Red Ripe Stage Research Articles

Magnitude of Genotype × Environment Interactions Affecting Tomato Fruit Quality

There is a growing interest by consumers to purchase fresh tomatoes with improved quality traits including lycopene, total soluble solids (TSS), vitamin C, and total titratable acid (TTA) content. As a result, there are considerable efforts by tomato breeders to improve tomato for these traits. However, suitable varieties developed for one location may not perform the same in different locations. This causes a problem for plant breeders because it is too labor-intensive to develop varieties for each specific location. The objective of this study was to determine the extent of genotype × environment (G×E) interaction that influences tomato fruit quality. To achieve this objective, we grew a set of 42 diverse tomato genotypes with different fruit shapes in replicated trials in three locations: North Carolina, New York, and Ohio. Fruits were harvested at the red ripe stage and analyzed for lycopene, TSS, vitamin C, and TTA. Analysis of variance (ANOVA) revealed that there were significant differences (P < 0.05) among tomato genotypes, locations, and their interaction. Further analysis of quality traits from individual locations revealed that there was as much as 211% change in performance of some genotypes in a certain location compared with the average performance of a genotype. Lycopene was found to be most influenced by the environment, whereas TTA was the least influenced. This was in agreement with heritability estimates observed in the study for these quality traits, because heritability estimate for lycopene was 16%, whereas that for TTA was 87%. The extent of G×E interaction found for the fruit quality traits in the tomato varieties included in this study may be useful in identifying optimal locations for future field trials by tomato breeders aiming to improve tomato fruit quality.

RELATIONSHIP BETWEEN PECTIN-METHYL ESTERASE ACTIVITY AND SOFTENING IN 'RAF' TOMATO FRUIT

'Raf' tomato has a higher organoleptic quality than many current cultivars, but it has very short shelf-life, is susceptible to chilling and mechanical injury during postharvest handling. Moreover, in this climacteric fruit ripening processes occur rapidly, particularly colour change. The softening of the fruit is due to the action of several enzymes, such as pectinmethyl esterase (PME) and polygalacturonase which play a joint role in this process. This paper studies the relationship between PME activity and softening of the fruits. Fruits harvested at the turning stage were stored at room temperature (24°C) for 4 days or 4°C for 28 days, until they reached the red-ripe stage. Colour, firmness and PME activity were determined. The data show that the fruits turned red in about 24 hours, as the tristimulus parameter (a) increased from -3 to +8. The firmness of the fruit declined progressively during the 4 days of storage, and PME activity also declined gradually, showing a high correlation between shelf life (time storage) and activity of PME enzyme. However, this correlation is not so marked between PME activity and fruit softening, suggesting that PME is not the only enzyme involved in this process.

Fruit‐specific overexpression of wound‐induced tap1 under E8 promoter in tomato confers resistance to fungal pathogens at ripening stage

Based on high economic importance and nutritious value of tomato fruits and as previous studies employed E8 promoter in fruit ripening-specific gene expression, we have developed transgenic tomato plants overexpressing tomato anionic peroxidase cDNA (tap1) under E8 promoter. Stable transgene integration was confirmed by polymerase chain reaction (PCR) and Southern analysis for nptII. Northern blotting confirmed elevated tap1 levels in the breaker- and red-ripe stages of T(1) transgenic fruits, whereas wild-type (WT) plants did not show tap1 expression in these developmental stages. Further, tap1 expression levels were significantly enhanced in response to wounding in breaker- and red-ripe stages of transgenic fruits, whereas wound-induced expression of tap1 was not detected in WT fruits. Confocal microscopy revealed high accumulation of phenolic compounds at the wound site in transgenic fruits suggesting a role of tap1 in wound-induced phenolic polymerization. Total peroxidase activity has increased remarkably in transgenic pericarp tissues in response to wounding, while very less or minimal levels were recorded in WT pericarp tissues. Transgenic fruits also displayed reduced post-harvest decay and increased resistance toward Alternaria alternata and Fusarium solani infection with noticeable inhibition in lesion formation. Conidiospore germination and mycelial growth of F. solani were severely inhibited when treated with E8-tap1 fruit extracts compared to WT fruits. 3-(4,5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide assay showed reduced spore viability when incubated in E8-tap1 fruit extracts. Thus, fruit-specific expression of tap1 using E8 promoter is associated with enhanced total peroxidase activity and high phenolic accumulation in fruits with minimized post-harvest deterioration caused by wounding and fungal attack in tomato fruits.

