Detached Tomato Fruit Research Articles

Calendula officinalis-A Great Source of Plant Growth Promoting Endophytic Bacteria (PGPEB) and Biological Control Agents (BCA).

The application of beneficial bacteria may present an alternative approach to chemical plant protection and fertilization products as they enhance growth and resistance to biotic and abiotic stresses. Plant growth-promoting bacteria are found in the rhizosphere, epiphytically or endophytically (Plant Growth Promoting Endophytic Bacteria, PGPEB). In the present study, 36 out of 119 isolated endophytic bacterial strains from roots, leaves and flowers of the pharmaceutical plant Calendula officinalis were further identified and classified into Bacillus, Pseudomonas, Pantoea, Stenotrophomonas and Rhizobium genera. Selected endophytes were evaluated depending on positive reaction to different plant growth promoting (PGP) traits, motility, survival rate and inhibition of phytopathogenic fungi in vitro and ex vivo (tomato fruit). Bacteria were further assessed for their plant growth effect on Arabidopsis thaliana seedlings and on seed bio-primed tomato plantlets, in vitro. Our results indicated that many bacterial endophytes increased seed germination, promoted plant growth and changed root structure by increasing lateral root density and length and root hair formation. The most promising antagonistic PGPEB strains (Cal.r.29, Cal.l.30, Cal.f.4, Cal.l.11, Cal.f.2.1, Cal.r.19 and Cal.r.11) are indicated as effective biological control agents (BCA) against Botrytis cinerea on detached tomato fruits. Results underlie the utility of beneficial endophytic bacteria for sustainable and efficient crop production and disease control.

New disease caused by Neoscytalidium dimidiatum devastates tomatoes (Solanum lycopersicum) in Turkey

A novel disease of tomato (Solanum lycopersicum L.) was observed in the Southeast Anatolia Region of Turkey. Symptoms were blight of all aerial parts of the plant, including stems, branches, leaves, petioles, flowers and fruits, defoliation, root rot, inner stem necrosis, and plant death. The disease was found in 13.9% of surveyed fields, with an incidence varying from 3% to nearly 75% (average 21.2%) of the plants in symptomatic fields. The average severity of blight on stem in fields with the symptomatic plant surveyed was 1.4%. A Botryosphaeriaceae species, identified as Neoscytalidium dimidiatum (Penz.) Crous & Slippers using morphological and cultural features, was consistently isolated from symptomatic roots, inner stems, and blighted leaves, shoots, stems, fruits and flowers. The partial nucleotide sequence data for three gene loci, including nuclear rDNA internal transcribed spacer (ITS), large subunit (LSU) genes and the translation elongation factor 1-alpha (TEF-1α), confirmed the morphological identification. Furthermore, sequence data of actin genes from N. dimidiatum was, for the first time, deposited to the GenBank. Koch's postulates were fulfilled by testing the susceptibility of different tomato tissues (leaves, stems, inner stems and roots of tomato seedlings, and detached tomato fruits and flowers) to N. dimidiatum inoculation. To our knowledge, this is the first report of N. dimidiatum on tomato.

Light regulation of vitamin C in tomato fruit is mediated through photosynthesis

Higher levels of irradiance result in higher accumulation of ascorbate in leaves and fruits. Photosynthesis and respiration are an integral part of the physiological mechanism of light regulation of ascorbate in leaves, but little is known about the light regulation of ascorbate in fruit. The aim of this study was to investigate whether fruit illumination alone is sufficient for ascorbate increase in tomato fruit and whether this light signal is mediated by respiration and photosynthesis. First the changes of ascorbate with the progress of fruit development were investigated and subsequently detached fruit of different tomato genotypes were exposed to different irradiances and spectra. Measurements were performed on ascorbate, respiration, photosynthesis and chlorophyll content of the fruit. When attached to the plant, there was no effect of development on ascorbate from the mature green to the red stage. Detached fruit stored in darkness did not accumulate ascorbate. However, when exposed to 300–600 μmol m−2 s-1 light detached mature green fruit (photosynthetically active) substantially accumulated ascorbate, while mature red fruit (non-photosynthetically active) did not respond to light. Photosynthesis correlated with this increase of ascorbate while no correlation between respiration and ascorbate was found. Spectral effects on ascorbate in detached tomato fruit were limited. These results indicate that the signal for light regulation of ascorbate is perceived locally in the fruit and that fruit illumination alone is sufficient for a considerable increase in ascorbate levels for as long as the fruit contains chlorophyll. It is shown that photosynthetic activity of the fruit is an integral part of the response of ascorbate to light in tomato fruit. The light induced increase in ascorbate levels occurred in a range of genotypes, indicating a universal effect of light to ascorbate in tomato fruit.

