1-MCP Pretreatment Research Articles

Early Chilling Injury Symptom Development and Recovery of Mature Green Banana: Involvement of Ethylene under Different Severities of Chilling Stress

The involvement of stress ethylene in early chilling injury (CI) symptom development of mature-green (MG) banana fruit was examined using the ethylene action inhibitor, 1-methyclopropene (1-MCP). MG banana fruit pretreated with 0 or 50 μg L−1 1-MCP were stored at two chilling temperatures, 5 °C or 10 °C, for 0, 1, 12, or 72 h (different CI stresses), then transferred to 20 °C (rewarming) for 2 d. Irreversible CI symptoms that developed during 72 h storage at 5 or 10 °C included vascular browning and epidermal color parameters (L*, chroma, and hue angle). Some CI symptoms drastically intensified during exposure to 5 or 10 °C for 72 h, even being exacerbated after rewarming. Fruit in the other treatments suffered milder CI, and the recovery response progressed from slight and reversible to severe and irreversible with longer durations of exposure to lower temperatures. The effect of 1-MCP pretreatment was to attenuate the effect of chilling in terms of the CI symptom development (i.e., the browning of sub-epidermal tissues and the increasing of electrolyte efflux) and to promote recovery after rewarming, especially for the fruit stored at 5 °C, indicating the potential involvement of ethylene in membrane structural alterations under CI stress.

1-MCP prevents ultrastructural changes in the organelles of Dendrobium petals that are induced by exogenous ethylene

Ethylene is a plant hormone that causes flower senescence. Dendrobium flowers are sensitive to ethylene and ethylene can induce premature senescence depending on the cultivar and the ethylene concentration. Dendrobium ‘Lucky Duan’ is one of the most sensitive cultivars to ethylene exposure. Open florets of ‘Lucky Duan’ were subjected to ethylene, 1-MCP, or 1-MCP plus ethylene treatments and compared with an untreated control. Ethylene induced earlier development of color fading, drooping and venation in petals, whereas 1-MCP pre-treatment counteracted these changes. Under light microscopy, epidermal cells and mesophyll parenchyma tissue around the vascular bundles of petals treated with ethylene showed collapsed cells whereas 1-MCP pre-treatment counteracted this collapse. An scanning electron microscopy (SEM) study confirmed clearly that ethylene treatment caused the collapse of mesophyll parenchyma tissue around vascular bundles. Ultrastructural changes were also studied using transmission electron microscopy (TEM) and showed that ethylene treatment induced morphological changes in conjunction with disorganization of the plasma membrane, the nuclei, chromatin, the nucleoli, myelin bodies, multivesicular bodies, and mitochondria including changes in size and number, breakages of membranes, enlargement of intercellular spaces and disintegration. 1-MCP pre-treatment was observed to counter these changes that were induced by ethylene. The role of ethylene-induced ultrastructural changes in the different organelles was apparently associated with membrane damage.

Delaying ripening using 1-MCP reveals chilling injury symptom development at the putative chilling threshold temperature for mature green banana.

