Balance between oxidative stress and the antioxidant system is associated with the level of cold tolerance in sweet potato roots

Authors: DE ARAUJO, NICOLAS - Universidade Federal De Vicosa; SANTOS, MIRELLE - Universidade Federal De Vicosa; DE ARAUJO, FERNANDA - Universidade Federal De Vicosa; VERAS, MARIO - Universidade Federal De Vicosa; TELLO, JEAN - Universidade Federal De Vicosa; ARRUDA, RAFAELA - Universidade Federal De Vicosa; Fugate, Karen; FINGER, FERNANDO - Universidade Federal De Vicosa

Submitted to: Postharvest Biology and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2020
Publication Date: 10/13/2020
Citation: De Araujo, N.O., Santos, M.N., De Araujo, F.F., Veras, M.L., Tello, J.P., Arruda, R.D., Fugate, K.K., Finger, F.L. 2020. Balance between oxidative stress and the antioxidant system is associated with the level of cold tolerance in sweet potato roots. Postharvest Biology and Technology. 172. Article e111359. https://doi.org/10.1016/j.postharvbio.2020.111359.
DOI: https://doi.org/10.1016/j.postharvbio.2020.111359

Interpretive Summary: Cold storage extends shelf-life and reduces sprouting in harvested sweet potatoes. Cold temperatures, however, can also cause internal tissue discoloration, skin darkening, and increase the prevalence of fungal diseases for this crop. These undesirable traits are commonly referred to as chilling injuries and occur when plants produce toxic substances in response to cold stress. Sweet potato cultivars vary in their susceptibility to chilling injury, although the reason for this variation is largely unexplored. To determine whether differences in susceptibility to chilling injury are due to differences in their defense mechanisms against these self-produced toxins, the defense mechanisms of two cold-sensitive (cultivars BRS Rubissol and BRS Cuia) and one cold-tolerant (cultivar Beauregard) sweet potato cultivars were compared during 60 days of cold storage. Chemical substances and enzymes that neutralize plant-produced toxins were greater in the cold tolerant cultivar, Beauregard. Cold conditions additionally elevated levels of two toxin neutralizing enzymes in this cultivar. These results indicate that the defense mechanisms examined are likely involved in the cold temperature tolerance of this cultivar. In the cold sensitive cultivars, BRS Rubissol and BRS Cuia, chemical compounds and an enzyme involved in their synthesis were identified that increased in concert with the development of chilling injury symptoms. These compounds and enzyme can be used to quantifiably measure chilling stress in sweet potato.

Technical Abstract: The balance between oxidative stress and antioxidant defense systems was investigated in roots of cold-sensitive (cvs. BRS Rubissol and BRS Cuia) and cold-tolerant (cv. Beauregard) sweet potatoes stored at 6 or 13 °C for 60 d. We hypothesized that the absence of chilling injury symptoms on cv. Beauregard stored at 6 °C depends on the induction capacity of enzymatic and non-enzymatic antioxidant systems. The manifestation of chilling injury symptoms on cvs. BRS Rubissol and BRS Cuia were associated with the loss of membrane integrity, increased lipid peroxidation, accumulation of hydrogen peroxide (H2O2), and low catalase (CAT) and ascorbate peroxidase (APX) activities. In these cold-sensitive cultivars, proline and total phenolics increased with the progression of chilling injury, acting as markers for cold sensitivity, and paralleled increased activity of phenylalanine ammonia-lyase. In contrast, constitutive levels of enzymatic and non-enzymatic antioxidants, as well as stress-induced increases in CAT and APX activities played an important role in the detoxification of H2O2 in the tolerant cv. Beauregard. Our results suggest that the balance between oxidative stress and antioxidant systems is involved in the tolerance of cv. Beauregard to chilling injury.