Genotype and Parental Combination Influence Efficiency of Cybrid Induction in Citrus by Electrofusion

Abstract

Interspecific hybridizations by electrofusion of embryogenic callus cells from `Seminole' tangelo (Citrus reticulata Blanco × C. paradisi Macf.), `Hazzara (Abohar)', or `Ohta' ponkan (C. reticulata Blanco) and leaf cells from `Lisbon' lemon [C. limon (L.) Burm. f.] or rough lemon (C. jambhili Lush.), respectively, were performed. Electrofusion of `Seminole' tangelo and `Lisbon' lemon, `Hazzara (Abohar)' and rough lemon, and `Ohta' ponkan and rough lemon resulted in 33, 43, and 36 plants, respectively. Seven to 10 plants in each combination were selected randomly and used to investigate nuclear and cytoplasmic genomes. Regenerated plants derived from electrofusion of `Seminole' tangelo and `Lisbon' lemon, and `Hazzara (Abohar)' and rough lemon possessed the same restriction fragment pattern for nuclear rDNA as that of the mesophyll parents and the same mitochondrial DNA (mtDNA) restriction pattern as that of the respective suspension parents, indicating that they were cybrids. In contrast, all the plants resulting from a combination between `Ohta' ponkan and rough lemon were confirmed by nuclear rDNA and mtDNA analysis to be somatic hybrids. The analysis of chromosome number supported the results of Southern blot hybridization. The results suggest that specific cell lines, parental combinations, or both can increase the efficiency of inducing cybrids in Citrus by electrofusion.