Hybrid Shoot Formation from Fused Daucus carota and D. capillifolius Protoplasts

Abstract

Summary Protoplasts from line C123, a 5-methyltryptophan (5MT) and azetidine-2-carboxylate (A2C) resistant cell line of Daucus carota that has lost the ability to regenerate whole plants, were fused using dextran with protoplasts of suspension cultured D. capillifolius. Somatic hybrids were selected initially by culture in 5MT levels which inhibit the growth of D. capillifolius and then for green pigmentation and embryoid formation. The fusion and selection produced plants, lacking roots, with leaves showing intermediate morphology between those of the parents. The chromosome numbers of embryoid root tips and suspension cultures were near 36 which is the sum of the parents. Analysis of four isozymes following electrophoresis showed that malate dehydrogenase and peroxidase resembled the carrot parent while leucine aminopeptidase was like D. capillifolius. The superoxide dismutase pattern was like that expected from a hybrid. Callus initiated from the hybrid plants showed resistance to both 5MT and A2C with the resistance being expressed as semi-dominant and dominant characters, respectively. The feedback control characteristics of anthranilate synthase correlate with the 5MT resistance in the parental and hybrid lines. These results demonstrate that amino acid analog resistance and plant regeneration ability can be used as complementing markers to select for fusion hybrids since both can be expressed in the hybrids.