STUDIES OF QUALITY AND NUTRIENT USE EFFICIENCY IN VEGETABLE CROPS GROWN UNDER DIFFERENT SUSTAINABLE CROPPING SYSTEM

Lo scopo del progetto di dottorato \ue8 stato quello di valutare gli effetti a livello fisiologico, biochimico e molecolare di prodotti biostimolanti su ortaggi da foglia (lattuga e rucola) e di approfondire la conoscenza sulla loro modalit\ue0 di azione. La prima parte del lavoro ha riguardato lo studio degli effetti di estratti acquosi di foglie (LE) e fiori (FE) di Borago officinalis L. su piante di lattuga, attraverso l\u2019utilizzo di tecniche di fenomica, agronomia, fisiologia e biochimica. I risultati ottenuti hanno mostrato come gli estratti di borragine siano in grado di aumentare il metabolismo primario e secondario nelle piante trattate. La concentrazione di flavonoidi totali, fenoli e proteine totali, come anche l\u2019attivit\ue0 in vitro della PAL e dei relativi livelli di proteine hanno mostrato un aumento a seguito dei trattamenti, in particolare dopo l\u2019applicazione dell\u2019estratto a base di fiori di borraggine. L\u2019estratto di fiori si \ue8 dimostrato efficace anche nel prevenire la degradazione dei pigmenti fotosintetici durante la conservazione post raccolta di foglie di lattuga. Si pu\uf2 quindi affermare che gli estratti a base di borragine, in particolare l\u2019estratto a base di fiori, sembrano possedere attivit\ue0 biostimolante su piante di lattuga. Gli stessi estratti sono stati applicati anche su piante di rucola, per verificare l\u2019influenza dei trattamenti sul metabolismo del nitrato e osservare le risposte indotte a livello molecolare. \uc8 stata effettuata l\u2019analisi dell\u2019espressione genica dei principali geni che codificano per gli enzimi coinvolti nel metabolismo del nitrato (nitrato reduttasi DtNR, nitrito reduttasi DtNiR, glutammato sintasi DtGLU, glutammina sintetasi DtGS1, trasportatore del nitrato DtNTR). Il risultato pi\uf9 interessante \ue8 stato, a livello biochimico, la marcata riduzione della concentrazione di nitrato nelle foglie di rucola a seguito dei trattamenti, influenza confermata anche dall\u2019incremento dell\u2019attivit\ue0 della nitrato reduttasi in vivo. I trattamenti hanno influenzato anche l\u2019espressione dei geni studiati, confermando che gli estratti testati hanno un ruolo nei processi fisiologici in cui tali geni sono coinvolti. Sono state anche svolte analisi mirate ad una migliore caratterizzazione gli estratti. \uc8 stata valutata l\u2019attivit\ue0 ormono-simile degli estratti su mutanti di mais e, considerando le numerose propriet\ue0 attribuite alla borragine, \ue8 stata anche testata la possibile attivit\ue0 allelopatica degli estratti sulla germinazione di differenti specie erbacee. L\u2019estratto a base di foglie ha mostrato un moderato effetto auxino-simile. Entrambi gli estratti di borragine sembrano possedere un effetto di inibizione sulla germinazione delle specie testate. \uc8 stata inoltre condotta un\u2019attivit\ue0 in collaborazione con un\u2019azienda multinazionale per valutare l\u2019efficacia di alcuni biostimolanti commerciali e prototipi sulla qualit\ue0 di ortaggi da foglia e sulla protezione contro stress di tipo abiotico (in particolare stress salino).The purpose of the Ph. D. research project was to investigate the effects of biostimulant products on leafy vegetables (lettuce and rocket) and deepen the knowledge on their mode of action. The first part of the work regarded the further deepening of the effects of aqueous extracts obtained from leaves (LE) and flowers (FE) of Borago officinalis L. on lettuce, involving phenomic, agronomic, physiological, and biochemical aspects. Results showed that borage extracts enhanced the primary metabolism. Total flavonoids and phenols, as well as the total protein levels, the in vitro PAL specific activity, and the levels of PAL-like polypeptides increased by all borage extracts, with particular regards to FEs. FEs also proved efficient in preventing degradation and inducing an increase in photosynthetic pigments during storage. In conclusion, borage extracts, with particular regard to the flower ones, appear indeed to exert biostimulant effects on lettuce. The borage extracts were also applied on rocket plants, to investigate the influence of treatments on nitrate assimilation pathway and on the molecular responses. Gene expression analysis of the main enzymes involved in the nitrate metabolism (DtNR, DtNiR, DtGLU, DtGS1, DtNTR) was evaluated. From the biochemical point of view, the most interesting result was surely the substantial reduction of nitrate level caused by both extracts, confirmed also by the increment of the NR in vivo activity. Borage treatments influenced also the gene expression, confirming that extracts have a role in the physiological processes in which the considered genes are involved. In addition, work regarding borage extracts characterization was carried out. The auxin- and gibberellin-like activity of extracts on maize mutants was explored and, due to the multitude properties attributed to borage, the allelopathic effects of borage extracts on seeds germination of different plant species was investigated. LE treatment seems to possess a slight auxin-like activity. The bioassay on allelopathic properties of borage LE and FE demonstrated that they exert an effect on seeds germination (inhibition effect). The work included also an activity carried out in collaboration with a private company to study the effectiveness of commercial biostimulants and prototypes on leafy vegetables quality and protection against abiotic stresses (salt stress)

