Tissue culture as a source of replicates in non-model plants: variation in cold tolerance in Arabidopsis lyrata ssp. petraea
Whilst genotype-environment interaction is increasingly receiving attention by ecologists and evolutionary biologists, such studies need genetically homogeneous replicates--a challenging hurdle in outcrossing plants. This could potentially be overcome by using tissue culture techniques. However, plants regenerated from tissue culture may show aberrant phenotypes and \"somaclonal\" variation. Here we examined the somaclonal variation due to tissue culturing using the response of the photosynthetic efficiency (chlorophyll fluorescence measurements for Fv/Fm, Fv/Fm and {Phi}PSII, representing maximum efficiency of photosynthesis for dark- and light-adapted leaves, and the actual electron transport operating efficiency, respectively) to cold treatment, compared to variation among half-sibling seedlings from three different families of Arabidopsis lyrata ssp. petraea. Somaclonal variation was limited and we could successfully detect within-family variation in change in chlorophyll fluorescence by cold shock with the help of tissue-culture derived replicates. Icelandic and Norwegian families exhibited higher chlorophyll fluorescence, suggesting higher cold tolerance, than a Swedish family. Although the main effect of tissue culture on Fv/Fm, Fv/Fm and {Phi}PSII was small, there were significant interactions between tissue culture and family, suggesting that the effect of tissue culture is genotype-specific. Tissue-cultured plantlets were less affected by cold treatment than seedlings, but to a different extent in each family. These interactive effects, however, were comparable to, or much smaller than the single effect of family. These results suggest that tissue culture is a useful method for obtaining genetically homogenous replicates for studying genotype-environment interaction related to adaptively relevant phenotypes, such as cold tolerance, in non-model outcrossing plants.