Alternative strategies for nitrogen fertilization of overwinter processing spinach (Spinacia oleracea L.) in Southern Italy

To identify the best practice for nitrogen (N) fertilization of overwinter processing spinach, two field experiments were carried out in the Foggia plain (Southern Italy), one of the most vocated area for leafy vegetables production. The field trials were aimed to define and suggest the proper fertilizer dose, typology and the right time of application. Experiment 1 evaluated four N fertilizer doses (0, 150, 225, 300 kg ha⁻¹) in a two-year field trial. Experiment 2 was aimed to assess the effect of the split distribution of prilled urea fertilizer in comparison with the application of nitrification inhibitor (DMPP) containing urea fertilizer, broadcasted at sowing.Spinach yield, yield quality (nitrate – NO₃⁻ – and carotenoids content), N-use efficiency and risk of soil nitrate (NO₃⁻-N) leaching were evaluated. The processing spinach yielded 37.8 and 3.6 t ha⁻¹ of fresh and dry yield, respectively (average of the two experiments). Fresh and dry yield among the fertilizing treatments were similar. Also the β-carotene and the lutein content of spinach leaves (19.5 and 38.1 mg kg⁻¹, respectively) were not affected by the N fertilizer dose. Conversely, the N dose strongly influenced the NO₃⁻ content of the leafy vegetable tissues (1286 mg kg⁻¹ on average, 58% lower than the limits imposed by the EC regulation). As expected, the different rainfall pattern influenced both the leaf NO₃⁻ content and the risk of soil NO₃⁻-N leaching. The results achieved demonstrated that, in order to get a favorable trade-off, among yield, yield quality, N-use efficiency and environmental impact, the processing spinach growers of the Foggia plain area should be encouraged to apply 225 kg N ha⁻¹ as maximum fertilization rate. Also, the split urea fertilizer application appeared as the more effective strategy for N fertilization of overwinter spinach in comparison with the use of the nitrification inhibitor containing urea fertilizer, being the last strategy not able to adequately match the N crop demand.     

Essential oils and silver nanoparticles (SNP) as novel agents to extend vase-life of gerbera (Gerbera jamesonii cv. ‘Dune’) flowers

The aim of this study was to evaluate the efficacy of silver nanoparticles (SNP) and essential oils as novel antimicrobial agents in extending the vase-life of gerbera (Gerbera jamesonii cv. ‘Dune’) flowers. The vase-life of flowers held in a solution containing 5 mg L⁻¹ SNP plus 6% sucrose was found to be significantly higher than with 8-HQC (8-hydroxyquinoline citrate) or control treatments. However, the vase-life was not different to that of flowers held in similar concentrations of silver nitrate. All gerbera flowers held in SNP solutions showed significantly higher relative fresh weight than the control. Vase-life of gerbera flowers was extended by addition of either 50 or 100 mg L⁻¹ carvacrol and either 1 or 2 mg L⁻¹ SNP from 8.3 to 16 d. In addition, the relative fresh weight and solution uptake of gerbera flowers were increased by addition of 100 mg L⁻¹ essential oils and 1 or 2 mg L⁻¹ SNP as compared to that of control flowers. Our results suggest the potential application of essential oils or SNP as novel alternatives to common chemicals used in preservative solutions for gerbera flowers.     

Low irradiance pulses improve postharvest quality of spinach leaves (Spinacia oleraceae L. cv Bison)

The aim of this work is to extend and improve the postharvest life of mature spinach leaves using clean technologies like the use of short pulses of light at low irradiance. After harvest spinach leaves were immediately sealed in polyethylene bags in the laboratory. These bags were placed in a dark chamber at 23 °C under continuous dark or with the application of light pulses (LP) consisting of 15 min each 2–6 h or 7 min each 2 h for 3 d. The chosen irradiance, 30 μmol m⁻² s⁻¹ PPFD, corresponded to the light compensation point previously measured in spinach plants under greenhouse conditions. After the leaves were treated with LP for 3 d, all the samples were transferred to a chamber at 4 °C under continuous dark for another week. Senescence was triggered in leaves under continuous dark after 3 d of storage and delayed in those receiving LP. In addition ascorbic acid and glutathione contents were kept higher in LP-treated than in untreated spinach. These trends were conserved after storage under continuous dark and refrigeration for another week. When LP was applied in combination with 1-MCP the antioxidant capacity was further improved. These results demonstrate that short LP of low irradiance can be used to extend and to improve postharvest life of mature spinach leaves.     

