Stem Xylem Characterization for Vitis Drought Tolerance

Climate Change Impacts on Plant Phenology: Grapevine (Vitis vinifera) Bud Break in Wintertime in Southern Italy

The effects of global warming on plants are not limited to the exacerbation of summer stresses; they could also induce dormancy dysfunctions. In January 2020, a bud break was observed in an old poly-varietal vineyard. Meteorological data elaboration of the 1951–2020 period confirmed the general climatic warming of the area and highlighted the particular high temperatures of the last winter. Phenological records appeared to be significantly correlated to wood hydration and starch reserve consumption, demonstrating a systemic response of the plant to the warm conditions. The eight cultivars, identified by single-nucleotide polymorphism (SNP) profiles and ampelographic description, grown in this vineyard showed different behaviors. Among them, the neglected Sprino, Baresana, Bianco Palmento, and Uva Gerusalemme, as well as the interspecific hybrid Seyve Villard 12.375, appeared to be the most interesting. Among the adaptation strategies to climate changes, the cultivar selection should be considered a priority, as it reduces the inputs required for the plant management over the entire life cycle of the vineyard. Hot Mediterranean areas, such as Salento, are a battlefront against the climate change impacts, and, thus, they represent a precious source of biodiversity for viticulture.

Multi-parameter characterization of water stress tolerance in Vitis hybrids for new rootstock selection

Drought in grapevine could be faced using tolerant rootstocks. The present work aims at the evaluation of 25 new genotypes potentially tolerant to drought by using recent methods of phenotypical screening (thermography and on-solid reaction spectroscopy). Plants were grown in well-watered and stressed field conditions. Proxi for transpiration, wood hydrophobicity and starch content were used to characterize and classify the genotypes. The predominant role of the environment was highlighted, nevertheless genotype and genotype × environment interaction showed significant variations as well. Hybrids were classified based on their steady, susceptible or adaptable behavior. The 14 most promising genotypes were identified, 5 of them showing two tolerance mechanisms. In the future, results from this experiment will support viticulture in water limited areas releasing new drought-tolerant interspecific hybrids to be tested after grafting with different scions.

Compound Synthesis or Growth and Development of Roots/Stomata Regulate Plant Drought Tolerance or Water Use Efficiency/Water Uptake Efficiency

Water is crucial to plant growth and development because it serves as a medium for all cellular functions. Thus, the improvement of plant drought tolerance or water use efficiency/water uptake efficiency is important in modern agriculture. In this review, we mainly focus on new genetic factors for ameliorating drought tolerance or water use efficiency/water uptake efficiency of plants and explore the involvement of these genetic factors in the regulation of improving plant drought tolerance or water use efficiency/water uptake efficiency, which is a result of altered stomata density and improving root systems (primary root length, hair root growth, and lateral root number) and enhanced production of osmotic protectants, which is caused by transcription factors, proteinases, and phosphatases and protein kinases. These results will help guide the synthesis of a model for predicting how the signals of genetic and environmental stress are integrated at a few genetic determinants to control the establishment of either water use efficiency or water uptake efficiency. Collectively, these insights into the molecular mechanism underpinning the control of plant drought tolerance or water use efficiency/water uptake efficiency may aid future breeding or design strategies to increase crop yield.

Utilization of a freeze-thaw treatment to enhance phenolic ripening and tannin oxidation of grape seeds in red (Vitis vinifera L.) cultivars

Phenolic ripening represents a major interest for quality wine producers. Nevertheless, climatic or genotypical limitations can often prevent optimal maturation process. During winemaking seeds can be easily separated and technologically processed to improve their quality. Relying on the key role of oxidation for phenolic ripening, a freeze-thaw treatment was proposed to improve the fruit quality for potential use in challenging growing conditions. The experiment was carried on in two distinctive viticultural areas, Michigan and Italy. Five cultivars (Cabernet Franc, Cabernet Sauvignon, Merlot, Pinot noir and Chambourcin) and six cultivars (Cabernet Sauvignon, Sangiovese, Syrah, Croatina, Barbera and Nebbiolo) were used in Michigan and Italy, respectively. Samples were collected at different phenological stages, to describe the natural ripening process and grape seeds were characterized before and after a freeze-thaw treatment. Colorimetric and spectrophotometric data highlighted similarities among natural and artificial seed ripening promising future applications for the wine industries.

Iron deficiency stimulates anthocyanin accumulation in grapevine apical leaves

Iron chlorosis is a diffuse disorder affecting Mediterranean vineyards. Beside the commonly described symptom of chlorophyll decrease, an apex reddening was recently observed. Secondary metabolites, such as anthocyanins, are often synthetized to cope with stresses in plants. The present work aimed to evaluate grapevine responses to iron deficiency, in terms of anthocyanin metabolism (reflectance spectrum, total anthocyanin content, HPLC profile and gene expression) in apical leaves of Cabernet sauvignon and Sangiovese grown in hydroponic conditions. Iron supply interruption produced after one month an increasing of anthocyanin content associated to a more stable profile in both cultivars. In Cabernet sauvignon, the higher red pigment accumulation was associated to a lower intensity of chlorotic symptoms, while in Sangiovese, despite the activation of the metabolism, the lower anthocyanin accumulation was associated to a stronger decrease in chlorophyll concentration. Gene expression data showed a significant increase of anthocyanin biosynthesis. The effects on the expression of structural and transcription factor genes of phenylpropanoid pathway were cultivar dependent. F3H, F3'H, F3'5'H and LDOX genes, in Cabernet sauvignon, and AOMT1 and AOMT genes, in Sangiovese, were positively affected by the treatment in response to iron deficiency. All data support the hypothesis of an anthocyanin biosynthesis stimulation rather than a decreased degradation of them due to iron chlorosis.

Characterization of iron deficiency symptoms in grapevine (Vitis spp.) leaves by reflectance spectroscopy

The work aims at the description of the iron deficiency symptoms in grapevine leaves by reflectance spectroscopy at the plant and leaf levels. 5 genotypes of Vitis spp. were selected and grown in hydroponic conditions with and without iron supply. 450 spectra were collected among basal, young and apical leaves, as well as veins and interveinal areas. Iron deficiency produced significant and characteristic modifications in the pigment accumulation, proportion and distribution in plants. Basal leaves resulted to have higher concentrations of photosynthetic pigments in stressed plants with respect to the control, probably due to compensation effects. Iron deficient plants had lower chlorophyll concentrations in young and apical leaves. In the apical zone, also the relative composition of pigments appeared to be modified, explaining the reddish-yellowish apex appearance of iron deficient vines. Finally, the pigment distribution along the shoot characterized the symptoms, as well as the spectral variations among veins and interveinal areas. These results could support future applications in vineyard management (e.g.: symptom identification and detection; precision fertilization) as well as breeding programs for new rootstock selections (e.g.: fast screenings of seedlings).