Protoplast fusion and early development of fusants

Somatic hybrids and cybrids of Senecio fuchsii Gmel. (x) jacobaea L

Twenty fusants of S. Jacobaea L. (chlorophyll deficient) (x) fuchsii Gmel. (wild-type) were investigated by studying chromosome number, isozymes, and restriction fragment length polymorphism (RFLP). Sublines were established from primary shoots, and clones were grown from isolated protoplasts. Out of the 12 hybrid lines 9 had the amphidiploid chromosome number of 80 (2x = 40) as concluded from each one subline. Three hybrid lines showed reduced chromosome numbers between 60 and 76, indicating karyotypic instability. Additive isozyme complements with peroxidase, esterase, malate dehydrogenase, and glutamate-oxalacetate transaminase activities were found. In the RFLP analyses, three ptDNA probes were able to demonstrate the origin of plastomes from either one or both parents, but singular chondriomes from either parent were traced with a mtDNA probe. The results of detailed studies with sublines and clones of two hybrid lines revealed that the chlorophylldeficiency mutation of one parental S. jacobaea clone is located in the genome and that of the other one is located in the plastome. Eight fusant lines were putative cybrids. Mutant plastids were not transmitted into the regenerated putative cybrid shoots. The mtDNA of S. jacobaea alone was detected with a mtDNA probe in seven putative cybrid lines; in one line mtDNA fragments of both the parents were traced. In three lines, the nucleus and the plastids only showed S. fuchsii characters, but the mtDNA was of S. jacobaea.