Postharvest characteristics of cut dahlia flowers with a focus on ethylene and effectiveness of 6-benzylaminopurine treatments in extending vase life

With the aim of extending vase life of cut dahlia flowers, we investigated the postharvest characteristics of the flowers. Our focus was on the role of ethylene on senescence and on treatments that have extended vase life of other flowers. Continuous exposure to ethylene at 2 or 10 μL L⁻¹ significantly accelerated petal abscission in cut flowers. Flowers continuously immersed in 1 or 10 μL L⁻¹ 2-chloroethylphosphonic acid (CEPA) solution wilted earlier than those treated with distilled water (DW) or 0.15 g L⁻¹ citric acid. Ethylene production from the ovary and ray petal was relatively high (4.5 and 0.9 nL g⁻¹ fresh weight h⁻¹, respectively) at harvest, but decreased gradually over 5 days. No remarkable increase in ethylene production was observed during senescence. Silver thiosulfate complex (STS), an inhibitor of ethylene action, did not extend the vase life of cut flowers, although a high silver concentration was detected in flower organs. In contrast, pulse treatment with 1-methylcyclopropene (1-MCP) and dip treatment with 6-benzylaminopurine (BA) extended the vase life of florets, and BA was more effective than 1-MCP when the flowers were held in both DW and CEPA. BA spray treatment extended vase life of cut ‘Kokucho,’ ‘Kamakura’ and ‘Michan’ flowers. These results suggest that dahlia flower senescence is partially regulated by ethylene, and BA is more effective in delaying the senescence of cut dahlia flowers than ethylene action inhibitors.     

Treatment with chlorine dioxide extends the vase life of selected cut flowers

The accumulation of bacteria in vase water is often associated with premature senescence in many cut flower species. In the present study, we tested the efficacy of aqueous chlorine dioxide (ClO₂) to extend flower display life by preventing the build-up of bacteria in vase solutions. The addition of 2 or 10 μL L⁻¹ ClO₂ to clean deionized water extended the vase life of Alstroemeria peruviana ‘Senna’, Antirrhinum majus ‘Potomic Pink’, Dianthus caryophyllus ‘Pasha’, Gerbera jamesonii ‘Monarch’, Gypsophila paniculata ‘Crystal’ and ‘Perfecta’, Lilium asiaticum ‘Vermeer’, Matthiola incana ‘Ruby Red’ and Rosa hybrida ‘Charlotte’ flowers by 0.9–13.4 d (7–77%) relative to control (i.e. 0 μL L⁻¹ ClO₂) stems. The beneficial effects of ClO₂ treatment were associated with a reduction in the accumulation of aerobic bacteria in vase water and on cut surfaces of flower stems. ClO₂ treatment was also effective in maintaining or extending the vase life of A. majus ‘Potomic Pink’, Dendrathema × grandiflorum ‘Albatron’, G. paniculata ‘Perfecta’ and M. incana ‘Ruby Red’ flowers even when stems were placed into water containing 10¹¹ CFU L⁻¹ bacteria. The efficacy of 10 μL L⁻¹ ClO₂ in vase water containing 0.2 g L⁻¹ citric acid and 10 g L⁻¹ sucrose to extend the display life of G. jamesonii ‘Lorca’ and ‘Vilassar’ flowers was equal to or greater than other tested biocides (i.e. aluminum sulfate, dichloroisocyanuric acid, 8-hydroxyquinoline sulfate, Physan 20™, sodium hypochlorite). Taken collectively, the results of the present study highlight the potential of aqueous ClO₂ for use as an alternative antibacterial agent in flower vase solutions.     

