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K is the most abundant cation in the grape berry. Here we focus on the most recent information in the long distance transport and partitioning of K within the grapevine and postulate on the potential role of K in berry sugar accumulation, berry water relations, cellular growth, disease resistance, abiotic stress tolerance and mitigating senescence. By integrating information from several different plant systems we have been able to generate new hypotheses on the integral functions of this predominant cation and to improve our understanding of how these functions contribute to grape berry growth and ripening. Valuable contributions to the study of K in membrane stabilization, turgor maintenance and phloem transport have allowed us to propose a mechanistic model for the role of this cation in grape berry development.

Under salinity, Vitis spp. rootstocks can mediate salt (NaCl) exclusion from grafted V. vinifera scions enabling higher grapevine yields and production of superior wines with lower salt content. Until now, the genetic and mechanistic elements controlling sodium (Na+) exclusion in grapevine were unknown. Using a cross between two Vitis interspecific hybrid rootstocks, we mapped a dominant quantitative trait locus (QTL) associated with leaf Na+ exclusion (NaE) under salinity stress. The NaE locus encodes six high-affinity potassium transporters (HKT). Transcript profiling and functional characterization in heterologous systems identified VisHKT1;1 as the best candidate gene for controlling leaf Na+ exclusion. We characterized four proteins encoded by unique VisHKT1;1 alleles from the parents, and revealed that the dominant HKT variants exhibit greater Na+ conductance with less rectification than the recessive variants. Mutagenesis of VisHKT1;1 and TaHKT1.5-D from bread wheat, demonstrated that charged amino acid residues in the eighth predicted transmembrane domain of HKT proteins reduces inward Na+ conductance, and causes inward rectification of Na+ transport. The origin of the recessive VisHKT1;1 alleles was traced to V. champinii and V. rupestris. We propose that the genetic and functional data presented here will assist with breeding Na+-tolerant grapevine rootstocks.

Improving crop salinity management requires enhanced understanding of salinity responses of leaf and fine-root traits governing resource acquisition, ideally in relation to ion accumulation at intra- or inter-specific levels. We hypothesized that these responses are coupled towards integrated resource conservation for plants under prolonged salt treatment. We tested the hypothesis with a glasshouse experiment on saplings of six contrasting Prunus hybrids, subjected to either control or salt treatment (reverse osmosis water versus 3.3 dS m -1 chloride solution containing mixed cations). Sample collections were carried out at 30 and at 60 days after the start of treatments. All six hybrids showed significantly higher lamina chloride concentration in response to salt treatment, with GF677 accumulating a lower concentration than the other five hybrids. There was significantly lower specific leaf area (SLA) in ‘Monegro’ and lower root tissue density (RTD) in ‘Nemaguard’ after 60 days – but not 30 days – of salt treatment. No hybrid showed concurrent significant decrease of SLA and specific root surface area (SRA) under salt treatment. The a priori known salinity-sensitive hybrid ‘Nemaguard’ not only showed decreased RTD and a negative relationship between root biomass and salt treatment duration, but also showed increased SRA without notable change of average root diameter. Lamina chloride accumulation and leaf gas exchange response were closely correlated along a gradient towards resource conservation from control to salt-treated plants in all hybrids, which was orthogonal to another gradient characterized by a hybrid-dependent modification of SLA, SRA, RTD and percentage of root length within the finest diameter class. This study highlighted the intraspecific differential resource investment strategies, reflected by the hybrid-specific salinity-response coordination among leaf and fine-root acquisitive traits.

Grapevines ( Vitis vinifera L., Vvi ) on their roots are generally sensitive to salt-forming ions, particularly chloride (Cl – ) when grown in saline environments. Grafting V. vinifera scions to Cl – -excluding hybrid rootstocks reduces the impact of salinity. Molecular components underlying Cl – -exclusion in Vitis species remain largely unknown, however, various anion channels and transporters represent good candidates for controlling this trait. Here, two nitrate/peptide transporter family (NPF) members VviNPF2.1 and VviNPF2.2 were isolated. Both highly homologous proteins localized to the plasma membrane of Arabidopsis ( Arabidopsis thaliana ) protoplasts. Both were expressed primarily in grapevine roots and leaves and were more abundant in a Cl – -excluding rootstock compared to a Cl – -includer. Quantitative PCR of grapevine roots revealed that VviNPF2 . 1 and 2.2 expression was downregulated by high [NO 3 – ] resupply post-starvation, but not affected by 25 mM Cl – . VviNPF2.2 was functionally characterized using an Arabidopsis enhancer trap line as a heterologous host which enabled cell-type-specific expression. Constitutive expression of VviNPF2.2 exclusively in the root epidermis and cortex reduced shoot [Cl – ] after a 75 mM NaCl treatment. Higher expression levels of VviNPF2.2 correlated with reduced Arabidopsis xylem sap [NO 3 – ] when not salt stressed. We propose that when expressed in the root epidermis and cortex, VviNPF2.2 could function in passive anion efflux from root cells, which reduces the symplasmic Cl – available for root-to-shoot translocation. VviNPF2.2, through its role in the root epidermis and cortex, could, therefore, be beneficial to plants under salt stress by reducing net shoot Cl – accumulation.