Effect of exogenous auxin on aroma volatiles of cherry tomato (Solanum lycopersicum L.) fruit during postharvest ripening

The phytohormone auxin has been proved to be involved in the regulation of quality traits in climacteric fruit ripening, but there was little information about the correlation between auxin and aroma volatiles in fruit. In the present study, the effect of auxin on aroma volatiles in tomato fruit during postharvest ripening was studied by treating detached tomato fruit at mature green stage with 2, 4-dichlorophenoxyacetic acid. The results showed that exogenous auxin delayed the ripening process of tomato fruit via inhibiting the ethylene production and the carotenoids accumulation, as well as the degradation of chlorophyll. In addition, exogenous auxin enhanced the accumulation of phenolic volatiles such as phenylacetaldehyde (1.57-fold), 2-phenylethanol (1.56-fold) and methyl benzoate (1.75-fold), and inhibited the production of 1-hexanol (56.59 %), 1-nitro-2-phenylethane (23.74 %), benzyl cyanide (45.69 %) and 2-isobutylthiazole (35.18 %). Exogenous auxin altered the expression of a number of key genes involved in the biosynthetic pathway of aroma volatiles, including induction of SlSAMT1, LePAR1and LePAR2, and inhibition of TomloxC, HPL, ADH2, LeCCD1s, LePAR1, LePAR2, LeAADCs, SlBCAT1. The log2 fold change of these genes ranged between -4.53 and 3.02 compared to that in the control group. Moreover, correlation analysis revealed that changes of apocarotenoids and amino acid-derived volatiles were positively correlated with the expressions of related genes in response to auxin. The present study provided valuable information for further elucidating the regulation of tomato fruit aroma as well as quality traits during ripening.

Characterization of Botrytis cinerea Isolates from Strawberry with Reduced Sensitivity to Polyoxin D Zinc Salt.

Polyoxin D is a Fungicide Resistance Action Committee (FRAC) code 19 fungicide that was recently registered for gray mold control of strawberry in the United States. In this study, we determined the sensitivity to polyoxin D zinc salt (hereafter, polyoxin D) of Botrytis cinerea isolates from 41 commercial strawberry farms in South Carolina, North Carolina, Maryland, Virginia, and Ohio and investigated the fitness of sensitive (S) and reduced sensitive (RS) isolates. Relative mycelial growth ranged between 0 and over 100% on malt extract agar amended with a discriminatory dose of polyoxin D at 5 μg/ml. Isolates that grew more than 70% at that dose were designated RS and were found in three of the five states. The 50% effective dose (EC50) values of three S and three RS isolates ranged from 0.59 to 2.27 and 4.6 to 5.8 μg/ml, respectively. The three RS isolates grew faster on detached tomato fruit treated with Ph-D WDG at recommended label dosage than S isolates (P < 0.008). In all, 25 randomly selected RS isolates exhibited reduced sporulation ability (P < 0.0001) and growth rate (P < 0.0001) but increased production of sclerotia (P < 0.0386) compared with 25 S isolates. Of 10 isolates tested per phenotype, the number of RS isolates producing sporulating lesions on apple, tomato, and strawberry was significantly lower compared with S isolates (P < 0.0001 for each fruit type). The results of this study indicate that resistance management is necessary for fungicides containing polyoxin D. To our knowledge, this is the first study demonstrating reduced sensitivity to FRAC 19 fungicides in B. cinerea isolates from the United States.

