Verticillium dahliae
(Kleb.) is a soil-borne pathogen able to cause yield losses in eggplant,
Solanum melongena
L., one of the most important vegetable crops in the Mediterranean basin. In this ...study, an experiment was conducted to assess physiological and biochemical mechanisms modulating the interactions between
S. melongena
cv. Violetta di Rimini and
V. dahliae
strain VdGL16 in leaves at different age (mature, intermediate and young; ML, IL and YL) up to 25 days post artificial root inoculation (dpi). At 8 dpi, infected ML showed a marked reduction of photosynthetic rate (4-fold lower than controls) associated with stomatal (reduced stomatal conductance) and mesophyll (concomitant increase of intercellular CO
2
concentration) limitations. Cell membrane integrity was compromised, and phylloptosis/death occurred. At 8 and 18 dpi, stomatal closure (−40 and − 53%, respectively) and biochemical alterations occurred in IL. At 18 dpi, the consumption of secondary metabolites suggested that antioxidant- and antimicrobial-defence responses were activated. However, photoinhibition, oxidative stress and water deficit were observed at the end of the experiment. These mechanisms were observed also in YL, as confirmed by the strong increase of tannins (+46%) followed by accumulation of other phenylpropanoids. Despite plant growth being maintained, reduction of leaf area and water deficit occurred. This study highlights the capacity of eggplant to activate dynamic biochemical mechanisms in response to fungal infection, even in susceptible genotypes, a starting point for comparisons with resistant material for selection.
In their natural environment, date palms are exposed to chronic atmospheric ozone (O3) concentrations from local and remote sources. In order to elucidate the consequences of this exposure, date palm ...saplings were treated with ambient, 1.5 and 2.0 times ambient O3 for three months in a free-air controlled exposure facility. Chronic O3 exposure reduced carbohydrate contents in leaves and roots, but this effect was much stronger in roots. Still, sucrose contents of both organs were maintained at elevated O3, though at different steady states. Reduced availability of carbohydrate for the Tricarboxylic acid cycle (TCA cycle) may be responsible for the observed reduced foliar contents of several amino acids, whereas malic acid accumulation in the roots indicates a reduced use of TCA cycle intermediates. Carbohydrate deficiency in roots, but not in leaves caused oxidative stress upon chronic O3 exposure, as indicated by enhanced malonedialdehyde, H2O2 and oxidized glutathione contents despite elevated glutathione reductase activity. Reduced levels of phenolics and flavonoids in the roots resulted from decreased production and, therefore, do not indicate oxidative stress compensation by secondary compounds. These results show that roots of date palms are highly susceptible to chronic O3 exposure as a consequence of carbohydrate deficiency.
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•O3 affects roots rather than leaves as a consequence of strong carbohydrate deficiency.•Sucrose levels still were maintained at the expense of other carbohydrates.•Carbohydrate deficiency in the roots caused oxidative stress.
Wheat blast is a devastating disease caused by the
pathotype of
.
is capable of infecting leaves and spikes of wheat. Although symptoms of wheat spike blast (W
B) are quite distinct in the field, ...symptoms on leaves (W
B) are rarely reported because they are usually inconspicuos. Two field experiments were conducted in Bolivia to characterize the change in W
B and W
B intensity over time and determine whether multispectral imagery can be used to accurately assess W
B. Disease progress curves (DPCs) were plotted from W
B and W
B data, and regression models were fitted to describe the nature of W
B epidemics. W
B incidence and severity changed over time; however, the mean W
B severity was inconspicuous before wheat began spike emergence. Overall, both Gompertz and logistic models helped to describe W
B intensity DPCs fitting classic sigmoidal shape curves. Lin's concordance correlation coefficients were estimated to measure agreement between visual estimates and digital measurements of W
B intensity and to estimate accuracy and precision. Our findings suggest that the change of wheat blast intensity in a susceptible host population over time does not follow a pattern of a monocyclic epidemic. We have also demonstrated that W
B severity can be quantified using a digital approach based on nongreen pixels. Quantification was precise (0.96 <
> 0.83) and accurate (0.92 < ρ > 0.69) at moderately low to high visual W
B severity levels. Additional sensor-based methods must be explored to determine their potential for detection of W
B and W
B at earlier stages.