Effects of ozone treatments on microbial quality and some chemical properties of lettuce,spinach, and parsley

The effects of distilled, ozonated (12 mg L⁻¹) and chlorinated (100 mg L⁻¹) water treatments on inactivation of Escherichia coli and Listeria innocua inoculated on lettuce, spinach, and parsley and on some chemical characteristics (chlorophyll a, chlorophyll b, ascorbic acid, and total phenolic contents and antioxidant activity) of these vegetables were investigated. Chlorine and ozone washes resulted in average log reductions (±standard error) of 2.9 ± 0.1 and 2.0 ± 0.3 for E. coli in the vegetables tested, respectively, while the efficiency of ozone (2.2 ± 0.1 log) was very close to that of chlorine (2.3 ± 0.1 log) on L. innocua. Aqueous ozone did not cause any detrimental effects on the chemical characteristics of the vegetables. The effect of gaseous ozone treatment (950 μL L⁻¹, 20 min) on microbial inactivation and the chemical characteristics of parsley were also determined. This treatment resulted in 1.0–1.5 log reductions in the numbers of both microorganisms but caused significant losses in important bioactive compounds of parsley. Ascorbic acid and total phenolic contents and antioxidant activity in ozone-treated samples were 40.1, 14.4, and 41.0%, respectively, less than the control samples.     

Hay yield and nitrogen harvest in smooth bromegrass mixtures with alfalfa and red clover in relation to nitrogen application

An experiment was conducted in order to investigate hay yield and nitrogen harvest in binary smooth bromegrass (Bromus inermis Leyss cv. Tohum Islah) mixtures with alfalfa (Medicago sativa L. cv. Kayseri) and red clover (Trifolium pratense L. cv. Tohum Islah) in Erzurum, Turkey for 5 years between 1991 and 1995. The Hay yield, nitrogen harvest, protein concentration and land equivalent ratio (LER) in the mixtures with alternating rows of 1:1, 2:1 and 1:2 of smooth bromegrass with alfalfa and red clover were compared to those in pure legume stands without any N-fertilizer application or pure smooth bromegrass stands that received 0, 50, 100 and 150 kg ha⁻¹ N. The mixtures had no N fertilization apart from 40 kg N ha⁻¹ in the establishment year. The dry matter production in all the mixtures receiving no N fertilizer application was higher than in pure legume stands. Pure grass stands were sustained only with the application of 150 kg ha⁻¹ N. The highest hay yields were obtained from the mixtures of smooth bromegrass (Sb) with red clover (Rc) (2Rc 1Sb) (14.65 t ha⁻¹) and with alfalfa (A) (1A 1 Sb) (14.49 t ha⁻¹). Although N application increased Sb yields in pure stands, the highest yields obtained with N fertilization were still lower than the yields in the mixtures without N application. The superiority of the mixtures was also reflected by their large N harvests (e.g. 355.9 kg N ha⁻¹ in 2Rc 1Sb plots) compared to pure Rc (317.8 kg N ha⁻¹), pure A (294.3 kg N ha⁻¹) and pure Sb stands that received 150 kg N ha⁻¹. The nitrogen harvest increased in pure Sb plots as the N doses applied increased. Furthermore, the protein concentration of the hay from the mixtures (158.2–165.7 mg g⁻¹) was equal to that of the pure A stands (165.7 mg g⁻¹) and higher than that of pure Sb stands (122.9 mg g⁻¹ at 150 kg N ha⁻¹ application) although the hay from pure Rc plots had the highest protein concentration (179.3 mg g⁻¹). The LER values were also higher in the mixtures (e.g. 1.28 in 1A 1Sb and 1.28 in 2Rc 1Sb plots) compared with the pure stands. The mixture plots also had a more balanced temporal distribution of hay. The grass component was more productive in early spring, whereas the legume fractions grew better in the summer. In conclusion, for a sustainable production of high-quality hay and greater N harvests without using N fertilizers, binary mixtures of Sb with A in alternating rows (1A 1Sb) were recommended for long-purpose stands and in alternation with double red clover rows (2Rc 1Sb) for short purpose stands under similar conditions. N application could be eliminated in the grass–legume mixtures without any yield depression.     

