Soluble sugars, phenolic acids and antioxidant capacity of grape berries as affected by iron and nitrogen

International audience

إنجليزي. Foliar nutrition is one of the effective cultural practices in vineyards. In this research, the effect of iron chelate (Fe-EDDHA) and urea, each in three levels of 0, 0.5 and 1%, was evaluated with an ANOVA completely randomized block in commercial vineyard (cv “Sultana”) located in Bahareh village of Malayer city (Iran). Vines were sprayed in three stages: a week before bloom (8 June), 2 weeks after bloom (29 June) and 5 weeks after bloom (20 July) during the growth seasons in 2015 and 2016. The grapes harvesting was done in mid-September according to the maturity level of untreated vines. In comparison with the other treatments, moderate levels (0.5%) of fertilizers allow to reach the highest glucose and sucrose concentration at harvest. Foliar spray of high iron chelate doses in combined with 0.5% urea caused a considerable increase in berries putrescine and spermine concentration. However, combination effects of urea and Fe-EDDHA with moderate level (0.5%) were the most efficient for spermidine accumulation of ‘Sultana’ grapevine. For the moderate levels (Fe-EDDHA 0.5%) of fertilizers treatment, most phenolic acids and anthocyanidins reached a peak, and the highest free radical scavenging capacities (DPPH) of grape samples were achieved. The activity superoxide dismutase, guaiacol peroxidase, catalase and ascorbate peroxidase increased with moderate levels of Fe-EDDHA in combination with high levels of urea treatments. However, the maximum glutathione reductase was obtained with 1% urea in combination with Fe-EDDHA at 1% concentrations. Altogether, data showed that iron and nitrogen are highly efficient to manage quality and nutritional potential of grape berries.