SOMATIC HYBRIDIZATION BETWEEN SOLANUM-TUBEROSUM AND SPECIES OF THE S-NIGRUM COMPLEX - SELECTION OF VIGOROUSLY GROWING AND FLOWERING PLANTS

Fusion experiments were performed between diploid (2n = 2x = 24) or te traploid (2n = 4x = 48) potato genotypes and four species of the Solan um nigrum complex, namely S. nigrum (2n = 6x = 72), S. villosum (2n = 4x = 48), S. chenopodioides (2n = 2x = 24) or S. americanum (2n = 2x = 24 and 2n = 6x = 72). All five accessions of the S. nigrum-species we re successfully hybridized with at least one of the potato genotypes. Somatic combining abilities were influenced by the ploidy level as wel l as the genotype of the parental species. The use of kanamycin or hyg romycin resistance as cell-selectable markersystem had no influence on somatic combining ability, but such markers can be useful to improve efficient selection of somatic hybrids in sufficient numbers. At least 20% of the hybrids of each successful combination performed well in v itro. However, only 60 genotypes out of 761 somatic hybrids were vigor ous as well as flowering in the greenhouse. Analysis of the DNA conten t of somatic hybrids could be used as a criterion for the indirect sel ection in vitro of hybrids that were vigorous in the greenhouse. Flowe ring somatic hybrids of S. nigrum (+) 2x potato and S. americanum (+) 4x potato were selected with the aim of introgression of resistance tr aits after recurrent backcrossing with cultivated potato.