Impact of a decontamination step with peroxyacetic acid on the shelf-life,sensory quality and nutrient content of grated carrots packed under equilibrium modified atmosphere and stored at 7 °C

Peroxyacetic acid (PAA) is a strong oxidizer and exerts antimicrobial properties. The effect of a decontamination step with 80 and 250 mg L⁻¹ PAA on shelf-life of grated carrots stored under equilibrium modified atmospheric packaging at 7 °C was determined and compared with the shelf-life of unwashed and water-washed carrots. Microbial parameters, including total aerobic plate count, numbers of lactic acid bacteria, Lactobacillae and yeasts, and sensory quality were evaluated. Next to these parameters, atmospheric gas composition, pH and nutrient content were also monitored. The suggested packaging configuration prevented CO₂ accumulation, but at the end of the study anoxic conditions were reached for unwashed carrots and carrots washed with 80 mg L⁻¹ PAA. The microbial shelf-life of water-washed carrots was 4 d based on the yeast count, whereas the flavour was not acceptable after 5 d. The total aerobic plate count and the yeast count determined the shelf-life of carrots treated with 80 mg L⁻¹ PAA on 5 d, whereas the flavour was unacceptable after 7 d. None of the microbial parameters determined the shelf-life of carrots washed with 250 mg L⁻¹ PAA. However, this treatment had already a pronounced adverse effect on the initial sensory quality. Water washing already decreased the content of all individually studied nutrients (−16 to −28%), except for lutein content and the antioxidant capacity. Additional losses after adding PAA on day 0 were found for α-tocopherol and phenols. Regardless of the applied treatment, α- and β-carotene remained stable during storage, whereas ζ-carotene, lutein and α-tocopherol were unstable. The phenol content and the antioxidant capacity of unwashed, water-washed and 80 mg L⁻¹ PAA-treated carrots increased significantly at the end of the storage period, whereas no changes were found in carrots treated with 250 mg L⁻¹ PAA.On the condition that carrots were packed under an adequate EMA, the 80 mg L⁻¹ PAA treatment showed possibilities for extending shelf-life without pronounced effects on nutrient content.     

Respiration rate response of four baby leaf Brassica species to cutting at harvest and fresh-cut washing

The influence of the first and second cutting at harvest on the physiological response of four baby leaf Brassica species was studied. The species were salad rocket (Eruca vesicaria), wild rocket (Diplotaxis tenuifolia), mizuna (Brassica rapa L. ssp. nipposinica) and watercress (Nasturtium officinale) stored at 1, 4, 8 and 12 °C. In addition, the microbial and metabolic behaviours of baby leaves were evaluated after different washing treatments including water, ozonated water (10 mg L⁻¹ total dose), ozonated water activated with ultraviolet C light (UV-C) and heat shock wash (50 °C, 1 min). Temperature had a significant effect on both respiration rate and post-cutting life. The production of CO₂ increased between 2- and 4-fold when temperature increased from 1 to 12 °C. Minor differences in leaf respiration rate between the first and second leaf cutting were observed for salad rocket and wild rocket, while leaves from the second cutting of mizuna and watercress leaves had a higher respiration rate than from the first cutting. Ozone, and ozone combined with UV-C, were the most efficient washing treatments in reducing total mesophilic counts, while heat shock treatment did not affect them. Additionally, naturally occurring Listeria spp. were controlled well in wild rocket and mizuna (<1 log cfu g⁻¹) when the ozone treatments were applied. On the other hand, respiration rates of the Brassica species were not substantially affected by the washing treatments when stored at 4 °C. Maximum CO₂ production was observed immediately after washing but decreased during the first 24 h of storage. Baby leaves washed with cold water consistently showed a lower respiration rate than the other washing treatments. Heat shock was the washing treatment that most influenced the increase in the respiration rate of baby leaves during storage at 8 °C.     

