Submitted to: American Society of Sugarbeet Technologists
Publication Type: Proceedings
Publication Acceptance Date: February 21, 2003
Publication Date: July 15, 2003
Citation: KLOTZ, K.L., CAMPBELL, L.G. COMPARISON OF SUCROSE CATABOLISM IN ROOTS OF THREE BETA VULGARIS L. GENOTYPES WITH DIFFERENT YIELD AND SUCROSE ACCUMULATING CAPACITIES. Proceedings of the 1st Joint International Institute for Beet Research and the American Society of Sugar Beet Technologists Congress. 2003. p. 505-509. Interpretive Summary: Sucrose degradation in sugarbeet root influences root size and sucrose concentration since sucrose degradation provides the energy and substrates needed to fuel growth and provides the sucrose concentration gradient that is the impetus for sucrose transport from the leaves to the root. Three families of enzymes are responsible for nearly all sucrose degradation in sugarbeet root: acid invertase, alkaline invertase and sucrose synthase. Previous research suggested that sucrose synthase may have a role in sucrose transport and growth of the root. To examine this observation more thoroughly, the activities of the major sucrose degrading enzymes were examined in a high yielding, low sucrose accumulating fodder beet variety, a commercial sugarbeet hybrid, and a low yielding, high sucrose containing sugarbeet breeding line. Enzyme activities were compared at five stages of development in relation to root mass, sucrose content, and accumulation of cell wall materials. Generally, the activities of all enzymes were greatest in the high yielding fodder beet variety and lowest in the sugarbeet breeding line. Sucrose synthase was the predominant sucrose degrading enzyme at all stages of development examined, and was closely correlated with the accumulation of cell wall materials. Although differences in sucrose content were observed, sucrose concentration or accumulation was not well correlated with any of the sucrose degrading enzymes examined.
Technical Abstract: Sucrose catabolism is a major determinant of sink strength in nearly all plants and affects sucrose partitioning to growing sinks as well as sink size and carbohydrate content. Three enzyme families are responsible for nearly all sucrose catabolism in sugarbeet roots: acid invertase, alkaline invertase and sucrose synthase. Previous work suggested that sucrose synthase may have a role in sink strength and root size in sugarbeet. To examine this observation more thoroughly, sucrose catabolism was compared in three Beta vulgaris genotypes with contrasting capacities for root yield and sucrose accumulation. Soluble acid invertase, cell wall acid invertase, alkaline invertase and sucrose synthase activities were compared at five stages of root development in a fodder beet hybrid (high yield, low sucrose content), a commercial sugarbeet hybrid (typical yield and sucrose content) and the sugarbeet breeding line, L19 (low yield, high sucrose content). Sucrose, glucose and fructose concentrations and mass accumulation were also determined. Generally, sucrolytic activity was greatest in the high yielding fodder beet and lowest in the low yielding L19 breeding line at any stage of development. Sucrose synthase activity was the predominant sucrolytic activity at all stages of development examined, and accounted for 90% or more of the total sucrolytic activity in fodder beet and sugarbeet hybrid roots by six weeks after planting and in L19 eight weeks after planting. Total sucrose synthase activity was positively correlated with nonextractable dry matter accumulation. Differences in sucrose concentration between genotypes were observed, although sucrose concentration or accumulation was not highly correlated with any of the major sucrolytic enzymes examined.