The ability of Prunus aviumx P-pseudocerasus 'Colt' to form somatic embryos in vitro contrasts with the recalcitrance of P-avium

Somatic embryos were induced on roots excised from in vitro plants of Prunu s avium x pseudocerasus 'Colt'. On medium containing 6-benzylamino purine ( BAP, 1.5 mu M) and 2,4-dichlorophenoxyacetic acid (2,4-D, 15 mu M), a mean of 25 (s.e. +/- 2.0) somatic embryos were produced on intact root systems a nd 15 (s.e. +/- 1.7) on roots systems cut into 10 mm pieces. Most somatic e mbryos were formed directly on intact roots and indirectly (from callus) on sectioned roots. A mean of 2.5 (s.e. +/- 0.25) secondary embryos per prima ry embryo were formed directly on primary embryos after they were transferr ed to medium containing BAP (1.5 mu M), indole-3-butyric acid (10 mu M) and 2,4-D (5 mu M). After transfer to a medium containing BAP (2 mu M) and gib berellic acid (GA(3), 3 mu M), shoots developed in 75% (s.e. +/- 7.3) of th e embryos. Somatic embryos were not induced on explants of in vitro roots o r shoots of P. avium, and were induced infrequently on zygotic embryos, alt hough a wide range of media were tested. Possible reasons for the contrasti ng embryogenic ability of 'Colt' and P. avium are discussed.