Increase in DNA fragmentation and the role of ethylene and reactive oxygen species in petal senescence of Osmanthus fragrans

In sweet osmanthus (Osmanthus fragrans Lour.) flowers, petal browning, partial abscission and wilting are the visible symptoms of senescence, 4–5 days after flowering, which seriously affect its ornamental and economic value. In the present study, DNA fragmentation was used as a marker to investigate the role of ethylene and reactive oxygen species (ROS) in flower senescence of O. fragrans ‘Liuye Jingui’. In intact plants, nuclear shrinkage and DNA fragmentation occurred at the late full flowering stage when senescence symptoms became visible. This coincided with a rapid increase in ethylene production, ROS generation and lipid peroxidation. To further determine the role of ethylene and ROS in flower senescence, cut flowers were treated with ethephon, silver thiosulphate (STS), hydrogen peroxide (H₂O₂), and vitamin C (Vc). The vase life of cut flowers was significantly prolonged by 0.2 mM STS and 2.5 mM Vc treatments, but reduced by 0.03% H₂O₂ and 500 mg L⁻¹ ethephon treatments, compared to distilled water. The percentage of DNA fragmentation was dramatically increased by ethephon but reduced by STS treatment throughout vase life. In contrast, the dramatic increase of DNA fragmentation in the H₂O₂ treated samples was only observed at day three, and clear petal abscission and rapid petal wilting occurred only with ethephon. Compared with the distinguishable nuclei and complete vacuoles in both STS treatment and distilled water, ethephon treatment caused substantial damage to large central vacuoles and other organelles, and many petal cells twisted out of shape due to a loss of cytoplasm, resulting in rapid petal wilting. Thus, it is concluded that ethylene plays an important role in flower senescence of sweet osmanthus, enhancing DNA fragmentation, damaging cellular structure, and leading to petal abscission and wilting. In addition, ROS is also involved in the regulation of late DNA degradation and lipid peroxidation.     

Determination of optimal sulfur dioxide time and concentration product for postharvest control of gray mold of blueberry fruit

Highbush blueberries (Vaccinum spp.) are a major export fruit crop of Chile which is stored at 0 °C and transported to markets in Asia, Europe, and the USA, using more than 15 d of maritime transportation. Under these conditions, gray mold caused by Botrytis cinerea can produce important economic losses. The effectiveness of sulfur dioxide (SO₂) concentration × time treatments on gray mold control was determined in the laboratory and validated prior to refrigerating the fruit, using pallet scale SO₂ fumigation treatment on the following blueberry cultivars: ‘Brigitta’, ‘Legacy’, ‘Liberty’ and ‘O’Neal’. In inoculated ‘Brigitta’ and ‘Liberty’ blueberries, gray mold prevalence varied from 97.2% to 97.5% in non-treated fruit, and this value was reduced from 7.9% to 6.1% in blueberries that were exposed to a SO₂ concentration × time (Ct) product of 400 (μL L⁻¹) h. The relationship between SO₂ Ct products and gray mold prevalence under laboratory conditions was best explained by exponential models, which had a determination coefficient (R²) that ranged from 0.88 to 0.96. The estimated EC₉₀ values varied between 245 and 400 (μL L⁻¹) h, and the SO₂ Ct between 250 and 350 (μL L⁻¹) h was validated using a pallet scale application treatment to obtain the best control and minimal variation. No visual phytotoxicity symptoms of SO₂ were observed with the Ct that was tested in this study. Therefore, SO₂ fumigation was demonstrated to be an effective and practical technology for reducing the risk of blueberry gray mold decay during storage, and further effort should be given to register the use of this product for blueberries in the main Chilean export markets.     

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.     

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.     

Internal ethylene concentrations in apple fruit at harvest affect persistence of inhibition of ethylene production after 1-methylcyclopropene treatment

