Somatic Embryogenesis And Transformation Of English Walnut (Juglans Regia L.)

Walnut, which produces both nuts and timbers, is one of the most important nut crops world-wide. Breeding of walnut by conventional methods is difficult due to its highly heterozygous characters and long generation cycles. Genetic engineering methods provide an attractive support to complement conventional breeding of walnut. However, the lacking availability of transformation protocols is still the major bottleneck in this approach. Somatic embryogenesis has been considered as the most promising method in genetic improvement not only because it is an efficient plant regeneration system but also it can make the superior genotype selection more efficiency when combined with genetic engineering and conventional methods. In walnut, somatic embryogenesis is highly important because somatic embryos are the only explant capable of regeneration after transformation.Since the first reports of somatic embryogenesis in walnut in 1985 and regeneration of transgenic walnut plants from somatic embryos in 1988, successful somatic embryogenesis and regeneration of transformed somatic embryos have been achieved. However, somatic embryogenesis and genetic transformation in walnut are still far from routine and many factors affect the frequency of somatic embryogenesis and genetic transformation. In an attempt to establish a protocol for walnut transformation, we obtained somatic embryos from various explants of English walnut (Juglans regia L.) and repetitively somatic embryo lines. By using the repetitively somatic embryos as target tissues we successed in recovery of transgenic plants after Agrobacterium tumefaciens mediation.To develop somatic embryogenesis in walnut, young intact ovules of'No.