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United States Department of Agriculture

Agricultural Research Service

Title: Qtl Affecting Soluble Carbohydrate Concentrations in Stored Onion Bulbs and Their Association with Flavor and Health-Enhancing Attributes

Authors
item Havey, Michael
item Galmarini, Claudio - INTA ARGENTINA
item Gokce, Ali Fuat - ULUDAG UNIV TURKEY
item Henson, Cynthia

Submitted to: Genome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 15, 2004
Publication Date: May 5, 2004
Citation: Havey, M.J., Galmarini, C.R., Gokce, A., Henson, C.A. 2004. QTL affecting soluble carbohydrate concentrations in stored onion bulbs and their association with flavor and health-enhancing attributes. Genome. 47:463-468.

Interpretive Summary: Onion bulbs possess two major types of health-enhancing compounds, thiosulfinates and fructans. Thiosulfinates are associated with enhanced cardiovascular health by reducing platelet aggregation. Consumption of fructans has been correlated with lower rates of corectal cancers. Although the fructans and thiosulfinates are synthesized by different biochemical pathways, traits associated with these compounds show significant correlations. Higher fructan concentration in the bulb is significantly correlated with higher pungency, longer bulb dormancy, and onion-induced antiplatelet activity (OIAA). We analyzed carbohydrate concentrations in onion bulbs to reveal major genes affecting fructan accumulation. On a fresh weight basis, the low-solids parent (AC43) possessed less sucrose than BYG15-23 and very little to no fructans. In order to remove differences in fresh weights of bulbs, we completed analyses of carbohydrates adjusted to a common dry weight. One genetic region was significantly associated with sucrose concentrations, all other traits were not significant. The region from the low-carbohydrate parent (AC43) showed a dominant effect and significantly reduced the amount of sucrose in bulbs. These studies indicate that variation for fructan accumulation was not due to genes responsible for fructan synthesis, but maybe by genes controlling the availability of sucrose to the onion bulb. These results are useful to onion breeders developing new, value-added cultivars with health-enhancing attributes by demonstrating the manipulation of carbohydrate concentrations and types will affect the quality of onion bulbs.

Technical Abstract: Onion bulbs possess two major classes of health-enhancing compounds, thiosulfinates and fructans. Thiosulfinates are associated with enhanced cardiovascular health due to their effects on platelet aggregation. Consumption of fructans has been correlated with lower rates of corectal cancers and decreased levels of serum chloresterol, phospholipids, and triglycerides. Although the fructans and thiosulfinates are synthesized by different biochemical pathways, traits associated with these compounds show significant phenotypic correlations. Higher fructan concentration in the bulb is significantly correlated with higher pungency, longer bulb dormancy, and onion-induced antiplatelet activity (OIAA). We analyzed carbohydrate concentrations in onion bulbs from replicated field trials of segregating families to reveal major loci affecting fructan accumulation. On a fresh weight basis, the low-solids parent (AC43) possessed less sucrose than BYG15-23 and very little to no polymerization of fructans. Neokestose, 1-kestose, and (6G,1)-nystose were the most prevalent fructans. More complex fructans of DP³3 comprised relatively minor components of the total fructans, each at 3% or less. In order to remove differences in fresh weights of bulbs, we completed statistical analyses of soluble solids content (SSC), glucose, fructose, sucrose, and fructan concentrations using dry weights as the covariant. Family means adjusted to a mean dry weight showed highly significant (P<0.001) differences for SSC, glucose, fructose, sucrose, 1-kestose, neokestose, and nystose(6-1), indicating that differences in these carbohydrate concentrations were not simply due to greater water retention by low-solids bulbs. One region on linkage group D was significantly (P=0.009) associated with sucrose concentrations, all other traits were not significant in the covariant analyses. The chromosome region from the low-solids parent (AC43) showed a dominant effect and significantly reduced the amount of sucrose in bulbs. One region on linkage group E was associated with different concentrations of glucose and fructose, all other traits were not significant (P<0.01) in the covariant analyses. The chromosome region from the high-solids parent (BYG15-23) showed a dominant effect and significantly increased the amount of glucose and fructose in bulbs. These studies indicate that variation for fructan accumulation was not due to variation at structural loci conditioning fructan synthesis, but maybe by genes controlling the availability of sucrose to the onion bulb.

Last Modified: 9/21/2014