| Protoplast culture following polyethylene-glycol (PEG)-induced fusion resulted in the regeneration of intergeneric somatic hybrid plants from the following combinations: 'Succari' sweet orange (Citrus sinensis (L.) Osbeck) + Severinia disticha (Blanco) Swing.; 'Hamlin' sweet orange (Citrus sinensis (L.) Osbeck) + S. disticha; 'Valencia' sweet orange (Citrus sinensis (L.) Osbeck) + S. disticha; 'Nova' mandarin-tangelo (Citrus reticulata Blanco x (Citrus reticulata Macf. x C. paradisi)) + S. disticha; 'Succari' sweet orange + Severinia buxifolia (Poir.) Tenore; 'Succari' sweet orange + Atalantia ceylanica (Arn.) Oliv.; 'Succari' sweet orange + Feronia limonia (L.) Swing.; and 'Nova' mandarin-tangelo (C. reticulata x (C. reticulata x C. paradisi)) + Citropsis gilletiana Swing. & M. Kell.. The somatic hybrid between 'Succari' sweet orange and F. limonia is the first report of successful hybridization of this wild species with Citrus, by any method.; Fusion experiments also resulted in the regeneration of the following interspecific somatic hybrids: 'Succari' sweet orange with 'Dancy' tangerine (Citrus reticulata Blanco), 'Minneola' tangelo (Citrus paradisi Macf. x Citrus reticulata Blanco), 'Murcott' tangor (purported Citrus reticulata X Citrus sinensis), 'Page' tangelo (Citrus reticulata Blanco x (Citrus paradisi Macf. x C. reticulata)), and 'Ponkan' mandarin (Citrus reticulata Blanco); 'Valencia' sweet orange with 'Minneola' tangelo, 'Murcott' tangor (purported C. reticulata X C. sinensis), and 'Page' tangelo; 'Hamlin' sweet orange with 'Ponkan' mandarin; and 'Rohde Red Valencia' sweet orange (Citrus sinensis (L.) Osbeck) with 'Dancy' tangerine.; Protoplasts of the first parental donor were isolated from either ovule-derived embryogenic calli or ovule-derived embryogenic suspension cultures, and protoplasts of the second parental donor were isolated from seedling leaves. Somatic hybrid plants were identified on the basis of leaf morphology, root tip chromosome number, and molecular marker analyses (isozyme or RAPD banding patterns).; All somatic hybrid plants produced in this research have been propagated in the greenhouse and will be evaluated in commercial field trials. Intergeneric combinations may show promise as Citrus rootstocks. Interspecific somatic hybrids, besides having possible use as a scion variety, will also be used later as tetraploid breeding parents in interploid hybridization with selected monoembryonic diploid scions to produce improved seedless triploids with fresh market potential. |
