Antioxidant properties of leaves from different accessions of grapevine (Vitis vinifera L.) cv. Tempranillo after applying biotic and/or environmental modulator factors

- Mycorrhizal inoculation improved levels of phenolics, flavonols, and anthocyanins in leaves.
- Mycorrhizal inoculation improved antioxidant activity of leaves at elevated temperatures.
- There was intra-varietal-dependent response of antioxidant properties of Tempranillo leaves.
- Wastes from mycorrhizal grapevines may be a valuable source of antioxidants.
- Antioxidant capacity of the above mentioned wastes was enhanced by high temperature.

Within climate change scenario, the maintenance of grape quality and wine characteristics will be the main concern for viticulture in the future years. However, changes in the composition of grapevine pruning wastes (i.e., leaves and stems) could be another interesting aspect as important antioxidant source for pharmaceutical industry due its richness in phenolic compounds beneficial for human health. To date, the effect of biotic and environmental factors in the accumulation of these compounds in leaves had received little attention. Therefore, the aims of study were (1) to evaluate the effect of biotic (mycorrhizal inoculation) and environmental (temperature) factors, alone or combined, on phenolic composition and antioxidant activity of leaf extracts of grapevine and (2) to determine whether such effects differed among accessions of the same cultivar of grapevine. The study was carried out using container-grown grapevines grown in greenhouses. Dormant Vitis vinifera (L.) cuttings of different accessions of Tempranillo were selected to get fruit-bearing cuttings. At transplanting, half of the plants of each accession were inoculated with the mycorrhizal inoculum and after fruit set, plants were exposed to two temperature regimes (24 °C/14 °C and 28 °C/18 °C (day/night)) to commercially berry ripe. Results showed that total phenolic content, antioxidant compounds like flavonols and anthocyanins, and antioxidant activity of leaves were improved with mycorrhizal inoculation under high temperature conditions. It was concluded that mycorrhizal inoculation of grapevines could contribute to preserve high level of antioxidant compounds of leaves in a future climate change scenario. However, the effects were strongly dependent of accession assayed, which indicated a significant intra-varietal diversity in the response of Tempranillo to biotic and environmental factors.