Fruit Ethylene Research Articles

Managing ‘Bartlett’ pear fruit ripening with 1-methylcyclopropene reapplication during cold storage

Repeated low-dose 1-MCP-applications were evaluated during cold storage of ‘Bartlett’ pear fruit to overcome long-term ripening inhibition of a high dose 1-MCP treatment at harvest. Fruit were exposed to 1-MCP at 0, 0.42, 4.2 or 42μmolm−3 at harvest in year one, and to 0, 0.42 or 42μmolm−3 in year two, and then stored in air at 0.5°C. In year two, fruit exposed to 1-MCP at 0.42μmolm−3 at harvest were retreated during cold storage once (after 38 days) or twice (after 38 and 68 days), when ethylene production in samples removed from cold storage exceeded 0.014ηmolkg−1s−1 within 7 days at 20°C. 1-MCP was re-applied once at 0.42 or 4.2μmolm−3 or twice at 0.42 or 4.2 then 42μmolm−3. In year one, fruit treatment at harvest with 4.2 or 42μmolm−3 1-MCP provided similar ripening delay during 120 days in storage followed by 7 days at 20°C, while fruit treated with 0.42μmolm−3 1-MCP was not different from the control. In year two, fruit treated at harvest with 0.42μmolm−3 1-MCP and retreated with 0.42μmolm−3 (when ethylene production was already high) did not delay subsequent fruit ripening. Fruit treated at harvest with 42μmolm−3 1-MCP or with 0.42μmolm−3 at harvest and then +4.2+42, had similar peel yellow color, TA and SSC, but higher firmness after 180 days storage, compared to control fruit after 60 days storage. After 180 days storage, the severity of superficial scald, senescent scald and core browning on fruit treated only at harvest with 42μmolm−3 were lower than on control fruit and similar to on fruit treated with 0.42μmolm−3 at harvest and then retreated with +4.2+42. Therefore, a low dose application of 1-MCP at harvest followed by reapplication with higher doses based on fruit ethylene production capacity after removal from cold storage can extend ‘Bartlett’ pear storage life while allowing ripening to occur after mid-term storage. The efficiency of this procedure will depend on timing and 1-MCP reapplication concentration.

A transcriptome approach towards understanding the development of ripening capacity in 'Bartlett' pears (Pyrus communis L.).

BackgroundThe capacity of European pear fruit (Pyrus communis L.) to ripen after harvest develops during the final stages of growth on the tree. The objective of this study was to characterize changes in ‘Bartlett’ pear fruit physico-chemical properties and transcription profiles during fruit maturation leading to attainment of ripening capacity.ResultsThe softening response of pear fruit held for 14 days at 20 °C after harvest depended on their maturity. We identified four maturity stages: S1-failed to soften and S2- displayed partial softening (with or without ET-ethylene treatment); S3 - able to soften following ET; and S4 - able to soften without ET. Illumina sequencing and Trinity assembly generated 68,010 unigenes (mean length of 911 bp), of which 32.8 % were annotated to the RefSeq plant database. Higher numbers of differentially expressed transcripts were recorded in the S3-S4 and S1-S2 transitions (2805 and 2505 unigenes, respectively) than in the S2-S3 transition (2037 unigenes). High expression of genes putatively encoding pectin degradation enzymes in the S1-S2 transition suggests pectic oligomers may be involved as early signals triggering the transition to responsiveness to ethylene in pear fruit. Moreover, the co-expression of these genes with Exps (Expansins) suggests their collaboration in modifying cell wall polysaccharide networks that are required for fruit growth. K-means cluster analysis revealed that auxin signaling associated transcripts were enriched in cluster K6 that showed the highest gene expression at S3. AP2/EREBP (APETALA 2/ethylene response element binding protein) and bHLH (basic helix-loop-helix) transcripts were enriched in all three transition S1-S2, S2-S3, and S3-S4. Several members of Aux/IAA (Auxin/indole-3-acetic acid), ARF (Auxin response factors), and WRKY appeared to play an important role in orchestrating the S2-S3 transition.ConclusionsWe identified maturity stages associated with the development of ripening capacity in ‘Bartlett’ pear, and described the transcription profile of fruit at these stages. Our findings suggest that auxin is essential in regulating the transition of pear fruit from being ethylene-unresponsive (S2) to ethylene-responsive (S3), resulting in fruit softening. The transcriptome will be helpful for future studies about specific developmental pathways regulating the transition to ripening.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1939-9) contains supplementary material, which is available to authorized users.