Illuminating tomato fruit enhances fruit vitamin C content

L-ascorbate (AsA; Vitamin C) is an anti-and pro-oxidant phytochemical essential for the proper functioning of the human body. Field grown tomato fruit (Solanum lycopersicum) contain substantial amounts of AsA. When grown in the greenhouse, tomato fruit typically have low levels of AsA. Light is the major regulatory abiotic factor for AsA in plants. The introduction of light emitting diodes (LED) in horticulture provides the opportunity for improving quality of plant products. AsA levels of tomato fruit increase with additional light applied to the plant. In this work we examine the effects of irradiance on AsA levels of tomato fruit when light is applied to the fruit. Detached tomato fruit were treated with different irradiance levels provided by LEDs in a climate controlled environment. Tomato fruit treated with 263 μmol m-2 s-1 of white light for 13 days contained 32% more AsA than fruit kept at lower irradiances or in darkness. The light induced biosynthesis of AsA and the role of soluble carbohydrates in AsA regulation is discussed.

Inhibitory effect of Xenorhabdus nematophila TB on plant pathogens Phytophthora capsici and Botrytis cinerea in vitro and in planta.

Entomopathogenic bacteria Xenorhabdus spp. produce secondary metabolites with potential antimicrobial activity for use in agricultural productions. This study evaluated the inhibitory effect of X. nematophila TB culture on plant pathogens Botrytis cinerea and Phytophthora capsici. The cell-free filtrate of TB culture showed strong inhibitory effects (>90%) on mycelial growth of both pathogens. The methanol-extracted bioactive compounds (methanol extract) of TB culture also had strong inhibitory effects on mycelial growth and spore germinations of both pathogens. The methanol extract (1000 μg/mL) and cell-free filtrate both showed strong therapeutic and protective effects (>70%) on grey mold both in detached tomato fruits and plants, and leaf scorch in pepper plants. This study demonstrates X. nematophila TB produces antimicrobial metabolites of strong activity on plant pathogens, with great potential for controlling tomato grey mold and pepper leaf scorch and being used in integrated disease control to reduce chemical application.

High external sucrose concentration inhibits the expansion of detached tomato fruits grown in a novel semi-open device

The effect of sap sucrose concentration on fruit expansion is poorly understood. We investigated the effects of sucrose concentration on growth of tomato fruits, detached from the plant after the cell multiplication phase. A semi-open device was built to grow detached fruits, where the fruit pedicel was immersed in a nutrient solution which was automatically replaced each day. About 22 d after anthesis, tomato fruits were harvested, disinfected in alcohol, and placed in the device with a sterile nutrient solution containing 5% sucrose. After about 1 wk, the sucrose concentration was either increased to 15% or maintained at 5%. The fruit expansion rate decreased when the sucrose concentration was increased, and after about 1 wk, these fruits weighed less than those grown at 5% sucrose. Although all the fruits in the device grew much less than those maintained on the plant, a high sap sucrose concentration applied to the excised fruits after the cell multiplication phase inhibited the expansion of tomato fruits. The device and method developed here will be useful for future studies of fruit growth.

Virus-induced gene silencing in detached tomatoes and biochemical effects of phytoene desaturase gene silencing

Virus-induced gene silencing (VIGS) is a technology that has rapidly emerged for gene function studies in plants. Many advances have been made in applying this technique in an increasing number of crops. Recently, VIGS has been successfully used to silence genes in tomato fruit through agroinfiltration of fruit attached to the plant. The phytoene desaturase ( Pds) gene has been widely used as a reporter gene in VIGS experiments, although little is known about the changes that occur due to its silencing in plants. In this paper, we describe the efficient silencing of the Pds gene through the VIGS approach in detached tomato fruits, which makes the VIGS procedure even more versatile and applicable. After 16 days of agroinfiltration, approximately 75% of the tomatoes showed Pds silencing symptoms, although the distribution of silenced areas was variable among fruits. To study the potential effects caused by Pds silencing in detached tomatoes, carotenoids and other semi-polar secondary metabolites were analyzed using Liquid Chromatography–Mass Spectrometry. In addition, potential differences in primary metabolites were analyzed using Gas Chromatography–Mass Spectrometry. The results indicated that the yellow phenotype observed in Pds-silenced fruit was mainly due to the lack of the red-colored lycopene and therefore to a more pronounced contribution of the yellow-orange carotenoids (lutein, violaxanthin, and zeaxanthin) to the final color of the fruits. Furthermore, the biochemical changes observed in Pds-silenced detached tomatoes suggested that carotenoid and other pathways, e.g. leading to alkaloids and flavonoids, might be affected by the silencing of this reporter gene, and this should be taken into consideration for future experimental designs.

