ORIGIN OF WALNUT SOMATIC EMBRYOS DETERMINED BY RFLP AND ISOZYME ANALYSIS

Somatic embryos derived from walnut (Juglans regia L.) ovule tissues were evaluated to determine whether they were of zygotic or maternal origin. Molecular markers were used to permit evaluation at an early stage, before whole plant development. Somatic embryos developed from potentially apomictic 'Sunland' and 'Cisco' ovule tissue isolated from bagged putatively unpollinated flowers. Phosphoglucomutase (PGM) isozyme analysis showed that all of these embryos, except one from each cultivar, carry the same zymotype as the maternal tissue. However, restriction fragment length polymorphism (RFLP) analysis combined with isozyme evaluation demonstrated that the tested embryos originated from zygotic rather than maternal tissues. This study demonstrates the application of molecular marker analyses, particularly RFLPS, evaluation of somatic embryo origin.