The effects of calcite silicon-mediated particle film application on leaf temperature and grape composition of Merlot (Vitis vinifera L.) vines under different irrigation conditions

This study examined whether the application of calcite-silicon mediated particle film (CaPF) at veraison can mitigate a drought-induced increase in leaf temperature on grapevine, thus contributing to improved leaf functionality, yield and grape composition traits. A total of 48 five-year-old Merlot (Vitis vinifera L.) vines grafted onto SO4 were grown (in 20 L PVC pots) under Mediterranean conditions (Southern Italy). The vines were pruned to two spurs with two winter buds irrigated daily to 100 % field capacity, and fertilised weekly. At veraison and using a 2×2 factorial experimental design, the two main factors, thermoregulation and water, were imposed at two levels: spraying with a thermoregulation compound (CaPF) and no spraying (NS); irrigation (WW) and drought stress (D)). A group of 24 vines was subjected to a 15-day drought period by receiving, every day, 25 % (D) of the daily water consumption of WW vines. The other 24 vines continued to be fully irrigated on a daily basis (WW). Twelve vines per group were sprayed (WW+CaPF, D+CaPF) with calcite-silicon mediate (3 % V/V) at the beginning of drought imposition, the remaining 24 vines were not sprayed (WW-NS, D-NS). Soil water moisture and stem water potential values were monitored from 11.30 to 13:30 nearly every week, and other vegetative and reproductive parameters were also measured. During the experiment, air temperature peaked at ≈35 °C at midday, VPD at about 3.7 kPa and PAR reached ≈2000 µmol m-2 s–1. Results show that in CaPF sprayed vines, leaf-air temperature differences were lower than in unsprayed vines in both irrigated and drought stressed groups. WW+CaPF vines retained significantly more leaf area and showed the highest value of accumulated vine transpiration. Calcite-silicon mediated particle film could enhance the resilience of grapevine to adverse environmental conditions and may contribute to preserve terroir elements in highly reputed wine grape growing areas. The study showed that foliar application of calcite silicon-mediated processed particles films can be used in arid regions to mitigate leaf temperatures in grapevines

A synthetic cytokinin primes photosynthetic and growth response in grapevine under ion-independent salinity stress

Aiding optimal plant–environment interaction would favor plant resilience against environmental constrains including salt stress. We test the hypothesis that 6-Benzylaminopurine (BAP) primes grapevine’s salt tolerance in vines (Vitis vinifera) received salt water (NaCl 100 mM) through the modulation of gene expression of BAP (AHK4, AHP1) and salt-stress (CAT, APX) inducible genes and morpho-physiological traits. A subgroup of vines had previously (48 h) been primed with BAP (80 mg/L) before salt stress. The gene expressions were 30% (CAT) and 56% (APX) lower in primed salt-stressed vines than that in un-primed. Salt treatment did not increase leaf Na+ but it lowered stomatal conductance (g s), photosynthesis (A), stem water potential (less negative) and photosystem-II efficiency (F v/F m). Chlorophyll-a concentrations were 30% higher in BAP-primed compared to un-primed. Adverse effects of salt were significantly reduced, maintaining high A/g s, F v/F m and growth. After the relief of the stress, the BAP primed vines had a fast recovery

The Genome of a Pathogenic Rhodococcus: Cooptive Virulence Underpinned by Key Gene Acquisitions

We report the genome of the facultative intracellular parasite Rhodococcus equi, the only animal pathogen within the biotechnologically important actinobacterial genus Rhodococcus. The 5.0-Mb R. equi 103S genome is significantly smaller than those of environmental rhodococci. This is due to genome expansion in nonpathogenic species, via a linear gain of paralogous genes and an accelerated genetic flux, rather than reductive evolution in R. equi. The 103S genome lacks the extensive catabolic and secondary metabolic complement of environmental rhodococci, and it displays unique adaptations for host colonization and competition in the short-chain fatty acid–rich intestine and manure of herbivores—two main R. equi reservoirs. Except for a few horizontally acquired (HGT) pathogenicity loci, including a cytoadhesive pilus determinant (rpl) and the virulence plasmid vap pathogenicity island (PAI) required for intramacrophage survival, most of the potential virulence-associated genes identified in R. equi are conserved in environmental rhodococci or have homologs in nonpathogenic Actinobacteria. This suggests a mechanism of virulence evolution based on the cooption of existing core actinobacterial traits, triggered by key host niche–adaptive HGT events. We tested this hypothesis by investigating R. equi virulence plasmid-chromosome crosstalk, by global transcription profiling and expression network analysis. Two chromosomal genes conserved in environmental rhodococci, encoding putative chorismate mutase and anthranilate synthase enzymes involved in aromatic amino acid biosynthesis, were strongly coregulated with vap PAI virulence genes and required for optimal proliferation in macrophages. The regulatory integration of chromosomal metabolic genes under the control of the HGT–acquired plasmid PAI is thus an important element in the cooptive virulence of R. equi