The Effects of Several Postharvest Treatments on Shelf Life Quality of Bunch Tomatoes

Bunch tomatoes (Lycopersicon lycopersicum L.) ‘Bandita’ cv. were hand-harvested at red ripe stage. The plants were grown on hanging carrying system with high wire support training in coco peat media in a plastic greenhouse located in Antalya (Turkey). Harvested fruits were divided to four groups for these treatments: (1) control-not treated; (2) tomato wax (Tomato wax is a wax formulated from 99% food grade mineral oil and 1% water); (3)Nutrient solution (1% potassium nitrate + 0.5% zinc sulfate + 1% calcium chloride + 0.1% boron + 0.2% copper sulfate + 0.5% ascorbic acid + 0.1% salicylic acid) and (4) Herbal oil (Herbal oil is a natural product obtained from hazelnut fruit membrane contains a high level of antioxidant). Bunches, placed in carton boxes, stored at 20°C temperature and 90±5% relative humidity for 16 days. Weight loss of bunches, firmness, respiration rate, ethylene production, colour, soluble solid content, pH, titratable acidity and sensory attributes (external appearance and taste-aroma of fruits and wilting and drying of calyxes) of tomatoes were evaluated during storage. Tomato wax treatment was limited the weight loss and preserved firmness better than the others. Tomato wax, nutrient solution and herbal oil treatments were limited the respiration rate. Ethylene production of nutrient solution treated fruits showed the highest value followed by herbal oil, tomato wax and control group. The highest colour change was found in control group. The lowest soluble solid content and the highest level of acidity were found in fruits treated with tomato wax. Control , herbal oil and nutrient solution treatments were lost marketable quality after 8 days of storage. TW treatment gave the best result and provided to store bunch tomatoes at good quality for 12 days.

Antioxidant Bioactive Compounds in Selected Industrial Processing and Fresh Consumption Tomato Cultivars

Four selected fresh consumption tomato varieties, harvested at different ripening stages (green, breaker, pink, red) and five industrial processing tomato varieties, harvested at red ripe stage, were analysed for lycopene and its isomers, β-carotene, total and individual phenolics, vitamin C and hydrophilic antioxidant activity. Tomato variety and ripening stage significantly affected carotenoids, total phenolic compounds and hydrophilic antioxidant activity when fresh consumption tomatoes were compared. The average of total lycopene content at the different ripening stages was 0.63, 12.20, 26.76 and 116.66 mg/kg of fresh weight (FW). Vitamin C ranged from 2.79 (breaker Cherry Pera) to 297.62 (red Cherry Pera) mg/kg FW. In green and breaker tomatoes, a positive correlation of hydrophilic antioxidant activity with vitamin C and chlorogenic acid was observed. However, in industrial tomato varieties (red ripe stage) and fresh consumption varieties harvested at pink and red stages, hydrophilic antioxidant activity was correlated with total phenolics and rutin. Tomato varieties for industrial processing did not show significant differences in total phenolic compounds and lycopene content. Lycopene ranged from 83.17 to 97.60 mg/kg FW, while total phenolic compounds varied between 257.91 and 284.13 mg/kg FW. Chlorogenic acid and rutin were the most abundant individual phenolics found in all the samples studied. Moreover, the content of total phenolics was always significantly correlated with the content of rutin. The amounts of all individual phenolics were affected by variety, with the exception of ferulic acid. Generally, these individual phenolics were more abundant in green and intermediate ripening stages, decreasing in full red tomatoes.

Transcriptional regulation of SlPYL, SlPP2C, and SlSnRK2 gene families encoding ABA signal core components during tomato fruit development and drought stress

