Reduced Ethylene Production Research Articles

EFFECT OF 1-MCP ON POSTHARVEST YELLOWING AND QUALITY OF ASIA PEAR (PYRUS BRETCHNEIDERI REHD. 'EARLY CRISP') DURING AMBIENT STORAGE

ISHS X International Controlled and Modified Atmosphere Research Conference EFFECT OF 1-MCP ON POSTHARVEST YELLOWING AND QUALITY OF ASIA PEAR (PYRUS BRETCHNEIDERI REHD. 'EARLY CRISP') DURING AMBIENT STORAGE

Involvement of Ethylene and Hydrogen Peroxide in Induction of Alternative Respiratory Pathway in Salt-Treated Arabidopsis Calluses

The role of ethylene and hydrogen peroxide (H₂O₂) in the induction of the alternative respiratory pathway (AP) in calluses from wild-type (WT) Arabidopsis and ethylene-insensitive mutant etr1-3 under salt stress was investigated. The capacity and the contribution of the AP to the total respiration were significantly induced by 100 mM sodium chloride (NaCl) in WT calluses but only slightly induced in etr1-3 calluses. Ethylene emission was enhanced in WT calluses under salt stress. Application of 1-aminocyclopropane-1-carboxylic acid (an ethylene precursor) further increased the AP capacity in WT calluses but not in etr1-3 calluses under salt stress. Reduction of ethylene production by aminooxyacetic acid (AOA, an ethylene biosynthesis inhibitor) in WT calluses eliminated the NaCl-induced increase of ethylene emission and inhibited AP induction under salt stress, suggesting that ethylene is required for AP induction. H₂O₂ enhanced ethylene production while ethylene reduced H₂O₂ generation in WT calluses under salt stress. In addition, ethylene and H₂O₂ modulated NaCl-induced alternative oxidase gene (AOX1a) expression and the increase in pyruvate content in WT calluses. Inhibition of the AP by salicylhydroxamic acid in WT calluses under salt stress resulted in severe cellular damage as indicated by the high content of H₂O₂, malondialdehyde and more electrolyte leakage. Taken together, ethylene and H₂O₂ are involved in the salt-induced increase of the AP, which plays an important role in salt tolerance in WT calluses, and ethylene may be acting downstream of H₂O₂.

Use of plant growth-promoting rhizobacteria to control stress responses of plant roots

Ethylene is a key gaseous hormone that controls various physiological processes in plants including growth, senescence, fruit ripening, and responses to abiotic and biotic stresses. In spite of some of these positive effects, the gas usually inhibits plant growth. While chemical fertilizers help plants grow better by providing soil-limited nutrients such as nitrogen and phosphate, over-usage often results in growth inhibition by soil contamination and subsequent stress responses in plants. Therefore, controlling ethylene production in plants becomes one of the attractive challenges to increase crop yields. Some soil bacteria among plant growth-promoting rhizobacteria (PGPRs) can stimulate plant growth even under stressful conditions by reducing ethylene levels in plants, hence the term “stress controllers” for these bacteria. Thus, manipulation of relevant genes or gene products might not only help clear polluted soil of contaminants but contribute to elevating the crop productivity. In this article, the beneficial soil bacteria and the mechanisms of reduced ethylene production in plants by stress controllers are discussed.

