LAUSR

ABSTRACT Grafting type and covering method of the graft union have significant effects on grafting success. Two experiments were conducted to determine the best method of grafting and the covering of graft union in walnuts during 2014 and 2015. In the first experiment, plants were grafted under a shade-house with 50% reduction of sunlight. Two methods of saddle and tongue grafting, and three covering methods of graft union including moist sawdust, moist mixed coverage (cocopeat + soil + manure) and plastic cover (control) were used. In the second experiment, two walnut cultivars, ‘Chandler’ and ‘Franquette’ were used as scions along with four grafting methods, including saddle, tongue, omega and V under outdoor conditions. In this experiment, graft unions were covered with moist sawdust. The results of the first experiment showed that, 4 weeks after grafting, the rate of graft-take was better in saddle grafting compared to tongue grafting (76.8 and 62%, respectively). Covering by moist sawdust was better than the other two covers. In the second experiment, the omega method caused the best quality of callus, the highest callused grafts (89.1%) and the most successful graft-take (81.6%). Meanwhile, V grafting caused the highest survival percentage (65.8%) and growth of scions (107.9 cm) after 6 months. Therefore, we recommend this method for grafting walnuts under outdoor conditions.