This paper introduces GRover (the grapevine rover), an adaptable mobile platform for the deployment and testing of proximal imaging sensors in vineyards for the non-destructive assessment of trunk and cordon volume and pruning weight. A SICK LMS-400 light detection and ranging (LiDAR) radar mounted on GRover was capable of producing precise (±3 mm) 3D point clouds of vine rows. Vineyard scans of the grapevine variety Shiraz grown under different management systems at two separate locations have demonstrated that GRover is able to successfully reproduce a variety of vine structures. Correlations of pruning weight and vine wood (trunk and cordon) volume with LiDAR scans have resulted in high coefficients of determination (R2 = 0.91 for pruning weight; 0.76 for wood volume). This is the first time that a LiDAR of this type has been extensively tested in vineyards. Its high scanning rate, eye safe laser and ability to distinguish tissue types make it an appealing option for further development to offer breeders, and potentially growers, quantified measurements of traits that otherwise would be difficult to determine.

The root system provides the interface between the plant and the soil that is responsible for water and nutrient uptake and transport. We hypothesized that almond trees in the commercial production environment could adjust their root acquisitive traits with distance vertically and horizontally from driplines as adaptive responses to within-orchard reductions in irrigation and nitrogen inputs. We compared the responses of root acquisitive traits under four years of treatments ranging from +W+N (15 ML ha−1 water and 300 kg ha−1 nitrogen per season) to −W−N (10.5 ML ha−1 water and 160 kg ha−1 nitrogen per season, with −W involving a 30% reduction in irrigation and −N involving a 46% reduction in nitrogen). Roots (<3 mm) were sampled through soil coring in the winters of 2017, 2018, and 2019. Root sampling was conducted along the vertical gradient and along the horizonal gradient (0 cm, 80 cm, and 240 cm from the dripline). Four years of treatments highlighted that the data variation was driven mainly by the difference between the +W and −W treatments (along PC1). Further, the difference between −W−N (combined resource reduction) and the other three treatments (+W+N, +W−N, and −W+N) contributed to the data variation (along PC2). Also, the temporal dynamics of treatment effects over 2017, 2018, and 2019 suggested a temporally strengthened +W−N effect to increase root biomass, average root diameter, specific root surface area (SRA), and specific root length (SRL) at deeper soil depths and at greater soil distances from driplines. These findings on the spatial and temporal plasticity of traits representing root resource acquisition capabilities highlighted the important role of root systems in maintaining crop productivity under reduced irrigation and nitrogen inputs.

Background Salt tolerance in grapevine is associated with chloride (Cl − ) exclusion from shoots; the rate-limiting step being the passage of Cl − between the root symplast and xylem apoplast. Despite an understanding of the physiological mechanism of Cl − exclusion in grapevine, the molecular identity of membrane proteins that control this process have remained elusive. To elucidate candidate genes likely to control Cl − exclusion, we compared the root transcriptomes of three Vitis spp. with contrasting shoot Cl − exclusion capacities using a custom microarray. Results When challenged with 50 MM Cl − , transcriptional changes of genotypes 140 Ruggeri (shoot Cl − excluding rootstock), K51-40 (shoot Cl − including rootstock) and Cabernet Sauvignon (intermediate shoot Cl − excluder) differed. The magnitude of salt-induced transcriptional changes in roots correlated with the amount of Cl − accumulated in shoots. Abiotic-stress responsive transcripts (e.g. heat shock proteins) were induced in 140 Ruggeri, respiratory transcripts were repressed in Cabernet Sauvignon, and the expression of hypersensitive response and ROS scavenging transcripts was altered in K51-40. Despite these differences, no obvious Cl − transporters were identified. However, under control conditions where differences in shoot Cl − exclusion between rootstocks were still significant, genes encoding putative ion channels SLAH3 , ALMT1 and putative kinases SnRK2.6 and CPK s were differentially expressed between rootstocks, as were members of the NRT1 ( NAXT1 and NRT1.4 ), and CLC families. Conclusions These results suggest that transcriptional events contributing to the Cl − exclusion mechanism in grapevine are not stress-inducible, but constitutively different between contrasting varieties. We have identified individual genes from large families known to have members with roles in anion transport in other plants, as likely candidates for controlling anion homeostasis and Cl − exclusion in Vitis species. We propose these genes as priority candidates for functional characterisation to determine their role in chloride transport in grapevine and other plants.