Storage at the putative chilling threshold temperature (CTT) to avoid chilling injury still limits postharvest handling of tropical fruit like banana in that ripening may occur at the CTT. To determine whether chilling injury (CI) symptoms would develop in mature green (MG) banana fruit if the CTT exposure was extended by inhibiting ethylene action and thus ripening, 1-methylcyclopropene (1-MCP) was applied. Individual ‘fingers’ from multiple ‘clusters’ of MG bananas were either immersed in water or 50 μg L−1 1-MCP (a.i.) solution and each treatment was divided into three subgroups for storage at 5.0°C (severe CI), 13.0°C (mild CI), or 14.0°C (CTT) ± 0.1°C. 1-MCP delayed ripening in terms of color change for 10 days for fruit stored at the CTT. Ethylene production by fruit at 5.0°C remained around 0.04 ng kg−1 s−1 with no obvious increase during 31-day storage. Ethylene production at 14.0°C (−1-MCP/+1-MCP) increased on Day 33 while increasing on Day 38 for 13.0°C fruit without 1-MCP and on Day 39 for fruit with 1-MCP. Peak climacteric ethylene occurred on Days 44 and 39 for 13.0 and 14.0°C fruit without 1-MCP, respectively, and on Days 59 and 51 for 13.0°C and 14.0°C 1-MCP-treated fruit, respectively. As hypothesized, longer exposure of MG banana fruit to the CTT of 14.0°C without onset of ripening as was allowed by prior 1-MCP treatment allowed CI to develop at that normally non-chilling temperature. Vascular browning was the first visual and most sensitive CI symptom in the experiment and was observed on Day 4 at 5.0°C, Day 10 at 13.0°C, Day 19 at 14.0°C without 1-MCP, and on Day 28 at 14.0°C with 1-MCP. Using a 1-MCP pre-treatment to remove the influence of ethylene from bananas stored at 13°C or 14°C also resulted in slight reduction in vascular browning severity. In conclusion, a putative safe temperature may become a CI temperature if the shelf-life-limiting factor is removed, allowing longer exposure. Chilling at the CTT caused relatively mild injury on fruit, and vascular browning is a sensitive indicator of CI status, while the light-adapted quantum yield of photosystem II [Y(II)] could be a non-destructive indicator of early CI stress in MG banana. Fruit at 13.0/14.0°C developed CI symptoms slightly later with 1-MCP than without 1-MCP. This suggests that ethylene might be involved in early CI symptom development.

Ethylene pretreatment induces phenolic biosynthesis of fresh-cut pitaya fruit by regulating ethylene signaling pathway

Understanding the role of signals involved in wounding responses allows designing and improving preservation technology of fresh-cut products. The present work evaluated the role of ethylene as a signal molecule on phenolic biosynthesis induced by wounding in fresh-cut pitaya fruit at the physiological and gene expression levels. Ethylene pretreatment positively promoted the increases of phenolics and flavonoids of fresh-cut pitaya fruit by improving activities and relative gene expressions of the pivotal enzymes in phenylpropanoid pathway. It accelerated reactive oxygen species (ROS) production at the beginning of storage but caused lower ROS levels during the middle and later periods. Moreover, fresh-cut pitaya fruit pretreated with ethylene showed lower ethylene production rate in comparison with the control, but higher expression levels of ethylene receptor genes (HuETR1 and HuETR2), transcription factor genes (HuEIN3s and HuERF1s) and lower expression levels of the negative ethylene regulator HuCTR1s. On the contrary, the ethylene receptor inhibitor, 1-MCP pretreatment not only reduced the wound-induced phenolic accumulation, prevented the activation of ROS and phenylpropane metabolism, but also inhibited the up-regulation of HuETR1, HuETR2, HuEIN3s and HuERF1s. Taken together, our present work suggested that ethylene pretreatment induced phenolic biosynthesis in fresh-cut pitaya fruit by regulating ethylene signaling pathway.

Ethylene Induces a Rapid Degradation of Petal Anthocyanins in Cut Vanda 'Sansai Blue' Orchid Flowers.