Analysis of gene functions by a syringe infiltration method of VIGS

Virus-induced gene silencing (VIGS) is a powerful tool for characterization of functional genes in tomato. In this study, we improved the syringe infiltration method on detached tomato fruits. With PDS (phytoene desaturase gene) used as a reporter gene, harvested mature green tomato fruits were syringe-infiltrated with agrobacterium strain GV3101 containing pTRV1 and pTRV2-LePDS, which resulted in color changing on the fruit surface. The changes in pigments and transcript abundance of PDS were compared between silencing sectors and control. In addition, factors of environmental conditions, such as temperature and humidity, were optimized for gene silencing, and other factors, including volume of agrobacterial culture, were also analyzed. Furthermore, this silencing method was confirmed by silencing LeRIN and LeACS2, which influenced fruit ripening process as positively regulating genes, and LeCTR1, which took part in ethylene signal transduction as a negatively regulating gene. Transcripts of LeRIN, LeCTR1, and LeACS2 were measured in the following analysis of gene silencing. All results indicated that an infiltration-based method is efficient for gene characterization during development and ripening of tomato fruits.

Color Changes and Antioxidant Content of Vine and Postharvest-ripened Tomato Fruits

Tomato fruit ripening is a complex, genetically programmed process that culminates in dramatic changes in texture, color, flavor, and aroma of the fruit flesh. The characteristic pigmentation of red ripe tomato fruit is the result of the de novo synthesis of carotenoids, mainly lycopene and β-carotene, which are associated with the change in fruit color from green to red as chloroplasts are transformed to chromoplasts. The aim of this study was to examine the effect of ripening conditions on color development and antioxidant content. Detached tomato fruit stored at 15 and 30 °C and vine-ripened fruits were studied to characterize the ripening process by Hue (°) index (CIELab color system), which is strongly influenced by the circumstances of ripening. Total polyphenols, ascorbic acid, and lycopene content of tomato fruits were analyzed at the end of the experiment. Changes in the color of fruit stored at 15 °C and vine-ripened fruit showed significantly higher a* compared with fruit stored at 30 °C. Storage temperature influenced positively ascorbic acid and negatively lycopene content, whereas total polyphenols did not show differences among the different ripening conditions.

CHANGES IN COLOUR AND ANTIOXIDANTS DURING VINE AND POSTHARVEST RIPENING OF TOMATO FRUIT

Tomato fruit ripening is a complex, genetically programmed process that culminates in dramatic changes in texture, colour, flavour, and aroma of the fruit flesh. The characteristic pigmentation of red ripe tomato fruit is due to the deposition of lycopene, the predominant carotenoid found in tomatoes, and of β-carotene, which are both associated with the change from green to red as chloroplasts are transformed to chromoplasts. Detached tomato fruit stored at 15°C and 30°C, and vine ripened fruit were studied to characterise ripening by Hue (°) index of the CIELab colour system, which is strongly influenced by ripening. Colour changes of fruit stored at 15°C and vine ripened fruit showed significant differences compared to fruit stored at 30°C. Polyphenols, vitamin C and lycopene content of tomatoes were analysed at the end of the experiment. Storage temperature influences vitamin C and lycopene content, while polyphenols did not show significant differences among the different storage conditions.

