SOMATIC EMBRYOGENESIS AND SHOOT REGENERATION FROM TRANSGENIC ROOTS OFTHE CHERRY ROOTSTOCK COLT (PRUNUS-AVIUM X P-PSEUDOCERASUS) MEDIATED BY PRI-1855 T-DNA OF AGROBACTERIUM-RHIZOGENES

Hairy roots were obtained after inoculation with Agrobacterium rhizoge nes strain NCPPB 1855 of the in-vitro-grown shoots of the cherry roots tocks Colt (Prunus avium x P. pseudocerasus) and Mazzard F12/1 (P. avi um L.). Not all putatively transgenic roots were able to grow in hormo ne-free medium. Mazzard F12/1 roots, induced with A. rhizogenes, did n ot differentiate any shoot or embryo, while both somatic embryos and s hoots differentiated from the transgenic roots of Colt in medium conta ining 1 mg/l 6-benzylaminopurine and 1 mg/l 1-naphthaleneacetic acid. Somatic embryos were capable of secondary embryogenesis, but few devel oped into whole plants. DNA hybridization showed both a different numb er of bands and signal intensity in each of the five transgenic shoot clones and embryos examined. In a morphogenetic in vitro test, leaf ex plants of the transgenic shoot clones showed an increased capacity to differentiate roots, although clones differed in their sensitivity to the hormone ratio. Clones from the transgenic shoots had not only an i ncreased rooting ability when grown in vitro but also exhibited variou s hairy root phenotypes when cultured in vitro and when transferred in to the greenhouse.