Using rootstocks to lower berry potassium concentrations in 'Cabernet Sauvignon' grapevines

Potassium is the most abundant cation in grape berries. It has important roles in grapevine physiology and winemaking. This study investigates the feasibility of using rootstocks to lower berry potassium concentrations ([K]) in 'Cabernet Sauvignon' grapevines. The ultimate target is to achieve lower pH and higher titratable acidity (TA) in grape juice so as to bring down the cost of acid adjustment during winemaking. The specific objective here is to provide new insights into the potential of particular rootstocks to modify K uptake by 'Cabernet Sauvignon' grapevines and their partitioning and accumulation into grape berries. The vineyard soils of a replicated rootstock trial located in the Limestone Coast of South Australia were characterised. Petiole, berry and juice nutrient content were assessed at oenological maturity of 'Cabernet Sauvignon' grown on eight different rootstocks. Rootstock had an impact on cations of the vegetative tissue of 'Cabernet Sauvignon', with Merbein 5512 having the lowest petiole [K]. The concentrations of major cations in the berry were, however, not altered by rootstock. While no particular rootstock stood out in limiting 'Cabernet Sauvignon' berry K accumulation, berries grown on the 'Börner' rootstock tended to have slightly lower concentrations (< 10 %) relative to vines on their own roots. Across the rootstocks, juice pH tended to increase with greater juice [K], while juice TA tended to decrease with greater juice [K]. It was found that juice TA was higher for the rootstocks 140 Ruggeri and 110 Richter, and juice pH tended to be lower for the rootstocks 110 Richter, 140 Ruggeri, Merbein 5512 and Merbein 5489. There was no effect of rootstock on total soluble solids.Zeyu Xiao, K. A. DeGaris, T. Baby, S. J. McLoughlin, B. P. Holzapfel, R. R. Walker, L. M. Schmidtke, and S. Y. Rogier

Vascular connections into the grape berry: the link of structural investment to seededness

Vascular bundles in the grape pedicel and berry contain the conduits, phloem and xylem, for transport of water, sugar, nutrients and signals into and through the grape berry and play a critical role in berry growth and composition. Here, we assess the vascular anatomy within the proximal region of the berry. Guided using a 3D berry model generated by micro-CT, differential staining of transverse sections of berries and receptacles was followed by fluorescent microscopy. Morphometric and vascular characteristics were analyzed within the central proximal region (brush zone, a fibrous extension from the pedicel vascular system into the berry) of the seeded cultivars Shiraz and Sauvignon Blanc, as well as the stenospermocarpic cultivars Ruby Seedless and Flame Seedless. Observations revealed a change in vascular arrangement from the receptacle into the berry brush zone and differences in xylem element size as well as xylem and phloem area relationships. Xylem anatomical and derived hydraulic parameters, as well as total tissue area of xylem and phloem varied between cultivars and in receptacle and berry components. Variation in vascular growth between grape pedicels and berries was independent of seededness. Differences in receptacle xylem vessel size and distribution could contribute to cultivar-dependent xylem backflow constraint.Zeyu Xiao, Sabrina Chin, Rosemary G. White, Aude M. Gourieroux, Vinay Pagay, Stephen D. Tyerman, Leigh M. Schmidtke and Suzy Y. Rogier

3D visualisation of voids in grapevine flowers and berries using X‐ray micro computed tomography

First published: 06 January 2021Background and Aim: X-ray micro computed tomography (micro-CT) is a non-destructive 3D imaging technique that has been applied to plant morphology and anatomical studies to gain a better understanding of physiological phenomena in vivo. It is particularly useful for imaging voids in undisturbed fragile tissues and therefore may be applied to the delicate flowers and soft berries of Vitis vinifera. The characterisation of gas spaces and channels can offer insights into the process of tissue aeration and this may have implications on cell function and vitality. We assessed the use of micro-CT to visualise voids within these reproductive organs. Methods and Results: The internal structures of flowers and berries were captured through rapid micro-CT scanning and subsequently were recreated in 3D using image processing. The relative positions of the developing flower parts encased within the flower cap were visualised. Low density/porous tissue was identified within the pedicel and receptacle, con- necting the lenticels with the interior of the berry. Voids were present in the proximal mesocarp of mature berries forming a ‘detachment zone’ in both seeded and seedless cultivars. Voids permeated the mesocarp of mature seedless grape cultivars, but not seeded grapes. Conclusion: Micro-CT offers new insights regarding the distribution of voids on the morphology and compositional hetero- geneity of organs that are difficult to dissect and/or view with light microscopy. Significance of the Study: A better understanding of the physiology and functionality of grapevine reproductive tissues may be achieved by 3D visualisation of internal structure in vivo.Z. Xiao, T. Stait-Gardner, S.A. Willis, W.S. Price, F.J. Moroni, V. Pagay … et al

The role of fruit exposure in the late season decline of grape berry mesocarp cell vitality