INTERACTIVE EFFECTS OF CA STORAGE, 1-METHYLCYCLOPROPENE AND METHYL JASMONATE ON QUALITY OF APPLE FRUIT

The present study evaluated how post-harvest treatments with 1-methylcyclopropene (1-MCP) or methyl jasmonate (MJ) impact 'Fuji' and 'Braeburn' apple fruit tolerance to controlled atmosphere (CA) storage conditions. Fruit harvested from a commercial orchard in north central Washington were cooled to 0.5°C within 36 h of harvest and then stored in air or CA with 2 kPa O 2 + 0.05 kPa CO 2 ; 0.25 kPa O 2 + 0.05 kPa CO 2 or 2 kPa O 2 + 3 kPa CO 2 for up to 6 months. Fruit were treated with 2 mM MJ or 1 μl·L -1 1-MCP at harvest. Both CA conditions and 1-MCP treatment reduced ethylene production, improved maintenance of firmness and titratable acidity and reduced incidence of core flush during long-term storage compared with untreated fruit stored in air. Treatment with 1-MCP was as or more effective than low CO 2 -CA storage for reducing ethylene production and preservation of firmness and acidity for both cultivars. 'Fuji' apples stored in 3 kPa CO 2 developed internal browning (CO 2 -injury) while fruit stored in 0.25 kPa O 2 with 0.05 kPa CO 2 or air did not, regardless of 1-MCP treatment. 'Braeburn' apples also developed internal browning during air- or CA-storage, regardless of CO 2 concentration. Severity of browning in 'Fuji' and 'Braeburn' apples stored in 3 kPa CO 2 was not altered by previous 1-MCP treatment. However, browning severity increased by the 1-MCP treatment when 'Braeburn' fruit were stored in air or low CO 2 CA. Treatment with MJ reduced severity of CO 2 -injury in fruit of both cultivars stored in high CO 2 CA. The treatment with 1-MCP and storage in air or CA with 2 kPa O 2 and low (≤0.05 kPa) CO 2 may be a practical strategy for maximum retention of firmness and acidity with minimum development of CO 2 -injury in susceptible cultivars.

SHORT-TERM EXPOSURES TO REDUCED O2 AND ELEVATED CO2 ATMOSPHERES DIFFERENTLY AFFECT THE RESPIRATORY CHARACTERISTICS OF GRAPEFRUIT AND MANDARIN

Respiratory responses of citrus fruit to controlled atmospheres (CA) are of great importance, since CA treatments can be used in postharvest handling only as long as they do not cause any detrimental effects on fruit quality. In this study, we evaluated the physiological responses of 'Star Ruby' grapefruit (Citrus paradisi Macf., 'Star Ruby') and 'Murcott' mandarin (Citrus reticulata Blanco, 'Murcott') to different concentrations of O 2 (5, 10, 15, and 21%) or CO 2 (0, 5, 10, and 20%) at 20°C for a short-term period (1 week). Exposure to reduced O 2 atmospheres greatly reduced respiration rates and internal CO 2 levels, but 5% O 2 dramatically increased juice ethanol, and to a lesser extent, acetaldehyde (AA) levels. Exposure to 5% and 10% O 2 reduced ethylene evolution rates in grapefruit but increased their levels in mandarin. Exposure to 10% and 20% CO 2 markedly increased respiration rates and internal CO 2 levels, but reduced ethylene production. Exposure to 20% CO 2 substantially increased juice ethanol and AA levels as compared with air controls, but to a less extent as compared with exposure to 5% O 2 atmosphere. Mandarin exhibited stronger and more rapid responses to reduced O 2 than grapefruit, as revealed by the accumulation of juice ethanol and AA, two important indicators of anaerobic respiration. Mandarin also showed earlier and higher increases in respiration rates and internal CO 2 levels than grapefruit following exposure to elevated CO 2 . Results indicate that reduced O 2 and elevated CO 2 atmospheres affect citrus fruit' respiratory characteristics differently. The possible mechanisms involved are briefly discussed.

1‐Methylcyclopropene affects the antioxidant system of apricots (Prunus armeniaca L. cv. Búlida) during storage at low temperature

Apricots (Prunus armeniaca cv. Búlida) were treated with 1 μL L⁻¹ [corrected] 1-methylcyclopropene (1-MCP) immediately after harvest and stored in air at 2 degrees C for 21 days. Antioxidant levels (ascorbic acid and carotenoids), enzymatic antioxidant activities (superoxide dismutase (SOD) and unspecific peroxidase (POX)) and total antioxidant capacity (trolox equivalent antioxidant capacity (TEAC)) were determined. The level of oxidative stress was also established by measuring ion leakage during storage. The changes in the antioxidant potential of apricots were related to the capacity of 1-MCP to increase their commercial life. 1-MCP-treated fruits exhibited higher SOD activity, whereas POX activity was significantly higher only after 21 days at 2 degrees C. Treated fruits also exhibited better retention of ascorbate and carotenoids and higher TEAC during storage. In accordance with these observations, lower ion leakage values were detected in 1-MCP-treated apricots. Taken together, these results suggest that 1-MCP conferred a greater resistance to oxidative stress. This, along with the reduction in ethylene production, could contribute to the increase in commercial life and nutritional value observed in 1-MCP-treated apricots.

