Tolerance to Postharvest Physiological Deterioration in Cassava Roots

Abstract

Cassava (Manihot esculenta Crantz) roots spoil 2 to 3 d after harvest because of postharvest physiological deterioration (PPD), which has remained an unsolved problem. Roots from different sources of germplasm were evaluated 5, 10, 20, and 40 d after harvest and some were found to be tolerant to PPD. Three genotypes showed zero levels of PPD even 40 d after harvest. Tolerance to PPD in roots with high carotenoid levels may be explained by their antioxidant properties. Irradiation of seeds in mutagenized populations may have silenced one of the genes involved in the expression of PPD. The tolerance to PPD found in other sources cannot be properly explained. The identification of several sources of resistance (and at least two different modes of action) suggests that now there are alternatives available for solving this problem, benefiting millions of resource‐limited farmers worldwide.

Extending Cassava Root Shelf Life via Reduction of Reactive Oxygen Species Production

“…A convenient control strategy for all farmers would be cultivars that have a longer shelf life. Sanchez et al (2005) showed that cassava cultivars with yellow roots (higher b-carotene content) have a delayed onset of PPD by 1 to 2 d. In addition, Morante et al (2010) surveyed different sources of germplasm and found delayed PPD (by up to 40 d) in three genotypes having high total carotenoid content (10.2-11.5 mg g 21 fresh weight compared with less than 1 mg g 21 fresh weight in most Figure 4. Overexpression of AOX reduces hydrogen peroxide and ROS accumulation in cassava roots.…”

“…It is feasible, from this model, that PPD may also be controlled by increased activities (via transgenic expression) of enzymes or metabolites that scavenge ROS, such as catalase, superoxide dismutase, peroxidase, and carotenoids. The oxidative stress model for PPD has also been supported by the discovery of highb-carotene varieties of cassava that have a longer shelf life than low b-carotene lines (Sanchez et al, 2005;Morante et al, 2010). b-Carotene is known to have antioxidant properties and is able to quench ROS (Smirnoff, 2005).…”

“…PPD was evaluated using the method described by Morante et al (2010) with some modifications. Cassava plants were harvested carefully to avoid physical damage.…”

Introductory Chapter: Cassava as a Staple Food

“…Given the marginal environments where cassava is grown, its postharvest processing is frequently afected by large distances to the processing centres and deicient transport infrastructure, speciically roads [29]. Cassava roots are also bulky, containing approximately 65% water, which leads extensively to the postharvest physiological deterioration (PPD) [29].…”

“…Cassava roots are also bulky, containing approximately 65% water, which leads extensively to the postharvest physiological deterioration (PPD) [29]. The short shelf life of the roots hinders many of the marketing options by increasing the likelihood of losses and thereby increasing the overall marketing costs [29]. In addition, the access to urban markets and processing facilities is restricted to production sites that are relatively close to them [30,31].…”