Factors that affect the efficacy of 1-methycyclopropene (1-MCP) treatment of apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] include cultivar and maturity. In this study, ‘McIntosh’, ‘Cortland’ and ‘Empire’ apples were categorized by internal ethylene concentrations (IECs) at harvest, treated with 1 μL L⁻¹ 1-MCP, and the IECs of individual fruit followed at 30 d intervals during air storage at 0.5 °C for 90 d. IECs at harvest ranged from <0.5 μL L⁻¹ to ≥100 μL L⁻¹, 51 < 100 μL L⁻¹, and 10 < 50 μL L⁻¹ for ‘McIntosh’, ‘Cortland’ and ‘Empire’, respectively. 1-MCP treatment resulted in a decrease of IECs in fruit of all cultivars by day 30 after harvest. During subsequent storage IECs remained low in fruit with <1 μL L⁻¹ at harvest, but in ‘McIntosh’, ‘Cortland’ increased in proportion to IECs at harvest, but not in ‘Empire’. The importance of initial IECs in fruit on the persistence of 1-MCP inhibition of ethylene production was confirmed in a further experiment, in which IECs in untreated and 1-MCP treated ‘McIntosh’ and ‘Empire’ apples were measured for up to 194 d. 1-MCP also decreased 1-aminocyclopropene-1-carboxylic acid (ACC) concentrations in fruit. The results of our study are consistent with the hypothesis that IEC modulates the sensitivity of climacteric fruit to 1-MCP.     

Effect of antimicrobial compounds on cut Gerbera flowers: Poor relation between stem bending and numbers of bacteria in the vase water

Gerbera flowers (Gerbera jamesonii) often show stem bending. In four cultivars (Tamara, Liesbeth, Cora, and Mickey), we tested the effects on bending of antimicrobial compounds (chlorine bleach, a slow release chlorine compound, 8-hydroxyquinoline citrate [HQC], silver nitrate, carvacrol and thymol), some combined with sugars. At concentrations used for other cut flowers, inclusion in the vase solution of several of the antimicrobial compounds delayed bending, had no effect, or hastened bending. Hastening of bending was found at higher concentrations. It was accompanied with visible damage on the stem ends. Results with HQC indicated high toxicity as it did not delay bending at any of the concentration tested (100–400 mg L⁻¹). At 200 mg L⁻¹ HQC induced growth of bacteria that were not found in the controls. The number of bacteria in the vase water showed a low correlation with bending. Visible toxicity on the stem surface was often associated with a high bacteria count. However, at relatively high concentrations of the antimicrobial compounds stem bending was associated with a low count. This indicated an effect other than bacteria. Water uptake was low in stems that bent early. It is hypothesized that material from dead stem cells resulted in a xylem blockage which led to early bending. Sucrose at 15 g L⁻¹ in combination with an antimicrobial compound (slow release chlorine, HQC) resulted in the absence of stem damage and produced much less bending than the same concentration of the antimicrobial compounds alone. Sucrose apparently counteracted the toxic effects of the antimicrobial chemicals.     

Postharvest physiology and volatile production by flowers of Ptilotus nobilis

Ptilotus nobilis (Lindl.) F. Muell. has potential in the floriculture industries as a cut flower crop. Ethylene production and respiration rates, fresh weight changes and volatile scent production from cut inflorescences of P. nobilis cultivars Passion (dark pink flowers) and Purity (white-green flowers) were measured during vase life. Inflorescence weight loss was significant (P < 0.001) during vase life with wilting and colour loss being the primary reasons for loss of vase life. Inflorescences ready for the cut market stored and at 22 °C had vase lives of >12 d. Ethylene production by inflorescences was low to negligible. Treatment with silverthiosulphate (STS) and ethylene had no effects on vase life. Evidently, ethylene did not play a role in determining the postharvest longevity of cut P. nobilis flowers. Respiration rates of inflorescences were high at harvest (>700 mg CO₂ kg⁻¹ FW h⁻¹) and declined gradually thereafter during vase life. Total volatile emissions followed a similar pattern. For Passion, respiration rates of immature florets were significantly greater (P = 0.02) than florets from other developmental stages while the calyx produced the most CO₂. For Purity, respiration rates of florets of different maturities did not differ and the reproductive tissue produced the most CO₂. Only fully opened mature florets with their stigma and anthers revealed, emitted significant quantities of volatiles (P < 0.001) and primarily from the calyx tissue for both cultivars. The individual volatiles differed somewhat for the two cultivars. However, both produced significant quantities of benzaldehyde, 3,5-dimethoxytoluene and benzyl alcohol. These compounds have previously been associated with desirable floral scent.     

