Responses of grapevines to two-spotted spider mite mediated biotic stress

The effect of feeding damage by two-spotted spider mite (Tetranychus urticae Koch.) on leaf-level physiological characteristic of grapevines was investigated. Uniform plants (Vitis vinifera L., cvs. Muskule and- Sultana) with unbranched solitary shoot having about five fully expended mature leaves were artificially infested with the mites (100 mites per leaf). After seven days of infestation, grapevine cultivars significantly differed in their support to mite density. Muskule showed sensitive characteristics by supporting a higher population density (240.75 mites per leaf) than Sultana (192.59 mites per leaf). Hence, the percentage of electrolyte leakage and cell membrane injury was much higher in the infested leaves of Muskule as compared to Sultana. In addition, mite feeding induced lipid peroxidation and protein degradation was observed only in Muskule. The relative chlorophyll content and photosynthetic activity in infested leaves of each cultivar was significantly lower than that of uninfected ones. Although, transpiration was not significantly altered in the infested leaves of grapevine, mite feeding caused a significant reduction in the leaf water content of both cultivars. There was a significant decrease in the levels of soluble sugar of the infested leaves in both cultivars as compared to the uninfected ones. When comparing the two cultivars, mite damage concerning above parameters was more striking in the leaves of Muskule than that of Sultana ones. Thus, proline, as a sensitive indicator signaling biotic stress intensity, accumulated in the infested leaves of both cultivars, especially in Muskule. Although, no change was observed in Ca, Mg, Mn and Fe concentrations, Na concentration of infested leaves significantly rose in both cultivars. In addition, mite attack significantly increased K, Zn and Cu uptake only in the leaves of Muskule plants.