Evaluation of physiological and morphological responses of Salix alba and Salix babylonica to witches’ broom gall

The gall formation in Salix species is caused by Candidatus phytoplasma trifolii. The present study was designed with the aim of evaluation of the morphological and physiological response of two species of Salix alba and Salix babylonica to gallers in the witches’ broom structure. The morphological responses of Salix species to gallers, denoted as biotic stress, were represented by growth suppression of leaves and shoots. Accordingly, the leaf area and shoot internodes significantly decreased, in comparison with healthy plants. The biotic stress can induce oxidative stress, which was observed in the present study with a high accumulation of H2O2 in galled tissues. High accumulation of H2O2 in the infected tissue damaged chlorophyll a and proteins. Even though Salix species induced the antioxidants catalase, peroxidase, proline, anthocyanins and phenols to scavenge reactive oxygen species (ROS), high accumulation of H2O2 was observed in galled tissues. Altogether, regardless of activation of antioxidants in response to galls-induced oxidative stress, ROS accumulation damaged photosynthetic apparatus and proteins.