Biochemical comparison in storage: Stress response between sweetpotato and cassava. (177)
Keywords:Sweetpotato, Cassava, Storage, Wounding, Infection, Physiological deterioration, Microbial deterioration, Phytoalexin
AbstractDuring storage after harvest, both sweetpotato (SP) and cassava (CV) showed different stress responses. When wounded, SP cured injury by forming a lignin layer at the cells very close to the surface, while CV suffered from physiological deterioration (PD), followed by microbial deterioration (MD). In wounded SP tissue, many enzymes such as phenylalanine ammonia-lyase (PAL), acid invertase, peroxidase (PERO), and polyphenol oxidase (PPO) were induced. Polyphenols such as chlorogenic acid (CA) and isoCA were produced and respiratory rates of tissue and mitochondria (Mt) were increased, including CN-insensitive respiration. When penetrated by some fungi such as Ceratocystis fimbriata or by larvae of some weevils such as Cylas formicarius, these changes appeared more vigorously, and additional ones occurred. There were productions of coumarins (umbelliferone), about 30 sesquiterpenes (ipomeamarone), ethylene, and cell death and discoloration by the penetration. Storage proteins were degraded and converted to other proteins. In wounded CV tissue, various changes involving PD were caused principally in the same way as in infected SP tissue. Both roots suffered from chilling injury, CV being more sensitive in the cold than SP.