Neutral and acidic electrolyzed water as emergent sanitizers for fresh-cut mizuna baby leaves

The effects of 40, 70 or 100 mg L^?1 free chlorine neutral and acidic electrolyzed water (NEW and AEW) during the washing and disinfection step, on quality attribute changes during shelf life of fresh-cut mizuna baby leaves, were studied. Physiological, nutritional, enzymatic, sensory, and microbial changes throughout 11 days at 5 °C were monitored. Results were compared to those reached with a conventional industrial treatment of 100 mg L^?1 NaClO at pH 6.5 and with a control washing with deionised water. Both NEW and AEW showed an inhibitory effect on natural microflora growth and retained the main quality attributes. Total chlorophyll content was preserved after shelf life. Initial total phenolic contents ranged between 1868 and 2518 mg CAE kg^?1 fw for AEW 40 and AEW 100 treatments respectively and slightly increased throughout shelf life. In contrast, after shelf life the total antioxidant activity recorded on the processing day decreased around 35%. Throughout shelf life EW induced an increase in catalase activity while superoxide dismutase activity decreased. Scanning electron microscopy of the leaves showed that neither NEW nor AEW affected their surface structure. To the best of our knowledge, the effects of NEW and AEW on bioactive quality parameters, as well as on antioxidant enzyme activities for fresh-cut baby leaves are first reported here. EW provides an alternative sanitizing technique to NaClO for maintaining the quality of fresh-cut mizuna baby leaves up to 11 days at 5 °C.     

Effects of phosphine fumigation on postharvest quality of four Chinese cut flower species

Chrysanthemum (White, Yellow, and Daisy), carnation (Master and Barbara), rose (Carola, Black magic, Diana, Champagne, and Avalanche), and Chinese rose (Golden Medallion, Diplomat, Marina, and Athena) are the main Chinese cut flower species produced for exportation. Cut flowers infested with quarantine pests need methyl bromide (MB) fumigation to satisfy phytosanitary requirements of importing countries. Phosphine (PH₃) is a potential alternative to methyl bromide. Development of phosphine as a phytosanitary treatment requires information regarding its phytotoxicity to cut flowers. Therefore phosphine fumigation at 24 °C and 2 °C was investigated to evaluate its effects on the postharvest quality of cut flowers. Phosphine fumigation for 6 h with dosages as high as 12.2 mg L⁻¹ at 24 °C produced no adverse effects on flower color, diameter, vase life, and other damage indices (DI) for all cultivars. However, different adverse effects on some cultivars were observed after 12 d fumigation at 2 °C. There were significant changes for color values of Carola, Black magic, Diana, Champagne, Avalanche, and Diplomat; significant decrease in flower diameter and vase life of Diana, Champagne, and Avalanche at 3.04 mg L⁻¹, white Chrysanthemum and Diploma at 1.52 and 3.04 mg L⁻¹; significant increase in DI of Champagne and Avalanche at 3.04 mg L⁻¹, and White chrysanthemum, Diana, and Diploma at 1.52 and 3.04 mg L⁻¹. In combination with information on phosphine toxicity to insect pests at ambient and low temperatures in the literature, it is suggested that phosphine fumigation could be a viable replacement of MB fumigation for quarantine treatment of these four cut flower species.     

Phosphorus management in low input stockless cropping systems: Crop and soil responses to contrasting P regimes in a 36-year experiment in southern France

