Plant Cell Reports 7: 301-304 (1988)
Regeneration by somatic embryogenesis of triploid plants from endosperm of walnut, Juglans regia L. cv Manregian
Walt Tulecke, Gale MeGranahan, and Hamid Ahmadi


Plants were regenerated by somatic embryogenesis from endosperm tissue of open-pollinated seeds of Juglans regia L. cv Manregian. These plants were obtained by growing endosperm tissue on media similar to those used for plant regeneration from walnut cotyledons (Tulecke and McGranahan 1985). The plants appear morphologically uniform and have a triploid chromosome number of 3n = 48. Nine plants have been grown to a young sapling stage in soil. This embryogenic line from endosperm has been maintained in culture for two years by the process of repetitive somatic embryogenesis.


Endosperm tissues in culture provide the material for regenerating plants with triploid chromosome number, as shown by the reports of the successful regeneration by organogenesis and somatic embryogenesis. Reviews on endosperm (Bhatnagar and Sawhney 1981), endosperm culture (Johri and Bhojawani 1977), and triploids in woody perennials (Lakshmi Sita 1987) have appeared recently. Research on walnut tissue culture has been reviewed (McGranahan et al. 1987) and includes reports on endosperm (Cheema and Mehra 1982), micropropagation (Driver and Kuniyuki 1984), somatic emhryogenesis (Tulecke and McGranahan 1985) and embryo rescue (McGranahan et al. 1986).

This work was undertaken to regenerate triploid walnuts for use in rootstock improvement. The induction of somatic embryos from a tissue culture of endosperm was the method used. It is but one of several techniques which may be useful in obtaining new germplasm for the walnut improvement program, especially if screening techniques can be developed and applied to early stages of propagation systems.