Decoding the fruit microbiome:A climate smart strategy to manage postharvest decays

There is an urgent necessity to shift our diets toward those rich in fruits and vegetables and at reduce postharvest losses of perishables.Approximately 20%-50%of fruits and vegetables are lost due to poor postharvest handling and pathogen infections in developing countries while it was estimated as 5%-35%in developed countries. Fresh fruits have evolved with a plethora of microorganisms having important roles in maintaining fruit health. However, little information is available on the dynamics, structure, and functional capacities of underpinning fruit microbiomes. The present review discussed environmental conditions favoring fruit-harbored antagonists and their different modes of action for suppressing postharvest pathogens in fruits. It also provides information on omics technologies such as next-generation sequencing (NGS),metaproteomics, metatranscriptomic, and metabolomics studies to characterize fruit microbiomes. With the advent of NGS and meta-omics technologies, microbiome research could bring remarkable development and understanding in succeeding biological treatments. In addition, they may provide us with a fundamental understanding of microclimate requirements for fruit microbiome establishment and microbiome shifts during post-harvest storage, which would be advantageous in developing composite biocontrol treatments for post-harvest decay management.

Modified Atmospheric Packaging and Its Effect on Postharvest Cannabis Quality

Cannabis sativa L. is used as fiber, food, and medicine in several countries. Though it is illegal for recreational use in most of the world, there are some countries that have legalized production and sale. There is a lot of research on production of cannabis, but less so on storage technologies. Cannabis contains several high value compounds, such as cannabinoids and terpenoids, that are susceptible to degradation via light, temperature, and oxygen. Several studies have explored temperature and light, and industry has adjusted accordingly. However, less is known about oxygen-induced degradation. Biochemical studies have demonstrated oxidative degradation of high value compounds, and many producers use some form of modified atmospheric packaging (MAP) for storage. However, the efficacy of MAP is unclear. The objective of this paper is to review our current understanding of MAP in postharvest cannabis storage and identify avenues where additional research is needed.

Alternative splicing of the PECTINESTERASE gene encoding a cell wall-degrading enzyme affects postharvest softening in grape

The firmness of table grape berries is a crucial quality parameter. Despite extensive research on postharvest fruit softening, its precise molecular mechanisms remain elusive. To enhance our comprehension of the underlying molecular factors, we initially identified differentially expressed genes(DEGs) by comparing the transcriptomes of folic acid(FA)-treated and water-treated(CK) berries at different time points. We then analyzed the sequences to detect alternatively spliced(AS) genes associated with postharvest softening. A total of 2,559 DEGs were identified and categorized into four subclusters based on their expression patterns, with subcluster-4 genes exhibiting higher expression in the CK group compared with the FA treatment group. There were 1,045 AS-associated genes specific to FA-treated berries and 1,042 in the CK-treated berries, respectively. Gene Ontology(GO) annotation indicated that the AS-associated genes in CK-treated berries were predominantly enriched in cell wall metabolic processes,particularly cell wall degradation processes. Through a comparison between treatment-associated AS genes and subcluster-4 DEGs, we identified eight genes, including Pectinesterase 2(VvPE2, Vitvi15g00704), which encodes a cell wall-degrading enzyme and was predicted to undergo an A3SS event. The reverse transcription polymerase chain reaction further confirmed the presence of a truncated transcript variant of VvPE2 in the FA-treated berries.Our study provides a comprehensive analysis of AS events in postharvest grape berries using transcriptome sequencing and underscores the pivotal role of VvPE2 during the postharvest storage of grape berries.