Abscisic acid as a potential chemical thinner for peach

Abstract:The objective of this work was to evaluate the effect of abscisic acid, applied at different rates and different fruit developmental stages, on the thinning of 'Chiripá' peach. Abscisic acid (ABA) at 500 mg L-1 was applied at three stages of fruit development based on lignin deposition: stage 1, at 24 days after full bloom (DAFB); stage 2, at 40 DAFB; and stage 3, at 52 DAFB. Only ABA application at stage 2 - 40 DAFB - reduced fruit set and the number of fruit per plant. Three ABA concentrations (350, 500, and 750 mg L-1) were then applied at 40 DAFB. All rates increased fruit ethylene production and fruit abscission.

English

Summary Commercial postharvest applications of 1-methylcyclopropene (1-MCP) to retain quality of ‘Jonagold’ apples of different harvest maturities and stored in air and controlled atmosphere conditions were investigated in three consecutive seasons in Southwest Germany. This cultivar is widely planted and most popular in this fruit-growing region. Fruit samples were removed from storage at bi- or three-monthly intervals during maximal 9 months storage periods. Thereafter, fruit were frequently evaluated over up to 10 days at 20°C to link instrumental data of ex-store fruit quality to sensory descriptions from consumer preference surveys. Fruit quality declined with storage duration; however, the degree of quality loss was much less severe under all storage conditions when fruit was treated with 1-MCP. Ethylene-dependent ripening processes such as softening, yellowing of the background colour and loss of titratable acidity were significantly more reduced in 1-MCP-treated ‘Jonagold’ apples than in untreated controls, concomitantly with lower rates of fruit respiration and fruit ethylene production. Data showed a good agreement between instrumental measurements and consumer scores for all evaluated fruit quality parameters. We conclude that flesh firmness and titratable acidity were the most important drivers of consumer preference. Interestingly, consumers, regardless of age and gender, preferred 1-MCP-treated fruit held in ultra-low oxygen storage. Although sensory evaluation studies are time-consuming and might have some flaws when attempting to generate representative results from consumer taste panels, they are a useful tool to assess product quality and consumer preference.

Mango (Mangifera indica L.) cv. Kent fruit mesocarp de novo transcriptome assembly identifies gene families important for ripening.

Fruit ripening is a physiological and biochemical process genetically programmed to regulate fruit quality parameters like firmness, flavor, odor and color, as well as production of ethylene in climacteric fruit. In this study, a transcriptomic analysis of mango (Mangifera indica L.) mesocarp cv. “Kent” was done to identify key genes associated with fruit ripening. Using the Illumina sequencing platform, 67,682,269 clean reads were obtained and a transcriptome of 4.8 Gb. A total of 33,142 coding sequences were predicted and after functional annotation, 25,154 protein sequences were assigned with a product according to Swiss-Prot database and 32,560 according to non-redundant database. Differential expression analysis identified 2,306 genes with significant differences in expression between mature-green and ripe mango [1,178 up-regulated and 1,128 down-regulated (FDR ≤ 0.05)]. The expression of 10 genes evaluated by both qRT-PCR and RNA-seq data was highly correlated (R = 0.97), validating the differential expression data from RNA-seq alone. Gene Ontology enrichment analysis, showed significantly represented terms associated to fruit ripening like “cell wall,” “carbohydrate catabolic process” and “starch and sucrose metabolic process” among others. Mango genes were assigned to 327 metabolic pathways according to Kyoto Encyclopedia of Genes and Genomes database, among them those involved in fruit ripening such as plant hormone signal transduction, starch and sucrose metabolism, galactose metabolism, terpenoid backbone, and carotenoid biosynthesis. This study provides a mango transcriptome that will be very helpful to identify genes for expression studies in early and late flowering mangos during fruit ripening.