Fertiliser recommendation systems should aim at a finer tuning of non-renewable P inputs for agronomic, environmental and economic reasons. Modern decision support systems should take into account the relevant soil characteristics, the P recycling capabilities of the cropping system, and crop requirements for attainable production in a range of soil/weather conditions. Unfortunately, information is still lacking for low input cropping systems in south-western France. In 1968 INRA Toulouse set up a P experiment, which has been going on for 36 years, on a deep alluvial silty-clay/clay soil with varying CaCO₃. Four P regimes (P0, P1, P2, P4) were arranged in four blocks with periodic changes in the fertiliser dressings. Wheat, maize, sunflower, sorghum and soybean were tested for grain yield (GY) and grain P concentration (GPC) response to soil Olsen P concentration. The highest GY were observed in both P2 and P4, although P1 yields were significantly lower in only 4 years out of 36. P0 resulted 32 times in lower yields than P2–P4 and 27 times in lower yields than P1. Wheat was the crop most sensitive to the absence of P fertilization (GY_P0/GY_Pmax = 0.72); maize and sorghum were intermediate (0.77) and sunflower was the less sensitive on average (0.83). As the highest GPC values were observed in the P4 treatments, P removal was maximum for P4 (21.9 kg P ha⁻¹ year⁻¹) and minimal in P0 (11.7 kg P ha⁻¹ year⁻¹). The critical soil Olsen P values for yield responses were determined using the Cate–Nelson and Mitscherlich approaches. Although the thresholds differ for the two methods (3.3–7.2 mg P kg⁻¹ with Cate–Nelson; 4.4–11.2 mg P kg⁻¹ with Mitscherlich), crops ranked similarly with both methods. Critical soil P values were lowest for maize and highest for sunflower, while wheat, soybean and sorghum had intermediate values. Because of low-input management and frequent water stress, critical values fall within the lower range of published values. Only in the P4 treatment were P-Olsen values potentially hazardous for the environment (>20 mg P kg⁻¹) 8–10 years after the beginning of the experiment. Annual P dressings of 17.5 kg P ha⁻¹ year⁻¹ (P1) were sufficient to achieve good yields but P dressings of 35 kg P ha⁻¹ year⁻¹ (P2) were necessary to stabilize soil P around the critical level in the calcareous part of the experiment.     

Control of postharvest grey mould (Botrytis cinerea Per.: Fr.) on strawberries by glucosinolate-derived allyl-isothiocyanate treatments

The vapours of allyl-isothiocyanate (AITC) were evaluated in in vitro and in vivo trials against Botrytis cinerea, a severe pathogen of strawberries. In in vitro trials AITC activity was assayed on conidial germination and mycelial growth of the fungus. The mycelium appeared less sensitive to AITC than conidia (EC₅₀ values of 1.35 mg L⁻¹ and 0.62 mg L⁻¹, respectively). In addition, AITC had a fungistatic effect against the pathogen, since the values of EC₅₀, for both parameters, increased by around 30% after AITC removal. In in vivo trials, ‘Tecla’ and ‘Monterey’ strawberries (spring-bearing and day-neutral cultivars, respectively) obtained from organic production and naturally infected by B. Cinerea, were exposed for 4 h in an atmosphere enriched by pure AITC or derived from defatted seed meals of Brassica carinata (0.1 mg L⁻¹, in a 0.1 m³ treatment cabinet). After 2 days at 0 °C and another 3–4 days at 20 °C, the fruit were evaluated for grey mould infections. The AITC treatment reduced the decay caused by the pathogen by over 47.4% up to 91.5%, significantly different from the untreated fruit. No significant differences were found between synthetic and glucosinolate-derived AITC. Residue analysis performed on fruit at the end of storage (7 d after treatment) showed values lower than 1 mg kg⁻¹. Total phenolic content and antioxidant capacity estimated in treated and untreated strawberries showed no significant difference between control and AITC treated fruit. Our results show it is possible to reduce the incidence of postharvest grey mould on strawberries with a treatment of AITC (0.1 mg L⁻¹) for 4 h, opening a potential application of biofumigation in the postharvest control of B. cinerea in strawberry.     

Characterization of sensitivity of grove and packing house isolates of Penicillium digitatum to pyrimethanil

In most northeast Argentinean citrus packing houses, postharvest fungicide treatments are based on the use of thiabendazole and imazalil. However, these fungicides have been used in a manner highly conducive to the selection and proliferation of resistant biotypes of Penicillium digitatum, the main fruit decay fungus in the area. Recently, a new fungicide, pyrimethanil (PYR), was introduced to control molds. Aims of this study were to determine the baseline sensitivities for PYR against isolates of P. digitatum considering its use in the region is not yet widespread and to evaluate the control of the fungus in vivo. One hundred and nine (109) P. digitatum isolates were collected from diseased fruit within citrus groves (43 isolates) and packing houses (66 isolates). EC₅₀ was determined for each isolate by measuring colony diameters on different agar dilutions of the fungicide. The mean EC₅₀ value of the green mold isolates collected from the groves was 0.14 ± 0.03 mg L⁻¹ while the mean EC₅₀ of those collected from packing houses was 0.13 ± 0.05 mg L⁻¹. No resistant isolates were found in the field where the fungicide is not used, while one isolate originated from a packing house showed an EC₅₀ of 3.40 mg L⁻¹, 26-fold higher than the mean level. This isolate was collected from lemons stored in cool rooms of a packing house where PYR had not been used. Fruit decay by sensitive isolates was reduced approximately 80% by PYR applied at 500–600 mg L⁻¹ by immersion for 60 s at room temperature to inoculated oranges and mandarins. In contrast, the resistant isolate was not controlled by PYR applied at 1000 mg L⁻¹. Thus, the introduction of PYR applied into packing houses should be done carefully and control strategies should be implemented in order to minimize the development of resistant isolates.     