In order to characterize the potential transcriptional regulation of core components of abscisic acid (ABA) signal transduction in tomato fruit development and drought stress, eight SlPYL (ABA receptor), seven SlPP2C (type 2C protein phosphatase), and eight SlSnRK2 (subfamily 2 of SNF1-related kinases) full-length cDNA sequences were isolated from the tomato nucleotide database of NCBI GenBank. All SlPYL, SlPP2C, and SlSnRK2 genes obtained are homologous to Arabidopsis AtPYL, AtPP2C, and AtSnRK2 genes, respectively. Based on phylogenetic analysis, SlPYLs and SlSnRK2s were clustered into three subfamilies/subclasses, and all SlPP2Cs belonged to PP2C group A. Within the SlPYL gene family, SlPYL1, SlPYL2, SlPYL3, and SlPYL6 were the major genes involved in the regulation of fruit development. Among them, SlPYL1 and SlPYL2 were expressed at high levels throughout the process of fruit development and ripening; SlPYL3 was strongly expressed at the immature green (IM) and mature green (MG) stages, while SlPYL6 was expressed strongly at the IM and red ripe (RR) stages. Within the SlPP2C gene family, the expression of SlPP2C, SlPP2C3, and SlPP2C4 increased after the MG stage; SlPP2C1 and SlPP2C5 peaked at the B3 stage, while SlPP2C2 and SlPP2C6 changed little during fruit development. Within the SlSnRK2 gene family, the expression of SlSnRK2.2, SlSnRK2.3, SlSnRK2.4, and SlSnRK2C was higher than that of other members during fruit development. Additionally, most SlPYL genes were down-regulated, while most SlPP2C and SlSnRK2 genes were up-regulated by dehydration in tomato leaf.

Spatial–temporal analyses of lycopene and sugar contents in tomatoes during ripening using chemical shift imaging

During the ripening process, fruit and vegetables undergo physico-chemical changes which affect their color, texture, aroma, and sugar content, etc. For tomatoes, color change is the main index of ripening stages, and it is associated with metabolized lycopene. In order to detect the internal changes of sugar and lycopene contents in tomatoes during ripening, chemical shift imaging (CSI) and high performance liquid chromatography (HPLC) analyses were employed. Imaging experiments on tomatoes were performed in a Bruker 7T MRI system using the gradient-echo sequence for scanning. Spatial distribution of the internal sugar and lycopene contents of tomatoes were, for the first time, revealed and compared before and after the ripening process. The CSI analysis showed that a linear relationship existed between CSI intensity and concentrations of sugar solutions in the range of 0.1–1.0 M. The CSI results indicate that there was no consistent trend in the variation of sugar signal intensity during ripening while the lycopene content significantly increased in the outer pericarp and columella of the tomatoes at the red ripe stage, as compared to the mature green stage. This observation for the sugar and lycopene signal intensities was further confirmed by HPLC analyses. The non-destructive CSI technique has potential as an efficient tool for the physiological analysis of fruit and vegetables.

Bioactive compounds and antioxidant activities during fruit ripening of watermelon cultivars

Changes in bioactive compounds and antioxidant activities of three commercial selections (Crimson sweet, Dumara and Giza) and two new selections (P503 and P403) of watermelon cultivars were investigated at four different fruit ripening stages (white, white-pink, pink and red-ripe). Lipophilic and hydrophilic antioxidant activities (LAA and HAA, respectively) were determined, and their correlations with total vitamin C, phenol, flavonoid, lycopene and β-carotene contents were studied. Ripening stage significantly influenced lycopene and β-carotene contents, as well as the LAA of all investigated watermelon cultivars. Good correlations between LAA and lycopene and β-carotene contents were found using the TEAC assay. At the red-ripe stage of ripeness, P503 cultivar showed the highest amount of lycopene (64.5mgkg−1 fw), whereas Dumara cultivar showed the highest level of β-carotene (2.1mgkg−1 fw). Giza cultivar scored first for total phenol (260.1mgGAEkg−1 fw), flavonoid (260.0mgREkg−1 fw) and total vitamin C (204.0mgkg−1 fw) contents. Although, the HAA of the studied watermelon cultivars was significantly influenced by the ripening stages, it only correlated to the amount of total phenols and flavonoids. These data confirm the important role played by genetic background and ripening stage in determining antioxidant potential of watermelon fruits. They also give valuable insights into the synthesis and accumulation of bioactive compounds in such fruits, and furthermore move us closer to identifying the harvesting period with the highest antioxidant potential.

