The potato is susceptible to water stress at all stages of development. We examined four clones of tetraploid potato, Cardinal, Desirée, Clone 37 FB, and Mije, from the germplasm bank of the National Institute of Agricultural Research (INIA) in Chile. Water stress was applied by suspending irrigation at the beginning of tuberization. Stomatal conductance, and tuber and plant fresh and dry weight were used to categorize water stress tolerance. Cardinal had a high susceptibility to water stress. Desirée was less susceptible than Cardinal and had some characteristics of tolerance. Mije had moderate tolerance and Clone 37 FB had high tolerance. Differential gene expression in leaves from plants with and without water stress were examined using transcriptome sequencing. Water stress-susceptible Cardinal had the fewest differentially expressed genes at 101, compared to Desirée at 1867, Clone 37 FB at 1179, and Mije at 1010. Water stress tolerance was associated with upregulation of the expression of transcription factor genes and genes involved in osmolyte and polyamine biosynthesis. Increased expression of genes encoding late embryogenesis abundant (LEA) and dehydrin proteins along with decreased expression of genes involved in nitrate assimilation and amino acid metabolism were found for clones showing water stress tolerance. The results also show that a water deficit was associated with reduced biotic stress responses. Additionally, heat shock protein genes were differentially expressed in all clones except for highly susceptible Cardinal. Together, the gene expression study demonstrates variation in the molecular pathways and biological processes in response to water stress contributing to tolerance and susceptibility.

Potato tuber yields depend on nitrogen (N) supply, which affects source–sink relations. Transcriptome sequencing of the foliar source using a single field trial identified gene expression responsive to 180 kg N ha⁻¹. The expression of N-responsive genes was further analyzed in the next stage using a NanoString nCounter over an expanded number of foliar samples from seven field trials with varying N rates, sites, and cultivars. Least absolute shrinkage and selection operator (LASSO) regression models of gene expression predictive of yield, total plant N uptake, and tuber-specific gravity (proxy for dry matter) were built. Genes in the LASSO model for yield were associated with source–sink partitioning. A key gene regulating tuberization and senescence, StSP6A Flowering locus T, was found in the LASSO model predicting tuber yield, but not the other models. An aminotransferase involved in photorespiratory N assimilation and amino acid biosynthesis was found in all LASSO models. Other genes functioning in amino acid biosynthesis and integration of sulfur (S) and N metabolism were also found in the yield prediction model. The study provides insights on N responses in foliage of potato plants that affect source–sink partitioning. Additionally, N-responsive genes predictive of yield are candidate indicators of N status.