Ethylene plays a major role in the regulation of flower senescence, including in the ethylene-sensitive Vanda ‘Sansai Blue’ orchid flowers. This cut flower is popular in Thailand due to its light blue big size florets possessing a beautiful shape pattern. In the present study, we further examined the rapid ethylene-induced process of active anthocyanin degradation in cut Vanda ‘Sansai Blue’ flowers, which occurred much before detection of other typical senescence-related symptoms. For this purpose, the cut inflorescences were exposed to air (control), 1 or 10 μl L−1 ethylene for 24 h, or to 0.2 μl L−1 1-methylcyclopropene (1-MCP) for 6 h followed by 10 μl L−1 ethylene for 24 h at 21°C, and the effects of these treatments on various parameters were assayed. While the fading-induced effect of ethylene was not concentration-dependent in this range, the ethylene treatment significantly reduced the flower vase life in a concentration-dependent manner, further confirming the separation of the bleaching process from senescence. Exposure of the inflorescences to 1-MCP pre-treatment followed by 10 μl L−1 ethylene, recovered both inflorescence color and anthocyanin content to control levels. Quantification of total anthocyanin content, performed by HPLC analysis on the basis of cyanidin-3-glocuside equivalents, showed that ethylene reduced and 1-MCP recovered the anthocyanins profile in non-hydrolyzed anthocyanin samples of Vanda ‘Sansai Blue’ florets, assayed at half bloom and bloom developmental stages. The results showed that the ethylene-induced color fading, observed immediately after treatment, resulted from a significant reduction in the levels of the two main anthocyanidins, cyanidin and delphinidin, as well as of other anthocyanidins present in low abundance, but not from changes in the levels of flavonols, such as kaempferol. This anthocyanin degradation process seems to operate via ethylene-increased peroxidase activity, detected at the bud stage. Taken together, our results suggest that the ethylene-induced rapid color bleaching in petals of cut Vanda ‘Sansai Blue’ flowers is an outcome of in-planta anthocyanin degradation, partially mediated by increased peroxidase activity, and proceeds independently of the flower senescence process.

Efficacy of 1-MCP on controlling ethylene sensitivity and extending vase life of sensitive and less sensitive cut orchid flowers

This study was conducted to investigate the effects of 1-MCP on the sensitivity to ethylene and postharvest quality of selected cut orchid flowers. Cut orchid flowers are considered as the ethylene sensitive but there are apparently variation in sensitivity among species, cultivars and hybrids. Low effective concentration of 1-MCP and its minimum residues have caused that 1-MCP been viewed as an important and safe candidate for replacing STS. Inflorescences of each Dendrobium ‘Darren Glory’ (DDG), D. ‘Sonia Bom’ (DSB), Mokara ‘Calypso Jumbo’ (MCJ) and M. ‘Chiti Gold’ (MCG) hybrids were purchased from a commercial farm. After harvest and transport to the Postharvest Lab they were divided into two groups and placed in two chambers. They exposed to 0 and 300 nL L-1 1-MCP for 4 hours. The chambers were opened for 1 hour airing. Then inflorescences of each chamber divided to two subgroups and treated with 0 and 1 µL L-1 ethylene gas, balanced with nitrogen. After 24 hours the chambers were opened and the inflorescences were taken out from them. The inflorescences were kept in the laboratory with normal condition. The most weight loss and longest vaselife was recorded in DDG and MCG with 44% and 14 days respectively. Meanwhile, maximum postharvest quality improvement was obtained by 1-MCP pretreatment in very sensitive cut orchid hybrids.

Effect of Postharvest 1-MCP Pre-treatment on the Quality and Freshness Maintenance of Cut Flower Cymbidium ‘In the mood'

Effect of Postharvest 1-MCP Pre-treatment on the Quality and Freshness Maintenance of Cut Flower Cymbidium ‘In the mood'

Effect of 1-MCP Pre-treatment on Postharvest Quality of Cut Lilium Oriental hybrid ‘Siberia’ Flower

Effect of 1-MCP Pre-treatment on Postharvest Quality of Cut Lilium Oriental hybrid ‘Siberia’ Flower

Abscission of flowers and floral organs is closely associated with alkalization of the cytosol in abscission zone cells.