Variation in Yellow Root Cassava (Manihot esculentus Crantz) Genotypes and Phenotypic Relationship for Selected Postharvest and Morphological Traits

This study evaluated the variation in yellow root cassava (Manihot esculentus Crantz) genotypes and phenotypic relationship for selected postharvest and morphological traits. The trial was established at the Njala Agricultural Research Centre experimental site, Njala, during 2017/2018 cropping season in a randomized complete block design with three replications. Findings showed that the higher the total carotene content (TCC) in yellow flesh cassava genotypes, the longer the rate of postharvest physiological deterioration (PPD). Genotypes TR-0051-TCC/17 and TR-0012-TCC/17 recorded higher TCC (18.9 µg/g and 13.6 µg/g) and longer rate of PPD (4.29 and 3.14), respectively. Genotypes TR-0051-TCC/17, TR-0016-TCC/17, TR-0028-TCC/17, TR-0012-TCC/17 and TR-0020-TCC/17 had the highest TCC values of 18.9 µg/g, 16.09 µg/g, 14.72 µg/g, 13.6 µg/g and 11.23 µg/g with corresponding higher color chart values of 6, 6, 6, 5, and 6, respectively. This suggests the direct dependence of TCC on the root parenchyma color intensity in yellow flesh cassava genotypes. Findings also show a direct relationship between morphological and postharvest traits in yellow flesh cassava genotypes that could be exploited for the genetic improvement of cassava for increased shelf life, nutrition and related quality traits, as well as conservation and utilization of the crop.

Structures and Functions of Cuticular Wax in Postharvest Fruit and Its Regulation:A Comprehensive Review with Future Perspectives

Cuticular wax plays a major role in the growth and storage of plant fruits.The cuticular wax coating,which covers the outermost layer of a fruit’s epidermal cells,is insoluble in water.Cuticular wax is mainly composed of very long-chain fatty acids(VLCFAs);their derivatives,including esters,primary alcohols,secondary alcohols,aldehydes,and ketones;and triterpenoids.This complex mixture of lipids is probably biosynthesized in the epidermal cells of most plants and exuded onto the surface.Cuticular wax not only makes the fruit less susceptible to microbial infection but also reduces mechanical damage to the fruit,thereby maintaining the fruit’s commodity value.To date,research has mostly focused on the changes,function,and regulation of fruit wax before harvest,while ignoring the changes and functions of wax in fruit storage.This paper reviews on the composition,structure,and metabolic regulation of cuticular wax in fruits.It also focuses on postharvest factors affecting wax composition,such as storage temperature,relative humidity(RH),gas atmosphere,and as exogenous hormones;and the effects of wax on fruit postharvest quality,including water dispersion,fruit softening,physiological disorders,and disease resistance.These summaries may be of assistance in better understanding the changes in cuticular wax in postharvest fruit and the resulting effects on fruit quality.

Effects of Trichosporon sp. in Combination with Calcium and Fungicide on Biocontrol of Postharvest Diseases in Apple Fruits

The capability of yeast Trichosporon sp., an antagonist isolated from peach fruit, in biological control was evaluated in apple ( Malus domestica Borkh. cv. Fuji) fruits, when inoculated with different concentrations of Botrytis cinerea Pers. and Penicillium expansum (Link) Thom, as well as in combination with calcium and fungicide. The concentrations of the yeast cells and pathogen spores obviously influenced disease incidence and lesion development in apples. There was a significant negative correlation between concentrations of the yeast cells and infectivity of the pathogens. When the yeast cell suspensions reached the concentration of 10 8 colony_forming units (CFU) /mL, there was no infection caused by B. cinerea and P. expansum with spore concentrations below 10 6 spores/mL in apple fruits. The yeast at concentrations of 10 6-10 7 CFU/mL in combination with fungicide (iprodione at 50 μL/L) provided control of decay caused by B. cinerea and P. expansum better than separate application. Effect of controlling gray mould and blue mould rots was enhanced when Trichosporon sp., even at low concentration of 10 5 CFU/mL, was applied in the presence of 1%-2% CaCl 2 in an aqueous suspension.