Characterization of 1-aminocyclopropane-1-carboxylic acid synthase (ACS) genes during nectarine fruit development and ripening

1-Aminocyclopropane-1-carboxylic acid synthases (ACS) are key regulatory enzymes involved in ethylene biosynthesis. In plants, ACS enzymes are encoded by a multigene family. In our study, six Pp-ACS genes were identified in nectarine (Prunus persica var. nectarina) based on the recently released peach genome sequence. To gain a better understanding of the nectarine ACS genes in fruit ethylene biosynthesis networks, ethylene evolution and the accumulation patterns of six Pp-ACS transcripts during fruit development and ripening in nectarine ‘CN13’ (melting type) and ‘CN16’ (stony hard type) cultivars were examined. Of the six Pp-ACS cDNAs isolated, two genes (Pp-ACS1 and Pp-ACS4) showed ripening-related increased expression during fruit development and ripening in nectarine ‘CN13’. Lack of Pp-ACS1 expression was solely responsible for low levels of ethylene production in nectarine ‘CN16’. The expression of Pp-ACS5 decreased during fruit development. The effects of phytohormones (auxin and ethylene) and low temperature (4 °C) on the levels of different Pp-ACS mRNAs were investigated. Finally, a model is proposed describing the critical regulation of Pp-ACS genes and their relationships to ethylene biosynthesis during nectarine fruit development and ripening.

Effects of Exogenous Ethylene on AC and Rin Tomato Fruit

The flesh firmness of AC andrinmutant tomato fruits picked freshly were the largest. Respiration rate and ethylene production were very low at this time. With ethylene production increase, fruit firmness began to decline. 100μL/L ethephon significantly increased AC tomato fruit ethylene release, respiration rate, ACS activity and ACO activity, and decreased flesh firmness. However, there were no significant differences inrinmutant between control and ethephon treatment. It was shown RIN transcription factor regulated ethylene biosynthesis by ACC synthase and ACC oxidase.

Ethylene Emission of Apples Treated with 1-Methylcyclopropene During Storage

Abstract The effect of post-harvest application of 1-methylcyclopropene (1-MCP) on ethylene emission in early-winter apple (cv. ‘Calville’), winter (‘Gloster’, ‘Golden Delicious’ and ‘Jonagold’), and late-winter cultivars (‘Granny Smith’, ‘Idared’ and ‘Reinette Simirenko’) w as investigated. The fruits were picked at a commercial harvest time and half of them were treated with 1-MCP (‘SmartFresh™’ 0.068 gm-3) for 24 h at 5 °C. Then both groups of apples were placed in a common storage at the temperature of 2 °C. The intensity of fruit ethylene emission (rate of ethylene production) was measured and 1 -MCP inhibition index was calculated. During storage, activity of ethylene emission by control apples of ‘Calville’ and ‘Golden Delicious’ showed typical climacteric pattern, while the intensity of ethylene emission of apples of other cultivars only increased gradually. The change of ethylene activity of early-winter apple cv. ‘Calville’ and winter cv. ‘Jonagold’, both treated with 1-MCP after harvest, had exponential character, especially actively increasing after 3 months of storage. At the same time ethylene emission of 1 -MCP treated fruits of other cultivars changed steadily to a low level and was effectively suppressed during the whole 6-month period of storage in normal atmosphere. The value of inhibition index of fruits treated by 1-MCP confirmed the consistent restoration of the ability to ethylene synthesis and thus to post-harvest ripening of some apples cultivars.