Utilization of correlation network analysis to identify differences in sensory attributes and organoleptic compositions of tomato cultivars grown under salt stress

In tomato production, salt stress is applied to improve the fruit quality. The change in sensory attributes and organoleptic compositions in salt-stressed tomato fruits have been extensively studied; however, little is known about their interaction with each other. Correlation network analysis provides a visual representation of biological systems and useful knowledge for metabolic data analysis of tomato fruits. The aim of this study is to identify the cultivar differences in sensory attributes and organoleptic compositions of tomato fruits grown under salt stress and to elucidate their interaction among different cultivars using correlation network analysis. Salt stress was applied by adding 100 mM NaCl to the nutrient solution. Fruits were harvested at red-ripe stage and used for the evaluation of sensory attributes such as sweetness, sourness, umami, and tomato like, and organoleptic compositions such as sugar, organic acid, amino acid, and sodium ion contents. Almost all of the sensory attributes and organoleptic compositions of the fruit were significantly high in salt-stressed cultivars compared to non-stressed cultivars, and significant differences were also observed among cultivars. The correlation network analysis of the control fruit showed that compared to other traits, sugar is one of the key traits for improvement of tomato fruit quality based on high connectivity and betweenness centrality. In contrast, a high degree of positive connectivity was not observed between organoleptic compositions and sensory attributes in the salt-stressed fruit network. These results indicate that the relationship between sensory attributes and organoleptic compositions in fruits were different between the control and salt-stressed cultivars, suggesting that the salt-stressed fruit may have a different circuit of relationship compared to control. Furthermore, based on the increase ratio (salt stress/control) network results, we suggest that the increased sugar, organic acid, and amino acid contents may have contributed to the salt stress-induced enhancement of sensory attributes.

Chilling and heating may regulate C6 volatile aroma production by different mechanisms in tomato (Solanum lycopersicum) fruit

Hexanal, Z-3-hexenal, E-2-hexenal, hexanol, and Z-3-hexenol are major tomato (Solanum lycopersicum L.) volatile aroma compounds derived from oxygenation of unsaturated fatty acids. Chilling and heating may suppress production of these C6 volatiles. The objective of this research was to determine the effects of chilling or heating on gene expression and enzyme activity of lipoxygenase (LOX), hydroperoxide lyase (HPL), and alcohol dehydrogenase (ADH), which catalyze key steps in C6 volatile production via the oxylipin pathway. ‘Tasti-Lee’ and ‘Sanibel’ tomatoes, harvested at different stages of fruit development, were ripened to full (red) ripe stage at 20°C. Fruit were then treated by either chilling (5°C for 5d) or heating (52°C hot water for 15min), then cooled with 23°C tap water to 25°C and placed at 20°C for 4d, or held continuously at 20°C as the control. Both chilling and heating reduced C6 aldehyde and alcohol aroma volatiles immediately after treatment, and the levels of aldehydes did not fully recover after 4d at 20°C. Chilling down-regulated expression of TomloxA, B, and C, but not D; however, it increased total LOX activity. Chilling also down-regulated HPL and ADH expression immediately after treatment, but, after 4d at 20°C, both genes were up-regulated compared to the control. HPL activity in chilled tomatoes was reduced, but recovered to control levels after 4d at 20°C. ADH activity in chilled fruit decreased after 4d at 20°C. On the other hand, heating greatly up-regulated TomloxB and C expression, even after 4d at 20°C, and slightly down-regulated TomloxA and D, while increasing overall LOX activity. Heating up-regulated both HPL and ADH, and that effect persisted for 4d at 20°C. However, heating reduced the activities of HPL for 4d at 20°C and ADH immediately after treatment. The results indicate that heating and chilling regulate C6 volatile production by different mechanisms. Chilling-induced inhibition of C6 volatile production may be due to down-regulation of gene expression, and subsequent reduction of HPL and ADH enzyme activities in the oxylipin pathway. Heating-inhibition of C6 volatile production, however, does not appear to be due to down-regulation of gene expression, but HPL and ADH activities were briefly suppressed.

Dynamic QTL and correlated characters of tomato soluble solid content

Two hundred and six F2:3 families from the cross between TD22 and HT-1-1-1-1 were used for dynamic QTL research of tomato soluble solid content and correlative traits, and correlation analysis of soluble solid content (SSC) with fruit weight (FW), fruit shape index (FSI), soluble sugar, vitamin C (VC), and organic acid at three different development stages. The results showed that there were differences in QTL loci for soluble solid content during the three stages of tomato fruit development. Four and eight QTLs were detected in green ripe stage and red ripe stage, respectively. These QTLs showed dynamic changes, and two markers LEaat006 and Tomato|TC162363 were detected in two stages, which might be useful in molecular-marker assisted selection (MAS). The result also showed that there was extremely significant difference in SSC at the three different stages, and its main correlative traits were different at different stages. Soluble solid content was positively correlated with soluble sugar, but negatively correlated with FW at green ripe stage; SSC was positively correlated with soluble sugar and organic acid at yellow ripe stage; SSC was positively correlated with soluble sugar and organic acid, but negatively correlated with fruit weight at red ripe stage. Based on correlation analysis of these traits, linear regression model was constructed. Non-tested varieties were used to test the fitness, and the result showed that it is well fitted, and the fitness is above 95%.

