In this research the effect of calcium sulfate (CaSO4; C1: 0%, C2: 1% and C3: 2%) combined to zinc sulfate (ZnSO4; Z1: 0%, Z2: 0.5% and Z3: 1%) was evaluated in commercial vineyard (Vitis vinifera cv “Sultana”) located in Jowzan Valley of Malayer city (Iran). Vines were sprayed two times in March, a week before bud wooly stage during two consecutive seasons, 2016 and 2017. The spring cold tolerance and some related physiological traits of vines were evaluated at three phenological stages of wooly bud, green tip and leaf emergence status. Application of CaSO4 and ZnSO4 in moderate level significantly delayed budbreak up to 9 day in compared to control vines. In green tip bud phenological stages, C2Z3 combined treatment showed the lowest LT50 (highest cold hardiness), although it did not significantly differ with obtained LT50 of C2Z2 treated vines. In green tip stage, higher glucose content was recorded in C2Z2 treatments. Fructose contents of C2Z2 treatment in wooly, green tip and leaf emergence stages approximately were 21%, 21%, 27% higher than control non-sprayed vines. In all three stages, vines sprayed with C2Z3 showed the highest putrescine concentration. In C2Z2 and C2Z3 treatments spermine and spermidine were higher compared to other treatments. In green tip stage also the vines treated with C2Z3 showed the highest abscisic acid (ABA) concentration in compared to other fertilizer treatments. The change pattern of gibberellins (GA) was in contrast with ABA change in buds during bud developmental stages and the always vines treated with C2Z2 or C2Z3 exhibited the lowest GA concentration and the control vines showed the highest amount of GA. In all sampling stages, vines treated with C2Z3 and C1Z1 (controls) having the least and highest endogenous auxin (IAA) in respectively. Altogether, data showed that calcium and zinc are highly efficient for spring frost tolerance increase in grapevine.