Amadurecimento de kiwis 'bruno' submetidos ao dano mecânico de impacto e ao tratamento com 1-metilciclopropeno

O objetivo do presente trabalho foi avaliar o efeito do dano mecânico por impacto e da aplicação de 1-MCP sobre o amadurecimento de kiwi 'Bruno'. Os tratamentos avaliados foram: (T1) controle (sem dano mecânico); (T2) dano mecânico com queda de 60 cm; (T3) dano mecânico com queda de 120 cm; (T4) 1-MCP (1µL L-1); e (T5) 1-MCP (1µL L-1) + dano mecânico com queda de 120 cm. Após a aplicação dos tratamentos, os frutos foram armazenados a 20±2 ÚC e 65±5% UR. O tratamento T3 ocasionou o aumento na atividade respiratória e da produção de etileno e reduziu a firmeza da polpa e a textura. O tratamento com 1-MCP ocasionou menor produção de etileno e na atividade respiratória e maior retenção de firmeza da polpa e da textura. A aplicação de 1-MCP em frutos submetidos ao dano mecânico por impacto proporcionou firmeza de polpa, textura e atividade respiratória e produção de etileno semelhantes ao tratamento controle. Pelos resultados constata-se que o tratamento com 1-MCP pode evitar a indução do amadurecimento ocasionado pelo dano mecânico em kiwis 'Bruno'.

Effects of brassinosteroids on postharvest disease and senescence of jujube fruit in storage

The effects of brassinosteroids (BRs) against blue mould rot caused by Penicillium expansum and on senescence of harvested jujube fruit were investigated. Brassinosteroids at a concentration of 5 μM effectively inhibited development of blue mould rot and enhanced the activities of defense-related enzymes, such as phenylalanine ammonia-lyase, polyphenoloxidase, catalase and superoxide dismutase. However, BRs did not have direct antimicrobial activity against P. expansum in vitro. BRs significantly delayed fruit senescence by reducing ethylene production and maintained fruit quality. It is suggested that the effects of BRs on reducing decay caused by P. expansum may be associated with induction of disease resistance in fruit and delay of senescence.

Physiology and quality response of harvested banana fruit to cold shock

Experiments were conducted to examine softening and quality responses of harvested banana fruit to cold shock treatment intended to extend shelf-life. Fruit were immersed in ice-water for 1 h, then treated with or without 100 μL L −1 ethylene for 24 h at 24 °C, and finally stored at 20 °C. Fruit firmness, chlorophyll content, ethylene production, respiration rates, contents of pectin, starch and sugar, and the activities of the cell wall modifying enzymes polygalacturonase (PG), pectin methylesterase (PME) and CMCase (cellulase, endo-1,4-β-glucanase) were analyzed. Total amylase activity was also measured. Immersion in ice-water for 1 h effectively inhibited ripening-associated processes, including peel de-greening and pulp softening during storage or ripening. The delay in ripening was also manifest in reduced ethylene production and respiration rates. The inhibition of softening by cold shock treatment was related to decreased PG and PME activities, that is, retardation of pectin solubilization/degradation. Reduced activities of CMCase and total amylase and conversion of starch to sugar by ice-water immersion also contributed to the delay in softening of harvested banana fruit.