Plant cation-chloride cotransporters (CCCs) have been implicated in conferring salt tolerance. They are predicted to improve shoot salt exclusion by directly catalyzing the retrieval of sodium (Na⁺ and chloride (Cl⁻) ions from the root xylem. We investigated whether grapevine (Vitis vinifera[Vvi]) CCC has a role in salt tolerance by cloning and functionally characterizing the gene from the cultivar Cabernet Sauvignon. Amino acid sequence analysis revealed that VviCCC shares a high degree of similarity with other plant CCCs. A VviCCC-yellow fluorescent protein translational fusion protein localized to the Golgi and the trans-Golgi network and not the plasma membrane when expressed transiently in tobacco (Nicotiana benthamiana) leaves and Arabidopsis (Arabidopsis thaliana) mesophyll protoplasts. AtCCC-green fluorescent protein from Arabidopsis also localized to the Golgi and the trans-Golgi network. InXenopus laevisoocytes, VviCCC targeted to the plasma membrane, where it catalyzed bumetanide-sensitive ³⁶Cl⁻, ²²Na⁺, and ⁸⁶Rb⁺ uptake, suggesting that VviCCC (like AtCCC) belongs to the Na⁺-K⁺-2Cl⁻ cotransporter class of CCCs. Expression ofVviCCCin an Arabidopsiscccknockout mutant abolished the mutant's stunted growth phenotypes and reduced shoot Cl⁻ and Na⁺ content to wild-type levels after growing plants in 50 mM NaCl. In grapevine roots,VviCCCtranscript abundance was not regulated by Cl⁻ treatment and was present at similar levels in both the root stele and cortex of threeVitisspp. genotypes that exhibit differential shoot salt exclusion. Our findings indicate that CCC function is conserved between grapevine and Arabidopsis, but neither protein is likely to directly mediate ion transfer with the xylem or have a direct role in salt tolerance.

BACKGROUND AND AIMS: The effect of rootstock on chloride (Cl⁻) and sodium (Na⁺) exclusion capacity and yield of Chardonnay and Shiraz was investigated in the final 2 years (2007/08 and 2008/09) of a long‐term (14‐year) saline irrigation trial. METHODS AND RESULTS: Chardonnay and Shiraz, on own roots and on nine rootstocks, were irrigated for the first 12 seasons with water of electrical conductivity (ECᵢw) of 2.1 dS/m, with 7.15 ML/ha the mean total applied. The final two seasons were years of water restrictions, where the vines were irrigated with water of (mean) ECᵢw of 1.65 dS/m at a seasonal application of 3.04 ML/ha. Vines on own roots had a relatively low yield, for example 2.0 kg/vine (Chardonnay) and 8.8 kg/vine (Shiraz), and a high concentration of both chloride and sodium in grape juice (>1000 mg/L for Chardonnay and >500 mg/L for Shiraz). Ramsey and 1103 Paulsen rootstocks produced a high yield of 11–12 kg/vine with Chardonnay, and Ramsey and C7 produced a high yield of 23.5–24.5 kg/vine with Shiraz. Chardonnay on C5 and Shiraz on C7 rootstocks had the lowest concentration of grape juice chloride and sodium (in each case <50 mg/L). CONCLUSIONS: Yield, a measure of salt tolerance, was positively correlated with rootstock‐conferred vigour, measured by scion pruning mass. Neither yield nor pruning mass correlated with the concentration of either chloride or sodium in grape juice or in trunk wood, except that Shiraz yield correlated negatively with trunk wood Cl⁻. SIGNIFICANCE OF THE STUDY: This is the first long‐term (>10 years) study to compare the effect of rootstocks on the tolerance of Chardonnay and Shiraz to salinity.

Under salinity, Vitis spp. rootstocks can mediate salt (NaCl) exclusion from grafted V. vinifera scions enabling higher grapevine yields and production of superior wines with lower salt content. Until now, the genetic and mechanistic elements controlling sodium (Na + ) exclusion in grapevine were unknown. Using a cross between two Vitis interspecific hybrid rootstocks, we mapped a dominant quantitative trait locus ( QTL ) associated with leaf Na + exclusion ( NaE ) under salinity stress. The NaE locus encodes six high‐affinity potassium transporters ( HKT ). Transcript profiling and functional characterization in heterologous systems identified Vis HKT 1;1 as the best candidate gene for controlling leaf Na + exclusion. We characterized four proteins encoded by unique Vis HKT 1;1 alleles from the parents, and revealed that the dominant HKT variants exhibit greater Na + conductance with less rectification than the recessive variants. Mutagenesis of Vis HKT 1;1 and Ta HKT 1.5‐D from bread wheat, demonstrated that charged amino acid residues in the eighth predicted transmembrane domain of HKT proteins reduces inward Na + conductance, and causes inward rectification of Na + transport. The origin of the recessive Vis HKT 1;1 alleles was traced to V. champinii and V. rupestris . We propose that the genetic and functional data presented here will assist with breeding Na + ‐tolerant grapevine rootstocks.