Micro-propagation of Most Important Walnut Cultivars and Stocks in Syria

Muhsen Al-Sewei 
General Commission for Scientific Agricultural Research-
Homs Research Center
Aleppo University, Faculty of Agriculture
2007

Abstract

This study has been carried out at the plant tissue culture laboratory at Aleppo Research Center during the period of 2003-2006 with the aim of developing an efficient method for micro-propagation of three important walnut cultivars (Hartley, Serr, Belhsen-2) in order to make these cultivars available for fruit growers for the aim of improving walnut production in Syria.
A full successful and detailed in vitro propagation system for the following walnut cultivars Hartley, Serr, and Belhsen-2 has been developed.
Shoot tips, single nodes and auxiliary buds excised from adult trees grown in the field under natural conditions at Gosea Al-Kharab Research Center, Homs Province were used as primary explants
which were surface-disinfected using HgCl2 or with sodium or calcium hypochlorite followed by three rinses with sterile distilled water. They were then placed onto three media (MS, DKW, WPM) containing a combination of growth regulators at different concentrations (Kinetin or BA at 0.5, 1 or 2 mg/l) each with IBA or NAA at 0.1 mg/l. Multiplication rate of 5-fold was achieved every 4 weeks.
Rooting was achieved within 2-4 weeks using 1.5-2 cm long shoot tips excised from proliferation cultures and grown on half or full strength agar-gelled media containing (IBA, NAA) at a concentration of 2, 3, 4 or 5 mg/l with a maximum rooting efficiency of 80 %. However, low concentrations of auxin decreased percentage of rooting 30-60%. But high concentrations decreased percentage of rooting and the callus formation.
On media containing 1/2MS + 4 mg/l IBA +Activated charcoal, a maximum rooting efficiency of 85% was obtained within 2-4 weeks.
Also dark treatment during the rooting phase has been studied, so that one week was the best treatment concerning the percentage of rooting.
Rooted plantlets were transplanted into pots with a mixture of 2:1 (v/v) peat:perlite and covered with a plastic bags and acclimatized gradually to field conditions by making holes in the bags throughout 5-6 weeks. Acclimatization took about 4 weeks where the bags were removed completely with 65-75 % efficiency.