Effect of Chitosan with Different Molecular Weights on Postharvest Quality of Chinese Chive Scapes

[Objective] The purpose of this study was to determine the effect of chitosan with different molecular weights on quality and lignification of postharvest Chi- nese chive scapes （Allium tuberosum Rottler ex Sprengel）. [Method] Some physio- logical and biochemical indexes such as weight loss, decay index, opening rate of flowers, chlorophyll and ascorbic acid content, respiration rate, the activities of enzymes, lignin and cellulose content of Chinese chive scapes treated with three kinds of chitosan with different molecular weights were investigated during the room stor- age at 20 ℃ to simulate shelf life. [Result] The results showed that all the treat- ments of chitosan with different molecular weights significantly delayed weight loss, decay index and opening rate of flowers, maintained higher chlorophyll and ascorbic acid content, inhibited respiration rate, reduced the activities of enzymes phenylala- nine ammonia lyase, cinnamyl alcohol dehydrogenase and peroxidase, and retarded lignin and cellulose accumulation during the storage of Chinese chive scapes. However, high molecular weight chitosan has better preservation effect on Chinese chive scapes. [Conclusion] The results suggest that the coating treatment of high molecu- lar weight chitosan may be a promising technique to maintain postharvest quality of Chinese chive scapes.

Progress on Light-controlled Preservation Technology of Postharvest Vegetables

Preservation technology of light control has received the widespread atten- tion for its safety, green, environmental-protection, high efficiency. It has become the hotspot in the area of postharvest vegetables preservation. It could mainly be divid- ed into three categories： LED preservation, UV preservation and radiation preserva- tion. This paper systematically reviewed the mechanisms of different preservation technology of light control, summarized the research progress of light-controlled tech- nology in the physiological characteristics regulation, maintenance of nutritional quali- ty and microbial control of postharvest vegetables at home and aborad, and prospected the further studies on preservation technology for postharvest vegetables.

Effect of Postharvest Treatments on Quality and Shelf Life of Mandarin (Citrus reticulata Blanco)

Nepal produces large quantity of mandarin (Citrus reticulata Blanco) annually but faces big losses due to improper postharvest treatments. The experiment was carried out during 2012-2013 with the objective of assessing the effect of different postharvest treatments on quality and shelf life of mandarin. The postharvest treatments were: wax emulsion at 10%, bavistin at 0.1%, wax at 10% with bavistin at 0.1%, calcium chloride at 1%, Jeevatu at 5% along with untreated fruits as a control. The experiment was conducted for four weeks of storage at ambient condition in Nepal Agricultural Research Council, Khumaltar, Kathmandu. Wax in combination with bavistin was found as the most effective in reducing the physiological loss in weight, whereas bavistin proved to reduce decay loss up to four weeks of storage. The fruits treated with wax alone and with combination of bavistin retained maximum firmness, juice percentage, vitamin C and palatability rating during the storage. The minimum total soluble solid and maximum titrable acidity were recorded in the fruits treated with wax plus bavistin. The present findings indicate that mandarin can be stored up to four weeks when treated with wax as well as wax with bavistin in the condition with 14°C - 18°C temperature and 45% - 73% relative humidity.

Development of Cold-Chain for Postharvest Loss Reduction of Chinese Cabbage(Brassica campestris L.ssp.Pekinensis)

Cold-chain is a well-known method for reducing postharvest losses and low-cost cooling technology has not previously been tested as part of postharvest handling in Cambodia.The objective of this study was to measure postharvest loss,quality changes,and safety concerns of Chinese cabbage(Brassica campestris L.ssp.pekinensis),during transportation using a cold-chain and compared to current farmers’employing ambient-chain practices.The quality and safety of Chinese cabbage were further evaluated by using ambient storage and Coolbot-powered cold chamber storage with and without modified atmosphere packaging(MAP).The samples were transported from farm sources in Battambang Province to a Phnom Penh specialty wholesale market.Postharvest loss was evaluated by measuring weight loss and visual quality measurements,in addition to various physiochemical and nutritional quality measurements.In addition,food safety was evaluated by quantifying total coliforms and Enterobacteriaceae,as well as the Salmonella spcies,and Escherichia coli.The results revealed that the cold-chain avoided postharvest loss,as indicated by produce weight gain of 14%on market arrival due to rehydration while inside the ice box during transport.In contrast,the traditional practice of ambient transport(28-31°C,62-78%relative humidity)resulted in very high postharvest loss,comprising 11%weight loss and 10%visual quality loss,for a total loss of 21%.Moreover,leaf yellowing found no marked influence on shelf life as L*,a*and b*values did not greatly differ with treatment.The total soluble solids(TSS),titratable acidity(TA),pH and vitamin C content were not significantly affected during storage.Food safety indicators(coliforms,Enterobacteriaceae,Salmonella and Escherichia coli)were lower in cold-chain storage than ambient-chain with lower counts of coliform bacteria,Enterobacteriaceae,and Salmonella spp.than traditionally handled produce.Escherichia coli was detected only in cold-chain produce.MAP had no effect on these food safety indicators.