Verticillium spp., including V. nonalfalfae and V. dahliae, are known vascular wilt pathogens of the invasive Ailanthus altissima (tree-of-heaven) in the United States and in Europe. Herein we ...provide evidence of the presence of a previously unreported wilt disease of A. altissima in Tuscany (Central Italy). Several isolates were collected from two locations and identified as V. dahliae, based on microscopical features of conidiophores, conidia and microsclerotia. Genomic DNA was extracted from the mycelium, the ITS region was amplified and the sequence was deposited in GenBank as VdGL16 (accession no. MK474459). BLASTn analysis showed 100% similarity with V. dahliae. To confirm pathogenicity of VdGL16, inoculations of Ailanthus seedlings were performed with the root dipping technique whereas mature trees were stem-inoculated. All inoculated seedlings exhibited wilt symptoms after 20 days, while mature Ailanthus trees showed wilting and dieback after six months. The pathogen was easily re-isolated from seedlings and re-identified as V. dahliae, thus satisfying Koch’s postulates. Results from intraspecific resistance screening of nine seed sources from across Italy revealed that Ailanthus provenances from all the six sampled regions were susceptible to V. dahliae. Stem inoculated adult plants exhibited abundant production of epicormic sprouts along the stem within six months, and most of these sprouts wilted following initial dieback of the main stem; furthermore, sprouting from the crown was intense. Petioles and rachises tissues of leaves fallen from infected trees were a good source for re-isolation of the pathogen; we proved that such petioles and rachises can effectively transfer the fungus to healthy Ailanthus seedlings via root infections. Host-specificity of the V. dahliae isolate VdGL16 was also determined on 40 non-target species/varieties/cultivars. The isolate caused disease in herbaceous species belonging to five botanical families: Asteraceae, Lamiaceae, Leguminoseae, Linaceae and Solanaceae. Given the difficulties in countering Ailanthus invasion with mechanical and chemical methods, the biological control using Verticillium may provide an efficient, low cost and sustainable control of this invasive species.
•Genetic factors did not influence the Verticillium dahliae-Ailanthus pathosystem.•Different Ailanthus provenances are not related to specific ecotypes.•Citizen science: a fine approach to fill data ...gaps in invasive species distribution.•Citizen science supports the collection in Ailanthus samples across/outside Italy.
Ailanthus altissima (Mill.) Swingle is considered one of the worst invasive alien plant species (IAPS) in Europe, able to cause several disturbances to ecosystems and economic issues. To date, the control methods applied are often ineffective, restricted or under assessment by the scientific community, as in the case of Verticillium dahliae (a promising biological control agent to counteract this species). Citizen science initiatives aim to involve the public in the research process to generate genuine outcomes and, in the case of invasive species, represent a valuable additional tool in their earlier detection, monitoring and management. Here, seventy-two citizens were recruited to recognize and record A. altissima across and outside Italy, as well as to collect leaf and seed samples to allow professional scientists to perform the molecular characterization of the Italian (and more) gene pool and, subsequently, test the susceptibility of these provenances to V. dahliae. The collected material matched the identification for the 97% of the cases, and included 129 accessions divided in four genetic groups (with a high percentage of variability, as typically observed for other IAPS subjected to frequent movements and the constant supply of new propagules). Verticillium dahliae inoculation of plants from different provenances selected for each genetic group, revealed a very high mortality (≥93%) independently to the origin area. These outcomes confirm the high susceptibility of A. altissima to the fungal pathogen, and lead to speculate that V. dahliae seems to have no limits in counteracting Ailanthus populations, at least at the Italian level.
