Enhancing Sucrose Accumulation: Identifying Gene Targets for Manipulation

Between 1950 and 1970, the introduction of new sugarcane varieties and improved crop husbandry in the South African sugar industry contributed to substantial gains in sucrose yield. However, in the subsequent three decades to date, sucrose yield has remained approximately constant, despite an increased rate of variety releases. This lack of progress is a phenomenon common to many sugar industries and has been ascribed to the narrow genetic base of germplasm used in breeding programmes. Consequently, in several industries, modern molecular technologies are being used in concert with more conventional strategies in bids to improve sucrose yield traits in both sugarcane breeding stock and individual lines with commercial potential. One strategy has focused on the genetic modification of the activity of single endogenous sugarcane genes or the expression of single heterologous genes in an attempt to increase the proportion of photoassimilate accumulating as stored sucrose in the culm. This approach has met with mixed success and given that plants are adept at metabolic compensation, it is increasingly acknowledged that robust manipulation of sucrose deposition in the sugarcane stalk may depend on the co-ordinated manipulation of the activity of several genes. However, the capacity to identify and subsequently modify multiple gene targets is contingent on the availability of comprehensive knowledge of the key regulatory steps governing sucrose accumulation. This presentation reviews recent attempts at the molecular manipulation of sucrose accumulation in sugarcane and describes how genomic approaches are being applied at SASEX to enhance the potential of such endeavours.