Understanding mechanisms of potato cold hardiness by merging physiological, genetic and molecular approaches

While cultivated potatoes are frost sensitive, many wild Solanum species are known to be frost hardy. This diversity provides an ideal model system to study freezing tolerance and cold acclimation mechanisms. The aim of this study was to gain a better understanding of potato cold response by utilizing physiological, genetic and molecular approaches.;We studied two factors that contribute to frost survival: rate of cold acclimation and deacclimation. Results demonstrated differences in the rates of cold acclimation among wild potatoes: the species studied can be divided into: (i) early acclimators; (ii) late acclimators; (iii) progressive acclimators; (iv) nonacclimators. Variability was also found in the rate of cold deacclimation. We also found that the rates of cold acclimation and deacclimation were not related to the cold acclimation capacity of a given species.;To provide insights into the genetics of freezing tolerance and cold acclimation in potato and contribute valuable information for potato improvement via marker assisted selection, a partial genetic linkage map was constructed using randomly amplified polymorphic DNA (RAPD) and simple sequence repeat (SSR) in a backcross population derived from two wild diploid potato species (frost tolerant acclimating S. commersonii and frost sensitive nonacclimating S. cardiophyllum). The linkage map spanned 479.4 cM, including 77 RAPD markers and two SSR markers. Quantitative trait loci for nonacclimated relative freezing tolerance (NARFT) and cold acclimation capacity (CAC) were detected at separate regions. NARFT and CAC were poorly correlated. These results agree with previous studies reporting cold hardiness as polygenic trait and that these two traits have independent genetic control.;Previous studies revealed an increase in linoleate in the purified plasma membrane fraction of potato leaves during cold acclimation, suggesting that the activity of specific desaturases may be modulated during cold acclimation. Desaturase Delta9 gene expression was studied before and after cold acclimation in cultivated S. and wild S. commersonii at the transcript level. While S. commersonii exhibited an increase in Delta9 desaturase transcript levels after cold acclimation, S. tuberosum exhibited no change. These results show that the increase in Delta9 desaturase gene transcripts during cold acclimation is associated with potato cold acclimation response.