In vivo changes in the cytosolic pH of abscission zone (AZ) cells were visualized using confocal microscopic detection of the fluorescent pH-sensitive and intracellularly trapped dye, 2',7'-bis-(2-carboxyethyl)-5(and-6)-carboxyfluorescein (BCECF), driven by its acetoxymethyl ester. A specific and gradual increase in the cytosolic pH of AZ cells was observed during natural abscission of flower organs in Arabidopsis thaliana and wild rocket (Diplotaxis tenuifolia), and during flower pedicel abscission induced by flower removal in tomato (Solanum lycopersicum Mill). The alkalization pattern in the first two species paralleled the acceleration or inhibition of flower organ abscission induced by ethylene or its inhibitor 1-methylcyclopropene (1-MCP), respectively. Similarly, 1-MCP pre-treatment of tomato inflorescence explants abolished the pH increase in AZ cells and pedicel abscission induced by flower removal. Examination of the pH changes in the AZ cells of Arabidopsis mutants defective in both ethylene-induced (ctr1, ein2, eto4) and ethylene-independent (ida, nev7, dab5) abscission pathways confirmed these results. The data indicate that the pH changes in the AZ cells are part of both the ethylene-sensitive and -insensitive abscission pathways, and occur concomitantly with the execution of organ abscission. pH can affect enzymatic activities and/or act as a signal for gene expression. Changes in pH during abscission could occur via regulation of transporters in AZ cells, which might affect cytosolic pH. Indeed, four genes associated with pH regulation, vacuolar H(+)-ATPase, putative high-affinity nitrate transporter, and two GTP-binding proteins, were specifically up-regulated in tomato flower AZ following abscission induction, and 1-MCP reduced or abolished the increased expression.

Effect of a low oxygen atmosphere combined with 1-MCP pretreatment on preserving the quality of ‘Rojo Brillante’ and ‘Triumph’ persimmon during cold storage

For the purpose of prolonging the storage of ‘Rojo Brillante’ and ‘Triumph’, the main persimmon varieties cultivated in Spain, the effect of a controlled atmosphere based on 4–5% O2+N2, applied alone or in combination with 1-MCP pretreatment, was evaluated herein after storage at 1°C for up to 90 days and subsequent simulated shelf life conditions at 20°C. Our results showed for the first time that ‘Triumph’, a cultivar hitherto considered insensitive to chilling injury when cultivated under Spanish conditions, manifests flesh gelling and drastic fruit softening during cold storage, both of which are important symptoms of chilling injury in persimmon. ‘Rojo Brillante’ and ‘Triumph’ fruit showed different responses to the controlled atmosphere (CA) conditions studied. For ‘Rojo Brillante’, the combination of CA and 1-MCP pretreatment substantially alleviated chilling injury (flesh softening and gelling). However, all the fruit stored under CA, pretreated with 1-MCP or not, manifested internal flesh browning. For ‘Triumph’ fruit, the combined use of 1-MCP pretreatment and CA storage retarded fruit softening and markedly alleviated flesh gelling. This treatment was not associated with manifestations of internal disorders, and helped extend the storage period up to 90d, plus 5d at 20°C. CA-exposed fruit also displayed considerably fewer black spots caused by Alternaria alternata. Therefore, although the 1-MCP pretreatment and CA storage combination based on 4–5% O2+N2 must be considered a useful technology to prolong the storage of ‘Triumph’ as it preserves internal and external fruit quality, it is necessary to optimise the appropriate CA storage conditions for ‘Rojo Brillante’.

Rhodosporidium paludigenum induced resistance in Ponkan mandarin against Penicillium digitatum requires ethylene-dependent signaling pathway