Improvement of Apple Quality and Storability by a Combination of Heat Treatment and Controlled Atmosphere Storage

The effects of two nonchemical methods [controlled atmosphere (CA) storage and postharvest heating, alone or combined] on the quality (firmness, taste, color, and skin wax) and storability (losses resulting from bruising and fungal decay) of apples were investigated in a 3-year study. Fruits of two cultivars (cv. Aroma and cv. Ingrid Marie) were mechanically wounded on two opposing sides, inoculated with conidial suspensions of one of three pathogens [Pezicula malicorticis (bull's eye rot), Penicillium expansum (blue mould), and Colletotrichum gloeosporioides (bitter rot)], exposed to 40 °C for four different exposure periods (24, 48, 72, and 96 h), and stored either in air (21.0 kPa O2 + 0.03 kPa CO2) or in CA storage (2.0 kPa O2 + 2.0 kPa CO2) for 4 months. Effect of postharvest heating on bruise susceptibility of air- or CA-stored apples was also investigated. Cultivar Aroma apples generally showed higher bruise susceptibility than cv. Ingrid Marie. The sun-exposed side of apples was less sensitive to bruising than the shaded side and red phenotypes of these two cultivars also showed increased resistance to bruising as compared with standard phenotypes. Heat treatment and CA storage, either alone or in combination, decreased bruise occurrence in both cultivars. Pz. malicorticis was the more aggressive storage pathogen for both apple cultivars followed by P. expansum and C. gloeosporioides. The highest decay severity occurred in inoculated and nonheat-treated apples stored in air. Heat treatment, especially in combination with CA storage, showed an eradicative effect on the pathogens without any negative effects on apple quality. Heat treatment maintained flesh firmness during storage, reduced ethylene production, and caused clearly visible changes in epicuticular wax structure, resulting in a higher resistance to bruising or to natural and artificial infections with the pathogens. The effective exposure period could be reduced to 24 h, because a combination of heat treatment (at 40 °C for 24 h) and CA storage showed the best protective effect against bruising and fungal decay. This combined treatment decreased bull's eye rot by 86% and 60% and bitter rot by 73% and 65% in cv. Aroma and cv. Ingrid Marie, respectively, in comparison with untreated apples.

Preharvest Aminoethoxyvinylglycine Plus Postharvest Heat Treatments Influence Apple Fruit Ripening after Cold Storage

The impact of heat plus aminoethoxyvinylglycine (AVG) treatments alone or in combination on ripening of four apple cultivars has been studied. A solution of AVG was applied to ‘Lodi’, ‘Senshu’, ‘Redchief Delicious’, and ‘Red Fuji’ apple trees ≈4 weeks before normal harvest at 124 g·ha−1 a.i. After harvest, half of each group of control and AVG-treated fruit was heated at 38 °C for 4 days and then stored at 4 °C for 30 days. After cold storage, AVG and heat individually suppressed ethylene production of ‘Senshu’ and ‘Redchief Delicious’ but not of ‘Lodi’ or ‘Red Fuji’. The combination of AVG with heat treatment reduced ethylene production the most consistently in each cultivar except ‘Lodi’, suggesting some additive effect of the treatments. The respiration rate after cold storage was not consistently affected by any treatment. AVG alone and with heat maintained firmness of ‘Lodi’, AVG plus heat maintained it in ‘Senshu’, but neither ‘Redchief Delicious’ nor ‘Red Fuji’ firmness responded to the treatments. AVG-treated ‘Lodi’ and ’Redchief Delicious’ fruit, heated fruit of all cultivars, and AVG plus heat in all had lower titratable acidity than controls after cold storage. Although there were no effects of any treatment on fruit soluble solids concentration, the combined treatment increased the soluble solids:titratable acidity ratio of all cultivars, although heat or AVG alone had no consistent effects. Total ester production by ‘Redchief Delicious’ peel tissue after cold storage was reduced 44% by AVG and 70% or more by heat and AVG plus heat. There were no differences in peel alcohol acyltransferase activity among the treatments, supporting the hypothesis that substrate availability was the limiting factor for ester synthesis in treated fruit. Overall, heat plus AVG treatment did not provide any advantage over each alone for maintaining apple fruit quality during short-term cold storage.

