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

Effects of Two Doses of Organic Extract-Based Biostimulant on Greenhouse Lettuce Grown Under Increasing NaCl Concentrations

The enhancement of plant tolerance toward abiotic stresses is increasingly being supported by the application of biostimulants. Salinity represents a serious problem in the Mediterranean region. To verify the effects deriving from the application of biostimulants, trials on Romaine lettuce plants under salt exposure were performed, in greenhouse. Plants were subjected to three NaCl solutions with 0.8, 1.3, and 1.8 dS/m of electrical conductivity. The volume of the solution was 200 mL/plant and delivered every 3 days. Biostimulant treatments started after crop establishment and were: control (water) and two doses (0.1 or 0.2 mL/plant) of the commercial biostimulant Retrosal® (Valagro S.p.A), containing calcium, zinc, and specific active ingredients. Four Retrosal® treatments were applied, every 7 days, directly to the substrate. Non-destructive analyses were conducted to assess the effects on leaf photosynthetic efficiency. At harvest, plants fresh weight (FW) and dry weight were determined, as well as the concentration of chlorophylls, carotenoids, total sugars, nitrate, proline, and abscisic acid (ABA). The biostimulant tested increased significantly the FW of lettuce (+65% in the highest dose) compared to controls. Results indicate that treatments positively affected the chlorophyll content measured in vivo (+45% in the highest dose) and that a general positive effect was observable on net photosynthesis rate. Retrosal® seems to improve the gas exchanges under our experimental conditions. The total sugars levels were not affected by treatments. Biostimulant allowed maintaining nitrate concentration similar to the untreated and unstressed controls. The increasing levels of water salinity caused a raise in proline concentration in control plants (+85%); biostimulant treatments at 0.2 mL/plant dose kept lower the proline levels. All plants treated with the biostimulant showed lower value of ABA (-34%) compared to controls. Results revealed that Retrosal® is able to stimulate plant growth independently from the salinity exposure. However, treated plants reached faster the commercial maturity stage. The fresh biomass of control at the end of experiment, after 30 days, ranged from 15 to 42 g/head, while in biostimulant treated plants ranged from 45 to 94 g/head. The product applied at maximum dose seems to be the most effective in our experimental conditions

Evaluation of postharvest storage and treatments in cut ruscus foliage

Danae racemosa (L.) Moench is an important cut foliage in the ornamental market. During postharvest, leaf senescence symptoms are leaf yellowing, weight loss and/or abscission of leaves. The aim of this work was to evaluate the effect of pre-treatments for 24 h with glycerol and Thidiazuron (TDZ) on Danae vase life before and after storage. Treatments were applied in vase water containing glycerol 0.1, 1 or 10 mM, 10 μM TDZ and a combined treatment of 10μM TDZ plus 10 mM glycerol. The effect of treatments was evaluated through the determination of vase life, chlorophyll content, chlorophyll a fluorescence parameters, sucrose and total sugars content. The cut foliages were stored in sealed plastic bags and placed in a dark room at 4°C for two months. The vase life, before and after storage, was determined in a controlled chamber set to 20°C and RH 50-60% with a light intensity of 20 μmol m-2 s-1. Results demonstrated that 10μM TDZ plus 10 mM glycerol was the most effective treatment in maintaining quality during vase life of stored and not stored cut foliage

The Impact of COVID-19 on Horticulture: Critical Issues and Opportunities Derived from an Unexpected Occurrence

The COVID-19 pandemic is causing many victims worldwide and has generated a serious economic crisis. Substantial changes have occurred in the food and ornamental production chains. The aim of the present review has been to summarize some of the main effects that the pandemic is having on horticulture and on the new habits of people. Infections and quarantine measures have prevented the regular flow of certain goods and of connected services. Cases of shortages and/or surpluses, a lack of the availability of labor, and a reduction in demand for some food products and flowers have occurred. New food production approaches have emerged and a reconnection between farmers and consumers has been spreading, thereby facilitating product distribution. Moreover, during the forced isolation, people have had to face periods of stress. The benefits that can be derived from leisure activities related to flowers and ornamental plants, and from access to nature and urban green spaces are increasingly being recognized as relevant. The seriousness of the pandemic will inevitably lead to lasting changes. Therefore, the vulnerability of the pre-COVID-19 distribution chains should be considered and a new food production chain should be drawn up, to increase the resilience of such systems