Genotypic differences in post-storage photosynthesis and leaf chloroplasts in response to ethylene and 1-methylcyclopropene in Aglaonema

This study investigated the effects of ethylene in storage and 1-methylcyclopropene (1-MCP) pretreatment on post-storage leaf senescence as measured by changes in photosynthesis and chloroplast degradation of two Aglaonema cultivars. Potted plants of ‘Chalit's Fantasy’ and ‘White Tip’ with or without 1-MCP treatment (600 nL L⁻¹ 1-MCP for 6 h) were exposed to 3.0 μL L⁻¹ ethylene, while being stored for 5 d at 16 °C in the dark, and then placed under an indoor environment for further observation. Plants that did not receive 1-MCP and ethylene served as controls. Ethylene did not affect the stomatal conductance in either cultivar. Ethylene reduced the net CO₂ assimilation rate and F_v/F_m (potential photochemical efficiency of photosystem II) in ‘White Tip’, but not in ‘Chalit's Fantasy’. Chloroplast number in a palisade or spongy mesophyll cell did not differ among treatments in ‘Chalit's Fantasy’. However, ethylene-treated ‘White Tip’ had fewer chloroplasts in the mesophyll cells, had more and larger plastoglobules in the chloroplasts, and had looser granal stacking with enlarged thylakoid lumens. ‘Chalit's Fantasy’ plants that were treated with 1-MCP before exposure to ethylene had higher net CO₂ assimilation rates and stomatal conductance than the control or plants that were exposed to ethylene without 1-MCP pretreatment. 1-MCP pretreatment mitigated the injurious effect of ethylene on ‘White Tip’ by increasing net CO₂ assimilation rate and F_v/F_m, and maintaining the quantity and structural integrity of chloroplasts.     

The combined effects of aqueous chlorine dioxide,fumaric acid,and ultraviolet-C with modified atmosphere packaging enriched in CO2 for inactivating preexisting microorganisms and Escherichia coli O157:H7 and Salmonella typhimurium inoculated on buckwheat sprouts

The combined effects of a sanitizer mixture, ultraviolet-C (UV-C), and modified atmosphere packaging (MAP) on the quality of non-inoculated and inoculated (Escherichia coli O157:H7 and Salmonella typhimurium) buckwheat sprouts were examined. Buckwheat sprouts were treated with a sanitizer mixture (comprising 100 mg L⁻¹ aqueous ClO₂ and 0.3% fumaric acid) and 2 kJ m⁻² UV-C, packaged under two different conditions (air and CO₂ gas) and storage for 8 d at 4 °C. The combination of the sanitizer mixture and UV-C treatment reduced the initial counts of preexisting microorganisms in the buckwheat sprouts by 1.9 log CFU g⁻¹ and reduced the initial inoculated counts of E. coli O157:H7 and S. typhimurium on buckwheat sprouts by 3.0 and 2.3 log CFU g⁻¹, respectively. The preexisting microorganisms and inoculated pathogens in buckwheat sprouts packaged under CO₂ gas were significantly reduced during storage following the combined treatment compared to those of the control by above 95%. Differences in Hunter L^*, a^*, and b^* values among the treatments were negligible. The combined sanitizer mixture and UV-C treatment increased the sprout rutin content by 147%, but there was no significant difference in 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity between treatments during storage. Therefore, the combination of sanitizer mixture made from aqueous ClO₂ and fumaric acid, UV-C irradiation, and MAP can improve the microbial safety and quality of buckwheat sprouts.     

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.     

A neural network technique to develop a vase life prediction model of cut roses

We developed neural network (NN) models using environmental, morphological, and physiological parameters to predict the vase life of cut roses grown in a greenhouse. These parameters were obtained during the growing and pre-marketing stages. A back-propagation training algorithm was used to develop the vase life prediction model. The network consisted of 29, 26, and 1 processing units in the input, hidden, and output layers, respectively. The NN was trained using the data of 123 cut ‘Asami Red’ roses and was validated using other data obtained from 30 cut roses. The results showed that the NN model had a relatively higher predictability (r² = 0.886, RMSEP = 0.984) between the predicted and observed values. Mixed data of rose cultivars ‘Asami Red’, ‘Bridal Pink’ and ‘Sonia’ were used to train the model. The validated model using the test data of the three cultivars still showed a good predictability (r² = 0.835, RMSEP = 1.126). The analyses showed that the NN model can predict the vase life of cut roses better than traditional statistical methods. Thus, we conclude that the NN is a superior approach to predict and guarantee the vase life of cut roses.     

