Effect of rootstock growth characteristics on Persian Walnut minigrafting

Vegetative propagation of Persian walnut encounters a major problem in Iran growing conditions. This experiment was carried out to study the physiological effects of rootstock as regards herbaceousness or woodiness, and with respect to the presence of leaf on it or not on minigrafting success. Throughout the study, 1.5-2.5 cm length Persian walnut scions were minigrafted on herbaceous vs. softwood (with or without leaf) walnut rootstocks grown for a few weeks in controlled conditions. Results indicated that the existence of leaf on the rootstock had negative effects on the success of minigrafting in either leafy or leafless rootstocks (48 and 56 percent, respectively). A significant difference was observed between herbaceous and softwood rootstocks. Softwood rootstocks benefited from 56% success as compared with 46% in herbaceous ones. Interaction effect was also observed between kind of rootstock and leaf existence as the existing leaf increased grafting success in herbaceous rootstocks while decreasing it in softwood ones. The negative effect of leaf on minigrafting of softwood rootstocks was in so far as it decreased grafting success from 73% in leafless rootstocks to 43% in leaf bearing ones. Leaf had no significant effect on the time needed for the graft to take, yet it enhanced the graft success on herbaceous rootstocks more than it did on softwood ones. The soluble sugar content at the grafting point of leaf bearing softwood rootstock was more than that for the leafless ones, however grafting success was not dependent upon sugar content. This difference came maybe from substances made through either young or older leaves in either herbaceous or softwood rootstocks that were transported to the grafting union point and subsequently affecting the graft success and scion growth. The grafted plants had desirable survival and growth rates till one year past the experiments.