Dominance relationships for genes conferring resistance to broomrape (Orobanche cumana wallr) in sunflower

Abstract

The holoparasitic angiosperm sunflower broomrape (Orobanche cumana Wallr) is currently regarded as one of the most important constraints of sunflower production in many areas in Southern Europe and the Black Sea region. Breeding for resistance is considered to be the most effective and feasible method of controlling sunflower broomrape. Commercial hybrids cultivated in Spain carry the Or1 to Or5 genes that confer resistance to races A to E. However, a new race, designated F, has been identified. Germplasm with race F resistant genes derived from wild and cultivated sunflowers has been developed. Dominance reaction of these genes is an essential feature that determine the breeding method to produce race F resistant sunflower hybrids. Crosses between different sources of race F resistant lines, including those derived from wild and cultivated sunflower, and different susceptible parental lines were made. Allelic crosses between race F resistant lines, as well as crosses between race F resistant lines and race E resistant lines were also carried out. F1 plants, F2 plants, and their parental lines were evaluated for their disease reaction to race F or race E of broomrape. Different dominance reactions and inheritance mechanisms for broomrape resistance were observed. These depended on the race of broomrape, the source of race F resistance, and also the susceptible parental line used for the cross. The relevance of the results obtained for sunflower breeding for resistance to sunflower broomrape is discussed.