Intergeneric somatic hybrid plants of Citrus sinensis cv. Hamlin and Poncirus trifoliata cv. Flying Dragon

Intergeneric somatic hybrid plants between Hamlin sweet orange Citrus sinensis (L.) Osbeck] and Flying Dragon trifoliate orange (Poncirus trifoliata Raf.) were regenerated following protoplast fusion. Hamlin protoplasts, isolated from an habituated embryogenic suspension culture, were fused chemically with Flying Dragon protoplasts isolated from juvenile leaf tissue. The hybrid selection scheme was based on complementation of the regenerative ability of the Hamlin protoplasts with the subsequent expression of the trifoliate leaf character of Flying Dragon. Hybrid plants were regenerated via somatic embryogenesis and multiplied organogenically. Hybrid morphology was intermediate to that of the parents. Chromosome counts indicated that the hybrids were allotetraploids (2n=4x=36). Malate dehydrogenase (MDH) isozyme patterns confirmed the hybrid nature of the regenerated plants. These genetically unique somatic hybrid plants will be evaluated for citrus rootstock potential. The cell fusion, selection, and regeneration scheme developed herein should provide a general means to expand the germplasm base of cultivated Citrus by intergeneric hybridization with related sexually incompatible genera.Abbreviations MDH malate dehydrogenase - CTV citrus tristeza virus - MT Murashige and Tucker basal medium - BH3 protoplast culture medium, Grosser and Chandler, 1987 - PEG polyethylene glycol - GA3 giberellic acid - BA N-(phenylmethyl)-1 H-purin-6-amine - HCl hydrochloric acid Florida Agricultural Experiment Station Journal Series No. 7972