Submitted to: Sunflower International Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/12/2000
Publication Date: N/A
Citation: 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 resist- ance genes alreay 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 reaction of advanced interspecific hybrids (amphiploids and BCnF1) and their parents, previously evaluated against known races, to an O. cernua population which included the F race. Results indicated that the wild perennial Helianthus species were immune, the interspecific amphiploids retained a high level of resistance, and the more advanced progenies segregated for resistant and susceptible plants. Those resistant tplants are being selected for further evaluations and the development of resistant germplasm.
Technical Abstract: The emergence of virulent populations of broomrape (Orobanche cumana Wallr.), which overcame the resistance of sunflower (Helianthus annuus L.) hybrids in southern Spain created an urgent need for new resistance genes. This study reports the transfer of broomrape resistance from wild perennial Helianthus species into cultivated sunflower. Wild parental species, H. angustifolius L., H. divaricatus L, H. gracilentus A. Gray, H. hirsutus Raf., H. maximiliani Schrader, H. nutallii T. & G., and H. strumosus L. were immune to three broomrape populations, including population SE296 with predominately race F, the strain that overcame the Or5 resistance gene. Most amphiploids were highly resistant, suggesting dominant effects of the resistance genes. Backcross (BC2F1) progeny derived from diploid perennial Helianthus species segregated for broomrape resistance. BC2F2 progeny from selected BC2F1 plants resistant to the virulent broomrape population SE296 had 34 to 38 chromosomes, with 37% of the plants having the diploid sunflower chromosome complement of 2n=34. Six BC2F3 families from selected resistant diploid BC2F2 plants, derived from diploid species H. grossesserratus Martens, H. maximiliani, H. divaricatus, and H. angustifolius, had an average of 52% of the plants immune to population SE296, suggesting that one or a few genes controlled the resistance. This study documents the successful transfer of genes for broomrape resistance from wild perennial Helianthus species into cultivated sunflower utilizing interspecific amphiploids as a bridge. These diploid broomrape resistant lines provide valuable germplasm for the improvement of cultivated sunflower.