Effects of Active Modified Atmosphere Packaging on Postharvest Quality of Shiitake Mushrooms (Lentinula edodes) Stored at Cold Storage

The effects of active modified atmosphere packaging （MAP） on the postharvest quality of shiitake mushrooms stored at cold temperature （4°C） were investigated.The gas components were 2% O2 ＋7% CO2 （MAP1）,2% O2 ＋10% CO2 （MAP2） and 2% O2 ＋13% CO2 （MAP3）,respectively.The results showed that active MAP could extend the shelf-life of shiitake mushrooms to 17 d and the concentration of carbon dioxide could influence the postharvest quality of shiitake mushrooms.MAP2 treatment inhibited the increase in respiration rate and malondinaldehyde （MDA） contents,delayed the decrease in firmness,soluble sugar and vitamin C,and obviously reduced the activity of polyphenol oxidase （PPO） and the degree of browning,therefore maintaining better quality.

Postharvest Treatment with β-Aminobutyric Acid Induces Resistance Against Dry Rot Caused by Fusarium sulphureum in Potato Tuber

The effectiveness ofpostharvest β-aminobutyric acid （BABA） treatment was studied for inducing resistance against dry rot caused by Fusarium sulphureum in tubers and slices of two potato cultivars （resistant cultivar Shepody and susceptible cultivar Xindaping）. The results showed that BABA at 100 mmol L-1 significantly reduced lesion diameter in inoculated both tubers and slices. The chemical at 100 mmol L-1 showed an effective reduction in infection ability ofF. sulphureum inoculated 48 and 72 h after treatment in slices of resistant cultivar, and 72 and 96 h in susceptible ones. BABA increased the activitives of peroxidase （POD）, polyphenoloxidase （PPO） and phenylalanine ammonialyase （PAL）, and accumulated the contents of lignin, flavonoids and phenolics in slices. The resistant cultivar had a stronger resistant response than the susceptible one. These findings suggest that the BABA treatment can induce the resistance in potato tubers, however, the inducing degree depends on the original level of resistance present in each cultivar.

Pre-harvest spraying of oxalic acid improves postharvest quality associated with increase in ascorbic acid and regulation of ethanol fermentation in kiwifruit cv. Bruno during storage

The kiwifruit trees(Actinidia deliciosa cv.Bruno)were sprayed with 5 mmol L-1 oxalic acid(OA)or water(as control)at 130,137 or 144 d after full-blossom,and then the fruit were harvested at commercial maturity and stored at room temperature(20±1)℃ for 13 d.The effect of pre-harvest spraying of OA on postharvest quality of kiwifruit was evaluated during storage.The OA spraying slowed the increase in soluble solids content(SSC)and decrease in titratable acid(TA),as well as increased contents of ascorbic acid(AsA)and total-AsA accompanied with higher AsA/DHA ratio in kiwifruit during storage.Moreover,the OA spraying significantly reduced the contents of acetaldehyde and ethanol in kiwifruit,along with significant decrease in activities of enzymes involved in ethanol fermentation metabolism during the later period of storage,which was beneficial to control off-flavor associated with over accumulation of ethanol during postharvest.It was suggested that pre-harvest spraying of OA might maintain the postharvest quality of kiwifruit in relation to delay in fruit ripening,AsA maintenance and regulation of ethanol fermentation.

