Influence of Beet necrotic yellow vein virus and freezing temperatures on sugar beet roots in storage

Authors: Strausbaugh, Carl; Eujayl, Imad

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/7/2017
Publication Date: 4/23/2018
Citation: Strausbaugh, C.A., Eujayl, I.A. 2018. Influence of Beet necrotic yellow vein virus and freezing temperatures on sugar beet roots in storage. Plant Disease. 102:932-937. https://doi.org/10.1094/PDIS-10-17-1575-RE.
DOI: https://doi.org/10.1094/PDIS-10-17-1575-RE

Interpretive Summary: Rhizomania caused by Beet necrotic yellow vein virus (BNYVV) is a yield limiting sugar beet disease that was observed to influence root resistance to freezing in storage. Thus, studies were conducted to gain a better understanding of the influence BNYVV and freezing on sugar beet roots to improve pile management decisions. Based on roots produced under high and low rhizomania pressure and subjected to a temperature series from 24 to 32 F, internal root temperature remained unchanged at 28 F even when ambient air was lowered to 26 and 24 F. The roots from the BNYVV susceptible cultivar produced under high rhizomania pressure suffered more frozen root tissue at 26 F than roots from this cultivar produced under low rhizomania pressure or roots from resistant cultivars produced under either disease pressure level. Roots from all treatments had elevated levels of frozen tissue damage at 24 F. Frozen tissue was found to be highly correlated with discolored root tissue and sucrose reduction, but only a weak relationship was present when compared with root weight loss. These data suggest that BNYVV will not only lead to yield and sucrose loss in susceptible sugar beet cultivars, but also more frozen root tissue as temperatures drop below 28 F. Based on these observations, the air used to cool roots in nonfrozen sugar beet piles throughout the winter should not drop below 28 F to maximize sucrose retention.

Technical Abstract: Rhizomania caused by Beet necrotic yellow vein virus (BNYVV) is a yield limiting sugar beet disease that was observed to influence root resistance to freezing in storage. Thus, studies were conducted to gain a better understanding of the influence BNYVV and freezing on sugar beet roots to improve pile management decisions. Roots from five commercial sugar beet cultivars (one susceptible and four resistant to BNYVV) were produced in fields under high and trace levels of rhizomania pressure and subjected to storage using five temperature regimes ranging from 0 to -4.4 C for 24 hours. After cold treatment, eight-root samples were stored in a commercial indoor storage building (set point 1.1 C) for 50 days in 2014 and 57 days in 2015. Internal root temperature, frozen and discolored tissue, and moisture and sucrose loss were evaluated. The air temperature at 0, -1.1, and -2.2 C matched internal root temperature, but internal root remained near -2.2°C when air temperature was dropped to -3.3 and -4.4 C. In a susceptible cultivar produced under high rhizomania pressure, the percentage of frozen tissue increased (P < 0.0001) from an average of 0 to 7% at 0, -1.1, and -2.2 C up to 16 to 63% at -3.3 C and 63 to 90% at -4.4 C depending on year. Roots from the susceptible cultivar produced under low rhizomania pressure and those from the resistant cultivars from both fields only had elevated (P < 0.05) frozen tissue at -4.4 C in 15 of 18 cultivar-year combinations. Frozen tissue was related to discolored tissue (r^2 = 0.91), weight loss (r^2 = 0.12 to 0.28) and sucrose reduction (r^2 = 0.69 to 0.74). Thus, BNYVV will not only lead to yield and sucrose loss in susceptible sugar beet cultivars, but also more frozen root tissue as temperatures drop below -2.2 C. Based on these observations, the air used to cool roots in nonfrozen sugar beet piles throughout the winter should not drop below -2.2 C to maximize sucrose retention.