January 13-17, 2007
Town & Country Convention Center
San Diego, CA
Steven V. Raines1 , Cynthia A. Henson2 , Michael J. Havey3
Fructans are soluble carbohydrates composed of chains of fructose attached to a basal sucrose molecule. Substantiated human health benefits of fructan consumption include increased absorption of calcium and magnesium, and reduced triglycerides in the blood stream. Fructans also act as a prebiotic, selectively encouraging growth of beneficial bifidiobacteria and lactobacilli in the gastro-intestinal tract. In onion, higher fructan concentrations are correlated with greater soluble solids content and higher pungency. A region on onion chromosome 5 accounted for a significant portion of the phenotypic variation for dry matter and pungency. However, this region showed no significant effects on soluble solids content, dry matter, or pungency when the family means were adjusted for dry weights. This indicates that the region on chromosome 5 may affect relative water content of bulbs; the accumulation of high concentrations of fructans reduces water retention, concentrating the organosulfur compounds responsible for pungency. We analyzed fructans from replicated field trials of families segregating across this target region and are using a candidate gene approach to identify the factors affecting fructan accumulation. To isolate possible candidates, a cDNA subtraction library was created to enrich for sequences differentially expressed in high and low fructan accumulating genetic backgrounds.