Evaluation of the photosynthetic efficiency of sweet sorghum under drought and cold conditions

Sweet sorghum, a C4 crop of tropical origin, is gaining momentum as a multipurpose feedstock to tackle the growing environmental, food and energy security demands. Under temperate climates sweet sorghum is considered as a potential bioethanol feedstock, however, being a relatively new crop in such areas its physiological and metabolic adaptability has to be evaluated; especially to the more frequent and severe drought spells occurring throughout the growing season and to the cold temperatures during the establishment period of the crop. The objective of this thesis was to evaluate some adaptive photosynthetic traits of sweet sorghum to drought and cold stress, both under field and controlled conditions. To meet such goal, a series of experiments were carried out. A new cold-tolerant sweet sorghum genotype was sown in rhizotrons of 1 m3 in order to evaluate its tolerance to progressive drought until plant death at young and mature stages. Young plants were able to retain high photosynthetic rate for 10 days longer than mature plants. Such response was associated to the efficient PSII down-regulation capacity mediated by light energy dissipation, closure of reaction centers (JIP-test parameters), and accumulation of glucose and sucrose. On the other hand, when sweet sorghum plants went into blooming stage, neither energy dissipation nor sugar accumulation counteracted the negative effect of drought. Two hybrids with contrastable cold tolerance, selected from an early sowing field trial were subjected to chilling temperatures under controlled growth conditions to evaluate in deep their physiological and metabolic cold adaptation mechanisms. The hybrid which poorly performed under field conditions (ICSSH31), showed earlier metabolic changes (Chl a + b, xanthophyll cycle) and greater inhibition of enzymatic activity (Rubisco and PEPcase activity) than the cold tolerant hybrid (Bulldozer). Important insights on the potential adaptability of sweet sorghum to temperate climates are given.

Influence of plant structure, cultural pratices and environmental conditions on the development of the bacterial canker of kiwifruits

Italy has a preeminent rank in kiwifruit industry, being the first exporter and the second largest producer after China. However, in the last years kiwifruit yields and the total cultivated area considerably decreased, due to the pandemic spread of the bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa). Several climatic conditions and cultural practices affect the development of the bacterial canker. This research work focused on the impact of agricultural practices and microclimate conditions on the incidence and epidemiology of Psa in the orchard. Therefore, the effect of fertilization, irrigation, use of bio-regulators, rootstock, training system and pruning were examined. The effect of different tunnel systems was analyzed as well, to study the plant-pathogen interaction. Considering the importance of insects as vectors in other pathosystems, the role of Metcalfa pruinosa in the spread of the bacterial canker was investigated in controlled conditions. In addition, quality and storage properties of fruits from infected plants were assessed. The study of all these aspects of the agronomic practices is useful to define a strategy to limit the bacterial diffusion in the orchard. Overall, excess nitrogen fertilization, water stress, stagnant water supplies, pruning before summer and the high number of Metcalfa pruinosa increased the Psa incidence. In contrast, tunnel covers may be useful for the control of the disease, with special attention to the kind of material.

Organismi acquatici e ambiente: meccanismi biochimici di interazione, risposta e adattamento

