Author
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SEILER, GERALD |
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Submitted to: Proceedings Sunflower Research Workshop
Publication Type: Proceedings Publication Acceptance Date: 2/15/1997 Publication Date: N/A Citation: N/A Interpretive Summary: Diseases are a major limiting factor of sunflower production world-wide. Cultivated sunflower is susceptible to many diseases caused mainly by fungi, and to a lesser extent by bacteria and viruses. The susceptibility of cultivated sunflower may be due to the co-evolution of sunflower and the diseases. While this may have been a disadvantage, it could also be an advantage. Since they co-evoluted together, certain populations and species had to evolve resistance to survive. These are the populations of the wild species which we are seeking. The frequency of disease resistance genes from the wild species varies from frequent for rust, Verticillium wilt, and downy mildew to very limited for Sclerotinia wilt. The diversity of wild species with disease resistance is also impressive because we can choose from five-to-ten different wild species as our resource for genes. Several successful transfer of genes from the wild species into cultivated sunflower have been accomplished for rust downy mildew, Verticillium wilt, stem canker, powdery mildew, and charcoal rot. Many other genes have been identified, but await our ability to transfer the genes from the wild to the cultivated sunflower. With the advent of biotechnology we should be able to more efficiently move specific resistance genes stored in the wild species into cultivated sunflower. This will make the wild species an even more valuable genetic resource. Technical Abstract: Disease control in sunflower is essential for maximum production. The most effective control measure is genetic resistance. To successfully have genetic resistance, one needs to have a source of resistance genes. Since cultivated sunflower is susceptible to most diseases, sources of resistance need to be identified from the wild species and transferred to the crop species. The objective of this research was to present an overview of the wild species which have been identified as potential sources of disease resistance and give examples where the genes have been transferred into a cultivated background such as germplasm populations or inbred lines. Sources of resistance genes from the wild species are discovered for the following diseases: rust, downy mildew, Verticillium wilt, Sclerotinia wilt, Phomopsis stem canker, charcoal rot, Phoma black stem, Rhizopus head rot, Alternaria leaf spot, powdery mildew and a root parasite, broomrape. There appears to be a high frequency and species diversity for resistance genes for rust, downy mildew and Verticillium wilt. No resistance genes for Sclerotinia wilt have been identified in the wild species, only tolerance genes. Many resistance genes have been successfully incorporated into cultivated sunflower. The use of biotechnological techniques will hopefully allow us to move only the resistance gene of interest and not undesirable linked genes. |