Delay ripening of ‘Qingnai’ plum ( Prunus salicina Lindl.) with 1-methylcyclopropene

‘Qingnai’ plum fruit were treated with 0, 250, 500 or 1000 nL L −1 of 1-methylcyclopropene (1-MCP) for 6 h and stored at 20 °C. The fruit firmness, peel color, chlorophyll content, titratable acidity (TA), respiration rate and ethylene production, chlorophyllase, pectin methylesterase (PME) and polygalacturonase (PG) activities were monitored during postharvest ripening of ‘Qingnai’ plums. ‘Qingnai’ plums without 1-MCP treatment soften very rapidly at room temperature after harvest, showing a continuing decrease in hue angle, chlorophyll content, TA and increase in chlorophyllase, PME and PG activities during postharvest storage. In contrast, the 1-MCP-treated fruits showed reduced ethylene production and respiration rate and delayed softening, which was associated with the reduction in the activity of PME and PG. The 1-MCP treatment also significantly inhibited the chlorophyllase activity and peel color development in ‘Qingnai’ plums during postharvest ripening at 20 °C. These results suggest that 1-MCP treatment may be useful for maintaining the fruit quality and extending the postharvest shelf-life of ‘Qingnai’ plums.

Involvement of ethylene in the rooting of seedling shoot cultures of Bixa orellana L.

Using seedlings derived from the shoot apex of annatto (Bixa orellana L. cv. Bico-de-Pato) we observed the rooting frequency of B. orellana, the number and length of roots and the rate of ethylene production during 30 d in culture. The rhizogenesis response was affected by auxins (NAA or IBA) and by both the ethylene biosynthesis precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and the inhibitor 2-aminoethoxyvinylglycine (AVG). Auxin supplementation to the medium resulted in root induction, ethylene production, and an undesirable callusing in the epidermal and cortical tissues. Irrespective of the presence of auxins, supplementing the medium with ACC promoted ethylene biosynthesis and callusing, which resulted in increased cell proliferation mainly in the cortical and vascular tissues, while the epidermis was mostly unaltered. In both ACC and auxin-supplemented medium, increased ethylene production and callusing occurred, suggesting a synergistic effect between these two responses. ACC was capable of inducing adventitious root formation, but the roots produced had a wrinkled appearance when compared to normal roots. Conversely, AVG reduced ethylene production and callusing, while the epidermis, cortex, and inner tissues remained unaltered, regardless of the presence of auxins. AVG was beneficial in these aspects, although its application led to a reduction in the number of roots and in the average root length. In conclusion, it was not possible to establish a direct relation between ethylene and rooting, but we hypothesize that, under the experimental conditions described, ethylene may enhance tissue sensitivity to auxin. However, ethylene did not seem essential to the rhizogenesis process in annatto.

Effect of Nitric Oxide on Ethylene Synthesis and Softening of Banana Fruit Slice during Ripening

The effects of nitric oxide (NO) on ethylene synthesis and softening of ripening-initiated banana slice were investigated. Fruit firmness, color, and contents of starch and acid-soluble pectin (ASP) were measured. In addition, ethylene production, 1-aminocyclopropane-1-carboxylic acid (ACC) content, expression and activities of ACC synthase (ACS) and ACC oxidase (ACO), and activities of cell-wall-modifying enzymes, polygalacturonase (PG), pectin methylesterase (PME), and endo-beta-1,4-glucanase, were analyzed. Application of NO reduced ethylene production, inhibited degreening of the peel and delayed softening of the pulp. The decrease of ethylene production was associated with the reduction in the activity of ACO and the expression of the MA-ACO1 gene. Moreover, the NO-treated fruit showed a lower expression of the MA-ACS1 gene but higher ACS activity and ACC content. In addition, NO treatment decreased the activities of PG, PME, and endo-beta-1,4-glucanase and maintained higher contents of ASP and starch, which may account for the delay of softening. We proposed that the inhibition of ACO activity and transcription of gene MA-ACO1 by NO resulted in decreased ethylene synthesis and the delay of ripening of banana slice.