The transcriptional response of apple alcohol acyltransferase (MdAAT2) to salicylic acid and ethylene is mediated through two apple MYB TFs in transgenic tobacco.

Volatile esters are major factors affecting the aroma of apple fruits, and alcohol acyltransferases (AATs) are key enzymes involved in the last steps of ester biosynthesis. The expression of apple AAT (MdAAT2) is known to be induced by salicylic acid (SA) or ethylene in apple fruits, although the mechanism of its transcriptional regulation remains elusive. In this study, we reveal that two apple transcription factors (TFs), MdMYB1 and MdMYB6, are involved in MdAAT2 promoter response to SA and ethylene in transgenic tobacco. According to electrophoretic mobility shift assays, MdMYB1 or MdMYB6 can directly bind in vitro to MYB binding sites in the MdAAT2 promoter. In vivo, overexpression of the two MYB TFs can greatly enhance MdAAT2 promoter activity, as demonstrated by dual luciferase reporter assays in transgenic tobacco. In contrast to the promoter of MdMYB1 or MdMYB6, the MdAAT2 promoter cannot be induced by SA or ethephon (ETH) in transgenic tobacco, even in stigmas in which the MdAAT2 promoter can be highly induced under normal conditions. However, the induced MYB TFs can dramatically enhance MdAAT2 promoter activity under SA or ETH treatment. We conclude that MdMYB1 and MdMYB6 function in MdAAT2 responses to SA and ethylene in transgenic tobacco, suggesting that a similar regulation mechanism may exist in apple.

Enhanced flux of substrates into polyamine biosynthesis but not ethylene in tomato fruit engineered with yeast S-adenosylmethionine decarboxylase gene

S-adenosylmethionine (SAM), a major substrate in 1-C metabolism is a common precursor in the biosynthetic pathways of polyamines and ethylene, two important plant growth regulators, which exhibit opposing developmental effects, especially during fruit ripening. However, the flux of various substrates including SAM into the two competing pathways in plants has not yet been characterized. We used radiolabeled (14)C-Arg, (14)C-Orn, L-[U-(14)C]Met, (14)C-SAM and (14)C-Put to quantify flux through these pathways in tomato fruit and evaluate the effects of perturbing these pathways via transgenic expression of a yeast SAM decarboxylase (ySAMDC) gene using the fruit ripening-specific promoter E8. We show that polyamines in tomato fruit are synthesized both from Arg and Orn; however, the relative contribution of Orn pathway declines in the later stages of ripening. Expression of ySAMDC reversed the ripening associated decline in spermidine (Spd) and spermine (Spm) levels observed in the azygous control fruit. About 2- to 3-fold higher levels of labeled-Spd in transgenic fruit (556HO and 579HO lines) expressing ySAMDC confirmed the enzymatic function of the introduced gene. The incorporation of L-[U-(14)C]Met into Spd, Spm, ethylene and 1-aminocyclopropane-1-carboxylic acid (ACC) was used to determine Met-flux into these metabolites. The incorporation of (14)C-Met into Spd/Spm declined during ripening of the control azygous fruit but this was reversed in fruits expressing ySAMDC. However, incorporation of (14)C-Met into ethylene or ACC during ripening was not altered by the expression of ySAMDC in the fruit. Taken together these results show that: (1) There is an inverse relationship between the production of higher polyamines and ethylene during fruit ripening, (2) the inverse relationship between higher polyamines and ethylene is modulated by ySAMDC expression in that the decline in Spd/Spm during fruit ripening can be reversed without significantly altering ethylene biosynthesis, and (3) cellular flux of SAM in plants is homeostatically regulated based on its demand for competing pathways.

Characterisation of ethylene pathway components in non-climacteric capsicum.