Effects of cinnamon extract,chitosan coating,hot water treatment and their combinations on crown rot disease and quality of banana fruit

The antifungal activities of cinnamon extract (CE), piper extract (PE) and garlic extract (GE) were evaluated on banana crown rot fungi (Colletotrichum musae, Fusarium spp. and Lasiodiplodia theobromae) in vitro. The assay was conducted with extracts of CE, PE and GE with concentrations of 0, 0.1, 0.5, 1.0, 5.0, 10.0 and 0.75 g L⁻¹ of carbendazim (CBZ) on potato dextrose agar at room temperature. CE completely inhibited conidial germination and mycelial growth of all fungi at 5.0 g L⁻¹. PE totally suppressed mycelial growth of all fungi at 5.0 g L⁻¹ and conidial germination at 10.0 g L⁻¹ except for Fusarium spp. GE had no significant effects but low concentrations (0.1 and 0.5 g L⁻¹) enhanced germ tube elongation of the three fungi. The ED₅₀ values were higher for mycelial growth than for conidia except for Fusarium spp. Combined treatments were investigated on crown rot development in banana fruit (Musa AAA group ‘Kluai Hom thong’). Treatments included 5.0 g L⁻¹ CE, 1% (w/v) chitosan solution, hot water treatment (HWT, 45 °C for 20 min), CE plus chitosan, CE plus HWT and 0.75 g L⁻¹ of CBZ, applied before and after inoculation of the fruit. Crown rot development was assessed during storage at 13 °C for 7 weeks. Disease development was least (25%) on CE treated fruit after inoculation compared to CBZ but was higher when CE was applied before inoculation. Chitosan significantly delayed ripening as in terms of peel color, firmness, soluble solids and disease severity. CE showed no negative effects on quality of fruit. CE plus HWT caused unacceptable peel browning.     

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.     

Effects of ethylene on volatile emission and fragrance in cut roses: The relationship between fragrance and vase life

The relationship between fragrance and vase life and the role of ethylene on volatile emission in cut rose flowers was investigated. No relationship was observed between the amounts of volatile compounds emitted and vase life when fragrant and non-fragrant rose cultivars were compared. Neither ethylene production nor respiration rate of flowers was directly related with vase life. Volatile production during vase life was differential and independent among volatiles originating from different biosynthetic groups. Ethylene did not play a role in the regulation of volatile emission in rose flowers. Endogenous ethylene production was very low in most of the cultivars and did not show autocatalytic production trends. Volatile emission patterns during vase life did not parallel endogenous ethylene production. Exogenous ethylene exposure had differential effects among all cultivars, regardless of the fragrance of the flower. Fragrant cultivar ‘Osiana’ was highly sensitive to exogenous ethylene, with petals abscising within 24 h of ethylene (1 μL L^?1) exposure while other fragrant cultivars ‘Erin’ and ‘Lovely Dream’ had low ethylene sensitivity. Volatile production was unaffected by exogenous ethylene. The results of this study indicate that volatile emission in cut roses is not regulated by endogenous or exogenous ethylene and occurs independently of petal senescence and/or abscission. These results provide a better understanding of the complexity of volatile emission in rose flowers.     

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.     

