Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: December 31, 2010
Publication Date: N/A
Interpretive Summary: Sunflower cultivation continues to be pushed into lower-fertility soils and other marginal environments where drought and high or low temperatures continually take their toll on the yield. The challenge for the sunflower breeding community is to breed sunflower adaptable to these marginal environments and at the same time increase seed yield. 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. They also provide the cytoplasm that is the basis of all hybrid sunflowers. The estimated economic contribution of the wild species to the cultivated sunflower is between $269 and $384 million dollars per year. Since wild sunflower and the sunflower crop are native to North America, associated pests have coevolved in natural communities, thus providing the opportunity to search for pest resistance genes in the diverse wild species. Significant progress has been made in collecting and preserving wild species, increasing the genetic diversity available for crop improvement. Thus far, only a small portion of the available diversity has been exploited. The future direction of research will include the transfer of target genes from wild relatives into domesticated sunflower with improved genetic backgrounds adapted to local conditions. This will be facilitated by introgression of favorable alleles from alien germplasm, pyramiding favorable alleles for specific traits, and simultaneously improving the maximum number of traits. New sunflower hybrids will possess pest and disease resistance genes from distantly related or even unrelated plants and other organisms. To keep sunflower an economically viable global crop, researchers must strive to combine the best conventional and modern molecular approaches available. This will require a multidisciplinary team approach and a commitment to a long-term integrated genetic improvement program.
Technical Abstract: Crop wild relatives, which include the progenitors of crops, have been undeniably beneficial to modern agriculture, providing plant breeders with a broad pool of potentially useful genes. Wild relatives of crop plants typically are genetically much more diverse than related cultivated lineages. Genetic diversity contributes to long-term preservation of species by allowing them to adapt quickly to changes in their environment. The genus Helianthus, besides constituting the basic genetic stock from which cultivated sunflower originated, continues to contribute specific characteristics for cultivated sunflower improvement, but still has a tremendous amount of genetic diversity yet to be exploited. The wild sunflower species are adapted to a wide range of habitats and possess considerable variability for most agronomic and achene quality characters, and reaction to insects and disease pathogens. A recent survey of introduced genes in 13 crops of major importance to global food security from the mid-1980s to 2005 reported that sunflower has seven contributed traits, the fifth highest of the crops surveyed. The estimated economic contribution of the wild species to the cultivated sunflower is between $269 and $384 million dollars per year. There is a continued need to collect, maintain, evaluate and enhance wild Helianthus germplasm for future improvement of cultivated sunflower. The genetic diversity of the wild species can make a significant contribution to the global sunflower industry by providing genes for resistance (tolerance) to pests and environmental stresses. New sunflower hybrids will possess pest and disease resistance genes from distantly related or even unrelated plants and other organisms. To keep sunflower an economically viable global crop, researchers must strive to combine the best conventional and modern molecular approaches available. This will require a multidisciplinary team approach and a commitment to a long-term integrated genetic improvement program.