Factors affecting germination of somatic embryos of Persian walnut (Juglans regia L.) and their conversion to plantlets

Somatic embryos which were derived from immature cotyledons of a Persian walnut genotype had been grown on DKW medium supplemented with gelrite 0.3% and ABA (2 mg l-1). For maturation, somatic embryos were treated with chilling pre-treatment (one month in dark at (3-4C), different desiccation methods (fast, slow and full) and combination of chilling and desiccation treatments. The experiment was conducted as RCD in tissue culture laboratory of College of Abouraihan, University of Tehran, Iran in 2007. After three weeks, plantlets obtained from this treatment were transferred to six plantlets developing media (including full and half strength DKW with different levels of sucrose and activated charcoal). Without any pretreatment, 26% of somatic embryos germinated, while those treated with cold-pretreatment germinated at 54% with both shoots and roots. Somatic embryos treated with fast, slow and full desiccation, germinated at 27, 37 and 57% with both shoots and roots, respectively. Cold storage for two months in combination with full desiccation resulted in higher amounts of somatic embryos germination (73%) which had both shoots and roots. Adding activated charcoal and sucrose, also reducing amounts of macro and micro nutrients did not have significant effect on shoot length. Adding activated charcoal enhanced root development.