Broomrape (Orobanche Cumana Wallr.) resistance breeding utilizing wild Helianthus species

Wild Helianthus species possess valuable resistance genes for sunflower broomrape (Orobanche cumana Wallr.), especially the 39 largely underutilized perennial species. Resistance to race F has been transferred into a cultivated background via bridging of interspecific amphiploids. More recently, a single dominant gene resistant to race G was identified in annual H. debilis ssp. tardi-florus and transferred into cultivated HA 89. Interspecific crosses between wild annual Helianthus species and cultivated lines are relatively easy compared to those involving wild perennial species, which were made easier only after the development of embryo rescue techniques. Interspecific amphiploids resulting from colchicine treatment of F1 hybrids provide bridging materials for transferring genes without relying on embryo rescue. Among the diploid, tetraploid, and hexaploid perennial species, the speed of gene utilization follows the ploidy level of diploids, tetraploids, and hexaploids due to the time-consuming backcrosses required to eliminate the extra chromosomes in the latter two groups. In the development of pre-breeding materials, the retention rate of genetic material of the wild species is another concern with each additional backcross. For crosses involving tetraploid and hexaploid wild perennials, the use of 2n=51 chromosome F1 or BC1F1 generation, as pollen source, could accelerate chromosome reduction to 2n=34 in BC1F1 or BC2F1, resulting in useful materials with fewer backcrosses for trait selection.This work is partially funded by a National Sclerotinia Grant awarded to C.C. Jan.Peer Reviewe