Antioxidant and Mineral Composition of Three Wild Leafy Species : A Comparison Between Microgreens and Baby Greens

Wild plants may play an important role in human nutrition and health and, among them, many are the leafy species. We hypothesized that the wild greens could be profitably grown as microgreens and baby greens, specialty products whose market is increasing. We compared three wild leafy species (Sanguisorba minor Scop., Sinapis arvensis L., and Taraxacum officinale Weber ex F. H. Wigg.) harvested at the microgreen and baby green stages. Seedlings were grown hydroponically in a half-strength Hoagland nutrient solution under controlled climatic conditions. At harvest, the yield was assessed, and chlorophylls, carotenoids, anthocyanins, phenolic index, nitrate, and mineral elements were measured in the two types of product. The potential contribution to human mineral intake was calculated, and the possible risk due to the presence of metals potentially detrimental for health was estimated. Results showed that micro/baby greens of the studied wild plants achieved competitive yields and could contribute to the dietary intake of macroelements, microelements, and non-nutrient bioactive compounds. On the other hand, the wild greens showed high amounts of nitrate and traces of some metals potentially detrimental for health, suggesting the need for caution in the use of wild species for producing microgreens and baby leaves

Benzothiadiazole enhances ascorbate recycling and polyphenols accumulation in blueberry in a cultivar-dependent manner

Benzothiadiazole (BTH) is a functional analogue of salicylic acid able to induce systemic acquired resistance in many horticultural crops. The aim of the work was to investigate how BTH may affect i) fruit quality, ii) ascorbic acid (AsA) oxidation and recycling metabolism and iii) phenolic compounds accumulation, during development and ripening of berries from the two selected cultivars. Blueberry (Vaccinium corymbosum L.) plants (cv ‘Brigitta’ and ‘Duke’) were treated with 0.118 mM BTH every two weeks during ripening, then all fruits of each plant were harvested and divided in four developmental stages. Results indicated that BTH had no marked effects on fruit quality parameters. During the first developmental stage, BTH negatively affected dry matter in both cv, while soluble solids and AsA content were affected in ‘Duke’. In fully ripe berries, BTH reduced dry matter in ‘Duke’ and enhanced soluble solids content in ‘Brigitta’, while diminishing titratable acidity. AsA content was positively affected by BTH in ‘Duke’, but not in ‘Brigitta’. The effect of BTH on the enzymes involved in AsA recycling was recorded in berries at the third (fruit more than half pigmented) and fourth developmental stages. After treatment, in both cv ascorbate peroxidase (APX) activity increased in fully ripe berries, while monodehydroascorbate reductase (MDHAR) activity was stimulated at the third ripening stage. Conversely, the activities of dehydroascorbate reductase (DHAR) and glutathione reductase (GR) were enhanced only in ‘Brigitta’ and in ‘Duke’, respectively. BTH stimulated total polyphenols, flavonoid and anthocyanin accumulation in ‘Brigitta’ and in ‘Duke’ at the third and fourth ripening stages. In fully ripe berries, BTH enhanced the accumulation of delphinidins, cyanidins, petunidins and peonidins in ‘Brigitta’, while in ‘Duke’ it increased all classes of anthocyanidins, including malvidin. On the contrary, the relative proportion of the individual anthocyanins was only slightly affected by BTH treatment, mainly regarding delphinidin and malvidin at the third and fourth stage of ripening of ‘Duke’ and ‘Brigitta’, respectively. These results show that preharvest BTH application can positively impact on fruit bioactive compounds levels, affecting AsA recycling and content and increasing polyphenols accumulation in fruit, but partly depending on cv and ripening stage

The Mixing Ratio and Filling-Amount Affect the Tissue Browning and Antioxidant Properties of Fresh-Cut Baby Leaf Lettuce (Lactuca sativa L.) and Rocket (Eruca sativa Mill.) Grown in Floating Growing Systems

Different types of baby leaf vegetables (BLV) are often mixed and packaged as salad mixes. This work has evaluated the effects of BLV mixing ratios (100% lettuce ‘Lollo Bionda’, 100 LB; 75% lettuce + 25% rocket, 75 LB; 50% lettuce + 50% rocket, 50 LB) and the weight filling amount (125 g filling amount, 125F; 250 g, 250F) on the antioxidant properties and browning potential (BP) of lettuce and rocket baby leaves during storage for 9 days at 4 °C in the dark. The samples were packaged in thermos-sealed bags previously prepared using polypropylene film. The results showed that the 50 LB mix had preserved high amounts of chlorophylls and internal nutrients on d9, regardless of the filling amount. No visible browning symptoms were detected in the 50 LB samples. The 50 LB × 125F mix was found to be the most efficient strategy to maintain the antioxidant property of BLV. Thus, the optimisation of the mixing ratio and its combination with an appropriate filling amount could represent an effective postharvest practice