BackgroundClimacteric fruit exhibit high ethylene and respiration levels during ripening but these levels are limited in non-climacteric fruit. Even though capsicum is in the same family as the well-characterised climacteric tomato (Solanaceae), it is non-climacteric and does not ripen normally in response to ethylene or if harvested when mature green. However, ripening progresses normally in capsicum fruit when they are harvested during or after what is called the ‘Breaker stage’. Whether ethylene, and components of the ethylene pathway such as 1-aminocyclopropane 1-carboxylate (ACC) oxidase (ACO), ACC synthase (ACS) and the ethylene receptor (ETR), contribute to non-climacteric ripening in capsicum has not been studied in detail. To elucidate the behaviour of ethylene pathway components in capsicum during ripening, further analysis is therefore needed. The effects of ethylene or inhibitors of ethylene perception, such as 1-methylcyclopropene, on capsicum fruit ripening and the ethylene pathway components may also shed some light on the role of ethylene in non-climacteric ripening.ResultsThe expression of several isoforms of ACO, ACS and ETR were limited during capsicum ripening except one ACO isoform (CaACO4). ACS activity and ACC content were also low in capsicum despite the increase in ACO activity during the onset of ripening. Ethylene did not stimulate capsicum ripening but 1-methylcyclopropene treatment delayed the ripening of Breaker-harvested fruit. Some of the ACO, ACS and ETR isoforms were also differentially expressed upon treatment with ethylene or 1-methylcyclopropene.ConclusionsACS activity may be the rate limiting step in the ethylene pathway of capsicum which restricts ACC content. The differential expression of several ethylene pathway components during ripening and upon ethylene or 1-methylclopropene treatment suggests that the ethylene pathway may be regulated differently in non-climacteric capsicum compared to the climacteric tomato. Ethylene independent pathways may also exist in non-climacteric ripening as evidenced by the up-regulation of CaACO4 during ripening onset despite being negatively regulated by ethylene exposure. However, some level of ethylene perception may still be needed to induce ripening especially during the Breaker stage. A model of capsicum ripening is also presented to illustrate the probable role of ethylene in this non-climacteric fruit.

1-MCP nos aspectos fisiológicos e na qualidade pós-colheita de maçãs Eva durante o armazenamento refrigerado

O objetivo deste estudo foi verificar o efeito de doses específicas do composto 1-metilciclopropeno (1-MCP), após a colheita, nos aspectos fisiológicos e na qualidade físico-química de maçãs Eva durante o armazenamento refrigerado. Após a aplicação dos tratamentos com diferentes doses de 1-MCP (0, 10, 50, 100 e 500mg L-1), os frutos foram armazenados em câmara fria 0,5°C (±0,5) por até 135 dias. O armazenamento refrigerado juntamente com a aplicação de 1-MCP resultou em uma menor produção de etileno, principalmente nos frutos tratados com as doses de 10, 50 e 100mg L-1. O grupo controle perdeu 45% de sua firmeza, enquanto os grupos tratados perderam, em média, 27% de sua firmeza. O parâmetro C de cor identificou frutos com cor mais intensa aos 135 dias de armazenamento e o ângulo Hue mostrou que, quando tratados com as doses de 10 e 50mg L-1, os frutos apresentaram-se mais amarelados, evidenciando melhor ação do 1-MCP em baixas concentrações. Frutos que não foram submetidos aos tratamentos apresentaram maior relação sólidos solúveis e acidez, demonstrando assim maior atividade metabólica.

Expression and regulation of the ethylene receptor PpERS gene during pear fruit development and following salicylic acid treatment

A gene encoding an ethylene receptor protein was isolated from pear (Pyrus pyrifolia). This gene, designated PpERS (GenBank accession No. KC517482), was 1,918 bp in length with an open reading frame encoding a protein of 638 amino acids that shared high similarity with another pear ethylene receptor protein PpERS1, and two apple ethylene receptor proteins MdERS and MdERS1. The PpERS was grouped into the ETR1 subfamily of ethylene receptor based on its conserved domain and phylogenetic status. The PpERS gene contained five exons interrupted by four introns. Quantitative RT-PCR indicated that PpERS was differentially expressed in pear tissues and predominantly expressed in petals, shoots, anthers, and 160 days after full bloom fruit. The PpERS expression was regulated during fruit development. In addition, the PpERS gene expression was regulated by salicylic acid (SA) and ethylene in fruit. The results indicated that PpERS might participate in ethylene and SA signaling transduction during pear fruit development.