Jasmonate-induced ripening delay is associated with up-regulation of polyamine levels in peach fruit

Methyl jasmonate (MJ, 0.20mM) and its synthetic analog n-propyl dihydrojasmonate (PDJ, 0.22mM) were applied to peach fruit (Prunus persica L. Batsch) at a late developmental stage under field conditions (in planta). On the basis of a previously demonstrated jasmonate (JA)-induced ripening delay in peach, the effects of JAs on the time course of the endogenous polyamine (PA) accumulation and expression of their biosynthetic genes arginine decarboxylase (ADC), ornithine decarboxylase (ODC), spermidine synthase (SPDS) and S-adenosylmethionine decarboxylase (SAMDC) were evaluated in control and JA-treated fruit during the 21-d trial period. In parallel, the main ripening-related parameters (ethylene production, flesh firmness and soluble solids contents) were measured, and transcription profiles of aminocyclopropane-1-carboxylic acid oxidase (PpACO1) and of two ethylene perception genes were evaluated. PDJ, but not MJ, reduced ethylene production and fruit softening, impaired PpACO1 transcription and altered the expression of PpERS1 (ethylene sensor 1), but not the expression of PpETR1 (ethylene receptor 1). In the epicarp and mesocarp, the pattern of PA accumulation was altered in a biphasic manner leading to a higher overall PA level in PDJ-treated fruit. Short and long term increases in putrescine, spermidine and/or spermine, the latter only in the epicarp, were observed in PDJ-treated fruit. MJ induced this behavior only with putrescine in the mesocarp. PpADC transcription was also enhanced soon after the PDJ treatment. Since PDJ-treated fruit were less ripe, their higher PA concentrations in treated fruit are discussed in light of the dual role of these molecules as stress/defense protective compounds and rejuvenating effectors.

Response of Jujube Fruits to Exogenous Oxalic Acid Treatment Based on Proteomic Analysis

In this study, we found that oxalic acid (OA) at the concentration of 5 mM could delay jujube fruit sene-scence by reducing ethylene production, repressing fruit reddening and reducing alcohol content, which consequently increased fruit resistance against blue mold caused by Penicillium expansum. In order to gain a further understanding of the mechanism by which OA delays senescence and increases disease resistance of jujube fruit, we used a proteomics approach to compare soluble proteome of jujube fruits treated with water or 5 mM OA for 10 min. A total of 25 differentially expressed proteins were identified by using electrospray ionization quadrupole time-of-flight tandem mass spectrometry (ESI-Q-TOF-MS/MS). Among these proteins, alcohol dehydrogenase 1, which plays a direct role in ethanol metabolism, was repressed, and the abundances of three photosynthesis-related proteins was enhanced in jujube fruit after OA treatment. The protein identified as a cystathionine beta-synthase domain-containing protein, which can regulate ethylene precursors, was also induced by OA treatment. The activity of 1-aminocyclopropane-1-carboxylic acid synthase was significantly suppressed in OA-treated jujube fruit. In addition, three proteins related to the defense/stress response were up-regulated by OA, and contributed to the establishment of systemic resistance induced by OA in jujube fruits. These results indicated that OA treatment might affect ethanol and ethylene metabolism, resulting in delaying senescence, and increase resistance of jujube fruits against fungal pathogens.

Ethylene insensitivity impedes a subset of responses to phosphorus deficiency in tomato and petunia

The role of ethylene in growth and developmental responses to low phosphorus stress was evaluated using ethylene-insensitive 'Never-ripe' (Nr) tomato and etr1 petunia plants. Low phosphorus increased adventitious root formation in 'Pearson' (wild-type) tomato plants, but not in Nr, supporting a role for ethylene in adventitious root development and showing that ethylene is important for this aspect of phosphorus response. Low phosphorus reduced ethylene production by adventitious roots of both genotypes, suggesting that ethylene perception--not production--regulates carbon allocation to adventitious roots at the expense of other roots under low phosphorus stress. With the exception of its effect on adventitious rooting, Nr had positive effects on growth and biomass accumulation in tomato whereas etr1 tended to have negative effects on petunia. This was particularly evident during the recovery from transplanting, when the effective quantum yield of photosystem II of etr1 petunia grown with low phosphorus was significantly lower than 'Mitchell Diploid', suggesting that etr1 petunia plants may undergo more severe post-transplant stress at low phosphorus availability. Our results demonstrate that ethylene mediates adventitious root formation in response to phosphorus stress and plays an important role for quick recovery of plants exposed to multiple environmental stresses, i.e. transplanting and low phosphorus.