Besides abiotic constraints, plants along the coastal urban areas must face additional cues such as saline aerosol, which impact net plant CO2 assimilation (Pn), reducing biomass and influencing ...their aesthetic features. In this study, three species (Photinia × fraseri, P; Escallonia rubra, E; and Feijoa sellowiana, F) were subjected to saline nebulization (SN) with a 100 mM NaCl solution. Analyses were performed at 0, 10, and 20 days by monitoring the ion accumulation in plant organs, leaf osmotic potentials, gas exchange, chlorophyll a fluorescence parameters, and chlorophyll contents. Overall, E-SN plants absorbed more Na+ and Cl− in leaves than P-SN and F-SN ones. This phenomenon was influenced by leaf ‘wettability’ features such as the contact angle of water droplets, droplet retention, and water storage capacity, and the effectiveness of translocating these ions on twig tissues. SN increased the leaf osmotic potential (regardless of species). At 10 days (i.e., moderate stress conditions), Pn declined in all SN species, but more severely (−82 %) in E-SN plants. The observed Pn reductions were due to different limiting factors according to the plant species: Pn was reduced by non-stomatal limitations in P-SN plants, stomatal closure in F-SN, and a combination of both in E-SN individuals. At 20 days (i.e., severe stress conditions), in all SN-plants, lower values in all the physiological parameters than controls were observed, indicating a low tolerance to prolonged SN. The work shows that non-destructive physiological measurements provide a reliable assessment of plant tolerance to SN, which can help growers to select ornamental species suitable for coastal green areas.
We present details on a new measurement of the muon magnetic anomaly, \(a_\mu = (g_\mu -2)/2\). The result is based on positive muon data taken at Fermilab's Muon Campus during the 2019 and 2020 ...accelerator runs. The measurement uses \(3.1\) GeV\(/c\) polarized muons stored in a \(7.1\)-m-radius storage ring with a \(1.45\) T uniform magnetic field. The value of \( a_{\mu}\) is determined from the measured difference between the muon spin precession frequency and its cyclotron frequency. This difference is normalized to the strength of the magnetic field, measured using Nuclear Magnetic Resonance (NMR). The ratio is then corrected for small contributions from beam motion, beam dispersion, and transient magnetic fields. We measure \(a_\mu = 116 592 057 (25) \times 10^{-11}\) (0.21 ppm). This is the world's most precise measurement of this quantity and represents a factor of \(2.2\) improvement over our previous result based on the 2018 dataset. In combination, the two datasets yield \(a_\mu(\text{FNAL}) = 116 592 055 (24) \times 10^{-11}\) (0.20 ppm). Combining this with the measurements from Brookhaven National Laboratory for both positive and negative muons, the new world average is \(a_\mu\)(exp) \( = 116 592 059 (22) \times 10^{-11}\) (0.19 ppm).
We present a new measurement of the positive muon magnetic anomaly, \(a_\mu \equiv (g_\mu - 2)/2\), from the Fermilab Muon \(g\!-\!2\) Experiment using data collected in 2019 and 2020. We have ...analyzed more than 4 times the number of positrons from muon decay than in our previous result from 2018 data. The systematic error is reduced by more than a factor of 2 due to better running conditions, a more stable beam, and improved knowledge of the magnetic field weighted by the muon distribution, \(\tilde{\omega}'^{}_p\), and of the anomalous precession frequency corrected for beam dynamics effects, \(\omega_a\). From the ratio \(\omega_a / \tilde{\omega}'^{}_p\), together with precisely determined external parameters, we determine \(a_\mu = 116\,592\,057(25) \times 10^{-11}\) (0.21 ppm). Combining this result with our previous result from the 2018 data, we obtain \(a_\mu\text{(FNAL)} = 116\,592\,055(24) \times 10^{-11}\) (0.20 ppm). The new experimental world average is \(a_\mu (\text{Exp}) = 116\,592\,059(22)\times 10^{-11}\) (0.19 ppm), which represents a factor of 2 improvement in precision.
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