Cercospora leaf spot impacts on postharvest disease and respiration of affected sugarbeet roots

Authors: HENDERSHOT, CARLY - Michigan State University; RUTH, SARAH - Michigan State University; BLOOMINGDALE, CHRIS - Michigan State University; CORDER, HOLLY - Michigan State University; Goodwill, Tom; BEAUDRY, RANDY - Michigan State University; Hanson, Linda; WILLBUR, JAIME - Michigan State University

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: n Michigan, sugarbeet (Beta vulgaris) is stored for up to 200 days after harvest. During this time, sugar loss occurs due to energy use from respiration. Additional losses can be caused by factors like rot. A foliar disease in the field, Cercospora leaf spot (CLS) has been reported to predispose sugarbeet to storage rot. To investigate impacts of CLS on storage rot, beets with designated “high” or “low” in season CLS levels were tested for storage rot development in storage. Root slices were inoculated with one of three fungal pathogens, Botrytis cinerea, Fusarium graminearum, or Penicillium vulpinum, or given a medium control. Lesion size was measured after seven days. Across three CLS-susceptible commercial sugarbeet varieties, there were no significant differences between storage rot levels for any of the tested, hand-harvested beets regardless of CLS severity level in 2020 or 2021 (P>0.05). When CLS-susceptible and -resistant material was tested, CLS effect were inconsistent, with only one factor showing a significant difference at two out of six time points across years. It was noted that, of the three pathogens, B. cinerea consistently caused more severe storage rot than the other two pathogens tested and varieties varied significantly in the amount of damage caused by the storage pathogens. This may be useful for future efforts in variety development for storage.

Technical Abstract: In Michigan, sugarbeets (Beta vulgaris) are stored for up to 200 days post-harvest, during which sugar loss may occur due to energy use from respiration and factors like rot. Cercospora leaf spot (CLS) has been considered a potential predisposing factor for increased storage rot. To investigate these impacts, field and postharvest studies evaluated storage rot symptom development in beets with designated ‘high’ or ‘low’ in-season CLS severity. Root slices of beets from each CLS level were inoculated with Fusarium graminearum, Botrytis cinerea, or Penicillium vulpinum and symptoms assessed after seven days. Across three CLS-susceptible commercial varieties, there were no significant differences between storage rot susceptibility to any of the tested pathogens in hand-harvested beets, regardless of CLS level, at any storage timepoint in 2020 or 2021 (P > 0.05). In studies using CLS-susceptible and -resistant germplasm and varieties, CLS effects were inconsistent and only significant in one parameter at two of six storage timepoints across years (P < 0.05). Across storage pathogens, prior CLS level also did not impact root respiration or the change in respiration rate from initial to final storage timepoint in either 2021 or 2023 (P > 0.05). Of note, B. cinerea caused more severe symptoms than other pathogens in these studies (P < 0.05). Finally, varietal responses differed significantly to storage pathogens (P < 0.05) and may be of interest to future cultivar development efforts. This research increases our understanding of factors contributing to potential storage losses, which will improve yield and profit for sugar growers.