Vitis vinifera and drought stress: physiological and anatomical responses

Climate change represents a threat to natural ecosystems as well as to agricultural production, due to the increase in the frequency and intensity of drought. Like many other crops, the grapevine, despite being considered a drought tolerant crop, is threatened by climate change which can lead to a reduction in yields and grape quality and to the modification of the geographical distribution of the wine-growing areas. Multiple mechanisms and responses to counteract the negative effects of the water deficit are put in place by grapevine. Stomatal regulation, osmoregulation, reduction of growth and modification of xylem architecture are some of these acclimations. To support the adoption of strategies and actions in vineyard to face drought, the study of these mechanisms and responses is crucial. The purpose of this thesis fits into this context. In particular, it aims to contribute to the understanding and verifying any involvement of structural anatomical characters of the xylem or of non-structural carbohydrates (NSCs) in the response to the water deficit, in different Vitis vinifera cultivars. To this end, this thesis envisaged the design and implementation of experiments in which modulation of the NSCs content and the eventual relationship of this with other variables (i.e., xylem anatomy, degree of embolism, growth) were investigated by imposition of water deficit with variable intensity and duration. What emerged from this work is that in young potted plants of Vitis vinifera, there is a NSCs-mediated response to short and severe drought stress, although there are slight differences between cultivars with different hydraulic behaviors (i.e., isohydric and anisohydric). The accumulation of low molecular sugars in the period of stress could represent an acclimation strategy carried out by the grapevine with a potential role of osmoregulation, and / or refilling and / or energetic support, consistently with what proposed by other authors. The response to drought stress in anisohydric cultivars would also involve short-term anatomical modifications at the xylem level (i.e., reduction of the lumen of the newly produced tracheary elements) and a recovery mechanism of embolized vessels that could be driven by a possible thickening of the wall due to the adhesion of hygroscopic aqueous gels mediated by maltose-maltodextrin accumulation. The involvement of NSCs as osmo-compatible solutes has been blurred in the case of less intense and more lasting drought stress, where decrease of plant growth appears to be the key adaptive mechanism

Can agriculture be eco-friendly? Plant extracts as grapevine defense inducers

Secondary metabolites confer a first set of defenses against pathogens and herbivore attack. The use of plant extracts (PE), enriched in these compounds, could represent an additional practice in environment friendly grapevine pest management. During biotic stress, the induction of different pathogenesis-related (PR) gene-expression, such as chitinase, often occurs. In the present work, four different plant extracts were tested for their modulation of chitinase activity in either grapevine suspension cell cultures (GSC) and plants

Yield and Quality of Essential Oils in Hemp Varieties in Different Environments

Due to its possible utilization in cosmetics, medicine and crop protection, as a valuable alternative to petrochemical-derived products, hemp essential oil is now considered a product with high value added and a promising marketing potential. This experiment was conducted with the aim of evaluating the effect of four different locations of Northern Italy during two years (four environments) and three hemp monoecious varieties on the production and quality of essential oils (EOs) obtained by inflorescences harvested at full flowering of female flowers. The highest inflorescence yield was obtained at Maiano 2017, where a superficial groundwater layer (1.5 m) was present, with values that ranged from 1.69 of Fedora to 2.06 t ha 121 of Futura. EOs production ranged between 3.4 and 4.9 L ha 121 , affected mainly by the variety effect. The terpene in EOs, very similar between varieties and environments, was mainly composed of sesquiterpenes (caryophillene and humulene, as the most abundant) rather than monoterpenes (\u3b1-pinene, \u3b2-myrcene and trans-\u3b2-ocimene, in particular). Phytocannabinoids, and in particular cannabidiol (CBD), were not removed from tissues by the steam during hydrodistillation, and if this is confirmed by further experiments, the residual biomass, now considered as waste, could assume significant importance as a source for further utilization

Germination performance of alien and native species could shape community assembly of temperate grasslands under different temperature scenarios