The research is focused on the relationship between some Mg2+-dependent ATPase activities of plasma- and mitochondrial membranes from tissues of cultured marine bivalve molluscs and potentially stressful environmental conditions, such as the exposure to contaminants both of natural origin (ammonia nitrogen, the main contaminant of aquaculture plants) and of anthropic source (alkyltins). The two filter-feeding bivalve species selected colonize different habitats: the common mussel Mytilus galloprovincialis binds to hard substrates and the Philippine clam Tapes philippinarum burrows into sea bottom sandy beds. The choice of typical species of coastal waters, extremely suitable for environmental studies due to their features of poor motility, resistance to transport and great filtering efficiency, may constitute a model to evaluate responses to contaminants of membrane-bound enzyme activities involved in key biochemical mechanisms, namely cell ionic regulation and mitochondrial energy production. In vitro and in vitro approaches have been pursued. In vitro assays were carried out by adding the contaminants (NH4Cl and alkyltins) directly to the ATPase reaction media. In vivo experiments were carried out by exposing mussels to various tributyl tin (TBT) concentrations under controlled conditions in aquaria. ATPase activities were determined spectrophotometrically according to the principles of the method of Fiske and Subbarow (1925). The main results obtained are detailed below. In Tapes philippinarum the interaction of NH4 +, the main form of ammonia nitrogen at physiological and seawater pHs, with the Na,K-ATPase and the ouabaininsensitive Na-ATPase was investigated in vitro on gill and mantle microsomal membranes. The proven replacement by NH4 +of K+ in the activation of the Na,KATPase and of Na+ in the activation of the ouabain-insensitive ATPase displayed similar enzyme affinity for the substituted cation. on the one hand this finding may represent one of the possible mechanisms of ammonia toxicity and, on the other, it supports the hypothesis that NH4 + can be transported across the plasma membrane through the two ATPases. In this case both microsomal ATPases may be involved and co-operate, at least under peculiar circumstances, to nitrogen excretion and ammonia detoxification mechanisms in bivalve molluscs. The two ATPase activities stimulated by NH4 + maintained their typical response to the glycoside ouabain, specific inhibitor of the Na,K-ATPase, being the Na++ NH4 +-activated ATPase even more susceptive to the inhibitor and the ouabain-insensitive ATPase activity activated indifferently by Na+ or NH4 + unaffected by up to 10-2 M ouabain. In vitro assays were carried out to evaluate the response of the two Na-dependent ATPases to organotins in clams and mussels and to investigate the interaction of TBT with mussel mitochondrial oligomycin-sensitive Mg-ATPase. Since no literature data were available, the optimal assay conditions and oligomycin sensitivity of mussel mitochondrial MgATPase were determined. In T. philippinarum the ouabain-insensitive Na-ATPase was found to be refractory to TBT both in the gills and in the mantle, whereas the Na,K-ATPase was progressively inhibited by increasing TBT doses; the enzyme inhibition was more pronounced in the gills than in the mantle. In both tissues of M. galloprovincialis the Na,K-ATPase inhibition by alkyltins decreased in the order TBT>DBT(dibutyltin)>>MBT(monobutyltin)=TeET(tetraethyltin) (no effect). Mussel Na-ATPase confirmed its refractorimess to TBT and derivatives both in the gills and in the mantle. These results indicate that the Na,K-ATPase inhibition decreases as the number of alkyl chains bound to tin decreases; however a certain polarity of the organotin molecule is required to yield Na,K-ATPase inhibition, since no enzyme inhibition occurred in the presence of tetraalkyl-substituted derivatives such as TeET . Assays carried out in the presence of the dithioerythritol (DTE) pointed out that the sulphhydrylic agent is capable to prevent the Na,K-ATPase inhibition by TBT, thus suggesting that the inhibitor may link to -SH groups of the enzyme complex.. Finally, the different effect of alkyltins on the two Na-dependent ATPases may constitute a further tool to differentiate between the two enzyme activities. These results add to the wealth of literature data describing different responses of the two enzyme activities to endogenous and exogenous modulators . Mussel mitochondrial Mg-ATPase was also found to be in vitro inhibited by TBT both in the gills and in the mantle: the enzyme inhibition followed non competitive kinetics. The failed effect of DTE pointed out that in this case the interaction of TBT with the enzyme complex is probably different from that with the Na,K-ATPase. The results are consistent with literature data showing that alkyltin may interact with enzyme structures with different mechanisms. Mussel exposure to different TBT sublethal doses in aquaria was carried out for 120 hours. Two samplings (after 24 and 120 hrs) were performed in order to evaluate a short-term response of gill and mantle Na,K-ATPase, ouabain-insensitive Na-ATPase and Mg-ATPase activities. The in vivo response to the contaminants of the enzyme activities under study was shown to be partially different from that pointed out in the in vitro assays. Mitochondrial Mg-ATPase activity appeared to be activated in TBTexposed mussels with respect to control ones, thus confirming the complexity of evaluating in vivo responses of the enzyme activities to contaminants, due to possible interactions of toxicants with molluscan metabolism. Concluding, the whole of data point out that microsomal and mitochondrial ATPase activities of bivalve molluscs are generally responsive to environmental contaminants and suggest that in some cases membrane-bound enzyme activities may represent the molecular target of their toxicity. Since the Na,K-ATPase, the Na-ATPase and the Mg-ATPase activities are poorly studied in marine bivalves, this research may contribute to enlarge knowledge in this quite unexplored field.