Antioxidant activity and bioactive compound changes during fruit ripening of high-lycopene tomato cultivars

Changes in bioactive compounds and antioxidant activities of an ordinary (Rio Grande) and three high-lycopene (HLY 13, HLY 18 and Lyco 2) tomato cultivars (cvs) were studied at four different fruit ripening stages (green, green-orange, orange-red and red-ripe). Lipophilic and hydrophilic antioxidant activities (LAA and HAA, respectively) were determined and their correlations with ascorbic acid (AsA), dehydroascorbic acid (DHA), total vitamin C (AsA+DHA), phenolics, flavonoids, total carotenoid and lycopene contents were investigated. The stage of ripening significantly influenced the total carotenoid and lycopene contents, as well as the LAA of all investigated tomato cvs. Good correlations between LAA and both total carotenoid and lycopene contents were found using either the TEAC assay or the FRAP assay. During ripening, cvs HLY 13 and HLY 18 exhibited more than 100% higher total carotenoid and lycopene contents compared to Rio Grande. At the red-ripe stage, cv HLY 18 accumulated the highest phenolic and flavonoid contents. However, Lyco 2 showed the highest levels of DHA and total vitamin C. Although, the HAA of studied tomato cvs were also significantly influenced by the ripening stages, HAA resulted correlated only to the levels of phenolics and flavonoids when the TEAC assay was used. However, using the FRAP assay, the HAA were well correlated to the total vitamin C and DHA contents.

Chemical manipulation of tomato growth and associated biochemical implications on flavonoid, lycopene and mineral contents

The consumption of tomato (Solanum lycopersicon) has been linked with reduced risk of chronic degenerative diseases. Therefore, this study was carried out to investigate the biochemical implications of bioregulator application on flavonoids, lycopene, calcium, magnesium, potassium, sodium, phosphorus and iron contents of tomato. Seeds of the tomato, genotype JM 94/47 were subjected to pre –germination treatment by soaking in 60, 100 and 140mg/L of indole-acetic acid (IAA), indole butyric acid (IBA) and naphthalene acetic acid (NAA) and planted. The ripe tomato fruits were harvested at the orange red ripe stage and some biochemical parameters were investigated. The analysis results showed that flavonoid and lycopene content were significantly (p < 0.05) increased in tomato plants treated with IAA, IBA and NAA compared to control. The flavonoid content ranged from 0.081 to 0.169 mg/100 g while the 100 mg/L NAA resulted in the highest lycopene concentration of 1.16 µg/100 gfwb and assayed minerals were also increased in tomatoes treated with all bioregulators. These results indicate that pre – sowing seed treatment with 1AA, IBA and NAA have profound effect on improving the quality of tomato, especially the phytonutrients examined. Key words: Bioregulators, flavonoids, lycopene, minerals, Solanum lycopersicon.

Influence of Auxin Bioregulators on Physiological Changes and Shelf-Life of Tomatoes

Influence of Auxin Bioregulators on Physiological Changes and Shelf-Life of Tomatoes Tomato (Solanum lycopersicon) is one of the most popular and extensively consumed vegetable crops worldwide. Their highly perishable nature poses great limitation to their marketability over long distances. We have earlier demonstrated that the 100 mg·L-1 concentration of the bioregulators Indoleacetic acid (IAA), indole butyric acid (IBA) and naphthalene acetic acid (NAA) is suitable for tomato growth under field conditions. We have also reported the effects of these bioregulators on tomato fruit yield and postharvest quality. In this study, the shelf - life and associated physiological changes of fruits of five bioregulator - treated tomato genotypes in practical conditions of storage time and temperature were investigated. Seeds of the tomato genotypes namely NHLy 11, NHLy 12, NHLy 13, NHLy 15 and NHLy 16 were subjected to treatments with 100 mg·L-1 concentrations of the bioregulators IAA, IBA, NAA and distilled water (control) before planting. The fruits were harvested at the orange - red ripe stage. Sensory and visual fruit changes were determined and deterioration level measured during storage trials for up to ten days in order to evaluate their quality. The results revealed that the bioregulator - treated tomato genotypes generally exhibited better storage features than those of controls, with the NAA - treated NHLy 12 genotype having the highest storability index of 6.00 after ten days of storage. The present findings show that treating tomatoes with bioregulators, especially the ones used in this work improves their storage at ambient conditions.