Delayed ripening and improved fruit processing quality in tomato by RNAi-mediated silencing of three homologs of 1-aminopropane-1-carboxylate synthase gene

The ripening hormone, ethylene is known to initiate, modulate and co-ordinate the expression of various genes involved in the ripening process. The burst in ethylene production is the key event for the onset of ripening in climacteric fruits, including tomatoes. Therefore ethylene is held accountable for the tons of post-harvest losses due to over-ripening and subsequently resulting in fruit rotting. In the present investigation, delayed ripening tomatoes were generated by silencing three homologs of 1-aminocyclopropane-1-carboxylate (ACC) synthase (ACS) gene during the course of ripening using RNAi technology. The chimeric RNAi-ACS construct designed to target ACS homologs, effectively repressed the ethylene production in tomato fruits. Fruits from such lines exhibited delayed ripening and extended shelf life for ∼45 days, with improved juice quality. The ethylene suppression brought about compositional changes in these fruits by enhancing polyamine (PA) levels. Further, decreased levels of ethylene in RNAi-ACS fruits has led to the altered levels of various ripening-specific transcripts, especially the up-regulation of PA biosynthesis and ascorbic acid (AsA) metabolism genes and down-regulation of cell wall hydrolyzing enzyme genes. These results suggest that the down-regulation of ACS homologs using RNAi can be an effective approach for obtaining delayed ripening with longer shelf life and an enhanced processing quality of tomato fruits. Also, the chimeric gene fusion can be used as an effective design for simultaneous silencing of more than one gene. These observations would be useful in better understanding of the ethylene and PA signaling during fruit ripening and molecular mechanisms underlying the interaction of these two molecules in affecting fruit quality traits.

The Effect of MethyI Jasmonate on Ethylene Production, ACC Oxidase Activity and Carbon Dioxide Evolution in the Yellowish-Tangerine Tomato Fruits (Lycopersicon esculentum Mill.)

The yellowish-tangerine tomato (cv. Bursztyn) in the green, light yellow and yellow stages of ripening were treated with 0.1% and 1.0% of methyl jasmonate (JA-Me) in lanolin paste and kept for several days and then they were evaluated for production of ethylene, ACC oxidase activity and CO<sub>2</sub> evolution. Production of endogenous ethylene in mature green fruits was low and increased during ripening. JA-Me stimulated ethylene production and ACC oxidase activity in all investigated stages of fruit ripening. Slices excised from mature green fruits produced highest amount of carbon dioxide as compared to more advanced stages of ripening. JA-Me in O,1 % and 1,0% concentrations increased significantly CO<sub>2</sub> evolution in green fruits, while in light yellow and yellow fruits only higher concentration of JA-Me stimulated carbon dioxide production.

Post-harvest 1-methylcyclopropene and ethephon treatments differently modify protein profiles of peach fruit during ripening

