Analysis of chromatin, nuclear DNA and organelle composition in somatic hybrids between Solanum tuberosum and Solanum sanctae-rosae

A protoplast fusion strategy has been applied to advance aspects of a potat o breeding programme. A sub-population of somatic hybrids, selected for agr onomic potential, between tetraploid Solanum tuberosum cv. Brodick and a di ploid EBN2 accession, S, sanctae-rosae was subjected to detailed molecular analysis. This study reports the use of simple sequence repeats (SSRs) to i dentify nuclear hybrid genomes and PCR and DNA-DNA analysis to determine or ganelle composition in somatic hybrids derived from these parents. SSR anal ysis revealed somatic hybrids containing the genetic background of S. tuber osum cv. Brodick with some specific markers from S, sanctae-rosae. One soma tic hybrid contained the chloroplasts derived from S. sanctae-rosae, and se veral hybrids had detectable RFLP mitochrondrial DNA profiles, indicating g enetic re-arrangements. We also examined the use of DNase I sensitivity to the genomic and ribosomal RNA sequences in these somatic hybrids as an indi cator of changes in chromatin structure. Chromatin and DNAse I analysis sho wed differential sensitivity to increasing levels of nuclease; DNA from sev eral somatic hybrids was found to be resistant to DNase I compared to the p arental plants. The significance of the findings to somatic cell genetics a nd plant breeding studies is discussed.