Genomics approaches for the identification of genes determining important traits in sugarcane

Sugarcane is a genetically complex polyploid grass, which makes the identification of associations between genes and traits difficult. Genomics science facilitates characterization of entire eukaryote genomes at the DNA sequence level, but for crop plants with complex genomes such as sugarcane, gene characterization is currently best achieved via expressed sequence tag (EST) analysis where sequence information is restricted to genes that are actually functioning in a particular tissue or situation. DNA microarrays allow simultaneous expression analysis of thousands of genes. Current work on EST and array analysis of gene expression in sugarcane is reviewed and insights on stem functions associated with maturation and sucrose accumulation are discussed. A strategy for associating gene expression with a trait is described in which individuals exhibiting particular traits are selected from segregating populations of sugarcane and their gene expression profiles compared. A preliminary experiment to test the feasibility and experimental design for this 'genetical genomics' strategy on a population segregating for sugar content is described. Given the complex genetics of sugarcane, this strategy and refinements of it, represent an attractive pathway to the identification of candidate genes that may control sugar accumulation and other traits in sugarcane.