THE RESPONSE CHARACTERISTICS OF JAPANESE RADISH (DAIKON) TO MECHANICAL WOUND STRESS
The postharvest damage caused by physical stresses (compression, shock, vibration) during packing, storage, and transportation in bulk influences the quality and the yield of fresh produce. Under a model transport practice using bulk container, we found three predominant types of physical wound symptoms (indent/abrasion, cracking, and peeling) of Japanese radish (Daikon, Raphanus sativus var. longipinnatus). Additionally, the types of damage of Daikon were observed differently, depending on the specific layers in the container. In order to understand the basic changes in molecular mechanisms in relation to mechanical/physical stress of Daikon, we have utilized mechanical wounding as the stress stimulus to study the expression of candidate stress-responsive genes in Daikon. The predominant increases in RsCHI (chalcone isomerase-encoding gene) and RsPAL (phenylalanine ammonia lyase-encoding gene) expression levels were observed at 4 h and 6 h since the wounding treatment. In contrast, the expression level of RsSOD (superoxide dismutase-encoding gene) was detected at low level, and the significant increase in expression of RsSOD was found at 10 h and 12 h after the treatment. An increase in expression of candidate stress-responsive genes of Daikon demonstrates the change in cellular response to the mechanical wound stress. It appears that the physical damage of Daikon was likely affected by transport under bulk condition. Moreover, applying a mechanical wounding stimulus clearly affected the expression of stress-responsive genes (RsCHI and RsPAL). The rapid expression of these genes may consequently affect the cellular metabolism and quality changes of Daikon. The further study in order to find acceptable level of gene expression to avoid the development of severe damage of Daikon should be taken into consideration. Additionally, the appropriate design of packaging conditions for the actual transport condition will enable to distribute Japanese radishes by newly developed bulk container without the unacceptable level of damages.
Shiina, T., Umehara, H., Kaneta, T., Nakamura, N., Ito , Y., Thammawong, M., Yoshida , M., Soga , A. and Nakano, K. (2013). THE RESPONSE CHARACTERISTICS OF JAPANESE RADISH (DAIKON) TO MECHANICAL WOUND STRESS. Acta Hortic. 1005, 247-252
Daikon, gene expression, mechanical stress, physical damage