Expression and location of endo-β-mannanase during the ripening of tomato fruit, and the relationship between its activity and softening

Endo-beta-mannanase is thought to play a role in tomato fruit ripening by participating in the degradation of cell walls. Its spatial and temporal expression during ripening was examined, as was the relationship between its activity and softening of the fruit using a large number of tomato lines, and by suppression of transcription of the endo-beta-mannanase (LeMan4a) gene. Immunolocalization studies showed that the enzyme is expressed in the fruit cell wall at all ripening stages, but it is not active during the initial green stage; this is not due to the presence of inhibitors of its activity, nor due to changes in its mRNA sequence. Transient expression in onion epidermal cells of endo-beta-mannanase transcripts fused to green fluorescent protein resulted in the expressed enzyme being localized to the cell walls. Transgenic tomato plants expressing a GUS gene attached to the LeMan4a promoter showed that this occurs initially during ripening in the skin and outer pericarp of the fruit, and later in the skin and throughout the pericarp. Fruit firmness and activity of endo-beta-mannanase were not strongly correlated during ripening of many lines of tomato. Several plants of cv. Micro-Tom were transformed using RNA interference (mRNAi) and antisense RNA strategies to suppress transcription of the LeMan4a gene. When endo-beta-mannanase activity was much reduced in the transgenic fruits, their firmness was higher compared to those of control fruits at the turning and orange-color stages, but at the red-ripe stage firmness was similar between the two fruit types. We suggest that while the enzyme does participate in fruit ripening it alone is not sufficient to cause hydrolysis of the cell walls which results in their weakening; it likely plays a cooperative role with other known wall-modifying enzymes, and/or is involved in cell wall rearrangement.

C22 Isomerization in α-Tomatine-to-Esculeoside A Conversion during Tomato Ripening Is Driven by C27 Hydroxylation of Triterpenoidal Skeleton

Compositional analysis by liquid chromatography/mass spectrometry of triterpenoid glycosides in different tomato cultivars, ripening stages, and parts of fruits showed that alpha-tomatine was generally most abundant in the flesh of the mature green stage, whereas esculeoside A was predominant in that of the red ripe stage. The sum of these glycoalkaloids was more or less constant, suggesting that alpha-tomatine is converted to esculeoside A during ripening. Besides various substitutions, the C22alphaN --> C22betaN isomerization is an important step in this transformation. By quantum chemical calculations it was shown that hydroxylation at C27 of the triterpenoidal skeleton is the driving force behind the isomerization. For the protonated form of the glycoalkaloid (predominant at the pH of tomato tissue), the C22betaN configuration becomes more favorable than that of C22alphaN, through the extra energy provided by the hydrogen bond between the protonated nitrogen and the lone pair of the oxygen of the C27-OH.

Biomechanics of isolated tomato (Solanum lycopersicum) fruit cuticles during ripening: the role of flavonoids.

Flavonoids accumulate in tomato (Solanum lycopersicum L.) fruit cuticles during ripening. Their quantitative contribution to the biomechanical properties of the cuticle is studied in six tomato genotypes which show presence or absence of these compounds at the red ripe stage of fruit development. Tomato cuticles with flavonoids at red ripe showed a dramatic increase of these compounds between mature green and red ripe stages together with a significant increase in the elastic modulus. On the other hand, cuticles without flavonoids displayed a similar biomechanical behaviour at mature green and red ripe stages. The absence of flavonoids could also be related with a predominance of the viscoelastic performance of the cuticle. Thus, the increase of phenolics in tomato fruit cuticles during ripening is correlated with a more rigid cutin network that reinforces the mechanical function of polysaccharides which tend to diminish at this stage due to cell wall disassembly. A role of phenolics as biomechanical modulators of the cuticle behaviour is proposed.

