Stochastic changes affect Solanum wild species following autopolyploidization

Polyploidy is very common within angiosperms, and several studies are in progress to ascertain the effects of early polyploidization at the molecular, physiological, and phenotypic level. Extensive studies are available only in synthetic allopolyploids. By contrast, less is known about the consequences of autopolyploidization. The current study aimed to assess the occurrence and extent of genetic, epigenetic, and anatomical changes occurring after oryzaline-induced polyploidization of Solanum commersonii Dunal and Solanum bulbocastanum Dunal, two diploid (2n=2×=24) potato species widely used in breeding programmes. Microsatellite analysis showed no polymorphisms between synthetic tetraploids and diploid progenitors. By contrast, analysis of DNA methylation levels indicated that subtle alterations at CG and CHG sites were present in tetraploids of both species. However, no change occurred concurrently in all tetraploids analysed with respect to their diploid parent, revealing a stochastic trend in the changes observed. The morpho-anatomical consequences of polyploidization were studied in leaf main veins and stomata. With only a few exceptions, analyses showed no clear superiority of tetraploids in terms of leaf thickness and area, vessel number, lumen size and vessel wall thickness, stomata pore length and width, guard cell width, and stomatal density compared with their diploid progenitors. These results are consistent with the hypothesis that there are no traits systematically associated with autopolyploidy.