VARIATION OF PLASTID AND MITOCHONDRIAL DNAS IN THE GENUS DAUCUS

Plastid and mitochondrial DNAs from suspension cultures of Daucus carota subsp. sativus cv. Danvers, D. carota subsp. gummifer, D. capillifolius, and D. pusillus were compared by restriction endonuclease fragment analysis. Organelles isolated from protoplasts of suspension cultures were purified using a one-step sucrose gradient. Plastid DNA fragment patterns for subsp. sativus, subsp. gummifer, and capillifolius were indistinguishable in Pstl, SalI and XhoI enzyme digests. No variation was detected in BamHI or HindIII digests between subsp. sativus and capillifolius. Pusillus plastid DNA varied significantly when compared to the other Daucus cultures. The size of the plastid genome of each species as determined by fragment addition, was estimated at 155 kb. Restriction digests of the mitochondrial DNAs generated a large number of fragments which when totaled established a size of 386–468 kb for the genomes. Densitometer scans of the fragment patterns indicate the bands were present in variable stoichiometry. Up to 26% of the fragments generated by PstI, SalI and HindIII digests were homologous in size among the four mitochondrial genomes. A further comparison of mitochondrial fragments indicated a closer homology of subsp. sativus to capillifolius than to subsp. gummifer or pusillus as was also found with the plastid genomes.