Physiological, molecular, and genetic mechanism of action of the biostimulant QuantisTM for increased thermotolerance of potato (Solanum tuberosum L.)

Abstract

Abstract Background Raising global temperatures limit crop productivity and new strategies are needed to improve the resilience of thermosensitive crops such as potato (Solanum tuberosum L.). Biostimulants are emerging as potential crop protection products against environmental stress, however their mechanism of action remains largely unknown, hindering their wider adoption. We used comprehensive physiological, molecular, and mass spectrometry approaches to develop understanding of the mechanism of plant thermotolerance exerted by the biostimulant, QuantisTM, under heat stress. Using orthologues gene mutations in Arabidopsis thaliana we report heat-defence genes, modified by QuantisTM, which were also investigated for potential overlapping functions in biotic stress defence to Sclerotinia sclerotiorum and Rhizoctonia solani. Results QuantisTM enhanced PSII photochemical efficiency and decreased thermal dissipation of potato grown under heat stress. These effects were associated with upregulation of genes with antioxidant function, including PR10, flavonoid 3′‐hydroxylase and b-glucosidases, and modulation of abscisic acid (ABA) and cytokinin (CK) activity in leaves by QuantisTM. The biostimulant modulated the expression of the heat-defence genes, PEN1, PR4 or MEE59, with functions in leaf photoprotection and root thermal protection, but with no overlapping function in biotic stress defence. Protective root growth under heat stress, following the biostimulant application, was correlated with enhanced CK signalling in roots. Significant upregulation of StFKF1 consistent with tuberization promoting effects and increase in endogenous concentration of ABA and CK in potato leaves modulated by QuantisTM resulted in 8% tuber weight increase and 42% larger tuber size, thus mitigating negative effects of heat stress on tuber growth. Conclusions QuantisTM application prior to heat stress effectively primed heat tolerance responses and alleviated temperature stress of S. tuberosum L. and A. thaliana by modulating the expression and function of PR4 and MEE59 and by regulating CK activity above and below ground, indicating that the mechanism of action of the biostimulant is conserved, and will be effective in many plant species. Thus, a biostimulant application targeting the most susceptible crop developmental stages to heat disorders can be effectively integrated within future agronomy practices to mitigate losses in other thermosensitive crops.