Frederick G. Gmitter Jr.Department of Fruit Crops, Citrus Research and Education Center University of Florida, Institute of Food and Agricultural Sciences, 700 Experiment Station Road, Lake Alfred, FL 33850
Protoplasm culture following polyethylene glycol (PEG) -induced fusion resulted in the regeneration of somatic hybrid plants from the following six parental combinations: Citrus sinermis (L.) Osbeck cv. Hamlin + Severinia buxifolia (Poir.) Tenore (Chinese box-orange); C. reticulate Blanco cv. Cleopatra + Poncirus trifoliata (L.) Raf. cv. Flying Dragon; C. reticulate cv. Cleopatra + Swingle citrumelo (C. paradisi Macf. × P. trifoliata); C. sinensis cv. Hamlin + C. jambhiri cv. Rough lemon; C. sinensis cv. Valencia + C. jambhiri cv. Rough lemon; and C. paradisi cv. Thompson + `Murcott' tangor (purported hybrid of C. reticulate × C. sinensis). Diploid plants were regenerated from nonfused embryogenic culture-derived protoplasts of `Cleopatra' mandarin and `Hamlin' and `Valencia' sweet orange, and from nonfused leaf-derived protoplasts of Rough lemon and `Mnrcott'. Regenerated plants were classified according to leaf morphology, chromosome number, and isozyme analyses. All of the somatic hybrids reported herein are tetraploid (2n = 4x = 36), with the exception of the `Hamlin' + S. buxifolia hybrid, which was unexpectedly found to have a chromosome number of 2n = 27. These six new somatic hybrids have potential in citrus scion and rootstock improvement for commercial use.