Rising temperatures due to climate change are expected to interplay with biological invasions, and may enhance the spread and growth of some alien species upon arrival in new areas. To successfully invade, a plant species needs to overcome multiple biological barriers. Among the crucial life stages, seed germination greatly contributes to the final species assembly of a plant community. Several studies have suggested that alien plant success is related to their high seed germination and longevity in the soil. Hence, our aim is to test if the germination potential of alien seeds present in the seed bank will be further enhanced by future warming in temperate dry grasslands, an ecosystem that is among those most prone to biological invasions. We designed a laboratory germination experiment at two temperatures (20 and 28 °C), to simulate an early or late heat wave in the growing season, using seeds from nine common grassland Asteraceae species, including native, archaeophyte and neophyte species. The test was performed on both single and mixed pools of these categories of species, using a full-factorial orthogonal design. The warmer germination temperature promoted neophyte success by increasing germination probability and germination speed, while negatively impacting these parameters in seeds of native species. The co-occurrence of native and archaeophyte seeds at the lower temperature limited the invasiveness of neophytes. These results provide important information on future management actions aimed at containing alien plant invasions, by improving our knowledge on the possible seed-bank response and interaction mechanisms of common species occurring in disturbed natural areas or restored sites

Vernalization affects the germination performance of the wetland endangered species Eleocharis carniolica

Eleocharis carniolica W.D.J. Koch (Cyperaceae) is an endangered wetland spike rush mainly threatened by habitat loss and fragmentation. Understanding the germination ecology of this species is essential to perform successful conservation and restoration actions. In this study, we investigated the effect of vernalization (i.e. cold stratification), gibberellic acid (GA3) and chemical scarification on seed germination of E. carniolica from wild populations in northern Italy. The results showed that vernalization (i.e. 8-weeks at 4(degrees)C) significantly improved germination probability, speed, and uniformity compared to non-stratified seeds. Gibberellic acid treatment alone or in combination with vernalization did not show a significant improvement in germination. Chemical scarification using sodium hypochlorite increased germination probability, with 8 h of scarification showing the highest success rate. However, 24-h scarification had a negative impact on germination. Overall, vernalization was found to be the most effective method to enhance germination in E. carniolica. These findings provide valuable insights into the seed germination ecology of this endangered species, aiding in its exsitu conservation, propagation, and in-situ restoration efforts. Moreover, they have important implications on future germination dynamics of this endangered species, especially with predicted climate change scenarios

Antifungal activity of chili pepper extract with potential for the control of some major pathogens in grapevine

Background: In the recent years, biofungicides have drawn increasing interest in vineyard for a more sustainable integrated and copper-limited pest management. Among alternatives, botanicals could represent valuable tools, being rich sources of biologically active compounds. Conversely to the well-known antioxidant and biological properties in relation to health benefits, investigation on bioactivity of hot pungent Capsicum sp. products against fungal phytopathogens in vineyard is still scarce. Therefore, the present study aimed at exploring the biologically active compounds profile of a chili pepper (Capsicum chinense Jacq.) pod extract and its antimicrobial properties against some of the major fungal and Oomycetes pathogens of grapevine, including Botrytis cinerea Pers., Guignardia bidwellii (Ellis) Viala & Ravaz and Plasmopara viticola (Berk. & M.A. Curtis) Berl. & De Toni. Results: The ethyl acetate-extracted oleoresin from the most pungent varieties was rich in capsaicinoids and polyphenols (371.09 and 268.5 μg mg-1 dry weight, respectively). Capsaicin and dihydrocapsaicin, hydroxycinnamic and hydroxybenzoic acids and quercetin derivatives were the most abundant, while carotenoids represented only a minor fraction. The oleoresin was efficient to inhibit all three pathogenic fungi and ED50 values were determined, evidencing that G. bidwellii was the more sensitive (0.233 ± 0.034 mg mL-1 ). Conclusion: The results suggested a potentiality of chili pepper extract for the control of some important grapevine pathogens, their possible application being helpful for the recommended limitation in extensive use of copper in vineyard. The complex mixture of high amounts of capsaicinoids, associated to specific phenolic acids and other minor bioactive components might contribute for the observed antimicrobial action of chili pepper extract