Effect of Postharvest UV-C Irradiation on Phenolic Compound Content and Antioxidant Activity of Tomato Fruit During Storage

Mature-green tomato fruit （Solanum lycopersicum cv. Zhenfen 202） were exposed to different UV-C irradiation at 2, 4, 8, and 16 kJ m-2 and then stored under the dark at 14°C and 95% relative humidity （RH） for 35 d. Of these four doses, UV-C irradiation at 4 and 8 kJ m-2 significantly increased total phenolic contents in present tomato fruit by 21.2 and 20.2%, respectively. Furthermore, UV-C irradiation at 4 or 8 kJ m-2 promoted the accumulation of total flavonoids and increased the antioxidant activity. 2 or 16 kJ m-2 UV-C irradiation also enhanced antioxidant activity, but to a lesser extent. Seven phenolic compounds, viz., gallic acid, （＋）-catechin, chlorogenic acid, cafferic acid, syringic acid, p-coumaric acid, and quercetin in tomato fruit were identified and quantified by HPLC. Gallic acid was the major phenolic compound in tomato fruit and significantly correlated with antioxidant activity. 4 or 8 kJ m-2 UV-C irradiation significantly increased the contents of gallic acid, chlorogenic acid, syringic acid, p-coumaric acid, and quercetin. The optimum dose of UV-C irradiation in terms of increased phenolic compound content and enhanced Antioxidant activity was determined to be 4 or 8 kJ m-2.

First report of Athelia bombacina causing postharvest fruit rot on pear

Pear is an important fruit crop in the world. An uncharacterized disease has been observed on pear fruits during cold storage ir~ Suning, Shenzhou, Xinji and other locations in Hebei Province, China. The incidence rate of the disease has reached 10%, and sometimes up to 20%. A particular fungus was consistently isolated from the infected pear fruit and cultured. Based on its morphology, molecular characteristics, pathogenicity and ITS sequence, the fungus was identified as Athelia bombacina. To our knowledge, this is the first report of Athelia bombacina causing postharvest fruit rot on pear.

Basic helix-loop-helix(bHLH)transcription factor MdbHLH3 negatively affects the storage performance of postharvest apple fruit

The storage period of fleshy fruits greatly affects their quality and selection,and is largely controlled by genetic factors.Therefore,it is imperative to elucidate how genetic factors affect fruit ripening and its storage.Here,we evaluated the postharvest storage properties of the basic helix-loop-helix(bHLH)transcription factor MdbHLH3-overexpressing transgenic Royal gala apple fruits.During storage,the contents of starch,malic acid,fructose,glucose,and sucrose in fruits of three MdbHLH3 transgenic lines were always higher than those of the wild-type(WT)control.Interestingly,the sugar-acid ratio also showed the same trend during fruit storage.Additionally,the fruit firmness decreased with increasing storage time,and the contents of cell wall components such as water-soluble pectin and cellulose in transgenic fruits were higher than those in control fruits,while the firmness of transgenic fruits was lower than that in WT control fruits.Though the ethylene release rate in both showed the same trend(firstly increasing,then decreasing,and finally peaking)in 90-day stored fruits,transgenic apples had higher ethylene levels than the WT control throughout storage.Furthermore,the activities of membrane peroxidase,antioxidant enzymes,and fruit ripening enzymes in all transgenic fruits were significantly higher than those in the WT control.Thus,our findings show how MdbHLH3 negatively regulates and reduces apple storage time.This may prove useful for not only developing biotechnological strategies,but also support traditional breeding programs,to help improve the storage time of fleshy fruits.

