Occurrence of fig mosaic disease in Tuscany, Central Italy: Characterization of new fig mosaic virus isolates, and elucidation of physiochemical responses of infected common fig cv. Dottato

Fig mosaic disease (FMD) is a major disease affecting fig trees, for which only fig mosaic virus (FMV) has been identified as etiological agent. In the present study, trees of common fig cv. Dottato, belonging to the old Tuscan germplasm, were investigated to pioneering (i) evaluate the presence of FMV in Tuscany (Central Italy), as well as other FMD-associated viruses previously reported in Italy, (ii) type and phylogenetically characterize the reported FMV isolates, and (iii) elucidate some physiological and biochemical responses of fig trees challenged by FMV. Although many studies on FMD have been carried out in Southern Italy, the present study represents the first identification of the disease in another Italian area. This work (i) showed that FMD is present also in Central Italy, also suggesting a wider diffusion than what has been reported so far; (ii) confirmed that the disease is caused by FMV, tested positive in both symptomatic and asymptomatic leaves (100 and 27% of tested samples, respectively); and also fig fleck-associated virus (FFKaV) was reported; (iii) identified three new FMV isolates (i. e., Dot-1, Dot-2 and Dot-3, deposited in GenBank), which resulted not close to other FMV Italian isolates; and (iv) pioneering elucidated that FMV impaired photosynthesis and organic acid biosynthesis in symptomatic leaves, but negative effects occurred also in asymptomatic ones in terms of photosynthetic and accessory pigments. More research should be carried out to improve our knowledge on FMD diffusion and FMV (and FFKaV) genetic features, as well on the effects of this regulated non quarantine pest on fig trees, also investigating its fruits representing an ancient source of food and health

Design, development, and assessment of a High-Throughput Screening (HTS) system for the macroscopic root water uptake modeling

Climate change is responsible for the increasing frequency and intensity of abiotic stresses generating water scarcity conditions. There is a need to breed plants adapted to future environmental conditions and resistant to water stress. This study presents a High-Throughput Screening (HTS) system for continuously and simultaneously monitoring plant stress response to drought in a semi-controlled environment. The HTS system combines a gravimetric weighing system with soil moisture and atmospheric sensors. In operative terms, the system was tested on the Sage (Salvia officinalis L.) under two soil water deficit treatments managed according to a feedback control irrigation scheduling. The system was able to model the sage water stress function following the root water uptake macroscopic approach. The threshold of soil water status below which crop water stress occurred was also identified. The gravimetric-based daily evapotranspiration (ETa) and the time domain reflectometry (TDR)-based root wateruptake (RWU) rates showed a high correlation during the drying when the evaporation flux is minimal. Moreover, the effects of soil bulk density on the root density and the plant biomass were evaluated, indicating the importance of carrying out a homogeneous procedure of the pot-filling process

Significance of phenylpropanoid pathways in the response of two pomegranate cultivars to salinity and ozone stress

Secondary metabolites play a pivotal role in defense mechanisms, especially in plant-environment interactions. However, there are still difficulties in ascertaining the metabolic effect of their production due to individual and/ or combined stress, given the variety of simultaneous and interconnected effects of multiple stresses to metabolic processes in plants. Here, two pomegranate cultivars (Wonderful and Parfianka) were subjected to moderate levels of salt (i.e., 100 mM NaCl for 35 consecutive days) and sequentially exposed to a realistic O3 concentration (i.e., 100 ppb for 5 h) to evaluate how NaCl treatment and/or O3 fumigation alter the leaf polyphenolic composition, and what is the role of metabolites and enzymes involved in the phenylpropanoid pathway during sequential abiotic stresses. Wonderful leaves responded to NaCl or O3 treatments through the production/ accumulation of cinnamic acid derivatives (more than 3-fold higher than controls) and by exhibiting chemical composition plasticity against oxidative stress. The unchanged concentrations of benzoic acid derivatives indicate that treated Wonderful leaves could diversify the components of polyphenolic compounds and induce the biosynthesis of the components available (e.g., ellagitannins and punicalagin). During sequential abiotic stresses, Wonderful leaves needed few cellular adjustments to maintain oxidative stress under control (especially during the recovery time). On the other hand, Parfianka leaves had phenolics/polyphenolics amount (at constitutive level) suitable to face out the environmental changes (occurring singly or sequentially) so that no rearrangement of metabolites and enzymes involved in the phenylpropanoid pathway was required. Consequently, it is possible to conclude that Parfianka is more salt- and O3-tolerant than Wonderful

Macroscopic root water uptake modelling using High-Throughput Screening (HTS) systems: Design and Validation