A proteomic approach based on two-dimensional polyacrylamide gel electrophoresis (2-DE) and MALDI-TOF/TOF techniques has been used in this work to study the effect of 1-methylcyclopropene (1-MCP) and 2-chloroethylphosphonic acid (ethephon) on the protein profiles of melting peach fruit (cv. Huiyulu) during ripening. The extracted proteins from the 1-MCP-treated and ethephon-treated peach fruit were used. More than 600 protein spots were detected by means of 2-DE and 38 differently expressed spots (P<0.05) were selected to be excised and analyzed using MALDI-TOF/TOF, and 35 were finally confidently identified according to the peach EST database downloaded from Genome Database for Rosaceae and NCBI database. Among the 35 successfully identified protein regulated by 1-MCP and ethephon, 26 proteins were modulated by 1-MCP and 27 proteins were regulated by ethephon. Meanwhile, 8 proteins were down-regulated by 1-MCP and up-regulated by ethephon, and 5 proteins down-regulated by ethephon but up-regulated by 1-MCP. Differently expressed proteins belonged to different metabolic pathways including energy and metabolism (34.29%), cell structure (22.83%), protein fate (17.14%), stress response and defense (14.29%) and ripening and senescence (8.57%). All these indicated that the regulation patterns by 1-MCP and ethephon at proteomic level are complicated, involving various metabolic pathways. Ethephon could induce the expressions of 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), abscisic acid stress ripening-like protein (ASR) and cell structure-related proteins, such as tubulin and actin, accelerate the glycolytic metabolisms, regulate the galactose and glutamine metabolism, and modulate the methionine metabolism. 1-MCP could inhibit the degradation of starch, weaken the metabolism of glycolytic pathway, strongly depresses the expression of ACO and ASR, and induce the expression of chaperonin 60 and HSPs in ripening peach fruit. Taken together, the present study will be informative for exploring the exact roles of ethylene in peach fruit ripening and explaining the molecular mechanism of peach ripening.

THE INTERACTION BETWEEN ETHYLENE AND POLYAMINES DURING RIPENING OF OLIVE FRUIT

Ripening is a complex and highly regulated phenomenon involving many endogenous and environmental factors, all of which must be correctly balanced in order to achieve the best fruit quality. Ripening control in olive is an important issue because, owing to early harvest and long storage times, fruit quality (oil/canning) can deteriorate before reaching the consumer. Ethylene and polyamines are known to have opposite effects in relation to fruit ripening and senescence. In fact, polyamine and ethylene physiologies may be linked during fruit development. This work describes the changes in endogenous free polyamines levels and ethylene production during fruit development from two cultivars of Olea europaea L. (‘Arbequina’ and ‘Picual’). Ethylene production (the 1-aminocyclopropane-1-carboxylic acid (ACC) level) has been determined by gas chromatography and polyamine content (putrescine, spermidine and spermine) by dansylation and separation of dansyl derivatives by HPLC. To investigate the relationships between ethylene and free polyamines in olive fruit, the effect of exogenous polyamines (putrescine and spermidine) and aminooxy-acetic acid (AOA, inhibitor of ethylene biosynthesis) on polyamines and ACC levels was also examined in ripening olive fruit. Fruit treatments were performed in planta.

Effect of high temperature on color, chlorophyll fluorescence and volatile biosynthesis in green-ripe banana fruit

Banana (Musa AAA group) is one of the most consumed fruits in the world. It has been reported that chlorophyll breakdown and color formation in banana is inhibited by ripening temperatures above 24 °C. At this temperature thylakoid membranes are retained resulting in reduced chlorophyll degradation. In this study, green mature, untreated banana fruit were obtained from a local wholesale market and half of the fruit were subjected to ethylene treatment at 10 μL L −1 for 24 d. After ethylene treatment, both treated and untreated fruit were stored at 20 °C or 30 °C for 7 d. Fruit were sampled after 0, 1, 4 and 7 d of storage and evaluated for color, chlorophyll fluorescence, volatile production and expression of genes related to volatile biosynthesis. Storage at 30 °C reduced yellow color development in the peel, decreased chlorophyll fluorescence (Fv/Fm), but increased Fo, indicating possible heat stress of the fruit. A total of 19 volatile compounds were identified using SPME/GC/MS. Both ethylene treatment and high temperature enhanced volatile production. The increase of Fo and hexanoate and acetate esters are coincided with the stress of high temperature. Using real time PCR (qPCR), expression of genes related to volatile biosynthesis including branched-chain amino acid transaminase ( BCAT), lipoxygenase (LOX), hydroperoxide lyase ( HPL), pyruvate decarbolxylase ( PDC), alcohol dehydrogenases ( ADH, short and medium chains), and alcohol acetyl transferase ( AAT) were investigated in both peel and pulp tissues. Among the tested genes, BCAT, HPL, ADH and AAT in peel and pulp tissues increased significantly in response to ethylene and storage at 30 °C. PDC, ADH and BCAT (in pulp tissue) were induced by storage at 30 °C in ethylene-treated fruit. LOX decreased during ripening and storage at 30 °C in the peel, but increased in the pulp tissue of ethylene-treated fruit. This study demonstrates that both ethylene and high temperature influence volatile biosynthesis in banana fruit at the transcriptional level and confirms findings that high temperature causes stress in banana fruit during ripening.

