Protoplast Isolation, Culture, and Plant Regeneration from Passiflora

The family Passifloraceae contains over 580 woody or herbaceous species (1 ), the majority of species within the genus Passiflora being found in tropical South America. Passiflora eduhs fv. flavicarpa is considered to be the most important species (2 ) because of its value in the fruit juice industry. Additionally, this species is resistant to the soil-borne pathogen Fusarium oxysporum and, consequently, is frequently used as a rootstock onto which is grafted P edulis Sims. Interspecific sexual hybridization has been attempted in Passiflora breeding programs, using wild-type germplasms to transfer disease resistance and other potentially desirable traits into cultivated species. However, fertile hybrids have been difficult to obtain (3 ). Somatic hybridization provides a means of circumventing such sexual incompatibilities. Indeed, novel fertile somatic hybrids have been produced between P. eduhs fv. flavicarpa and Passiflora incarnata (4 ). Since the latter species can survive winter temperatures of −16�C, such transfer of cold tolerance to the commercial crop would permit cultivation in more temperate climates (5 ). Somatic hybrid plants have also been produced between P edulis fv. flavicarpa and Passiflora amethystina, Passiflora cincinnata, Passiflora giberti , and Passiflora alata , respectively (6 ).