Proposal for Evaluating Plant Stress via Steady State Fluorescence

Chlorophyll fluorescence analysis is a powerful tool to estimate photosystem II (PSII) performance under standard or biotic or abiotic stress condition. An important limiting factor in measuring these chlorophyll fluorescence parameters in a high throughput phenomics system is the availability of a flashing light source, used to block the photosynthetic apparatus, that is large and homogeneous enough for whole plants. Until recently such systems were limited to smaller plants such as Arabidopsis. Instead larger phenomic systems were, and often still are, built with imaging chambers that measured chlorophyll fluorescence under steady state conditions. Under these conditions only a single fluorescence value for each image pixel is measured and the quantum efficiencies cannot be calculated. In this study we investigate the use of hue component of the HSI (hue, saturation, intensity) colour space, which is analogous to the light spectrum, from plant chlorophyll fluorescence light as a parameter to measure plant stress and compared it to those parameters derived from traditional chlorophyll fluorescence. kinetics. Tomato plants were treated to heat or drought stress and subsequently chlorophyll fluorescence kinetic measurements were taken as well as images at steady state fluorescence. By analysing the chlorophyll fluorescence hue channel we were able to detect differences from control plants in both the heat shocked and drought induced plants while the standard photosystem II yield measurement was only capable of measuring differences in the heat shocked plants. These results appear to suggest that the analysis of chlorophyll fluorescence light in the hue channel is capable of identifying perturbations due to abiotic stress in tomato plants. Currently we are continuing to investigate whether this method is applicable as a general method for more plant species and abiotic stresses

Drought phenotyping in Vitis vinifera using RGB and NIR imaging

This study examined whether morphophysiological traits (i.e., leaf area, plant water consumption, leaf water potential) of drought stressed grapevines (Vitis vinifera L.) might be determined through the use of non-destructive RGB and NIR image-based analysis techniques for possible implementation of affordable phenotyping. The study was carried out at a centre which is part of the European Plant Phenotyping Network (EPPN) also aiming at contribute to the standardisation of phenotyping protocols. Four groups of 20 potted vines each were subjected to various irrigation treatments restoring 100% (control), 75% (IRR75%), 50% (IRR50%) and 25% (IRR25%) of their daily water consumption within a 22-day period of drought imposition. Leaf gas exchanges, leaf water potential (Ψ), photosystem II efficiency (Fv/Fm), RGB and NIR data were simultaneously collected during drought imposition. Values of Ψ in IRR25% vines reached −1.2 MPa pre-dawn, in turn stomatal conductance and net photosynthetic rate reached values as low as approx. 0.02 mol H2O m−2 s–1 and 1.0 μmol CO2 m−2 s–1, respectively. Through a cross-validation analysis, this study modelled (R2 = 0.78) the estimation of plant canopy area based on the number of pixel of RGB images of vines under various drought levels. Estimated leaf area was employed to calculate water consumption per unit leaf area, which resulted correlated (R2 = 0.86) with Ψ. Results revealed a correlation between Ψ and Dark Green colour class (R2 = 0.71) and suggest a new working hypothesis concerning the phenotyping of leaf (or petiole) angle. NIR and Dark Green colour fraction decreased with increasing levels of drought while the Yellow one increased. The outcomes presented may strengthen the role of RGB and NIR based images to identify the occurrence of water-stress in Vitis spp. and contribute to both the standardisation of phenotyping protocols pursued by the global phenotyping community and the possible development of new tools for precision irrigation in a HTP domain