Climate change and intensive agriculture are responsible for the increasing frequency and intensity of abiotic stresses generating conditions of water scarcity. Currently, there is the need to select and release, in a short time, plants adaptable to the current and future environmental conditions and resistant to biotic and/or abiotic stress. This study presents the design and validation of a High-Throughput Screening (HTS) system for the continuous and simultaneous monitoring of the plant stress response to drought in a semi-controlled environment. Structurally, the HTS-system is formed by three hardware segments to detect with high-frequency the agrometeorological variables (i.e., atmometry), the weights (i.e., gravimetry), and the soil water content (SWC) (i.e., time domain reflectometry, TDR) of sixteen pots in which the medicinal crop Salvia officinalis L (sage) was grown. Two irrigation treatments, one based on full irrigation and the second on soil water deficit conditions, were applied following a feedback control irrigation scheduling protocol, and an automated micro-irrigation system was designed to manage them. The system was able to model the sage water stress function following the root water uptake (RWU) macroscopic approach. The threshold of soil water status below which crop water stress occurred was also identified. The gravimetric-based daily evapotranspiration (ETc act) and the time domain reflectometry (TDR) -based RWU rates showed a high correlation, which allowed validating the RWU indicators based on soil moisture sensors to estimate the ETc act fluxes

Phenylpropanoids are key players in the antioxidant defense to ozone of European ash, Fraxinus excelsior

Physiological and biochemical responses to ozone (O3) (150 ppb, 8 h day−1, 35 consecutive days) of two Italian provenances (Piedmont and Tuscany) of Fraxinus excelsior L. were evaluated, with special attention to the role of phenylpropanoids. Our results indicate (i) the high O3 sensitivity especially of Piedmont provenance (in terms of visible injury, water status, and photosynthetic apparatus); (ii) although the intra-specific sensitivity to O3 between provenances differs (mainly due to different stomatal behaviors since only Tuscany plants partially avoided the uptake of the pollutant gas), both provenances showed detoxification and defense mechanisms; (iii) the crucial participation of phenylpropanoids, with a key role played by flavonoids (especially quercitrin): among this class of metabolites, isoquercitrin is the principal player in the lower O3 sensitivity of Tuscany plants, together with lignins; (iv) although coumarins (typical compounds of Fraxinus) were severely depressed by O3, isofraxidin was triggered suggesting a key role in reactive oxygen species (ROS) detoxification, as well as trans-chalcone. Furthermore, the different behavior of verbascoside and oleuropein among provenances lead us to speculate on their influence in the tentatively repair or acclimation shown by Piedmont plants at the end of the exposure. Finally, the intra-specific O3 sensitivity may be also due to de novo peaks triggered by O3 not yet associated to some chemicals

Living in a Mediterranean city in 2050: broadleaf or evergreen ‘citizens’?

The predicted effects of global change (GC) will be exacerbated in the more densely populated cities of the future, especially in the Mediterranean basin where some environmental cues, such as drought and tropospheric ozone (O3) pollution, already mine seriously plant survival. Physiological and biochemical responses of a Mediterranean, evergreen, isohydric plant species (Quercus ilex) were compared to those of a sympatric, deciduous, anisohydric species (Q. pubescens) under severe drought (20% of the effective daily evapotranspiration) and/or chronic O3 exposure (80 ppb for 5 h dayâ1 for 28 consecutive days) to test which one was more successful in those highly limiting conditions. Results show that (i) the lower reduction of total leaf biomass of Q. ilex as compared to Q. pubescens when subjected to drought and drought à O3 (on average â59 vs â70%, respectively); (ii) the steeper decline of photosynthesis found in Q. pubescens under drought (â87 vs â81%) and drought à O3 (â69 vs â59%, respectively); (iii) the increments of malondialdehyde (MDA) by-products found only in drought-stressed Q. pubescens; (iv) the impact of O3, found only in Q. pubescens leaves and MDA, can be considered the best probes of the superiority of Q. ilex to counteract the effect of mild-severe drought and O3 stress. Also, an antagonistic effect was found when drought and O3 were applied simultaneously, as usually happens during typical Mediterranean summers. Our dataset suggests that on future, the urban greening should be wisely pondered on the ability of trees to cope the most impacting factors of GC, and in particular their simultaneity

Physiochemical responses of Ailanthus altissima under the challenge of Verticillium dahliae: elucidating the decline of one of the world’s worst invasive alien plant species

