Analysis of the plastome and chondriome origin in plants regenerated after asymmetric Solanum ssp. protoplast fusions

Protoplasts from potato cultivars used as recipient parents were fused with irradiated protoplasts from wild Solanum donor species. Regenerated plants were analysed by RAPDs to identify hybrids. Irradiation of donor protoplasts with ionizing irradiation induced a broad range of donor nuclear DNA elimination in the asymmetric hybrids. Usage of chloroplast (cp)- and mitochondrial (mt)-specific PCR markers made it possible to trace the different origins of the cp genome in seven fusion combinations, as well as the mt genomes in two fusion combinations. Regenerated plants with recipient nucleus and plastome markers from the donors were found in six of the seven analysed fusion combinations. Protoplast fusion has generated novel mt genome combinations consisting of different portions of the mt genomes from the fusion partners. Selection of heterofusion products based on fluorescence markers is an efficient method to obtain asymmetric Solanum hybrids and cy- brids from most fusion combinations. Possible models for cybrid formation are discussed.