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Time vs drought: leaf age rather than drought drives osmotic adjustment in V. vinifera cv. Pinot Noir
Elena Farolfi, Francesco Flagiello, Federica De Berardinis, Soma Laszlo Tarnay, Jan Reščič, Astrid Forneck, Jose Carlos Herrera, 2023, published scientific conference contribution abstract

Abstract: Global warming and increased frequency and/or severity of drought events are among the most threatening consequences of climate change for agricultural crops. In response to drought, grapevine (as many other plants) exhibits osmotic adjustment through active accumulation of osmolytes which in turn shift the leaf turgor loss point (TLP) to more negative values, allowing to maintain stomata opened at lower water potentials1. We investigated the capacity of Pinot noir leaves to modulate their osmotic potential as a function of: (i) time (seasonal osmoregulation), (ii) growing temperatures, and (iii) drought events, to enhance comprehension of the resilience of grapevines in drought conditions. We performed trails under semi-controlled field conditions, and in two different greenhouse chambers (20/15 °C vs 25/20 °C day/night). For two consecutive vegetative seasons, grafted potted grapevines (Pinot noir/SO4) were subjected to two different water regimes for at least 30 days: well-watered (WW) and water deficit (WD). Via pressure-volume (PV) curves and osmometer measurements we derived the leaf osmotic adjustment capability and TLP, while monitoring the plant gas exchange and water potential. Surprisingly, lower water potentials in WD vines throughout the season and in all situations (field and greenhouse) did not trigger osmoregulation, changes in TLP nor a modification of the modulus of elasticity. PV curves provided clear evidence that both temperature and water availability do not stimulate active osmotic adjustment in Vitis vinifera cv. Pinot Noir. Conversely, there is a clear impact of seasonal osmoregulation throughout the growing season2, decreasing the osmotic potential at full turgor by an average of 0.46 MPa in 90 days. Lack of osmotic adjustment in response to drought observed in this cultivar suggests Vitis genotypes have a broad spectrum of responses to drought and the strategy adopted to cope with it is highly dependent on the cultivar under analysis.
Keywords: grapevine, drought, osmotic adjustment, osmoregulation, turgor loss point
Published in RUNG: 21.11.2023; Views: 191; Downloads: 0
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Biological role of Grapevine fanleaf virus (GFLV) in winegrowing region of Northern Primorska
Anastazija Jež Krebelj, 2015, doctoral dissertation

Abstract: Grapevines (Vitis vinifera L.) represent one of the most important crops in the world in terms of both production and economic importance. Grapevines are exposed to many types of abiotic stresses (e.g., drought, flooding, low and high temperature, salinity) and biotic stresses (e.g., viruses, bacteria, phytoplasma, fungal disease) during their life-cycle. Therefore, grapevines elicit the appropriate defence mechanisms. In the first part of this study, we monitored the occurrence of Grapevine fanleaf virus (GFLV) infection, which causes progressive decline of infected grapevines and lowers their yield. Grapevines were also tested for the presence of other viruses important for grapevines: Arabis mosaic virus (ArMV), Grapevine leafroll associated virus (GLRaV)-1, -2, -3, -4, -9, Grapevine virus A (GVA), Grapevine fleck virus (GFkV) in this study; and by Cigoj (2015): Grapevine virus B (GVB), Tomato black ring virus (TBRV), Grapevine chrome mosaic virus (GCMV), Tomato ringspot virus (ToRSV), Raspberry ringspot virus (RpRSV), Strawberry latent ringspot virus (SLRSV), and Tobacco ringspot virus (TRSV). Using ELISA, the presence of the following grapevine viruses were detected: GFLV, (GFkV), (GVA), and Grapevine leafroll associated viruses- 1, -2, -3,. A wide range of GFLV symptoms caused by grapevine fanleaf disease in naturally infected vineyards were observed, including leaf, shoot and cluster malformations and leaf yellowing. GFLV is disseminated by its biological vector X. index, and through vegetative propagation of virus-infected material. The spread of GFLV in the vineyards was investigated here. We constructed a spatio-temporal study of the GFLV titres during the seasons and throughout the grapevine, for its distribution in different grapevine organs through the season. This study shows that young leaves have high virus titres through the whole vegetative period, while mature leaves, tendrils and flower/ berry clusters only have high titres at the beginning of the vegetative period. The seeds retain high virus titres after berry colouring. Phloem scrapings were shown to contain lower virus titres during the vegetative period, with an increase outside and at the beginning of the vegetative period. In flower/ berry clusters, mature leaves and tendrils, the GFLV titres decrease significantly over the vegetative period. Additionally, different GFLV titres were shown in five different cultivars, and different combinations of mixed infections with other grapevine viruses influenced the GFLV titre differently. Finally, correlation between the magnitude of symptom appearance and GFLV titres was analysed. Grapevines adapt to abiotic stresses and biotic stresses by the expression of a wide range of stress-responsive genes, which are thought to have key roles in stress tolerance and survival. SWP of the infected grapevines through the season was lower than SWP measured for healthy grapevines. For both seasons, there were significant differences in SWP measurements between healthy and GFLV-infected grapevines of ‘Schioppettino’ trained using the single Guyot training system. SWP and RHC of the GFLV-infected grapevines were reduced compared to the healthy controls. The water deficit triggered the production of ABA, which induced the expression of the stress-related gene RD22. Additionally, this study shows that the WRKY gene that is involved in the ABA signalling network is regulated by water deficit. Plant defence responses to water stress also included up-regulation of the F3H2 and LDOX genes, which are involved in anthocyanins synthesis. GFLV infection significant impacted upon the expression of genes involves in ABA biosynthesis, as NCED1 and NCED2, and upon two genes involved in the early stages of anthocyanins synthesis, as CHS2 and F3H1. We also showed that the combination of grapevine cultivar, training system, and environmental conditions impacts on gene expression
Keywords: Vitis vinifera L., grapevine, Grapevine fanleaf virus, GFLV, grapevine disease, virus titre, distribution, fluctuation, ELISA, qPCR, ABA, drought, water status, water deficit, SWP, RHC, anthocyanins, gene expression
Published in RUNG: 27.07.2015; Views: 7896; Downloads: 411
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