Submitted to: Journal of Sugarbeet Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/18/2004
Publication Date: 7/1/2004
Citation: Klotz, K.L., Campbell, L.G. 2004. Sucrose catabolism in developing roots of three beta vulgaris genotypes with different yield and sucrose accumulating capacities. Journal of Sugarbeet Research. 41(3):73-88
Interpretive Summary: Sucrose catabolism has been implicated as a major determinant of sugarbeet root yield and sucrose content. Three enzyme activities, sucrose synthase, alkaline invertase, and acid invertase, are responsible for nearly all sucrose catabolism in sugarbeet roots, yet the influence of each of these activities on yield and sucrose content is largely unknown. Such information, however, would greatly aid efforts to increase sugarbeet root yield and sucrose content by directing breeding efforts, genetic manipulation, or altering the cultural practices that influence the activities of these enzymes. In pursuit of this information, the activities of sucrose synthase, alkaline invertase, and acid invertase were compared during root development in a high yielding, low sucrose accumulating fodder beet variety, an unusually high sucrose containing but low yielding sugarbeet breeding line, and a commercial sugarbeet hybrid chosen to be intermediate in yield and sucrose content to the other two lines. Sucrose synthase was found to be closely associated with root yield and the accumulation of cell wall materials, suggesting that it may be a factor in the partitioning of sucrose between the root and shoot of the plant and in promoting cell wall biosynthesis. Sucrose content was weakly associated with sucrose synthase activity and was unassociated with alkaline or acid invertase activities, suggesting that other factors are involved in the regulation of root sucrose concentration.
Technical Abstract: The functions of the major sucrolytic enzymes in sugarbeet (Beta vulgaris L.) roots are poorly understood, although a positive association between sucrose synthase activity and root size, and a negative association between soluble acid invertase activity and sucrose concentration have been documented. To test the veracity of these relationships and determine whether any major sucrolytic activities were associated with root yield or sucrose accumulation, the activities of the major sucrolytic enzymes, fresh and dry mass, and the content of sucrose, glucose, fructose and cell wall materials were measured in roots of three B. vulgaris genotypes with differing yield and sucrose accumulating capacities at five stages in their development. Across all genotypes and developmental stages, sucrose synthase activity was positively associated with root mass, water content, and accumulation of cell wall materials. No meaningful association was observed between alkaline invertase, soluble acid invertase and insoluble acid invertase activities and any of the physical or chemical properties examined. Although no new insights into the functions of acid and alkaline invertases were gained, these results indicate that sucrose synthase activity is a reliable indicator of root yield and may be a factor in root sink strength and the promotion of cell wall biosynthesis.