I. Mignani

Ascorbic acid metabolism during bilberry (Vaccinium myrtillus L.) fruit development

Bilberry (Vaccinium myrtillus L.) possesses a high antioxidant capacity in berries due to the presence of anthocyanins and ascorbic acid (AsA). Accumulation of AsA and the expression of the genes encoding the enzymes of the main AsA biosynthetic route and of the ascorbate-glutathione cycle, as well as the activities of the enzymes involved in AsA oxidation and recycling were investigated for the first time during the development and ripening of bilberry fruit. The results showed that the AsA level remained relatively stable during fruit maturation. The expression of the genes encoding the key enzymes in the AsA main biosynthetic route showed consistent trends with each other as well as with AsA levels, especially during the first stages of fruit ripening. The expression of genes and activities of the enzyme involved in the AsA oxidation and recycling route showed more prominent developmental stage-dependent changes during the ripening process. Different patterns of activity were found among the studied enzymes and the results were, for some enzymes, in accordance with AsA levels. In fully ripe berries, both AsA content and gene expression were significantly higher in skin than in pulp.

Influence of Ca2+ and 6-benzyladenine on chestnut (Castanea sativa Mill.) in vitro shoot-tip necrosis

Abstract Shoot apex necrosis affects in vitro chestnut cultures particularly during the rooting stage. Lack of cytokinins or Ca2+ deficiency in the culture medium have been reported to be responsible for occurrence of tip necrosis. In the present research the effects of three Ca2+ levels (3, 9 and 18 mmol l−1) were tested on C. sativa ‘Garrone rosso’ and ‘Clone 46’ shoots treated for rooting. Tissue Ca2+ content of the apical, middle and basal portion of both brown and healthy shoots was determined. In a second trial the tip necrosis related effect of the local (tip) application of CaCl2 (3 mmol l−1), BA (5 μmol l−1) and CaCl2 + BA (3 mmol l−1 and 5 μmol l−1) was tested on Clone 46 shoots, during rooting. With regard to Ca2+ concentration in the rooting medium, no significant difference could be detected from the three tested Ca2+ levels on tip necrosis but the highest one caused a drop in rooting ability. Regardless of Ca2+ concentration, Garrone rosso showed a lower percentge of the disorder and a higher affinity for calcium in terms both of uptake and ion translocation. The data of the second trial showed that the local application of 5 μmol l−1 BA completely eliminated tip necrosis while the application of CaCl2 + BA delayed the appearance of the disorder. Apex calcium content of shoots treated locally revealed that the most the healthy tissue contained higher calcium levels than the necrotic one. BA treated shoots contained the lowest ion levels, independently from their status.

Evaluation of borage extracts as potential biostimulant using a phenomic, agronomic, physiological and biochemical approach

Biostimulants are substances able to improve water and nutrient use efficiency and counteract stress factors by enhancing primary and secondary metabolism. Premise of the work was to exploit raw extracts from leaves (LE) or flowers (FE) of Borago officinalis L., to enhance yield and quality of Lactuca sativa ‘Longifolia,’ and to set up a protocol to assess their effects. To this aim, an integrated study on agronomic, physiological and biochemical aspects, including also a phenomic approach, has been adopted. Extracts were diluted to 1 or 10 mL L–1, sprayed onto lettuce plants at the middle of the growing cycle and 1 day before harvest. Control plants were treated with water. Non-destructive analyses were conducted to assess the effect of extracts on biomass with an innovative imaging technique, and on leaf photosynthetic efficiency (chlorophyll a fluorescence and leaf gas exchanges). At harvest, the levels of ethylene, photosynthetic pigments, nitrate, and primary (sucrose and total sugars) and secondary (total phenols and flavonoids) metabolites, including the activity and levels of phenylalanine ammonia lyase (PAL) were assessed. Moreover, a preliminary study of the effects during postharvest was performed. Borage extracts enhanced the primary metabolism by increasing leaf pigments and photosynthetic activity. Plant fresh weight increased upon treatments with 10 mL L–1 doses, as correctly estimated by multi-view angles images. Chlorophyll a fluorescence data showed that FEs were able to increase the number of active reaction centers per cross section; a similar trend was observed for the performance index. Ethylene was three-fold lower in FEs treatments. Nitrate and sugar levels did not change in response to the different treatments. Total flavonoids and phenols, as well as the total protein levels, the in vitro PAL specific activity, and the levels of PAL-like polypeptides were increased by all borage extracts, with particular regard 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 to indeed exert biostimulant effects on lettuce; future work will be required to further investigate on their efficacy in different conditions and/or species.

Cell Wall Physicochemical Properties as Indicators of Peach Quality During Fruit Ripening after Cold Storage

A comparative study between melting flesh peach fruit (Prunus persica L. Batsch cvs. Royal Glory and Morettini No 2) with contrasting tissue firmness during their on-tree ripening was conducted. Such fruit were cold stored (0 °C) for 4 and 6 weeks, and subsequently transferred at 25 °C (shelf life) for up to 5 days and evaluated for quality attributes and cell wall physicochemical properties. Data were partly unexpected, since fruit of the soft cultivar (Morettini No 2) were characterized by lower exo- and endo-PG activity, lower amounts of ethylene evolution, as well as higher amounts of endogenous calcium bound in the cell wall compared to fruit of the firmer cultivar (Royal Glory). These differences may be attributed to the incidence of chilling injury symptoms, evident as loss of juiciness in Morettini No 2 fruit, while Royal Glory fruit were characterized by acceptable appearance and eating quality even after 6 weeks cold storage plus 5 days shelf life, as the fruit softened gradually without cell rupture. Overall results showed that no direct relationship between cell wall physicochemical properties and sensory attributes can be established, indicating the complexity of peach fruit ripening. Since fruit of both cultivars presented similar tissue firmness after 5 days shelf life an attempt to distinguish normal peach fruit softening from cell rupture-chilling injury also has been made in the current study.

Nondestructive Apple Ripening Stage Determination Using the Delta Absorbance Meter at Harvest and after Storage

The delta absorbance (DA) meter is a handheld instrument which noninvasivelymeasures the chlorophyll content in fruits. In the present work, it was used to monitor the ripening process linked to the climacteric phase in apple (Malus ·domestica). The results [index of absorbance difference (IAD)] were correlated to quality attributes at harvest and after commercial scale storage at different conditions. Two cultivars (Red Delicious, Golden Delicious) were analyzed in two different seasons, whereas Morgenduft and Gala were analyzed only in the first and second seasons, respectively. In general, a linear reduction of the IAD values was observed in all apple cultivars along with the progression of ripening and ethylene biosynthesis.When ethylene productionwas inhibited by 1-methylcyclopropene (1MCP) treatment, the decrease of IAD values was markedly reduced. IAD threshold values for each cultivar were identified, delineating the central phase of the ethylene climacteric rise. Predictive models were built by correlating IAD index to the soluble solids concentration (SSC), titratable acidity (TA), and firmness measured at harvest and after removal from different storage regimes. The best model was developed for SSCprediction on ‘RedDelicious’ apple [ratio performance deviation (RPD) = 1.88] and for firmess evaluation in ‘GoldenDelicious’ apple (RPD = 1.84). Moreover, IAD values were consistently associated with the differences in fruit quality as affected by optimal and suboptimal storage conditions. The IAD, due to its acceptable accuracy and speed of assessment, can be a promising tool for assisting in sorting apples before and after storage in warehouses or commercial packing lines. IAD cannot totally replace standard ripening indices, but can effectively supplement data for these parameters.