Combination of peracetic acid and hot water treatment to control postharvest brown rot on peaches and nectarines

Brown rot caused by Monilinia spp. is the most important postharvest disease of stone fruit. From preliminary studies, the combination of 0.25% hydrogen peroxide, 0.02% peracetic acid (PAA) and 0.075% acetic acid, corresponding to 300 mg L⁻¹ of PAA, was selected to control Monilinia fructicola. Brown rot control was similarly controlled when the same concentration of PAA was applied with a PAA-based commercial product. In order to reduce PAA concentration, combinations of different concentrations and temperatures were evaluated. A treatment of 200 mg L⁻¹ of PAA at 40 °C for 40 s was selected to control pre-existing and future infections, different inoculum concentrations of M. fructicola and to control brown rot on naturally infected fruit. Brown rot was completely controlled with the selected treatment when peaches and nectarines were inoculated 0 h before the treatment but it was not controlled when infection time was increased to 24, 48 and 72 h. Also, the treatment significantly controlled brown rot at all inoculum concentrations evaluated (10³, 10⁴, 10⁵ and 10⁶ conidia mL⁻¹) in both peaches and nectarines, but no protection against future infections was observed. In naturally infected fruit, brown rot incidence was slightly but significantly reduced to 61 and 36% in ‘Roig d’Albesa’ and ‘Placido’ peaches, respectively, but not in nectarines. Immersion for 40 s in 200 mg L⁻¹ of PAA at 40 °C provides an alternative treatment to control only recent infections of Monilinia spp. whatever their concentration without generally affecting fruit quality.     

Gamma irradiation increases storability and shelf life of minimally processed ready-to-cook (RTC) ash gourd (Benincasa hispida) cubes

Radiation treatment in a dose range of 0.5–2.5 kGy in combination with low temperature storage (4–15 °C) was attempted for improvement in shelf life of ready-to-cook (RTC) ash gourd (Benincasa hispida). Parameters such as microbial load, color, firmness and sensory attributes were monitored during storage. Optimum processing conditions (2 kGy; 10 °C) resulted in improved shelf life of seven days compared to the non-irradiated controls. Total bacterial count of 1.57 × 10³ CFU/g was recorded at the end of storage period (12 d). Higher total phenolic content and total antioxidant activity was observed in irradiated samples as compared to control. Irradiated samples had total phenolic content of 103.3 ± 5.2 mg kg⁻¹ and total antioxidant activity of 384.2 ± 9.7 mg kg⁻¹ while corresponding values for control samples were 67.8 ± 5.4 and 115.5 ± 7.0 mg kg⁻¹ at the end of storage period. Irradiated samples (2 kGy) showed excellent sensory and visual qualities during entire storage period.     

Low temperature phosphine fumigation for postharvest control of Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae) on carnation

Phosphine (PH₃) fumigation with different concentrations and exposure durations at low temperature was studied to determine its effects on Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae) on carnations, and on postharvest quality. Laboratory tests showed that tolerance of L. huidobrensis to phosphine fumigation at 5 °C varied with different life stages. 1 d-old eggs and adults showed the highest susceptibility, and 3 d-old eggs was the most tolerant stage. In the fumigation tests of 3 d-old eggs with a range of phosphine concentrations from 0.46 to 2.73 mg L⁻¹ and exposure durations from 6 to 144 h at 5 °C, 85.96–282.08 h fumigation durations were required to achieve 99% mortality with different phosphine concentrations. The expression of C^0.77T = k was obtained, which indicated that exposure duration other than phosphine concentration was the critical factor in the toxicity of phosphine against the 3 d-old eggs of L. huidobrensis. Controlled atmosphere (CA) treatment with increased CO₂ and reduced O₂ had synergistic effects on phosphine toxicity. Phosphine fumigation could achieve 100% mortality for insects of L. huidobrensis on carnation, and had no significant adverse effects on vase life and damage indices of carnation at 1.92 mg L⁻¹ PH₃ and 8% CO₂ for 32 h, and at 3.44 mg L⁻¹ for 3 d at 5 °C. All results suggested that phosphine fumigation at low temperature could be used as an alternative for postharvest control of L. huidobrensis on carnations.     