Available online 27 November 2018Loss of cell vitality in the mesocarp of grape (Vitis vinifera L.) berries during late ripening is programmed and under genetic control. Environmental factors such as temperature and vine water status, however, have a strong influence on the onset and extent of cell death. Following preliminary observations made on field experiment fruit, the hypothesis that exposure (increased light interception and wind velocity) at the berry level is important to the progression of cell death was tested. Transpiration, mesocarp cell vitality and total soluble solids concentration were compared in exposed and sheltered berries within single Shiraz vines. At oenological maturity (24 °Brix), exposed berries exhibited the same extent of cell death as sheltered berries, and it was not until four weeks later that cell death was more extensive in the exposed treatment. Therefore, under the conditions of this study, increased exposure over the ripening period was not a strong predictor of the extent of cell vitality at maturity. However, the results are consistent with an increase in the importance of environmental effects (including rain and exposure) on mesocarp cell death over the course of berry development, particularly in overripe fruit.Simon J. Clarke, Suzy Y. Rogier

Effect of water stress and elevated temperature on hypoxia and cell death in the mesocarp of Shiraz berries

Background and Aim: Berry shrivel during ripening is cultivar dependent and is correlated with berry cell death (CD). We hypothesised that under heat stress and water stress, regions of the pericarp in Shiraz berries would become hypoxic depending on berry porosity, and that this would induce CD. Methods and Results: We measured CD and [O₂] across the pericarp in berries developed under the factorial combination of two thermal regimes (ambient and heated) and two irrigation regimes (irrigated and non-irrigated) in the Barossa Valley, South Australia. Heating increased ambient temperature by 0.6°C for irrigated and 1°C for non-irrigated vines but had no effect on water relations, while non-irrigation decreased stomatal conductance and stem water potential. Non-irrigation decreased berry [O₂] and increased both CD and ethanol concentration relative to irrigation. An association was established between mesocarp [O₂] and CD. Berry respiration and total berry porosity decreased during berry ripening, but relative locule air-space measured by X-ray micro-computed tomography increased late in ripening. Heating had little or no effect on CD or [O₂] but decreased berry porosity, which was not affected by irrigation. Conclusion: Water stress increased berry CD, which was associated with increased hypoxia. Significance of the Study: The association between berry [O₂] and CD provides insights into berry ripening with implications for yield and berry flavour.Z. Xiao, S. Liao, S.Y. Rogiers, V.O. Sadras and S.D. Tyerma

Effect of water stress and elevated temperature on hypoxia and cell death in the mesocarp of Shiraz berries

Background and Aim: Berry shrivel during ripening is cultivar dependent and is correlated with berry cell death (CD). We hypothesised that under heat stress and water stress, regions of the pericarp in Shiraz berries would become hypoxic depending on berry porosity, and that this would induce CD. Methods and Results: We measured CD and [O2] across the pericarp in berries developed under the factorial combination of two thermal regimes (ambient and heated) and two irrigation regimes (irrigated and non-irrigated) in the Barossa Valley, South Australia. Heating increased ambient temperature by 0.6°C for irrigated and 1°C for non-irrigated vines but had no effect on water relations, while non-irrigation decreased stomatal conductance and stem water potential. Non-irrigation decreased berry [O2] and increased both CD and ethanol concentration relative to irrigation. An association was established between mesocarp [O2] and CD. Berry respiration and total berry porosity decreased during berry ripening, but relative locule air-space measured by X-ray micro-computed tomography increased late in ripening. Heating had little or no effect on CD or [O2] but decreased berry porosity, which was not affected by irrigation. Conclusion: Water stress increased berry CD, which was associated with increased hypoxia. Significance of the Study: The association between berry [O2] and CD provides insights into berry ripening with implications for yield and berry flavour

Evidence of Bi-Directional Volatile-Mediated Communication between Drought-Stressed and Well-Watered Grapevines (Vitis vinifera L.)

The volatile-mediated interplay between stressed and non-stressed plants has been described in many studies involving both biotic and abiotic stresses as a one-way channel. However, very little is known about the molecular basis and mechanisms by which volatile organic compounds (VOCs) mediate plant communication between drought-stressed ‘emitter’ plants and non-stressed ‘receiver’ neighbours for the defence against impending stress challenges. Aiming to address this in grapevine, this study investigated the effect of two-way VOC exchange between stressed and non-stressed Vitis vinifera L. cv. Shiraz during drought and recovery using four treatments: isolated well-watered (WW) vines, isolated drought-stressed (DS) vines, and co-located DS ‘emitter’ and WW ‘receiver’ vines in a growth room. The results obtained from solid-phase microextraction (SPME) gas chromatography mass spectrometry (GC-MS) analysis showed a synchronised decline in α-pinene concentration in the co-located treatment vines and higher isoprene levels in the DS emitters compared to the isolated DS vines. Targeted gene expression analysis further identified the over-expression of a key gene, allene oxide synthase (AOS), in the jasmonic acid (JA) biosynthesis pathway during peak drought in the DS emitter. Transcript expression of chorismate synthase (CHORS) and α-pinene synthase (VvPNaPin1) showed similar trends in the DS emitter. The results suggest that isoprene and α-pinene may be interplant signalling molecules used by grapevine during drought. To the best of our knowledge, this is the first report of a bi-directional interaction in grapevine between the emitters and receivers under drought stress mediated by the JA and terpenoid biosynthesis pathways.Joanah Midzi, David W. Jeffery, Ute Baumann, Dimitra L. Capone, Suzy Y. Rogiers, and Vinay Paga