Oxidative stress responses during cassava post-harvest physiological deterioration

Abstract

A major constraint to the development of cassava (Manihot esculenta Crantz) as a crop to both farmers and processors is its starchy storage roots' rapid post-harvest deterioration, which can render it unpalatable and un-marketable within 24-72 h. An oxidative burst occurs within 15 min of the root being injured, that is followed by the altered regulation of genes, notably for catalase and peroxidase, related to the modulation of reactive oxygen species, and the accumulation of secondary metabolites, some of which show antioxidant properties. The interactions between these enzymes and compounds, in particular peroxidase and the coumarin, scopoletin, are largely confined to the vascular tissues where the visible symptoms of deterioration are observed. These, together with other data, are used to develop a tentative model of some of the principal events involved in the deterioration process.

Variation in cassava germplasm for tolerance to post-harvest physiological deterioration

“…In most cases, PPD develops from tissue damage, and dark blue staining of vascular tissue is observed, followed by a general discoloration of storage parenchyma (Buschmann et al, 2000;Koblitz, 2011). Microscopic analysis reveals the presence of colored occlusions and tyloses in xylem vessels, followed by an increase in respiration, changes in the lipid composition, accumulation of secondary metabolites, many with antimicrobial and antioxidant activity, and increased activity of several enzymes and peak levels of reactive oxygen species (Buschmann et al, 2000;Huang et al, 2001;Reilly et al, 2001Reilly et al, , 2003Reilly et al, , 2004Iyer et al, 2010).…”

Cassava postharvest physiological deterioration: a complex phenomenon involving calcium signaling, reactive oxygen species and programmed cell death

“…Root damage during harvest alters the equilibrium of natural physiological process of the exposed cells and subsequently their oxidative burst. Since PPD is a complex biological phenomenon, it is expected to involve early events (Buschmann et al 2000a) as the observed dark strips of vessels due to oxidation of cell components (Apostol et al 1989; Reilly et al 2004) as tissue wounding reaction (Beeching et al 2002). Later on, deterioration of cell allows microorganism growth.…”

“…In addition, an inversely correlation between light yellow parenchyma color of roots associated to high amount of carotenoid content and delaying of PPD was reported by Chavez et al (2007). In fact, it is suggested that cassava wound repair can occur if the root remains attached to the plant (Plumbey and Rickard 1991; Reilly et al 2004). Then, the problem takes place once the root is detached.…”

“…Although the wound response is present, the healing process and the subsequent down-regulation of the signals are insufficient or too low (Salcedo and Siritunga 2011). It is thought that at some point during evolution cassava roots lost their efficiency in wound repair (Reilly et al 2004). In addition, extent of PPD damage and speed of symptom development in roots was also associated to the genotypic as well as the environmental conditions increasing the complexity of the phenomenon (Reilly et al 2004).…”

“…It is thought that at some point during evolution cassava roots lost their efficiency in wound repair (Reilly et al 2004). In addition, extent of PPD damage and speed of symptom development in roots was also associated to the genotypic as well as the environmental conditions increasing the complexity of the phenomenon (Reilly et al 2004).

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