INTERGENERIC SOMATIC HYBRIDS BETWEEN CITRUS AND ATALANTIA OR SEVERINIA BY ELECTROFUSION, AND RECOMBINATION OF MITOCHONDRIAL GENOMES

Two intergeneric hybridizations through protoplast fusion between the embryogenic callus cells of 'Seminole' tangelo (Citrus reticulata Blan co X C. paradisi Macf.) and leaf cells of Indian atalantia (Atalantia monophylla DC.) or Chinese box-orange (Severinia buxifolia (Poir.) Ten ore) were performed to overcome the genetic incompatibility. We were s uccessful in regenerating whole plants of 16 somatic hybrids between ' Seminole' tangelo and Indian atalantia, and 46 somatic hybrids between 'Seminole' tangelo and Chinese box-orange, and hybridity was confirme d by Southern blot hybridization with rDNA. The mitochondrial DNA (mtD NA) of the somatic hybrids between 'Seminole' tangelo and Indian atala ntia was identical to that of 'Seminole' tangelo, when rrn 26 and cox I were used as probes. However, when atpA was used as a probe, a 'Semi nole' tangelo-specific fragment was found missing besides an Indian at alantia-specific fragment. The band pattern obtained by chloroplast DN A (cpDNA) analysis was identical to that of Indian atalantia. On the c ontrary, somatic hybrids between 'Seminole' tangelo and Chinese box-or ange showed the mtDNA band pattern identical to that of 'Seminole' tan gelo, when atpA and cox I were used as probes. However, analysis by rm 26 probe showed the presence of a part of a Chinese box-orange-specif ic band in addition to a 'Seminole' tangelo-specific band. The cpDNA o f the somatic hybrids was identical to that of Chinese box-orange. The se results suggest the occurrence of mitochondrial recombination betwe en parents.