Volatile profiles of ripening West Indian and Guatemalan-West Indian avocado cultivars as affected by aqueous 1-methylcyclopropene

Separate experiments were conducted with three major commercial avocado (Persea americana Mill.) cultivars grown in Florida: ‘Simmonds’ (early-season, West Indian race); ‘Booth 7’ (mid-season, Guatemalan-West Indian hybrid); and ‘Monroe’ (late-season, Guatemalan-West Indian hybrid). Fruit were harvested at preclimacteric stage and left untreated (Control) or treated 24 h after harvest with aqueous 1-methylcyclopropene (1-MCP) at 1.39 (treatment M1) or 2.77 μmol L⁻¹ a.i. (treatment M2) (75 or 150 μg L⁻¹) for 1 min at 20 °C. Whole fruit ripening was monitored at 20 °C/92% ± 3% R.H. and based on whole fruit firmness, respiration and ethylene evolution. Fruit volatiles were assessed at preclimacteric (24 h after harvest), mid-ripe (half of initial fruit firmness) and ripe maturity stages, from 100 g of chopped pulp using a purge and trap system. Untreated, firmer fruit ‘Monroe’ (268 N at harvest) ripened within 12 d of harvest while softer fruit ‘Simmonds’ (118 N) ripened within only 6 d. 1-MCP treatment extended ripening time from 33% (M1) to 83% (M2). All fruit softened normally, indicating the potential benefits of aqueous 1-MCP as a postharvest treatment for avocado when applied at these concentrations. Volatile profiles differed among the three cultivars with several compounds detected in only one cultivar, results that may contribute to a potential identification of the origin of the cultivar based on fruit volatile composition. The West Indian cultivar ‘Simmonds’ had much higher emission of hexanal (preclimacteric fruit) and cis-3-hexenal and cis-3-hexen-1-ol (ripe fruit) than the Guatemalan-West Indian hybrids ‘Booth 7’ and ‘Monroe’. On the other hand, these latter hybrids had much higher levels of alkanes than ‘Simmonds’. Treatment with 1-MCP increased emissions of alkanes during ripening of ‘Booth 7’ and ‘Monroe’. Total volatiles of avocado decreased during ripening mainly due to the significant reduction of sesquiterpenes, the main group of volatiles in all cultivars at harvest (‘Simmonds’, 53%; ‘Booth 7’, 78%; ‘Monroe’, 66%). β-Caryophyllene was the major compound at harvest, but decreased to less than 2% in ripe fruit, at which point most sesquiterpenes were not detected. Among the 10 sesquiterpenes commonly found in the avocado cultivars in this study, only α-Copaene had significantly higher emissions in mid-ripe fruit treated with the higher concentration of 1-MCP (2.77 μmol L⁻¹ a.i.), suggesting that ethylene participates in the regulation of this sesquiterpene.     

The effects of 1-MCP in cyclodextrin-based nanosponges to improve the vase life of Dianthus caryophyllus cut flowers

The present research investigated the effects of a non-volatile formulation of 1-methylcyclopropene (1-MCP) embedded in different cyclodextrin (CD)-based nanosponges (NSs) to extend the postharvest longevity of an ethylene-sensitive carnation cultivar. Cut flowers of Dianthus caryophyllus L. ‘Idra di Muraglia’ were treated with α- and β-CD-based nanosponge-1-MCP complexes (α- and β-NS complexes) in tap water to achieve two different concentrations of active ingredient (0.25 and 0.5 μL L^?1). Treated flowers were compared to cut stems exposed to equivalent concentrations of volatile 1-MCP as well as a tap water control with or without pure α- and β-NS. Identical nanoporous compounds were applied by perfusion to yield a total of 15 treatments. Twenty-four hours after the treatments were applied, the cut flowers were exposed to exogenous ethylene (1 ± 0.2 μL L^?1) for 24 h. The postharvest carnation flower and leaf quality in addition to ethylene production levels were determined daily (beginning 24 h after treatment). None of the α-NS complex applications statistically improved the vase life of cut flowers; however, β-NS complexes were effective in preventing senescence, reducing ethylene production (measured at nearly nil after 11 d), and maintaining original petal color longer. These results were particularly strong at the lowest concentration (0.25 μL L^?1) of β-NS complex. Overall, this method promoted cut flower longevity (loss of ornamental value after 14.7 d; complete damage at day 18.5) better than the commercial 1-MCP gaseous application method.