Cell lines and plants obtained after protoplast fusions of Rosa+Rosa,Rosa+Prunus and Rosa+Rubus

Summary Protoplasts of three Rosa cultivars were fused with each other, with protoplasts of Prunus `Colt' and with protoplasts of Rubus laciniatus, using polyethylene glycol 4000 as a fusogen. Protoplasts of Prunus were incapable of cell division and those of Rosa and Rubus were disabled by treatments with metabolic inhibitors, either iodoacetate (IOA) or rhodamine 6-G (R6G). Parental protoplasts were then fused in combinations that required complementation for their survival. RAPD analysis of 41 fusion-derived cell lines showed that two lines resulting from fusions of Rosa + Rosa and one from a fusion of Rosa + Prunus, contained some DNA markers from both fusion partners. The others contained markers of only one fusion parent. This showed that after protoplast fusion, the heterokaryons did not develop into cell lines with stable hybrid nuclei. Plants regenerated from cell lines derived from Rosa + Prunus and Rosa + Rubus fusions contained DNA markers of only Rosa and their DNA amounts were no greater than that of the Rosa parent. However, they differed morphologically from the Rosa parent to a remarkable degree, possibly because they inherited undetected genes of Prunus or Rubus, or because they were somaclonal variants of the Rosa parent. Alternative strategies for the production of somatic hybrids are discussed.