Antioxidizing Enzyme Activities in Chilling-sensitive and Chilling-tolerant Pepper Fruit as Affected by Stage of Ripeness and Storage Temperature

To study ripening-related chilling injury in pepper (Capsicum annuum L.), chilling-tolerant ‘Buchon’ and chilling-sensitive ‘Nockgwang’ fruit were harvested at mature green (MG), breaker (BR), and red-ripe (RR) stages and stored at 1, 5, and 10 °C for 21 d. ‘Buchon’ did not show surface pitting (SP) regardless of ripeness stage and storage temperature, whereas ‘Nockgwang’ at MG and BR exhibited SP at 1 and 5 °C. After 14 days of storage at 1 °C, chilling-sensitive ‘Nockgwang’ did not show SP when fruit were at the RR stage. Compared with ‘Buchon’, ‘Nockgwang’ at MG and BR had more electrolyte leakage increase during storage at 1 and 5 °C. ‘Buchon’ at all ripeness stages showed significantly higher ethylene production during storage regardless of storage temperatures. Contents of β-carotene and lycopene increased in both cultivars as ripening progressed. The contents of β-carotene and lycopene were similar between the two cultivars regardless of storage temperatures and ripeness stages. Susceptibility of pepper fruit to chilling appeared to be related to superoxide dismutase (SOD) and catalase (CAT). Activities of SOD and CAT were much higher in ‘Buchon’ than ‘Nockgwang’, more apparently at MG and BR. The results suggest that chilling-tolerant ‘Buchon’ and fruit at RR could have been equipped with a more efficient antioxidizing system, even if it was not clear whether oxidative stress is a cause or an effect of the CI in pepper.

Xyloglucan endotransglucosylase/hydrolases (XTHs) during tomato fruit growth and ripening

Depolymerization of cell wall xyloglucan has been proposed to be involved in tomato fruit softening, along with the xyloglucan modifying enzymes. Xyloglucan endotransglucosylase/hydrolases (XTHs: EC 2.4.1.207 and/or EC 3.2.1.151) have been proposed to have a dual role integrating newly secreted xyloglucan chains into an existing wall-bound xyloglucan, or restructuring the existing cell wall material by catalyzing transglucosylation between previously wall-bound xyloglucan molecules. Here, 10 tomato (Solanum lycopersicum) SlXTHs were studied and grouped into three phylogenetic groups to determine which members of each family were expressed during fruit growth and fruit ripening, and the ways in which the expression of different SlXTHs contributed to the total XET and XEH activities. Our results showed that all of the SlXTHs studied were expressed during fruit growth and ripening, and that the expression of all the SlXTHs in Group 1 was clearly related to fruit growth, as were SlXTH12 in Group 2 and SlXTH6 in Group 3-B. Only the expression of SlXTH5 and SlXTH8 from Group 3-A was clearly associated with fruit ripening, although all 10 of the different SlXTHs were expressed at the red ripe stage. Both total XET and XEH activities were higher during fruit growth, and decreased during fruit ripening. Ethylene production during tomato fruit growth was low and experienced a significant increase during fruit ripening, which was not correlated either with SlXTH expression or with XET and XEH activities. We suggest that the role of XTH during fruit development could be related to the maintenance of the structural integrity of the cell wall, and the decrease in XTHs expression, and the subsequent decrease in activity during ripening may contribute to fruit softening, with this process being regulated through different XTH genes.

Protein profiling in F&lt;sub&gt;1&lt;/sub&gt; and F&lt;sub&gt;2&lt;/sub&gt; generations of two tomato genotypes differing in ripening time

Pericarp polypeptide profiles were analyzed at three ripening stages in the F1 hybrid and the F2 population from the cross between the accessions: LA1385 (Lycopersicon esculentum var. cerasiforme) and 804627 (L. esculentum, a homozygous genotype for the nor mutant). Six polymorphic polypeptides were observed in LA1385, while no polymorphic polypeptides among ripening stages was observed in 804627. On the other hand, some polypeptides in the F1 hybrid were not observed in the parents whereas others were present in both parental genotypes and were unnoticeable in the hybrid genotype. From a cluster analysis on the protein profiles of the F2 population, the differential expression of proteins allowed to distinguish mature green (MG) stage from the others two stages, while for breaker stage (BR) and red ripe stage, the genetic background was more important in forming groups. The differential expression of proteins could be associated with fruit morphology traits such as a 72 kDa polypeptide present in MG stage with fruit diameter, height and mass and a 47 kDa polypeptide found in BR with fruit shelf life.