The proportions of glycoalkaloid aglycones are dependent on the genome constitutions of interspecific hybrids between two Solanum species ( S. brevidens and S. tuberosum)

Abstract

Wild Solanum species, related to the cultivated potato ( Solanum tuberosum L. ssp. tuberosum), generally contain high amounts of various glycoalkaloids, which are undesirable characters when expressed in edible potatoes. The aim of the present study was to define the influence of genome constitution alterations on the relative proportions of glycoalkaloid aglycones in a range of interspecific somatic hybrids between wild Solanum species ( S. brevidens Phil.) and cultivated potato. The S. brevidens parental species principally produced tomatidine aglycone and the S. tuberosum line produced solanidine aglycone. Plant material including primary interspecific somatic hybrids, their anther-derived haploids, and ‘second generation’ somatic hybrids were analysed in terms of their genome constitutions by using GISH (genomic in situ hybridisation). The genome constitutions of the primary hybrids were AAEE (tetraploid hybrids) and AAEEEE (hexaploid hybrids), with A-genomes from S. tuberosum and E-genomes from S. brevidens. The anther-derived diploid and triploid (somato)haploids regenerated from somatic hybrids had genome constitutions of AE and AEE. Gas chromatography-mass spectrometry (GC-MS) analysis of glycoalkaloid aglycones in leaf samples showed that the relative proportions of tomatidine aglycones were higher than that of solanidine or demissidine aglycones in all the somatic hybrids and their somatohaploids. Altering the genome constitution of the hybrids by adding S. tuberosum (AA) genome to the 3x somatohaploid (AEE) in order to produce ‘second generation’ somatic hybrids (AAAEE) had a significant effect on the proportions of aglycones. The relative amount of solanidine increased from 10% in the primary somatic hybrids and their somatohaploids up to the level of 29% in the ‘second generation’ somatic hybrids. The increased formation of solanidine was assumed to be based on a higher dose of A-genome in the ‘second generation’ somatic hybrids. This study demonstrated that specific undesirable traits derived from wild Solanum species, such as alien glycoalkaloid expression, could be reduced by production of ‘second generation’ somatic hybrids of potato.