The use of cytoplasmic markers in onion hybrid breeding.

We applied the RFLP approach to identify the cytoplasmic genotypes of selected onion breeding materials from Poland. For this purpose, mitochondrial DNA from cytoplasmic male-sterile (CMS) and male-fertile onions were hybridized with the probes for the following mitochondrial genes: atpA, atp6, atp9, cob, cox1, nad3, nad4 and nad6. S-, T- or C-cytoplasm was represented in each analyzed sterile accession. Some new polymorphisms shared by S- and C-cytoplasmic onions were identified. We also used currently available PCR markers to test if cytoplasmic heterogenity occurs within onion inbreds. A fraction of the plants bearing S-cytoplasm were found within two male-fertile lines, but such plants were not detected in the open-pollinated cultivars Sochaczewska, Wolska and Zytawska. Both the RFLP and PCR approaches gave some proof of existing mitochondrial heteroplasmy in onions