Development of SCAR markers and a semi-selective medium for the quantification of strains Ach 1-1 and 1113-5, two Aureobasidium pullulans potential biocontrol agents

Aureobasidium pullulans strains Ach 1-1 and 1113-5 are two effective biocontrol agents against Botrytis cinerea and Penicillium expansum on stored apples. In the present work, a monitoring system allowing their identification and quantification was developed. The methodology used consisted of the development of both molecular markers and a semi-selective medium. The random amplified polymorphic DNA (RAPD) technique was applied to a collection of 15 strains of A. pullulans, including Ach 1-1 and 1113-5. Five specific RAPD fragments were amplified for strain Ach 1-1 and three others for strain 1113-5. Among them, a fragment of 528 bp specific to strain Ach 1-1 (generated with the OPR-13 RAPD primer) and another one of 431 bp specific to strain 1113-5 (amplified with the OPQ-03 RAPD primer) were selected, cloned, sequenced, and used to design sequence-characterized amplified region (SCAR) primers. Three different SCAR markers were amplified: two specific to strain Ach 1-1 (189 bp and 387 bp) and one specific to strain 1113-5 (431 bp). These SCAR primers can clearly identify strains Ach 1-1 and 1113-5 among 14 strains of A. pullulans and among eight yeast strains commonly present on apple fruit surfaces. Their selectivity was also tested using DNA extracted from epiphytic microflora of the apple surface. As a semi-selective medium, PDA medium supplemented with 0.5 mg L⁻¹ euparen, 1 mg L⁻¹ sumico, 2.5 mg L⁻¹ hygromycin B, 30 mg L⁻¹ streptomycin sulphate, and 1 mg L⁻¹ cycloheximide was selected. It inhibited the development of the air microflora and appeared highly toxic for the epiphytic microflora of apple surface without altering the growth of the targeted strains Ach 1-1 and 1113-5. The combination of the semi-selective medium and SCAR markers provides a valuable monitoring tool to specifically identify and quantify A. pullulans strain Ach 1-1 and strain 1113-5 and could be used in future studies to evaluate their population dynamics under various laboratory and practical conditions.     

1-Methyl cyclopropene extends postharvest life of spinach leaves

Senescence of detached spinach leaves either untreated or treated with 0.1 or 1.0 μL L^?1 1-MCP has been investigated. 1-MCP treated leaves had higher chlorophyll content and photosystem II potential quantum yield (Fv/Fm) and lower solute leakage than untreated leaves after storage in darkness at 23 °C for 6 d, indicating a delay of senescence. Ethylene production was increased in spinach supplemented with 1-MCP after 3 d storage and then declined to the rates of untreated leaves. 1-MCP treated spinach had higher ascorbic acid and glutathione concentrations, and a low oxidised/reduced ratio for both antioxidants. Accumulations of ammonium and protein degradation were reduced by 1-MCP. The results presented here indicate that inhibition of ethylene sensitivity can be successfully used to extend the postharvest life of spinach leaves.     

Rheological and chemical predictors of texture and taste in dessert banana (Musa spp.)

