Insights into responses to elevated temperatures in Solanum tuberosum cultivars with contrasting sensitivity

Elevated temperatures caused by climate change threaten potato production. To understand heat stress adaptations and variety-specific responses, plants of a susceptible (Cecile) and a tolerant cultivar (Solara) were exposed to elevated temperatures (30/28 °C) for 21 days at tuberization stage. Phenotypic, physiological, transcriptional and metabolic changes were analyzed in comparison to ambient temperatures (21/19 °C). Heat stress caused shoot elongation and tuber weight loss, which were more pronounced in Cecile. Transcriptome analysis of leaf samples revealed a stronger decrease of photosynthesis-associated genes in the sensitive cultivar Cecile, which was associated with decreased chlorophyll fluorescence and an early senescence. These effects correlated with strongly elevated levels of salicylic acid and ethylene. In contrast, Solara showed delayed senescence and a higher expression of sugar and amino acid transporters suggesting an adaptive mechanism to maintain carbohydrate and amino acid allocation. The expression of known tuberization regulators including SP6A, exhibited a similar response to heat in both varieties, with decreasing expression of SP6A. Solara exhibited a constitutively higher expression of PEBP14/15 and MADS13, which potentially promote tuberization and may support tuber growth under heat. Regardless of variety, a few genes, such as HSP20 and HSP70, were induced by heat and may serve as heat stress marker genes. Altogether, the results indicate that delayed senescence, stable photosynthesis, efficient assimilate translocation, and differential regulation of tuberization pathways contribute to heat tolerance in Solara. These insights improve our understanding of the molecular basis of heat resilience and provide potential targets for breeding climate-resilient potato varieties.