Effects of the Fractionation of the Nitrogen Fertilization on Root Nitrate Uptake and Vine Agronomic Performance in Pinot Gris Grapevines in a Temperate Climate

The study aims to investigate at a physiological and molecular level the root absorption of nitrogen (N) during the annual cycle of grapevine. The study was performed on potted Pinot Gris plants grafted on Kober 5BB and grown for two consecutive years in a semi-controlled environment (Northeast, Italy). The study compared the response of plants N-fertilized in spring (T1), or in spring and in post-harvest (T2) or no-N fertilized (C). Results showed that under our climate conditions nitrate was taken up by the grapevines when applied both in spring or in spring and post-harvest. The nitrate acquisition in T1 roots is mediated at molecular and physiological level by a higher activation of high-affinity nitrate-transport system to take up nitrate in comparison to no-fertilized plants. Comparing the two N fertilization managements, the dynamic of nitrate uptake rates showed different patterns with an overall late response of High-Affinity Transport System when the application of part of N-fertilization was delayed to post-harvest (T2) in comparison to T1. Nevertheless, during the 2 years of the trial the fractionation of N fertilization applied in spring and post-harvest did not negatively affect the yield and quality parameters of vines. An increase of N concentration in T2 roots after two consecutive growing seasons may suggest that the fractionation can lead to beneficial effects on long period. Results of this work contribute to improve the comprehension of N acquisition in grapevine in order to optimize the use of N inputs in vineyard

Grapevine phyllosphere community analysis in response to elicitor application against powdery mildew

The reduction of antimicrobial treatments and mainly the application of environmentally friendly compounds, such as resistance elicitors, is an impelling challenge to undertake more sustainable agriculture. We performed this research to study the effectiveness of non-conventional compounds in reducing leaf fungal attack and to investigate whether they influence the grape phyllosphere. Pathogenicity tests were conducted on potted Vitis vinifera “Nebbiolo” and “Moscato” cultivars infected with the powdery mildew agent (Erysiphe necator) and treated with three elicitors. Differences in the foliar microbial community were then evaluated by community-level physiological profiling by using BiologTM EcoPlates, high throughput sequencing of the Internal Transcribed Spacer (ITS) region, and RNA sequencing for the viral community. In both cultivars, all products were effective as they significantly reduced pathogen development. EcoPlate analysis and ITS sequencing showed that the microbial communities were not influenced by the alternative compound application, confirming their specific activity as plant defense elicitors. Nevertheless, “Moscato” plants were less susceptible to the disease and presented different phyllosphere composition, resulting in a richer viral community, when compared with the “Nebbiolo” plants. The observed effect on microbial communities pointed to the existence of distinct genotype-specific defense mechanisms independently of the elicitor application

Ozone Improves the Aromatic Fingerprint of White Grapes

Ozone, a powerful oxidative stressor, has been recently used in wine industry as sanitizing agent to reduce spoilage microflora on grapes. In this study, we evaluated ozone-induced metabolic and molecular responses during postharvest grape dehydration. Ozone increased the contents of total volatile organic compounds (VOCs), which have a great impact on the organoleptic properties of grapes and wines. Among terpenes, responsible for floral and fruity aroma, linalool, geraniol and nerol were the major aromatic markers of Moscato bianco grapes. They were significantly affected by the long-term ozone treatment, increasing their concentration in the last phases of dehydration (>20% weight loss). At molecular level, our results demonstrated that both postharvest dehydration and ozone exposure induce the biosynthesis of monoterpenes via methylerythritol phosphate (MEP) pathway and of aldehydes from lipoxygenase-hydroperoxide lyase (LOX-HPL) pathway. Therefore, transcriptional changes occurred and promoted the over-production of many important volatile compounds for the quality of white grapes