Tissue-specific expression of the ethylene biosynthetic machinery regulates root growth in maize

Although the hormonal control of root growth and development has been extensively studied, relatively little is known about the role that ethylene plays in cereal root development. In this work, we have investigated how the ethylene biosynthetic machinery is spatially regulated in maize roots and how changes in its expression alter root growth. ACC synthase (ZmACS) expression was observed in the root cap and in cortical cells whereas ACC oxidase (ZmACO) expression was detected in the root cap, protophloem sieve elements, and the companion cells associated with metaphloem sieve elements. Roots from Zmacs6 mutants exhibited significantly reduced ethylene production, a smaller root cap of increased cell number but smaller cell size, accelerated elongation of metaxylem, cortical, and epidermal cells, and increased vacuolation of cells in the calyptrogen of the root cap, phenotypes that were complemented by exogenous ACC. Zmacs6 mutant roots exhibited increased growth when largely unimpeded, a phenotype complemented by exogenous ACC, whereas loss of ZmACS2 expression had less of an effect. In contrast, Zmacs6 plants exhibited reduced root growth in soil. These results suggest that expression of ZmACS6 is important in regulating growth of maize roots in response to physical resistance.

Combined treatment of aminoethoxyvinylglycine (AVG) and 1-methylcyclopropene (1-MCP) reduces melting-flesh peach fruit softening

The effects of postharvest application of aminoethoxyvinylglycine (AVG) and 1-methylcyclopropene (1-MCP) on ethylene production and fruit quality, and thus on transportation and shelf-life, were evaluated in melting-flesh peaches. AVG (150 mg L −1) significantly reduced ethylene production, and the effect was enhanced in combination with 1-MCP (1 μL L −1). However, fruit treated with AVG alone softened to untreated control levels 2 d after harvest (DAH). Treatment with 1-MCP significantly reduced the rate of softening until 2 DAH, but the fruit rapidly softened thereafter, and reached untreated control levels by 4 DAH. A combination of AVG and 1-MCP significantly reduced fruit tissue softening throughout ripening. The effect of each chemical on flesh firmness indicated that 1-MCP affected fruit response in the early stages of ripening up to 4 DAH, and AVG significantly reduced softening in the latter stages from 4 to 9 DAH. Peaches treated with AVG and 1-MCP retained their ground color during ripening, but the effect of each chemical on color is unclear. The present study indicates that combined treatment with AVG and 1-MCP significantly delays the ripening of melting-flesh peaches.

Edible coatings with antibrowning agents to maintain sensory quality and antioxidant properties of fresh-cut pears

The effect of alginate-based (2%, w/v), pectin-based (2%, w/v) and gellan-based (0.5%, w/v) edible coatings containing N-acetylcysteine at 0.75% (w/v) and glutathione at 0.75% (w/v) on gas exchange, antioxidant properties, sensory quality and microbial stability of fresh-cut ‘Flor de Invierno’ pears, was investigated for 14 d at 4 °C. The use of polysaccharide-based edible coatings increased the water vapor resistance and reduced ethylene production of coated fresh-cut pears. The incorporation of N-acetylcysteine and glutathione into coating formulations not only reduced microbial growth compared with samples not containing antioxidants but also was effective in preventing fresh-cut pears from browning for 2 weeks without affecting firmness of fruit wedges. The increased vitamin C and total phenolic content observed in pear wedges coated with alginate, gellan and pectin including antioxidants contributed to maintain their antioxidant potential. In addition, coatings with alginate or pectin best maintained sensory attributes of pear wedges for 14 d.