Influence of Drought and Wounding Stress on Soluble Phenols and Proteins in Potato Tubers

Potato is a valuable source for phytochemicals like vitamins, minerals, plant phenols, amino acids and proteins. However, environmental stress may affect the level of all these components. In this study, two purple breeding clones and one yellow fleshed cultivar (cv.) were assessed in their response to drought and wounding stress in two consecutive years. The plants were grown in the greenhouse under control (sufficient water supply) and with drought stress conditions. After harvest the tubers were analyzed for the content of soluble phenols and proteins in fresh tissue and after wounding. In addition, free amino acids (AAS) and activity of lipid acyl hydrolases (LAH) were assayed in control and drought stressed tubers. The results revealed significant differences in soluble phenols and proteins between genotypes, and that drought stress significantly increased the level of soluble proteins (P < 0.0001) and LAH activity (P < 0.001), but had no significant effect on the concentration of phenols. Moreover, total amounts of free AAS were higher in the drought stress variant. Wounding stress caused a significant increase of soluble phenols in cv. Agave. But, this was less prominent in purple clones which in general had higher contents of phenols. Proteins were also enhanced as a result of wounding, although, the effect of wounding stress on their level was smaller than that of drought stress.