To be able to account for sensory qualities earlier in the assessment of a new banana hybrid in a selection scheme, predicting the sensory perception of banana texture and taste by instrumental parameters was investigated. Thirteen cultivated banana and four new triploid hybrids were characterized by sensory profiling, and rheological and chemical analyses. Multilinear regressions were used to calibrate predictions using 13 cultivated bananas, and the quality of predictions was validated using four hybrids. The sensory characteristics sourness and sweetness were predicted by titratable acidity (R² = 0.68) and pH (R² = 0.66). Malate and citrate were the main contributors to sweetness and sourness. Astringency was predicted by total tannins (R² = 0.55). Rheological parameters from texture profile analyses (stress at fracture, fracturability) were more suitable than pulp puncture force to predict the sensory texture properties firmness (R² = 0.47) and melting (R² = 0.60). These textural properties were predicted by titratable acidity and dry matter content (R² = 0.62). Predictions of mealiness, adhesiveness, and heterogeneity were not efficient. Differences of 3.6–3.7 meq 100 g⁻¹ FW in titratable acidity or of 0.30 g 100 g⁻¹ FW in malate or citrate were required to ensure a detectable difference in sourness or sweetness (p = 0.9). Pulp puncture force needed to differ by a minimum of 0.9 N before a difference in firmness could be perceived by the panelists. In conclusion, while models to predict sourness and sweetness can now be used for high throughput phenotyping, we recommend additional tests for other sensory attributes.     

Application of low intensity light pulses to delay postharvest senescence of Ocimum basilicum leaves

Fresh basil (Ocimum basilicum L.) is a highly perishable leafy green vegetable with a storage life of 4–5 d at room temperature. Exposure of basil leaves to temperatures below 12 °C during storage results in chilling injury; therefore, refrigeration cannot be used to extend postharvest life of basil. Typically, leafy vegetables are stored in darkness or extremely low irradiance. Darkness is known to induce senescence, and the initial phase of senescence is reversible by exposure to light. In this work, we studied the effects of low-intensity white light pulses at room temperature on postharvest senescence of basil leaves. Daily exposure for 2 h to 30–37 μmol m⁻² s⁻¹ of light was effective to delay postharvest senescence of basil leaves. Chlorophyll and protein levels decreased, ammonium accumulated and leaves developed visual symptoms of deterioration (darkening) during storage in darkness. Light pulses reduced the intensity of these senescence symptoms. The photosynthesis light compensation point of basil leaves was 50 μmol m⁻² s⁻¹ i.e., higher than the intensity used in this study, and the effect of treatment with red light was the same as with white light, while far red light was ineffective. Light pulses exerted a local effect on chlorophyll loss, but the effect on protein degradation was systemic (i.e., spreading beyond the illuminated parts of the leaf blade). The results of this study indicate that daily treatment for 2 h with low intensity light (30–37 μmol m⁻² s⁻¹ every day) during storage at 20 °C is an effective treatment to delay postharvest senescence of basil leaves. The delay of postharvest senescence by low intensity light pulses seems to be mediated by phytochromes, and it is systemic for protein, and partially systemic for chlorophyll degradation.     

Essential oil vapours suppress the development of anthracnose and enhance defence related and antioxidant enzyme activities in avocado fruit

Anthracnose caused by Colletotrichum gloeosporioides is a major postharvest disease in avocados that causes significant losses during transportation and storage. Complete inhibition of the radial mycelia growth of C. gloeosporioides in vitro was observed with citronella or peppermint oils at 8 μL plate⁻¹ and thyme oil at 5 μL plate⁻¹. Thyme oil at 66.7 μL L⁻¹ significantly reduced anthracnose from 100% (untreated control) to 8.3% after 4 days, and to 13.9% after 6 days in artificially wounded and inoculated ‘Fuerte’ and ‘Hass’ fruit with C. gloeosporioides. GC/MS analysis revealed thymol (53.19% RA), menthol (41.62% RA) and citronellal (23.54% RA) as the dominant compounds in thyme, peppermint and citronella oils respectively. The activities of defence enzymes including chitinase, 1, 3-β-glucanase, phenylalanine ammonia-lyase and peroxidase were enhanced by thyme oil (66.7 μL L⁻¹) treatment and the level of total phenolics in thyme oil treated fruit was higher than that in untreated (control) fruit. In addition, the thyme oil (66.7 μL L⁻¹) treatment enhanced the antioxidant enzymes such as superoxide dismutase and catalase. These observations suggest that the effects of thyme oil on anthracnose in the avocado fruit are due to the elicitation of biochemical defence responses in the fruit and inducing the activities of antioxidant enzymes. Thus postharvest thyme oil treatment has positive effects on reducing anthracnose in avocados.