Author
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SEILER, GERALD |
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Submitted to: Meeting Proceedings
Publication Type: Proceedings Publication Acceptance Date: 5/25/2010 Publication Date: 6/23/2010 Citation: Seiler, G.J. 2010. Utilization of Wild Helianthus Species in Breeding for Disease Resistance. Proceedings of the International Sunflower Association (ISA) Symposium "Sunflower Breeding on Resistance to Diseases," June, 23-24, 2010, Krasnodar, Russia. p. 36-50. Available: http://www.agrowebcee.net/fileadmin/content/sunflower/files/International_Symposium_Sunflower_Breeding_On_Resistance_To_.pdf Interpretive Summary: Sunflower hybrids have an extremely narrow genetic base, using only a single female parent for all hybrids, making the crop extremely vulnerable to an impending disaster as seen in maize in the 1970s. There remains a need to increase the genetic diversity of cultivated sunflower due to the marked reduction in genetic diversity during domestication. Wild species of sunflower have been a source of resistance to many pests, especially for diseases. There are 51 species of wild sunflower, 14 annual and 37 perennial. In a recent survey of 13 major crops for introduced genes from wild ancestors, sunflower ranks fifth with seven traits. It is estimated that wild species contribute 270 to 385 million USD per year to just the USA's sunflower industry. Much of this value is derived from resistance genes for several major diseases including rust, downy mildew, Verticillium wilt, powdery mildew, Phomopsis stem canker, Sclerotinia wilt, charcoal rot, Phoma black stem, and the parasitic weed broomrape. The frequency of downy mildew resistance genes in the wild annual species is high with dominant genes controlling single specific races being the most common, while multiple-race resistance to all known races has been identified in only two populations of silver leaf sunflower. The frequency of rust resistance genes is also high in wild annual species with many populations containing rust-resistant plants, but immunity or total susceptibility is rarely found. Jerusalem artichoke has been a source of disease resistance genes for over 50 years. It has been particularly useful for stem-infecting diseases such as Sclerotinia stalk rot, Phomopsis stem canker, Phoma black stem, and charcoal rot. The perennial species also have provided resistance genes for broomrape, where most of the perennial species have been reported to have immunity to the parasite. Significant progress has been made in collecting and preserving the wild sunflower germplasm, but only a small portion of the available genetic diversity has been exploited for sunflower improvement. This germplasm will be important in the future as new races of diseases evolve and new diseases appear. Technical Abstract: There are 51 species of wild Helianthus, 14 annual and 37 perennial. The genus Helianthus, besides constituting the basic genetic stock from which cultivated sunflower originated, continues to contribute characteristics for cultivated sunflower improvement. In a recent survey of 13 major crops for introduced genes from wild ancestors, sunflower ranks fifth with seven traits. It is estimated that wild species contribute 270 to 385 million USD per year to just the USA's sunflower industry. Much of this value is derived from resistance genes for several major diseases including rust, downy mildew, Verticillium wilt, powdery mildew, Phomopsis stem canker, Sclerotinia wilt, charcoal rot, Phoma black stem, and the parasitic weed broomrape. The frequency of downy mildew resistance genes in the wild annual species is high with dominant genes controlling single specific races being the most common, while multiple-race resistance to all known races has been identified in only two populations of H. argophyllus. The frequency of rust resistance genes is also high in wild annual species with many populations containing rust-resistant plants, but immunity or total susceptibility is rarely found. Helianthus tuberosus has been a source of disease resistance genes for over 50 years. It has been particularly useful for stem-infecting diseases such as Sclerotinia stalk rot, Phomopsis stem canker, Phoma black stem, and charcoal rot. The perennial species also have provided resistance genes for broomrape, where most of the perennial species have been reported to have immunity to the parasite. Significant progress has been made in collecting and preserving the wild Helianthus species germplasm, but only a small portion of the available genetic diversity has been exploited for sunflower improvement. This germplasm will be important in the future as new races of diseases evolve and new diseases appear. |
