转反义ACC合成酶基因番茄与普通番茄果实植物内源激素含量的变化

 转反义 ACS( ACC合成酶基因 )番茄与普通番茄果实激素平衡方式不同。普通丽春番茄果实采前 IAA、Z+ ZR(玉米素 +玉米素核苷 )逐渐下降 ,GA在花后 40 d出现高峰 ,之后逐渐下降 ;ABA呈递增趋势 ;IAA/ ABA花后 2 0 d最高 ,花后 40 d至果实变色期变化不显著 ,但果实粉红期至红色期 IAA/ ABA显著下降。转反义 ACS番茄表现了与丽春番茄不同的变化趋势 ,其IAA/ ABA从花后 2 0 d至绿熟期呈上升趋势 ,而绿熟期至腐败期缓慢下降。转反义 ACS番茄生长类激素的含量在果实生长发育时期 (绿熟期之前 )与普通番茄没有显著差异 ,但在成熟衰老时期显著地高于普通番茄。     

Managing biological variation in skin background colour along the postharvest chain of ‘Jonagold’ apples

Skin background colour is an important quality aspect in the grading of ‘Jonagold’ apples, with consumers usually preferring fruit with a green background colour. However, apple handlers are usually faced with large fruit-to-fruit variability of background colour within a population of fruit. In this study, a stochastic modelling approach was used to describe how the initial fruit-to-fruit variability in the background colour of ‘Jonagold’ apples present at harvest, propagates throughout the postharvest chain. Two hundred and twenty ‘Jonagold’ apple fruit were harvested and stored at 1 °C or 4 °C, under different controlled atmosphere (CA) conditions for 6 months, followed by 2 weeks exposure to shelf-life conditions, during which the background colour and ethylene production of the individual fruit were measured. A kinetic model was developed to describe the postharvest loss of skin greenness, by assuming that the loss was principally due to chlorophyll breakdown, the rate of which was dependent on the endogenous ethylene concentration. Stochastic model parameters were identified, and by treating these parameters as fruit-specific, the model could account for more than 95% of the variability of the data. By treating the stochastic model parameters as random factors, the Monte Carlo method was used to model and describe the propagation of the fruit-to-fruit variability of the background colour within a population of fruit. The model developed in this study might allow better management of variability in quality along the postharvest chain, by predicting how the initial fruit-to-fruit variability within a batch of apples will propagate throughout the postharvest chain, as a function of storage and shelf-life conditions.     

Reduction of energy usage during storage and transport of bananas by management of exogenous ethylene levels

Unripe Australian-grown Cavendish and Lady Finger bananas were stored at 15, 20 and 25 °C in an atmosphere containing 0.001, 0.01, 0.1 and 1.0 μL/L ethylene in air and the green life was determined as the time to reach the respiratory climacteric. As expected, green life increased as the temperature and ethylene concentration decreased. The equation describing the relationship between temperature, ethylene concentration and green life of Cavendish bananas was applied to a five-day 3000 km road transport route from the major tropical production area to the major urban markets. It predicted that bananas transported in the prevailing mean summer temperature of 25 °C would not require refrigeration if the ethylene level did not exceed 0.58 μL/L while transport at the mean winter temperature of 14 °C fruit could withstand a level of about 0.90 μL/L without ripening en route. The equation was also applied to a shipment protocol of 19 days for bananas exported from Central America to southern Europe. This predicted that fruit could be transported without refrigeration if ethylene levels were maintained at 0.04 μL/L during the winter temperature of 17 °C and at 0.002 μL/L at the summer transport temperature of 24 °C. Since a range of technologies are available to maintain such low ethylene levels or reduce the action of ethylene, these findings suggest that the current refrigerated transport of bananas could be minimised or eliminated. The use of higher temperatures in the supply chain would reduce energy consumption with resultant environmental and economic benefits.     

Effects of chlorine dioxide treatment on respiration rate and ethylene synthesis of postharvest tomato fruit

Tomato fruit at the mature green stage were treated with ClO₂ gas in a sealed container for 12 h, and then stored at 23 °C with 85% relative humidity (RH) for 23 d. Respiration rate, respiration-related enzymes including phosphohexose isomerase (PHI), succinate dehydrogenase (SDH), and glucose-6-phosphate dehydrogenase (G-6-PDH) and 6-phosphogluconate dehydrogenase (6-PGDH), ethylene production, and the expression of LeAOX1a, LeCOX1, LeACS2, LeACS4 and LeACO1 genes were measured. The results showed that application of ClO₂ gas was effective in reducing total respiration, cytochrome pathway respiration and the expression of LeCOX1, but no significant reduction in the activities of respiration-related enzymes was observed during storage. Fruit treated with ClO₂ resulted in lower ethylene production. Furthermore, the expression of ethylene biosynthesis related genes, including LeACS2, LeACS4 and LeACO1 was reduced by the ClO₂ treatment. These results indicate that ClO₂ treatment might delay the ripening of tomato fruit, possibly by a mechanism involving suppression of respiration rate and ethylene biosynthesis.     

