Optimizing environmental conditions and irrigation regimes can improve grafting success in Persian walnut

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The propagation of Persian walnut (Juglans regia) using grafting or budding is often difficult due to envi­ronmental factors. Temperature fluctuation and plant water status affect root pressure (xylem sap exudation “bleeding”) during budding or grafting. An experiment was conducted to find the optimum irrigation regime for patch budding (in July) and tongue grafting (in March) of Persian walnut on Juglans regia rootstock un­der three environmental conditions (greenhouse, shade-house and outdoor). The grafted/budded plants were subjected to three irrigation regimes including 1-day, 3-day and 7-day for 4 weeks after grafting/budding. Callus formation and quality, and graft/bud-take were recorded after four weeks. The survival rate and growth of the scions were measured after three months. Based on the results, grafting success under greenhouse, shade-house and outdoor conditions were 66.7%, 42.6% and 17.6%, respectively. The highest graft/bud take (94.4%) was obtained under greenhouse conditions with patch budding. The lowest grafting success (0%) was observed under outdoor conditions with patch budding. Under the greenhouse conditions, irrigation of the grafted plants with 7-day interval resulted in the highest graft success and plant growth. Irrigation with 3-day intervals was the best regime under shade-house conditions, while daily irrigation regime was required to obtain the highest grafting success for the outdoor grown plants. In general, the present experiment re­vealed that modifying outdoor conditions by applying a shade-house equipped by a mist system in warmer area can improve bud-take and success especially in patch budding by 40.76 and 33.1%, respectively.