|Mcgrath, J Mitchell - Mitch|
Submitted to: American Society of Sugarbeet Technologists
Publication Type: Abstract Only
Publication Acceptance Date: 9/5/2002
Publication Date: N/A
Technical Abstract: This study examined sucrose accumulation in different breeding lines during the first weeks after emergence in order to identify early morphological and physiological differences correlated with final root sucrose content. Six germplasm lines (US H20, SR87, SR95, SR96, SR97, and Syngenta-Hilleshög E17, ranging in harvested sucrose contents from 15 to 18%) were planted with three replications. Plants were grown in the greenhouse under controlled temperature (15 to 22 C) and photoperiod (16 hours of light per day). Samples were harvested weekly from the third to the tenth week post-emergence. At each harvest, roots, leaves and hypocotyls were weighted and freeze-dried, and hypocotyl diameters were measured. Sucrose was extracted from freeze-dried roots with 80% ethanol and then analyzed with liquid chromatography (HPLC). Transverse sections of roots were also analyzed with the light microscope to detect anatomical differences between lines and during development. Sucrose concentration expressed as fresh weight increased from ca. 0.5% at the third week (all germplasm) to 10.7% in US H20 through 13.3% with E17 by the tenth week, with measured sucrose levels proportional to those from field-harvested beets over the entire eight-week experiment. Incremental changes in sucrose levels were not constant during this period, but followed a weekly step-wise trend alternating between higher then lower sucrose accumulation. Sucrose concentrations as dry weight were over 55% at the tenth week for all lines, and ranged between 3.5% to 8% at week 3. Differential gene expression analysis combined with examination of anatomical differences of root tissues during these alternate developmental stages may provide additional insight on the molecular mechanisms of sucrose accumulation in sugar beet.