Harvest and Postharvest Factors Affecting Bruise Damage of Fresh Fruits

Fresh fruits are susceptible to bruising, a common type of mechanical damage during harvest and at all stages of postharvest handling. In quest of developing and adoption of strategies to reduce bruise damage, it is of utmost importance to understand major factors influencing bruise susceptibility of fresh produce at these stages. This review presents a critical discussion of factors affecting bruising during harvest and postharvest handling of fresh fruits. Excessive compression forces during harvesting by handpicking or machines, and a series of impacts during harvesting, transport and packhouse operations can cause severe bruise damage. The review has further revealed that bruising is dependent on a number of other factors such as produce maturity, ripening, harvest time(during the day or season) and time lapse after harvest. The susceptibility to bruising is partly dependent on how these factors alter the produce physiological and biochemical properties, and the environmental conditions such as temperature, humidity and several other postharvest treatments. Hence, the successful applications of harvesting techniques by use of trained personnel and proper harvesting equipment are essential to reduce both the incidence and severity of bruising.Furthermore, the careful selection of postharvest handling temperature and other treatments can increase resistance of fresh produce to bruise damage.

Effects of INA on postharvest blue and green molds and anthracnose decay in citrus fruit

As a synthetic functional analog of salicylic acid, 2,6-dichloroisonicotinic acid(INA) is effective in inducing the host disease resistance of a plant against a pathogen. The effects of INA on controlling postharvest blue and green molds and anthracnose decay and defense-related enzymes on citrus fruits were investigated, and the ascorbic acid of naturally infected citrus flavedo was also measured. Results showed that 1.0 mmol L^(–1) INA treatments significantly reduced blue and green molds and anthracnose decay development on both wound-inoculated fruit and naturally-infected fruit compared with the control fruit. The treatment effectively enhanced the β-1,3-glucanase(GLU), chitinase(CHI), phenylalanine ammonia-lyase(PAL) and peroxidase(POD) activities and the polyphenol oxidase(PPO) in flavedo. The results presented here suggest that INA might be used as a chemical fungicide substitution to control postharvest diseases in citrus fruits.

Impact of Oriental Fruit Fly Postharvest Treatments on Avocado

The detection in August 2015 of the Oriental Fruit Fly (Bactrocera dorsalis Hendel, Diptera: Tephritidae) in the Redland area in Miami-Dade County, Florida triggered a quarantine that restricted the movement of fruit fly host material in an approximately 99-square mile (256-square kilometer) area. The quarantine affected 4000 acres of fruit bearing commercial avocado groves. Approved post-harvest treatments for B. dorsalis and avocado included in the USDA Treatment Manual were acceptable for immediate certification and movement of fresh avocados from the quarantine area. However, it was unknown if Florida avocados would meet quality standards (US combination grade) after the treatments. Three post-harvest treatments that combine methyl bromide fumigation and cold storage periods were tested on six avocado varieties from Florida. The treatments differed in the durations of the fumigation and cold treatment periods. A seven day transit period at 8.3°C (47°F) was added to account for the time when the fruit leaves the packing house until it is sold by retailers. None of the six varieties had met the US combination grade after the treatments and transit period. Treated fruit exhibited both internal (pulp) and external (skin) damage. Damage was attributed to the fumigation component of the treatment, but the six varieties tolerated the cold portion of the treatment. Damage by fumigation ranged from 26% - 100%. In general, the longer the fumigation period the worse the effect. The need for alternative post-harvest treatments for Florida avocados is discussed.

Advances and Strategies for Controlling the Quality and Safety of Postharvest Fruit

Fresh fruits are highly valued by consumers worldwide,owing to their delicious flavors,abundant nutrients,and health-promoting characteristics,and as such,fruits make up an important component of a healthy diet.The postharvest quality and safety of fresh fruit involve complex interactions among the fruit,environmental factors,and postharvest pathogens.Efficient regulation of fruit senescence and pathogen resistance,as well as disease-causing abilities of postharvest pathogens,is critical to understanding the fundamental mechanisms that underlie fruit quality and safety.This paper provides a comprehensive review of recent advances and currently available strategies for maintaining fruit quality and controlling major postharvest pathogens,mainly Botrytis cinerea and Penicillium expansum,which may promote sustainable and environmental-friendly development of the fruit industry.