insights into the complexity of resistance to broomrape, QTL validation is an important and often overlooked step for breeding. The aim of this study is to assess the effects of these QTLs in an unrelated genetic background and to identify QTLs that are stable and thus have the highest breeding value. To achieve this goal, resistant line HA-267 was crossed with a susceptible parental line HA-26-PR, and a mapping population consisting of 189 individuals was developed. Following phenotyping, we used selective bulked segregant analyses coupled with genotyping-by-sequencing (GBS) to re-map QTLs conferring resistance to broomrape population LP12BSR. A total of 7 QTLs were identified. The results confirmed that the effects of QTLs or7.1 and or12.1 was large and consistent. Importantly, an additional QTL located on sunflower chromosome 3 (or3.1), which was previously proven to control resistance to broomrape race E, appeared to have a larger effect in the new HA-267xHA-26-PR cross compared to the previous one (HA-267xOD-DI-82). These validated and stable QTLs will be prioritized in breeding, and associated molecular markers will facilitate marker-assisted selection.