Mapping of a new gene for resistance to broomrape races higher than F

Abstract

Broomrape (Orobanche cumana) is one of the most important parasitic plants that can drastically reduce sunflower yield. Breeding for resistance is regarded as the most effective and environmentally friendly control measure. Due to the constant changes in broomrape race composition, i.e. the emergence of races F and higher, the majority of the existing resistance genes have become insufficient for crop protection. In this paper we report the genetic analysis and mapping of a new resistance gene for broomrape races higher than F. Broomrape resistance was evaluated using F-1 plants and F-2:3 families derived from a cross between the resistant sunflower inbred line AB-VL-8 and the susceptible line L-OS-1. The results showed that F-1 plants were susceptible, indicating a recessive resistance. In the derived F-2 population and F-3 families, the resistance segregation deviated significantly from the one-gene Mendelian ratio. However, marker analysis revealed polymorphism only on LG3, indicating that presumably single gene in this region conferred the resistance. The closest marker to the gene, tentatively designated as or (ab-vl-8), was ORS683 with the genetic distance of 1.5 centimorgans. The discovery of or (ab-vl-8) will provide a much needed new sunflower resistance gene for new broomrape races, and the associated markers will facilitate the introgression of the gene into different sunflower lines.