Monitoring Effects of Ethanol Spray on Cabernet franc and Merlot Grapes and Wine Volatiles Using Electronic Nose Systems

The ability of two electronic nose systems (conducting polymer and surface acoustic wave-based) to differentiate volatiles of grapes and wines treated with an aqueous ethanol spray (5% v/v) at veraison was evaluated. Ethanol spray induced fruit ethylene production immediately posttreatment, which then declined progressively. The electronic nose evaluations of grape volatiles were compared with Cabernet franc and Merlot physicochemistry and with wine gas chromatographic and aroma sensory data. Canonical discriminant and principal component analysis found that both electronic nose systems and the physicochemical measures (Brix, TA, pH, color intensity and hue, total phenols, glycosides, and berry weight) were able to discriminate between ethanol-treated and untreated grapes and wines for both cultivars. Grape physicochemical treatment differences were due mainly to variations in hue, phenolic-free glycosides, and total phenols. Aroma sensory evaluations using a consumer panel differentiated between ethanol treatments and controls for Merlot, but not for Cabernet franc wines.

Fruit thinning in ‘Conference’ pear grown under deficit irrigation: Implications for fruit quality at harvest and after cold storage

Fruit thinning in pear is feasible for mitigation of water stress effects. However, it is not well known how fruit quality at harvest and after cold storage is affected by pre-harvest water stress. Even less is known about the effects of fruit thinning on quality under these circumstances. To elucidate these, we applied deficit irrigation (DI) and fruit thinning treatments to ‘Conference’ pear over the growing seasons of 2008 and 2009. At the onset of Stage II (80 and 67 days before harvest in 2008 and 2009, respectively), two irrigation treatments were applied: full irrigation (FI) and DI. FI trees received 100% of crop evapotranspiration (ETc). DI trees received no irrigation during the first three weeks of Stage II to induce water stress, but then received 20% of ETc to ensure tree survival. From bud-break until the onset of Stage II and during post-harvest, FI and DI trees received 100% of ETc. Each irrigation treatment received two thinning levels: no thinning leaving commercial crop load (∼180 fruits tree −1), and hand-thinning at the onset of Stage II leaving a light crop load (∼85 fruits tree −1). Under commercial crop loads, DI trees were moderately water-stressed and this had some positive effects on fruit quality. DI increased fruit firmness (FF), soluble solids concentrations (SSC) and acidity at harvest while no changes were observed in fruit maturity (based on ethylene production). Differences in FF and acidity at harvest between FI and DI fruit were maintained during cold storage. DI also reduced fruit weight loss during storage. But fruit size was reduced under DI. Fruit thinning under DI resulted in better fruit composition with no detrimental effect on fresh-market yield compared to un-thinned fruit. Fruit size at harvest and SSC values after five months of cold storage were higher in fruit from thinned trees than fruit from un-thinned trees. Fruit thinning increased fruit ethylene production, indicating advanced maturity. This may lead to earlier harvest which is desirable in years with impending drought. Fruit thinning is therefore a useful technique to enhance pear marketability under water shortage.