Natural infections of Verticillium spp. (Fungi, Ascomycota) on Ailanthus altissima have suggested to consider the biological control as a promising strategy to counteract this invasive plant, which is otherwise difficult to control by traditional mechanical and chemical treatments. Verticillium wilt is able to lead plants to death, throughout a pathogenic mechanism including vessel occlusions and production of degrading enzymes and phytotoxins. In this study, a 10 weeks open air pot experiment was set to investigate the ecophysiological and biochemical responses of Ailanthus trees artificially inoculated in the trunk with the V. dahliae strain VdGL16, previously isolated in Central Italy from the same host. Inoculated plants showed visible injuries starting from 2 weeks post inoculation (wpi), that progressively developed until a final severe defoliation. The fungal infection rapidly compromised the plant water status, and photosynthesis was impaired due to both stomatal and mesophyll limitations from 4 wpi, with subsequent detrimental effects also on PSII activity. Moreover, the disease altered the translocations of nutrients, as confirmed by cation and carbohydrate contents, probably due to a consumption of simple sugars and starch reserves without replacement of new photosynthesized. An accumulation of osmolytes (abscisic acid and proline) and phenylalanine (a precursor of phenylpropanoids) was also reported at 8 wpi, this being a response mechanism that needs to be further elucidated. However, the activation delay of such defence strategy inevitably did not avoid the premature defoliation of plants and the decline of physiochemical parameters, confirming the key role of Verticillium in Ailanthus decay

Cross‐Talk between Physiological and Metabolic Adjustments Adopted by Quercus cerris to Mitigate the Effects of Severe Drought and Realistic Future Ozone Concentrations

Global climate change represents a moving target for plant acclimation and/or adaptation, especially in the Mediterranean basin. In this study, the interactions of severe drought (20% of the effective daily evapotranspiration) and O3 fumigation (80 ppb, 5 h day−1, for 28 consecutive days) on (i) photosynthetic performance, (ii) cell membrane stability, (iii) hydric relations, (iv) accumulation of compatible solutes, and (v) lipophilic antioxidant compounds were investigated in young Quercus cerris plants. In addition to the typical drought-induced stomatal closure, imposition of water withholding dramatically influenced the profile of stress-associated metabolites, i.e., abscisic acid (ABA), proline, and lipophilic antioxidants. However, plants were not able to delay or prevent the negative effects of water deficit, the greatest impacting factor in this study. This translated into a steep decline of photosynthetic efficiency, leaf hydration, and membrane fluidity and permeability. When water stress was coupled with O3, plants orchestrated cross-talk among ABA, proline, and sugar in fully-expanded mature leaves, partially leading to a premature senescenc

Variations in physiological and biochemical traits of oak seedlings grown under drought and ozone stress

Despite the huge biodiversity characterizing the Mediterranean environment, environmental constraints, such as high sunlight and high temperatures alongside with dry periods, makes plant survival hard. In addition, high irradiance leads to increasing ozone (O3 ) concentrations in ambient air. In this era of global warming, it is necessary to understand the mechanisms that allow native species to tolerate these environmental constraints and how such mechanisms interact. Three Mediterranean oak species (Quercus ilex, Q. pubescens and Q. cerris) with different features (drought tolerant, evergreen or deciduous species) were selected to assess their biometrical, physiological and biochemical responses under drought and/or O3 stress (80-100 nl l(-1) of O3 for 5 h d(-1) for 77 consecutive days). Leaf visible injury appeared only under drought stress (alone or combined with O3 ) in all three species. Drought × O3 induced strong reductions in leaf dry weight in Q. pubescens and Q. cerris (-70 and -75%, respectively). Alterations in physiological (i.e. decrease in maximum carboxylation rate) and biochemical parameters (i.e. increase in proline content and build-up of malondialdehyde by-products) occurred in all the three species, although drought represented the major determinant. Q. ilex and Q. pubescens, which co-occur in dry environments, were more tolerant to drought and drought × O3 . Quercus ilex was the species in which oxidative stress occurred only when drought was applied with O3 . High plasticity at a biochemical level (i.e. proline content) and evergreen habitus are likely on the basis of the higher tolerance of Q. ilex

The effects of elevated tropospheric ozone on Carbon fixation and stable isotopic signatures of durum wheat cultivars with different biomass and yield stability

Tropospheric ozone (O3) enrichment caused by human activities can reduce important crop yields with huge economic loss and affect the global carbon cycle and climate change in the coming decades. In this study, two Italian cultivars of durum wheat (Claudio and Mongibello) were exposed to O3 (80 ppb, 5 h day−1 for 70 consecutive days), with the aim to investigate the changes in yield and biomass, ecophysiological traits, and stable carbon and nitrogen isotope values in plants, and to compare the stable isotope responses under environmental stressors. Both cultivars showed a relative O3 tolerance in terms of photosynthetic performance, but in cultivar Mongibello, O3 was detrimental to the grain yield and plant biomass. The δ13C values in the leaves of plants identified that the impact of O3 on CO2 fixation by RuBisCO was dominant. The δ15N value showed significant differences between treatments in both cultivars at seven days from the beginning of the exposure, which could be considered an early indicator of ozone pollution. Under increasingly frequent extreme climates globally, the relationships among stable isotope data, ecophysiological traits, and agronomic parameters could help breed future cultivars