This work determined if the ethylene dependent signal pathway was required for antagonist-mediated fruit defense mechanisms through investigation of disease resistance against Penicillium digitatum in Ponkan mandarin induced by 1-methylcyclopropene (1-MCP), an inhibitor of ethylene perception, and Rhodosporidium paludigenum. Blocking ethylene perception with 1-MCP resulted in an increase in ACS1, ACS2 and ACO expression, and consequently an increase in ethylene production during mechanical wounding and resistance induction. The expression of the ethylene receptors ETR1, ETR2 and ETR4 as well as ethylene response factor (ERF) were observed with similar responses to yeast and 1-MCP stimuli, with ETR3 mRNA accumulation being the most sensitive to yeast application while ERS1 was the least sensitive. When applied at concentrations greater than 500nLL−1, 1-MCP pre-fumigation significantly reduced the fruit's natural protection and R. paludigenum induced disease resistance to Penicillium decay, indicating that ethylene perception was involved in inducting disease resistance. Moreover, expression of the defensive genes CHI, β-1,3-glucanase, PAL and CIN up-regulated by yeast was inhibited to different degrees by the 1-MCP pre-treatment. This study provides evidence that the biocontrol yeast R. paludigenum increased disease resistance in Ponkan mandarin against P. digitatum infection due to ethylene and signaling pathway dependent mechanisms.

POTENTIAL USE OF 1-METHYLCYCLOPROPENE (1-MCP) TREATMENT TO REDUCE BUD AND FLOWER ABSCISSION IN MOKARA ORCHIDS

Mokara ‘Oriental Red’ and ‘Chao Praya Pink’ cut orchids were treated with or without 10 ppm 1-MCP for 4 h at 25°C. All samples were then exposed to 1 ppm ethylene for 16 h and placed in sugar solution at 25°C. In Mokara ‘Oriental Red’ cut orchids, 20-80% of the floral buds and 0-20% of the open flowers abscised within 1 week. However, in 1-MCP-treated samples, all floral buds and all open flowers were maintained during vase life in the first week, and abscised within 2 weeks of treatment. In Mokara ‘Chao Praya pink’, the 1-MCP pre-treatment also extended the vase life from 14 days in control to 21 days in treated samples. 1-MCP treatment also reduced ACC oxidase activity in ‘Chao Praya Pink’ cut orchid. Mokara ‘Oriental Red’ and Mokara ‘Chao Praya Pink’ cut orchids appear to respond well to 1-MCP pre-treatment, but further studies are required to confirm that effect.

Concentration of 1-methylcyclopropene and the duration of its application affect anti-ethylene protection in Phalaenopsis

Moth orchids (Phalaenopsis spp.) have become the world's most important potted flower crop. Flowers of Phalaenopsis are sensitive to ethylene, and 1-methylcyclopropene (1-MCP) pretreatment enables flowers to withstand ethylene stress. In this study, we investigated effects of 1-MCP concentration and duration of 1-MCP treatment on the protective effect in Phalaenopsis flowers. Pretreating potted Phalaenopsis amabilis with a 1-MCP concentration of as low as 0.005μLL−1 reduced the flower wilting percentage, indicating that as long as there is 1-MCP protection, the rapid wilting of flowers caused by ethylene can be delayed. However, in order to achieve absolute protection, the minimum concentration required was 0.1μLL−1. Pretreatment with 0.1μLL−1 1-MCP for 12h gave Phalaenopsis plants absolute protection such that the flowers were unaffected even when exposed to artificially high ethylene concentrations of up to 20μLL−1. The duration of 1-MCP pretreatment could substantially be reduced. A 0.5-h treatment was sufficient when the concentration of 1-MCP was increased to 0.2μLL−1. The results obtained above were then further confirmed on seven commercial cultivars, where 0.1μLL−1 1-MCP treatment for 1h was sufficient to achieve absolute protection against ethylene damage.

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 (600nLL−1 1-MCP for 6h) were exposed to 3.0μLL−1 ethylene, while being stored for 5d 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 Fv/Fm (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 Fv/Fm, and maintaining the quantity and structural integrity of chloroplasts.

