Effect of gum ghatti and SoluPotasse on phenological and physiological indices related to spring cold tolerance of grapevine

Background and Objectives: Spring cold is one of the main problems for grapevines in temperate regions, in some cases the severity of damage is very high and sometimes the entire crop will be lost. For this reason, it is necessary to use compounds that delay the bud burst and increase cold tolerance in vines. The present study was conducted with the aim of investigating the effect of foliar spraying of gum ghatti (GG) and SoluPotasse (SOP) on bud burst time and cold tolerance of Bidane-Sefid grapes.

Materials and Methods: This experiment was carried out factorially (2×3) based on a randomized complete block design with 3 replications (one vine per replication). The first factor included GG in two concentrations (0 and 0.5%) and the second factor included SOP in three concentrations (0, 1 and 2%). Foliar spraying of different concentrations of GG and SOP was done in two stages in late March and early April, just before wooly bud stage until the buds were fully swollen, using a 10-liter sprayer until the water-drip stage on the vines.

Results: According to the results, the highest effect of GG and SOP on bud burst time was related to the vines treated with 0.5% GG in combination with 2% SOP and the lowest effect was related to the control vines. Also, the highest days to bloom were related to the vines treated with 0.5% GG alone, and the lowest days to bloom were related to the vines treated with 1% SOP. Likewise, the highest percentage of fruit set was related to vines treated with 0.5% GG and 1% SOP. The highest and lowest content of ion leakage was related to control vines and vines treated with 0.5% GG + 2% SOP, respectively. Also, the highest content of malondialdehyde and hydrogen peroxide was related to the control vines and the lowest content of these membrane stability indices was related to those vines treated with the combination of 0.5% GG + 1% SOP. The highest content of proline and soluble carbohydrates was related to vines treated with 0.5% GG in combination with 1% SOP, and the lowest content of these osmoregulants was related to control vines. The highest content of total phenol was related to the vines treated with 1% SOP and the lowest content of this secondary metabolite was related to the control vines. The highest flavonoid content was related to the vines treated with the combination of 0.5% GG and 1% SOP, and its lowest content was related to vines sprayed with 0.5% GG alone. The leaf chlorophyll content was the highest in vines treated with 1% SOP alone. Similarly, the highest activity of catalase enzyme was related to vines treated with 0.5% GG in combination with 2% SOP, and the highest activity of guaiacol-peroxidase and protein content was related to those vines treated with 0.5% GG and 1% SOP. The highest content of abscisic acid and the lowest content of gibberellin were related to vines treated with 0.5% GG + 1% SOP. The highest spermine content was related to the vines treated with the second level of in combination with the second level of SOP. Moreover, the highest content of spermidine was related to the vines treated with 2% SOP alone.

Conclusion: In general, the application of GG as a polysaccharide coating in combination with SOP as a source of potassium by extending the dormancy time and increasing the concentration of abscisic acid and soluble sugars led to a delay in bud burst and increased spring cold tolerance in grapevine plants.