Storage duration, harvest injury, and fungal pathogens promote ethanol accumulation in postharvest sugarbeet roots

Authors: Fugate, Karen; Eide, John; MORIN, MERCEDES - North Dakota State University; FINGER, FERNANDO - Universidade Federal De Vicosa; LAFTA, ABBAS - North Dakota State University

Submitted to: PH96 International Postharvest Science Conference New Zealand
Publication Type: Abstract Only
Publication Acceptance Date: 7/7/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Sugarbeet (Beta vulgaris [L.]) roots are stored in large outdoor piles or sheds for up to 140 days before freezing for long-term storage or processing into sugar. During this storage period, roots are known to lose sucrose to respiration and storage diseases. However, recent observations by a U.S. sugarbeet processor suggest that additional sucrose may be lost due to ethanol formation. Presently, no studies have quantified ethanol production in stored sugarbeet roots or evaluated abiotic or biotic factors that may influence postharvest ethanol accumulation. Research was conducted to quantify ethanol production in stored roots and identify environmental and microbial factors that may promote its accumulation in storage. Changes in root ethanol concentration were determined as a function of time in storage and reduced ventilation, and in response to wounding and common storage pathogens. These studies demonstrated that ethanol concentration progressively increased with time in storage. However, reductions in oxygen concentration and increases in carbon dioxide concentration that were made to mimic the atmospheric conditions surrounding roots when ventilation is insufficient had no impact on ethanol concentration of stored roots. In contrast, wounding caused a small but significant increase in ethanol concentration, while infection of roots by the fungal pathogens, Botrytis cinerea and Penicillium vulpinum, increased ethanol concentrations by multiple fold. Examination of the expression of ethanol biosynthetic genes as a function of storage duration found that both of the two genes that encode pyruvate decarboxylase and two of the nine genes encoding alcohol dehydrogenase were upregulated during storage. These studies provide the first evidence for ethanol accumulation in stored sugarbeet roots and identify abiotic and biotic factors that affect ethanol accumulation during storage. This information is expected to aid the sugarbeet industry in developing strategies to reduce sucrose fermentative losses.