Molecular markers for cytoplasm in potato: male sterility and contributionof different plastid-mitochondrial configurations to starch production

Distinct parental cytoplasms were combined in symmetric tetraploid hybrids of potato by somatic cell fusion. This allowed, in the presence of nearly i sogenic nuclear genomes, to estimate the contribution of mitochondrial (mt) and chloroplast (cp) genomes to starch content. Analysis of mt-cp configur ations in the complete gene pool of german potato cultivars [2n=4x], in a r eciprocal dihaploid population [2n=2x], in di-haploid fusion parents [2n=2x ] and in their respective hybrids [2n=4x] made visible the effects of diffe rent cytoplasmic backgrounds and mitochondrial subgenomic rearrangements. G enotypes identified by markers as cytoplasm W gamma were associated with cy toplasmic male sterility. Evaluation of cytoplasmic types leads to the conc lusion, that in starch content the 'wild type' cytoplasms W alpha and W gam ma have a significant advantage to other cytoplasmic types (T beta, W delta , S epsilon). This results from the experiments with a reciprocal populatio n, 180 di-haploids, and from cultivar comparisons. In hybrids an interactio n between starch content and different mt-cp combinations could be found. I n general the highest field performance, measured in starch content and yie ld was associated with such cytoplasmic configurations which appeared to a high frequency within a population, when the segregation process was comple ted. This fact is explained by a selection advantage of clones with optimiz ed organellar segregation already during in vitro phase. PCR markers for cy toplasm differentiation are actualized on a website, http://www.flg.tum.de/ pbpz/mm/mt/hybrid.html.