Identification of putative chemical markers in white wine (Chasselas) related to nitrogen deficiencies in vineyards

Aim: Wine quality is influenced by the nitrogen nutrition of grapevines in the vineyard. A deficiency of this nutrient will affect grape quality, decrease yeast available nitrogen (YAN) and influence alcoholic fermentation. Chasselas wines from nitrogen-deficient grapes (YAN < 140 mg N/L) are systematically more astringent and bitter and less fruity than those from grapes with higher YAN content (Spring et al., 2014). The aim of this study was to identify chemical markers in wine linked to nitrogen deficiencies in the vineyard.Methods and results: Wine samples produced from grapes growing in nitrogen-deficient vineyards with nitrogen treatment (HN) and without it (LN) were used over four consecutive years (2006–2009). They were all analysed at the same time (2012) with electronic-nose, GC-MS and UHPLC-TOFMS techniques. A metabolomics approach was used for a comprehensive survey of volatile and nonvolatile compounds in order to identify markers related to nitrogen nutrition. Volatile markers with alcohol and ester functions and nitrogen-containing compounds were found and tentatively identified by GC-MS. Additionally, 16 nonvolatile markers were putatively identified by UHPLC-TOFMS, including compounds from diverse chemical classes, namely, amino acids, vitamins, hormones, organic acids, phenolic compounds and polysaccharides.Conclusion: The nitrogen nutrition of grapevines has a clear but complex effect on the chemical composition of wine. Several markers were tentatively identified and their role in wine composition discussed according to the actual knowledge reported in the literature.Significance of the study: This study is an important starting point for selecting the most relevant chemical markers in wine, and for determining whether organoleptic problems are related to nitrogen nutrition deficiency in the vineyard and changes in vineyard management are needed.

Cross-ecosystem transcriptomics identifies distinct genetic modules for nutrient acquisition in maize

Plants have evolved diverse strategies for the acquisition of the macro-nutrients phosphorus and nitrogen; e.g., mycorrhizal formation, root development, and secretion of chelators/hydrolases to liberate inorganic phosphate. Despite the extensive studies on the individual strategies, there is little information about how plants regulate these strategies in response to fluctuating environment. We approached this issue via profiling transcriptomes of plants grown in large environmental gradients. Roots, leaves, and root-zone soils of 251 maize plants were collected across the US Corn Belt and Japan. RNA was extracted from the roots and sequenced, and the leaves and soils were analyzed. Nineteen genetic modules were defined by weighted gene coexpression network analysis and functionally characterized according to gene ontology analysis, by which we found three modules that are directly involved in nutrient acquisition: mycorrhizal formation, phosphate-starvation response (PSR), and root development. Correlation analysis with soil and plant factors revealed that both phosphorus and nitrogen deficiencies upregulated the mycorrhizal module, whereas the PSR module was upregulated mainly by deficiency in phosphorus relative to nitrogen. Expression levels of the root development module were negatively correlated with those of the mycorrhizal module, suggesting that nutrient acquisition through the two pathways, mycorrhizas and roots, are opposite strategies that are employed under nutrient-deficient and -enriched conditions, respectively. The identification of the soil and plant factors that drive the modules has implications for sustainable agriculture; activation/optimization of the strategies is feasible via manipulating the factors. Overall, our study opens a new window for understanding plant response to complex environments.

Determination of Nutrient Supplementation by Means of ATR-FTIR Spectroscopy during Wine Fermentation

Nitrogen is a limiting factor for the development of wine alcoholic fermentation. The addition of nutrients and different nitrogen sources is a usual practice for many winemakers. Currently, there is a market trend toward wine that is additive-free and there are also restrictions on the amount of ammonium fermentation agents that can be added to the wine. In this work, the changes produced on the alcoholic fermentation by the addition of different nitrogen sources were evaluated by the use of ATR-FTIR. The results showed the feasibility of this technique to observe differences in the growth yeast capacity depending on the type of the nutrients added. A high influence on the development of the alcoholic fermentation was observed, especially at its exponential and the stationary phases. Moreover, the changes observed in the recorded spectra were related to the proteins and lipid esters composition of the yeast cell wall. This technique should be a useful tool to evaluate nitrogen deficiencies during winemaking although further studies should be done in order to evaluate more influential factors.

Fruit Phosphorous and Nitrogen Deficiencies Affect ‘Grand Pearl’ Nectarine Flesh Browning

Fruit flesh browning (FB) is a major component of cold storage disorders that limits fresh and fresh cut fruit consumption. Using fertigation, nutrient deficiencies were imposed on ‘Grand Pearl’ nectarines (Prunus persica var. nectarina) grown in sand culture for 8 years and postharvest flesh browning was studied over 2 years. Antioxidant activity, polyphenol oxidase activity, total phenolics, and fruit FB potential were evaluated. Nutrient deficiencies did not always result in leaf or fruit tissue deficiency, indicating complex interactions among nutrients during uptake and use in the plant and its fruit. Low phosphorus and nitrogen fruit concentrations were associated with biochemical browning reactions in fruit flesh at harvest and with fruit FB during storage, signs of a shorter market life and lower consumer quality. Currently recommended leaf and fruit nutrient critical values are based only on production and do not address postharvest quality. Further research is needed to determine new recommended leaf and fruit nutrient values suitable for both production and maintaining fruit quality during storage.

The impact of source or sink limitations on yield formation of winter wheat (Triticum aestivum L.) due to post-anthesis water and nitrogen deficiencies

The experiments were laid out to understand the mechanisms causing yield limitations imposed by post-anthesis water and nitrogen deficiencies in plants with modified source-sink ratios. Two soil-water regimes were allotted to the main plots. At anthesis, three levels of N were applied: none, 25% and 50% of total the N supply. Spike-halving caused reduction in grain yield at both water regimes and all N supply levels, showing that the reduction in grain number can not be compensated by a higher individual grain weight. Sink reduction by trimming 50% of the spikelets reduced grain number per ear by 38.5% and increased individual grain weight by 12.0%, which shows the plasticity in grain weight and grain set of wheat if sufficient assimilates are available. Additional nitrogen supply at anthesis had no significant effect on the total aboveground biomass, but increased grain yield through more allocation of dry matter to grains. Our findings suggest that for rainfed wheat with optimum N supply and supplemental irrigation, wheat growers should choose cultivars with a high grain number per ear and manage the crop to increase grain number per unit of land (sink capacity).