Cercospora Leaf Spot Impacts on Postharvest Disease and Respiration of Affected Sugarbeet Roots

In Michigan, sugarbeets (Beta vulgaris) are stored for up
to 200 days postharvest, during which time sugar loss may
occur as a result of energy use from respiration and factors
such as 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
sugarbeets with designated “high” or “low” in-season
CLS severity. Root slices of sugarbeets from each CLS
level were inoculated with Fusarium graminearum,
Botrytis cinerea, or Penicillium vulpinum, and symptoms
were assessed after 7 days. Across three CLS-susceptible
commercial varieties, there were no significant differences
among storage rot susceptibility to any of the tested
pathogens in hand-harvested sugarbeets, regardless of
CLS level, at any storage time point 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 out of six storage
time points across these 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 time point 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