Inheritance of resistance to race F of broomrape in sunflower lines of different origins

A new race F of broomrape overcomes all known resistance genes in cultivated sunflower, but recently, sources of resistance against race F have been developed. The objective of the present research was to study the inheritance of resistance to race F in crosses between 12 resistant sunflower breeding lines, derived from three different sources of resistance, and the susceptible male-sterile line P-21. Parental lines and F-1 , F-2 , F-3 and BC1 generations were evaluated for broomrape resistance. Segregations in the F-2 and BC1 to resistant parent approached resistant to susceptible ratios of 1 : 15 and 1 : 3, respectively, in most of the crosses, suggesting a double dominant epistasis. However, segregations of 3 : 13 and 1 : 1 for F-2 and BC1 , respectively, indicating a dominant-recessive epistasis, were also found. The F-3 data confirmed these results. Owing to the recessive nature of this resistance, it must be incorporated into both parental lines for developing resistant hybrid cultivars.