Author
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MCCORD, PER - Former ARS Employee |
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Submitted to: Achieving Sustainable Culture of Sugarcane
Publication Type: Book / Chapter Publication Acceptance Date: 7/14/2017 Publication Date: N/A Citation: N/A Interpretive Summary: Sugarcane is a genetically complex crop. High chromosome numbers, and multiple (and variable) copies of chromosomes make it a challenging species for research. Despite the challenges, geneticists and breeders have actively sought to use DNA marker technology to enhance breeding efforts. Markers have been used to genetic relationships, estimate genetic diversity, and to develop unique molecular fingerprints for variety identification. Numerous studies have been undertaken to identify markers linked to important agronomic traits, using a wide array of technologies, and analysis of data from individual crosses (families) and groups of less related individuals. Aside from disease resistance (in particular the Bru1 for brown rust resistance), the markers that have been found accounted for a relatively small portion of the variation in traits of interest. In part, this should not be surprising, as the two most important traits in sugarcane (biomass yield and sugar content) are most likely controlled by many genes, as well as environmental effects. More sophisticated statistical methods may yet identify individual markers that can be used directly in breeding. In addition, breeding programs may choose to validate existing markers and deploy them even if effects are relatively small, if the traits are of sufficiently high value. The method of genomic selection, which evaluates many markers simultaneously, holds promise for sugarcane, especially if the populations used to develop the models are large enough, and if models are developed to account for interaction between genes. Modern sugarcane is a young invention, and despite its challenges, we should expect to be able to utilize a combination of the latest marker technologies, sound trait data, and new sophisticated models to increase rates of improvement in this important crop. Technical Abstract: Despite the challenges posed by sugarcane, geneticists and breeders have actively sought to use DNA marker technology to enhance breeding efforts. Markers have been used to explore taxonomy, estimate genetic diversity, and to develop unique molecular fingerprints. Numerous studies have been undertaken to identify markers linked to important agronomic traits, using a wide array of marker technologies (gel, array, and sequence-based), and bi-parental linkage and association-based approaches. Aside from disease resistance (Bru1 in particular), the markers that have been found accounted for a relatively small portion of the variation in traits of interest. In part, this should not be surprising, as the two most important traits in sugarcane (biomass yield and sugar content) are quantitatively distributed. More sophisticated QTL mapping and modeling methods, including those that account for non-additive gene action, may yet identify individual markers that can be used directly in breeding. In addition, breeding programs may choose to validate existing trait-associated markers and deploy them even if effects are relatively small, if the traits are of sufficiently high value. Genomic selection holds promise for sugarcane, especially if training panels are of an appropriate size, and if models are developed to leverage non-additive variance. Modern sugarcane is a young invention, and despite its challenges, we should expect to be able to utilize a combination of the latest marker technologies, sound phenotypic data, and new sophisticated models to increase rates of genetic gain in this important crop. |
