Characterization of genotypic variation in stress gene expression and photosynthetic parameters in potato
Frost injury in potato can involve the interaction of both freezing temperatures and high light. Thus frosts can result in accumulation of activated oxygen species that change the redox potential of cells. Activated oxygen species can either act as signals that induce protection mechanisms or accelerate injury. In comparison with Solanum tuberosum L., Solanum commersonii Dun., is better adapted to low temperature. In this study the freezing tolerance was studied by isolating the cold-regulated genes glutathione S-transferase (ScgstF1), heat shock cognate 70 kDa (Schsc70) and dehydrin2 (Scdnh2) from S. commersonii and characterizing gene expression in potato genotypes that differ in freezing tolerance. Fluorescence measurements (Fv/Fm, 1 − qP) showed that photosynthesis of a freezing-tolerant genotype was transiently reduced during frost whereas in S. tuberosum the reduction was higher and irreversible damage occurred. In a freezing-tolerant genotype the transient reduction of photosynthesis occurred coincident with accumulation of ScgstF1 and Scdhn2 transcripts. In cold-acclimated and H2O2-treated plants, ScgstF1 and Scdhn2 accumulated in freezing-tolerant genotypes whereas Schsc70 transcript was more abundant in S. tuberosum. Pre-treatment with H2O2 also improved the freezing tolerance of S. commersonii suggesting that signal pathways associated with low temperature cold acclimation or H2O2 may overlap.