Chitosan nanocarriers-mediated delivery of double-stranded RNA "in planta"

Agriculture is currently facing numerous challenges: the rapid rise of the world population, the consequent growth in food demand, the global decrease in crop yield. Particularly regarding the last issue, climate change is worsening the environmental stresses that commonly affect crops, and the use of resources – such as fertilizers and pesticides – is highly inefficient and pollutant. In this context, research is looking for new approaches to improve crop productivity by more efficient and environmentally friendly practices. It has been shown that nanomaterials are suitable for the development of cutting-edge technologies with the aim of improving the delivery of bioactive substances on plants and to promote their resistance to biotic and abiotic stresses. Among organic polymers, chitosan, if used in the nanoscale form, shows both properties; it can induce biological responses concerning plant defense against diseases and pathogen attack, and it is particularly suitable as a carrier for several molecules. Another innovative method for the defense of crops is the exploitation of the spray-induced gene silencing (SIGS) based on the activation of the so-called RNA-interference (RNAi). It involves exogenous double stranded RNAs (dsRNAs) targeting an essential pathogen gene, which trigger the RNAi pathway leading to the translational repression by degradation of target homologous mRNAs. In our case, the research aimed to verify the feasibility of dsRNA distribution on plant surface by means of functionalized chitosan nanoparticles (CH-NPs), thus allowing the protection of the doping agent and its efficient delivery. Here we show the preliminary results regarding the characterization of CH-NPs, their loading with dsRNAs and their interaction with the leaf surface of Nicotiana benthamiana plants. The effects of the dose-dependent distribution were analyzed by confocal microscopy upon incorporation of a fluorescent probe

Comparison of leaf morpho-anatomical characters in Amaranthus spp.: phenotyping as an investigative tool for environmental and agricultural sciences

Plant phenotyping is an important tool that can provide insight into the interaction between plants and the environment, often as supporting information for genotype studies. The resulting knowledge can be useful in eco-physiological research, to understand how species adapt to their growing conditions and to biotic competition. In recent years, phenotyping techniques for the study of plant morpho-anatomical traits have developed in the field of the imaging analysis, starting from microscope images up to high scale acquisitions through remote sensing. In this work, we focused on the detailed study of single-leaf morphometric traits through the processing of photographic and confocal microscope acquisitions. Four species of Amaranthus were used, being plants of interest due to their high invasiveness into fields. Their morphological traits could become a useful tool to describe their adaptative responses and to define strategies for the sustainable management of the agro-ecosystem

Investigation of non-structural carbohydrates and xylem anatomy in petiole of grapevine varieties during water limitation and after re-irrigation

Water shortage (WS) during growing of Vitis vinifera L. can limit shoot growth and affect yield and fruit quality, as well as allocation of carbon reserves into perennial organs for the upcoming years. Varietal anatomical differences, such as specific mean xylem vessel diameter in petiole, are expected to influence water transport in canes facing water limitation. Several authors have also evidenced that non-structural carbohydrates (NSC) of adjacent living parenchyma are involved in the repair mechanism of embolized vessels. In this work, we evaluated NSC level and xylem anatomy in petiole of Cabernet Sauvignon and Syrah varieties, subjected to WS and subsequent water refilling in the summer of 2017. The anatomical analysis highlighted that Syrah had high frequency of classes of large vessels, and that the xylem differentiation of vascular bundles was also affected by WS. Moreover, petiole NSC content was significantly influenced by WS and recovery, supporting the hypothesis that starch mobilization was associated to an elevated concentration in soluble NSC. This effect was determinant for Cabernet Sauvignon, whose stress response seemed to be based mainly on NSC metabolism. Finally, Syrah, differently to Cabernet Sauvignon, sustained the WS-induced increase in soluble NSC of petiole also 18 h after re-watering