Sistemi innovativi per il miglioramento della qualità e della sicurezza degli alimenti

Nell’attuale contesto, caratterizzato da un’elevata attenzione alla qualità e alla sicurezza degli alimenti e alle soluzioni tese a garantirli, l’implementazione di sistemi microelettronici per il controllo del prodotto attraverso supporti miniaturizzati e a basso costo può risultare un’opportunità strategica. Oggetto della ricerca di dottorato sono stati lo studio dell’utilizzo di sensori e strumentazione innovativi per la misurazione ed il controllo di parametri ambientali di conservazione di prodotti alimentari e per la loro identificazione mediante la tecnologia della radiofrequenza. Allo scopo è stato studiato il contesto in cui operano gli attori principali della filiera agroalimentare ed è stata sviluppata un’idea di etichetta progettata per essere in grado di emettere attivamente segnale di allarme in caso di necessità (etichetta RFID intelligente semi-passiva). Il prototipo di chip, realizzato in via sperimentale, è stato validato positivamente, sia come strumento di misura, sia in termini di prestazione nel caso studio del monitoraggio della conservazione di un prodotto alimentare in condizioni controllate di temperatura e radiazione luminosa. Le significative evidenze analitiche di reazioni di degradazione dello stato qualitativo del prodotto, quali analisi di pH e colore, raccolte durante il periodo di osservazione di 64 giorni, hanno trovato riscontro con le misure rilevate dal chip prototipo. I risultati invitano ad individuare un partner industriale, con il quale sperimentare l’applicazione della tecnologia proposta.

Association mapping of stem rust resistance in durum wheat at the seedling and adult plant stages

In wheat, stem rust is known to rapidly evolve new virulence to resistance genes. While more than 50 stem rust resistance (Sr) loci have been identified in wheat, only a few remain effective, particularly against the highly virulent race Ug99 (TTKSK race) and a mixture of durum-specific races. An association mapping (AM) study based on 183 durum wheat accessions was utilized to identify resistance loci for stem rust response in Ethiopia over four seasons and artificial inoculation with Ug99 (TTKSK race) and a mixture of durum-specific races under field conditions as well as in greenhouse test at seedling stage under controlled conditions for resistance to four highly virulent stem rust races: TRTTF, TTTTF, (TTKSK (Ug99) and JRCQC. The panel was profiled with 1,253 SSR and DArT markers. Twelve QTL-tagging markers were significant (P < 0.05) across three to four seasons. The role of Sr13, Sr9, Sr14, Sr17, and Sr28 was confirmed. Thirteen significant markers were in regions with no Sr genes/QTLs. The results under controlled conditions showed that 15, 20, 19 and 19 chromosome regions harbored markers that showed significant effects for races TRTTF, TTTTF, TTKSK and JRCQC, respectively. These genomic regions showed marker R2 values ranging from 1.13 to 8.34, 1.92 to 17.64, 1.75 to 23.12 and 1.51 to 15.33% for races TRTTF, TTTTF, TTKSK and JRCQC, respectively. The study demonstrates that stem rust resistance in durum wheat is governed in part by shared loci and in part by race-specific ones. The QTLs identified in this study through AM will be useful in the marker-assisted development of durum wheat cultivars with durable stem rust resistance.

Influence of Electromagnetic Fields On Biological Signalling: An Experimental and Theoretical Approach

The primary goals of this study were to develop a cell-free in vitro assay for the assessment of nonthermal electromagnetic (EMF) bioeffects and to develop theoretical models in accord with current experimental observations. Based upon the hypothesis that EMF effects operate by modulating Ca2+/CaM binding, an in vitro nitric oxide (NO) synthesis assay was developed to assess the effects of a pulsed radiofrequency (PRF) signal used for treatment of postoperative pain and edema. No effects of PRF on NO synthesis were observed. Effects of PRF on Ca2+/CaM binding were also assessed using a Ca2+-selective electrode, also yielding no EMF Ca2+/CaM binding. However, a PRF effect was observed on the interaction of hemoglobin (Hb) with tetrahydrobiopterin, leading to the development of an in vitro Hb deoxygenation assay, showing a reduction in the rate of Hb deoxygenation for exposures to both PRF and a static magnetic field (SMF). Structural studies using pyranine fluorescence, Gd3+ vibronic sideband luminescence and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy were conducted in order to ascertain the mechanism of this EMF effect on Hb. Also, the effect of SMF on Hb oxygen saturation (SO2) was assessed under gas-controlled conditions. These studies showed no definitive changes in protein/solvation structure or SO2 under equilibrium conditions, suggesting the need for real-time instrumentation or other means of observing out-of-equilibrium Hb dynamics. Theoretical models were developed for EMF transduction, effects on ion binding, neuronal spike timing, and dynamics of Hb deoxygenation. The EMF sensitivity and simplicity of the Hb deoxygenation assay suggest a new tool to further establish basic biophysical EMF transduction mechanisms. If an EMF-induced increase in the rate of deoxygenation can be demonstrated in vivo, then enhancement of oxygen delivery may be a new therapeutic method by which clinically relevant EMF-mediated enhancement of growth and repair processes can occur.

