Inheritance of resistance to sunflower broomrape (Orobanche cumana Wallr.) in an interspecific cross between Helianthus annuus and Helianthus debilis subsp. tardiflorus

With 2 tables Abstract Sunflower broomrape ( Orobanche cumana Wallr.) constrains sunflower cultivation in many areas of Europe and Asia. Populations classified as race G that overcome all known resistance genes have recently appeared. The objective of this research was to study the inheritance of resistance to broomrape race G in a resistant accession of Helianthus debilis subsp. tardiflorus . Heads of H. debilis subsp. tardiflorus were emasculated and pollinated with pollen of the Helianthus annuus ‐susceptible line HA 89. BC 1 F 1 , BC 1 F 2 , BC 1 F 3 , BC 2 F 1 , BC 2 F 2 and BC 2 F 3 generations were developed and evaluated for broomrape resistance. F 1 plants were resistant, indicating dominance of resistance. BC 1 populations segregated in a ratio of one resistant to one susceptible plant, whereas BC 1 F 2 and BC 2 F 2 populations segregated in a ratio of three resistant to one susceptible plant, which was confirmed in the evaluation of the BC 1 F 3 and BC 2 F 3 populations. The results indicated that resistance to broomrape race G in H. debilis subsp. tardiflorus is controlled by dominant alleles at a single locus. This mode of inheritance will facilitate the introgression of resistance into elite cultivars.