The mechanism of differential susceptibility to alternaria black spot,caused by Alternaria alternata,of stem- and bottom-end tissues of persimmon fruit

In Israel, alternaria black spot (ABS), caused by Alternaria alternata, is the main postharvest factor that reduces quality and impairs storability of persimmon fruit Diospyros kaki cv. Triumph. The fungus infects the fruit in the orchard and remains quiescent until harvest, or starts development just before harvest, following rain or high humidity. During 2–3 months of storage at 0 °C, the pathogen colonizes the fruit, eliciting ABS symptoms. Susceptibility of the fruit to A. alternata attack is characterized by colonization in the upper, stem-end tissue, in contrast to lack of development at the bottom end. Comparison between the physiology of the stem-end and the bottom-end tissues showed greater production of ethylene and CO₂ in the former during early stages of fruit growth, and greater cracked areas and reduced chlorophyll levels in the later stages of growth, before harvest. Increasing fruit weight by increasing irrigation in the orchard enhanced the cracked area and susceptibility to ABS during growth and at harvest. Wound inoculation enhanced ABS colonization in both ends of the fruit, but more significantly in the upper stem end. The present results suggest that the differential susceptibility to ABS during storage is caused by a differential ripening process, and possibly, by increased maturity at the stem end, leading to cracking and increased ABS development.     

Advances in QTL mapping for ethylene production in apple (Malus × domestica Borkh.)

Ethylene is a gaseous hormone that coordinates several important physiological processes resulting in the final fruit quality in apple. Due to its genetic heterozygousity, apple offers the possibility to exploit the natural allelic variation existing at the level of two genes involved in the ethylene biosynthetic pathway, Md-ACS1 and Md-ACO1. The allelism of these two genes can be exploited for the advanced selection of genotypes characterized by low ethylene production, with a consequent extended postharvest storability. The impact of these two elements in ethylene control was verified using two specific apple populations (‘GDxBr’ and ‘FjxMG’) presenting distinct allelotype configurations. In the first progeny, two QTLs were identified in genetic positions corresponding with these genes, and for the first time the association of a QTL for ethylene production with Md-ACO1 in apple was established. However, the analysis carried out on the second population, homozygous for the allele of Md-ACS1 associated with a low ethylene production, suggested the possible involvement of other genetic elements in the regulation of ethylene production. In the end we also present, in parallel to the GC assessment, a novel methodology based on proton transfer reaction-time of flight-mass spectrometry (PTR-ToF-MS) for a more reliable, fast and efficient monitoring of the ethylene production in apple.     

外源多胺和乙烯对小麦籽粒品质的影响

以‘西农538’和‘周麦22’为材料,在灌浆期分别喷施亚精胺(Spd)、腐胺(Put)和乙烯(Eth),研究外源多胺和乙烯对小麦籽粒品质的影响。结果表明:灌浆期喷施Spd,2个品种籽粒的清蛋白、醇溶蛋白、谷蛋白和总蛋白相比对照均有所提高,面筋质量分数、沉降值等加工品质指标均有不同程度的上升趋势,直链淀粉质量分数下降但未达显著水平,小麦品质得到改善。而喷施Put的效果相反但未达到显著影响。Eth提高清蛋白和球蛋白质量分数,但显著降低醇溶蛋白和谷蛋白质量分数以及面筋质量分数、沉降值等加工品质指标。说明通过化学调控等途径增加籽粒Spd浓度或降低Put和Eth浓度,可以在一定程度上改善小麦的籽粒品质。     

The addition of rosehip oil improves the beneficial effect of Aloe vera gel on delaying ripening and maintaining postharvest quality of several stonefruit

In this work Aloe vera gel (AV) alone or with the addition of 10 or 2% rosehip oil was used as fruit edible coatings in a wide range of Prunus species and cultivars: peaches (‘Roma’ and ‘B-424-16’ flat type), plums (‘Red Beauty’ and ‘Songria’), nectarine (‘Garofa’) and sweet cherry (‘Brooks’). Following treatments, fruit were stored at 20 °C for 6 days and analysed for the effect of treatments on fruit ripening and quality parameters compared with uncoated fruit (control). The addition of the rosehip oil to AV gel reduced respiration rate in all fruit, and ethylene production in the climacteric ones (peaches, plums and nectarine). In addition, all the parameters related with fruit ripening and quality, such as weight loss, softening, colour change and ripening index, were also delayed in treated compared with control fruit, the effect being generally higher when rosehip oil was added to AV, and especially in those fruit that exhibited the highest ethylene production rates (‘Roma’ and flat type peaches). Although the highest effect was obtained with AV + rosehip oil at 10%, the sensory panel detected an excess of gloss and oiliness on the fruit surface, which was considered as a negative attribute. Thus, 2% rosehip oil added to AV could be used as an innovative postharvest tool to increase the beneficial effect of AV as an edible coating, especially in climacteric fruit showing high ethylene production rates.     

Chitosan applications pre- or postharvest prolong raspberry shelf-life quality

Raspberries are fruit with high metabolism that makes them very perishable, impairing their storage and shelf-life. Chitosan coatings have the potential to improve their postharvest life by reducing water loss, respiration rate and decay incidence. The purpose of this work was to study the effect of different concentrations of chitosan, applied pre- or postharvest, on the retention of quality attributes of fresh raspberries. The chitosan concentrations tested were 0 (control), 0.5, 1.0 or 2.0%. The postharvest treatment was applied immediately after harvest, dipping the fruit in the solutions for 5 min. The pre-harvest treatment was done with one hand-spray application per week for three weeks, starting when the fruit were just turning pink. In both experiments the fruit were stored at 0 °C and 90% RH. Pre- or postharvest use of chitosan at 1 or 2% was effective in maintaining titratable acidity and retarding respiration and ethylene production, weight loss and decay incidence. Application by both means resulted in the highest chitosan concentrations accelerating a reduction of ascorbic acid contents. Firmness was maintained only when the fruit were treated pre-harvest at 2%. Thus, application of chitosan at 1 or 2% postharvest and 2% pre-harvest was able to retain key raspberry quality attributes for 15 and 12 days, respectively.