Shoot regeneration and chromosome doubling in accessions of 2x(1EBN) and 4x(2EBN) wild Solanum species

The aim of this study was to double the somatic chromosome number of 2x(1EBN) and 4x(2EBN) Solanum species sexually isolated from 2x(2EBN) S. tuberosum haploids and 4x(4EBN) S. tuberosum varieties, respectively, for breeding purposes. In particular, shoot regeneration and chromosome doubling in plants regenerated from in vitro culture were investigated in the 2x(1EBN) S. brachistotrichum, S. bulbocastanum, S. cardiophyllum and the 4x(2EBN) S. acaule and S. fendleri wild species. Internode and leaf explants of each genotype were excised from plants propagated in vitro as shoot cultures. A two-step regeneration protocol was employed. Out of seven clones tested, six regenerated. Only in 2x(1EBN) genotypes did chromosome doubling occur, whereas the 4x(2EBN) genotypes only produced 4x regenerants. Regeneration frequencies and chromosome doubling were significantly higher from leaf explants compared to internodes. Significant differences between the 2x(1EBN) genotypes were found in regeneration ability but not in chromosome doubling. The potential use of genotypes with various EBN and ploidy level obtained is discussed.