The Residual Effect of 1-Methylcyclopropene on Protecting Phalaenopsis Flowers against Ethylene Injury

Phalaenopsis flowers are prone to wilting under ethylene (C2H4) stress. 1-Methylcyclopropene (1-MCP) can protect Phalaenopsis flowers against ethylene injury. In this study, we determined the residual effect of 1-MCP and how it is affected by temperature. The efficacy of multiple applications of 1-MCP was also investigated. The residual effect of 1-MCP was determined by pretreating blooming Phalaenopsis amabilis plants with 0.8 μL·L−1 1-MCP for 8 hours on Day 0 followed by 2 μL·L−1 ethylene fumigation for 12 hours on designated days. Without 1-MCP pretreatment, flowers began to wilt within 2 days after exposure to ethylene. Duration of the residual protection of 1-MCP on P. amabilis was ≈6 to 8 days during summer in Taiwan. Lower temperatures after 1-MCP application prolonged protection times. The full protection times under day/night temperatures of 25/20, 20/15, and 15/13 °C were 4 to 8, 10 to 13, and 13 to 17 days, respectively. Furthermore, multiple applications of 1-MCP extended the duration of 1-MCP protection against ethylene. Three applications increased the residual protection of P. amabilis by 1-MCP to at least 24 days.

Longevity of torch ginger inflorescences with 1-methylcyclopropene and preservative solutions

ABTRACT. This work aimed at the assessment of the influence of 1-MCP on ethrel action and on its association with preservative solutions on torch ginger. In the first experiment, the inflorescences were pre-treated with 1-MCP in sealed chambers at concentrations of 0, 1, 1.5, and 2.0 g m -3 , for 24 hours. Later, the inflorescences were submitted to the treatment with ethrel (100 μL L -1 ) in sealed chamber for 24 hours. In the second experiment, the inflorescences were pre-treated with 1.5 g m -3 of 1-MCP for 24 hours, being posteriorly transferred to vases containing water, Flower ® , Florissant ® , and water without 1-MCP pre-treatment. The fresh matter and the quality of the inflorescence were daily appraised using the scale grading. The best results were obtained for 1.5 g m -3 of 1-MCP. The association between 1-MCP and Florissant ® provided larger longevity and quality in the postharvest conservation, increasing in five days the longevity in relation to those kept only in water.

The role of 1‐methylcyclopropene in lignification and expansin gene expression in peeled water bamboo shoot (Zizania caduciflora L.)

Water bamboo shoot (WBS) (Zizania caduciflora L.) is a fleshy aquatic vegetable susceptible to lignification. In this study, effects of 1-methylcyclopropene (1-MCP) anti-ethylene treatment on lignification of harvested peeled WBS were investigated. Peeled shoots were treated with 0.5 µL L(-1) 1-MCP for 20 h at 20 °C and then stored at 20 °C for up to 9 days. Sensory quality, lignin content and activities of the lignification-associated enzymes peroxidase (POD) and phenylalanine ammonia lyase (PAL) were evaluated. Expression of expansin (ZcExp) was also assessed. 1-MCP application maintained better sensory quality and inhibited the increase in lignin content. Lessened lignification was associated with reduced activities of POD and PAL. Moreover, 1-MCP-treated shoots showed lower expression of the ZcExp gene. 1-MCP pretreatment suppressed the synthesis of lignin and thereby delayed lignification in peeled WBS.

Expression of genes associated with ethylene‐signalling pathway in harvested banana fruit in response to temperature and 1‐MCP treatment

Little attention has been paid to characterising the ethylene-signalling pathway genes in relation to abnormal ripening of harvested banana fruit during storage at high temperature. The aim of the present study was to investigate banana fruit abnormal ripening and the expression of ten genes associated with the ethylene-signalling pathway, namely MaACS1, MaACO1, MaERS1-4 and MaEIL1-4, at high temperature. Changes in these parameters of banana fruit at high temperature in response to 1-MCP pretreatment were also investigated. High temperature accelerated the decline in fruit firmness, increased ethylene production and inhibited degreening in banana fruit, resulting in fruit abnormal ripening. In addition, the expression of MaACS1, MaACO1, MaERS2, MaERS3, MaERS4, MaEIL1, MaEIL3 and MaEIL4 was enhanced in banana fruit stored at high temperature. However, application of 1-MCP prior to high temperature storage delayed fruit abnormal ripening and simultaneously suppressed the expression of MaACS1, MaERS2, MaERS3, MaEIL1, MaEIL3 and MaEIL4. The findings of this study suggested that the expression of genes associated with the ethylene-signalling pathway might be involved in banana fruit abnormal ripening at high temperature. Application of 1-MCP suppressed the expression of genes associated with the ethylene-signalling pathway, which may be attributed at least partially to 1-MCP delaying fruit abnormal ripening at high temperature.

