Production and analysis of intraspecific somatic hybrids of potato (Solanum tuberosum L.)

Abstract Photoplasts of two dihaploid lines of potato were fused to produce a large number of intraspecific somatic hybrid plants among which plants of the expected tetraploid level might be found. Fusion frequencies up to 12% (mean 7%) were observed using a revised polyethylene glycol fusion protocol. Fusion products were identified by the dual fluorescence emission from the chloroplasts in mesophyll protoplasts (red) and from the fluorescein diacetate stain in light and norflurazon bleached protoplasts (yellow-green). Hybrid cells were isolated 2–3 days after fusion and cultured at a cell density of 2000 cells/ml. From a total of 1363 isolated putative hybrid cells, 258 divided to form calli. Plants were regenerated from 166 of these. Isozyme analysis confirmed the hybrid nature in 57 of 58 analysed plants. Ploidy was determined in 51 plants; 12% were tetraploid, 41% hexaploid, 12% octoploid and 35% were mixoploid. Expression of isocitrate dehydrogenase isozymes indicated that the majority of the hexaploid hybrids contained 2 genomes of the bleached parent and one genome of the mesophyll parent. This study shows that tetraploid somatic hybrid potato plants can be obtained by the fusion and selection method presented.