Exogenous phosphite application alleviates the adverse effects of heat stress and improves thermotolerance of potato (Solanum tuberosum L.) seedlings.

Phosphite (Phi), an analog of phosphate (Pi) anion, is emerging as a potential biostimulator, fungicide and insecticide. Here, we reported that Phi also significantly enhanced thermotolerance in potatoes under heat stress. Potato plants with and without Phi pretreatment were exposed to heat stress and their heat tolerance was examined by assessing the morphological characteristics, photosynthetic pigment content, photosystem II (PS II) efficiency, levels of oxidative stress, and level of DNA damage. In addition, RNA-sequencing (RNA-Seq) was adopted to investigate the roles of Phi signals and the underlying heat resistance mechanism. RNA-Seq revealed that Phi orchestrated plant immune responses against heat stress by reprograming global gene expressions. Results from physiological data combined with RNA-Seq suggested that the supply of Phi not only was essential for the better plant performance, but also improved thermotolerance of the plants by alleviating oxidative stress and DNA damage, and improved biosynthesis of osmolytes and defense metabolites when exposed to unfavorable thermal conditions. This is the first study to explore the role of Phi in thermotolerance in plants, and the work can be applied to other crops under the challenging environment.