Effects and Modes od Action of Canopy Management Practices on Vine Physiology and Berry Composition in Organically-Cultivated cv. Sangiovese (Vitis Vinifera L.)

In organic and biodynamic vineyards, canopy management practices should be carefully and timely modulated, particularly in a context of climate change, for successfully achieving balanced plants, ventilated and exposed berries, elevated grape and wine quality. In 2013 and 2014, characterized by contrasting climatic conditions, the implications of post-veraison (late) or pea-size trimming, post-veraison or pre-harvest late defoliations and shoot-positioning (post-veraison) were assessed against long-shoots non treated controls, under field conditions on organically-cultivated cv. Sangiovese. The key agronomic and enological relevance of late trimming and defoliations clearly emerged in both seasons. Berry skin phenolics (e.g. anthocyanins, flavonols) increased markedly, without changes in technological parameters. In case of early trimming, such positive effects were observed only in 2013. Maintaining long shoots for shading decreased anthocyanins, flavonols and total phenolics concentrations and promoted the production of compact bunches. Experimental data strongly designated late trimming, a practice proved to contain yield and bunch compactness, as a valuable alternative to cluster thinning. Late trimming, defoliations and shoot positioning reduced the severity of Botrytis cluster rot. The highest levels of berry skins phenolic compounds in late trimmed and defoliated plants could have contributed control the severity of this pathogen. The enological benefits induced by late trimming and defoliations and shoot positioning emerged in both young and aged wines. For the first time, cell cultures from cv. Sangiovese berry tissues were obtained and enabled to investigate, in controlled conditions, the relations between mechanisms regulating secondary metabolism in grapevine cells and changes induced by environmental and agronomic factors. The Doctoral Dissertation strongly highlights the need to consider, for a proper interpretation of the multiple modifications induced by canopy management strategies, physiological mechanisms other than the canonic source-sink relationships, in particular their impact on the vine hormonal status.

Streptococcus agalactiae adapts to glucose stress conditions by modulating gene expression profile

Diabetes mellitus is considered a risk factor for Group B Streptococcus (GBS) infections. Typically, this pathology is associated to high glucose levels in the bloodstream. Although clinical evidences support this notion, the physiological mechanisms underlying GBS adaptation to such conditions are not yet defined. In the attempt to address this issue, we performed comparative global gene expression analysis of GBS grown under glucose-stress conditions and observed that a number of metabolic and virulence genes was differentially regulated. Of importance, we also demonstrated that by knocking-out the csrRS locus the transcription profile of GBS grown in high-glucose conditions was profoundly affected, with more than a third of glucose-dependent genes, including the virulence factor bibA, found to be controlled by this two-component system. Furthermore, in vitro molecular analysis showed that CsrR specifically binds to the bibA promoter and the phosphorilation increases the affinity of the regulator to this promoter region. Moreover, we demonstrated that CsrR acts as a repressor of bibA expression by binding to its promoter in vivo. In conclusion, this work by elucidating both the response of GBS to pathological glucose conditions and the underlined molecular mechanisms will set the basis for a better understanding of GBS pathogenesis.

Enhancing the efficiency of solar concentrators by controlled optical aberrations

The diameters of traditional dish concentrators can reach several tens of meters, the construction of monolithic mirrors being difficult at these scales: cheap flat reflecting facets mounted on a common frame generally reproduce a paraboloidal surface. When a standard imaging mirror is coupled with a PV dense array, problems arise since the solar image focused is intrinsically circular. Moreover, the corresponding irradiance distribution is bell-shaped in contrast with the requirement of having all the cells under the same illumination. Mismatch losses occur when interconnected cells experience different conditions, in particular in series connections. In this PhD Thesis, we aim at solving these issues by a multidisciplinary approach, exploiting optical concepts and applications developed specifically for astronomical use, where the improvement of the image quality is a very important issue. The strategy we propose is to boost the spot uniformity acting uniquely on the primary reflector and avoiding the big mirrors segmentation into numerous smaller elements that need to be accurately mounted and aligned. In the proposed method, the shape of the mirrors is analytically described by the Zernike polynomials and its optimization is numerically obtained to give a non-imaging optics able to produce a quasi-square spot, spatially uniform and with prescribed concentration level. The freeform primary optics leads to a substantial gain in efficiency without secondary optics. Simple electrical schemes for the receiver are also required. The concept has been investigated theoretically modeling an example of CPV dense array application, including the development of non-optical aspects as the design of the detector and of the supporting mechanics. For the method proposed and the specific CPV system described, a patent application has been filed in Italy with the number TO2014A000016. The patent has been developed thanks to the collaboration between the University of Bologna and INAF (National Institute for Astrophysics).