Factors affecting ethylene sensitivity and 1-MCP response in tulip bulbs

Ethylene has many detrimental effects on tulip quality, including increased bulb gummosis and respiration, reduced rooting, and increased flower bud abortion. In this work, bulbs of four cultivars were exposed to ethylene (10 μL L −1, with or without 1-MCP pretreatment) for different durations or at different times during the fall storage period. An experiment on post-ethylene storage temperature was conducted to test the hypothesis that a period of warm temperature after ethylene exposure is necessary to fully express ethylene injury symptoms that are seen months later after cooling and forcing. The degree of damage (flower abortion) in the sensitive cultivars ‘Apeldoorn’ and ‘World's Favourite’ increased as the duration of ethylene exposure increased to 10 and 16 d, respectively. This effect strongly depended on the timing of ethylene stress, as bulbs given ethylene late in the storage season showed more severe injury than early-treated bulbs. Bulbs that were cooled (9 °C) immediately after ethylene stress had higher flowering percentages than those stored at 17 °C for 2–4 weeks after ethylene stress, demonstrating that a period of warm temperature after ethylene exposure is necessary to allow full expression of the injury. This response was dependent on the cultivar and the timing of ethylene stress. When 1-MCP (1 μL L −1) was applied within 21–28 days prior to the start of ethylene exposure (2 weeks, 10 μL L −1), the ethylene sensitive varieties were protected. Putative ethylene-resistant cultivars ‘Friso’ and ‘Sevilla’ were unaffected by ethylene and showed no response to 1-MCP.

Effect of biocontrol agent Bacillus amyloliquefaciens and 1-methyl cyclopropene on the control of postharvest diseases and maintenance of fruit quality

Efficacy of biocontrol agent Bacillus amyloliquefaciens PPCB004 was evaluated on the control of anthracnose and phomopsis rot in ‘Solo’ papaya pre-treated with 1-methyl cyclopropene (100 μl) (1-MCP) during storage. This treatment was compared to the untreated control, commercial treatment (washing in chlorinated water), stand alone 1-MCP and PPCB004 treatment. Although fruit pre-treated with 1-MCP delayed the ripening (100% yellow) after cold storage by 9–10 d, it showed higher incidence and severity of anthracnose and phomopsis rot than the fruit subjected to commercial treatment. Application of PPCB004 after 1-MCP pre-treatment (1-MCP + PPCB004) reduced the anthracnose and phomopsis incidence and severity after cold storage (10 °C, 85% RH for 14 d) and ripening at 25 °C. The 1-MCP + PPCB004 treatment helped to retain the fruit firmness, overall quality and uniform yellow skin (100%) and flesh colour after ripening. The PPCB004 was effectively recovered from stand alone PPCB004 and 1-MCP + PPCB004 treated fruit after cold storage and ripening. The PPCB004 population showed an increase by 1 log units after ripening in 1-MCP + PPCB004 treated fruit. After ripening the recovery of PPCB004 population was higher (0.7 log units) in 1-MCP + PPCB004. The total recovery of fungal population on the fruit surface after ripening was lower in 1-MCP + PPCB004 and stand alone PPCB004 treated fruit. It can be concluded that application of B. amyloliquefaciens PPCB004 with 1-MCP pre-treated papaya (at 25–30% skin yellow stage) can significantly reduce disease incidence associated with 1-MCP treatment. This treatment has the potential for commercial application in the ‘organic’ papaya industry.