Submitted to: Plant Breeding
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2006
Publication Date: 1/1/2007
Citation: Velasco, L., Perez-Vich, B., Jan, C.C., Fernandez-Martinez, J.M. 2007. Inheritance of resistance to broomrape (Orobanche cumana wallr.) race F in a sunflower line derived from wild sunflower species. Plant Breeding. 126:67-71. Interpretive Summary: Genetic resistance to broomrape has been introduced from wild sunflower species into cultivars since the early work on sunflower breeding in the former USSR. The widespread use of resistant cultivars has resulted in the appearance of new races of the parasite capable of overcoming the resistance genes already in use (Or1-Or5). Recent studies have shown an evolution of sunflower broomrape races in Spain, with a new race, designated F, overcoming all the known resistance genes identified thus far. This paper reports the inheritance of race F resistance genes derived from wild perennial sunflower species. A thorough understanding of the resistance genes will lead to a more efficient utilization of these genes leading to the production of resistant sunflower hybrids.
Technical Abstract: Genetic resistance to broomrape (Orobanche cumana Wallr.) race F in sunflower line J1, with resistance genes derived from wild perennial species, has been reported to be controlled by dominant alleles at a single gene Or6. However, deviations from a monogenic dominance have been observed. The objective of the present research was to gain insight on the inheritance of resistance to broomrape race F in sunflower line J1. Crosses between J1 and the susceptible lines P21, NR5, and HA 821 were made and F1, F2, F3, and BC to both parents were evaluated. F1 populations showed both resistant (R) and moderately susceptible (MS) plants, with a maximum of five broomrapes per plant compared with >10 in the susceptible parents. This indicated incomplete dominance of Or6 alleles. F2 phenotypes were classified as R, MS, or susceptible (>5 broomrapes per plant). Three different segregations were observed: 3:1, 13:3, and 15:1 (R+MS: S), suggesting the presence of a second gene Or7 whose expression was influenced by the environment. Digenic model was confirmed in the evaluation of F2:3 families.