Morphological and molecular identification of Colletotrichum acutatum from tomato fruit

Colletotrichum gloeosporioides, Colletotrichum acutatum, Colletotrichum coccodes, and Colletotrichum dematium are the four main species of Colletotrichum that cause tomato anthracnose. In Serbia, the occurrence of anthracnose on tomato fruit has been recorded during the last several years. Typical fruit symptoms include dark, sunken, and circular lesion with orange conidial masses. Pathogen isolates were obtained from a diseased tomato fruits, on PDA medium forming a white to gray colonies. The cultures developed black acervuli around the center of the colony. Conidia were hyaline, aseptate, and fusiform or rarely cylindrical. Appressoria were smooth, simple, clavate to ovate, and varied from light to dark brown. Pathogenicity tests with representative isolates were conducted on symptomless, detached tomato fruits. All tested isolates caused anthracnose lesions on tomato fruit after 7 days of incubation. Koch?s postulates were fulfilled by reisolation from inoculated tomato fruits. PCR analysis (using species-specific primer pair, CaInt2/ ITS4) of genomic DNA from tomato isolates resulted in an amplification product of 490 bp, specific for C. acutatum, further confirming the identity of the pathogen. Based on morphological and molecular characteristics, the isolates from tomato fruit were determined as C. acutatum.

Effects of fruit characteristics and climatic conditions on tomato transpiration in a greenhouse

SummaryExperimental data of the transpiration and surface temperature of detached tomato fruits were collected to study and analyse how tomato fruit transpiration (E) was related to fruit characteristics, growth stage and climatic conditions. The measurements were carried out (i) in controlled conditions on fruits weighing between 10 and 140 g and (ii) during several summer days on fruits of 60–100 g under two greenhouse compartments with contrasted (high and low) levels of air vapour pressure difference (VPDa). The transpiration rate, when expressed on a fruit area basis (g cm–2 h–1 ), showed only a very slight dependence upon weight. Linear models relating E in unit area to (i) VPAa and (ii) VPD (fr-a) (fruit-to-air vapour pressure difference) by means of a total conductance to water vapour (gt), were proposed and their parameters were identified for fruits grown under the high and low VPD regimes. These models were able to explain a significant part of the observed variation in fruit transpiration. The parameters of the model differed with respect to growth conditions. The results evidenced the role of both fruit characteristics and climatic conditions on fruit transpiration and that the response of fruit transpiration to VPD could be separated into two components: (i) a short-term and reversible response which seems to be related to instantaneous changes in cuticular hydration linked to the prevailing VPD conditions and (ii) a long-term and irreversible response due to cuticle characteristics which depend on the average level of VPD experienced by the fruit during its growth.

Effect of a high-temperature stress on endo-β-mannanase and α- and β-galactosidase activities during tomato fruit ripening

Abstract Tomato fruit show physiological disorders when exposed to temperatures at or above 30 °C. It has been suggested that the α- and β-galactosidases (α- and β-Gal), as well as the endo-β-mannanase could play roles during fruit ripening. Their pattern of activities was followed in detached tomato fruit, and the degree of inhibition of the activity at high temperatures was evaluated. The potential resumption of the enzyme activity when fruits were transferred to a room-temperature environment was also studied. Mature-green fruits were incubated at: (a) 36 °C for 2 days, (b) 40 °C for 2 days, or (c) 40 °C for 2 days +36 °C for another 2 days. After heat treatments, fruits were transferred to a 21 °C dark environment. Control fruit were stored at 21 °C. In the control fruit, activity was higher for α-Gal than for β-Gal and revealed slightly increasing patterns toward the red-ripe stage. Endo-β-mannanase activity was not detected in mature-green tomatoes but appeared at the breaker stage and rose rapidly, reaching constant values at the red-ripe stage. The firmness and enzymatic activities of fruits initially treated at 36 °C for 2 days were similar to those of the control group. Galactosidase activity decreased in tomatoes incubated at 40 °C for 2 days; and in those whose heat treatment was extended another 2 days at 36 °C the α-and β-Gal reached a minimum of 1 5 and 1 25 , respectively, of the initial activity on the fourth day. The activity of the endo-β-mannanase could be detected only 6 days after the fruit had been transferred to a 21 °C environment and increased slowly up to 24% of that attained by the control group. α-Gal showed a low rate of recovery but β-Gal activity recovered after 16 days at 21 °C. Results could be associated with an active role of these enzymes on the fruit softening process.

The climacteric respiration rise in attached and detached tomato fruit

Abstract The classification of tomato fruit as climacteric, exhibiting a characteristic rise in respiration during ripening, has been questioned. A recent investigation using a static gas collection system has suggested that only detached fruit show a peak in respiration, whilst no such rise was evident in tomato fruit attached to the plant. The associated rise in ethylene production during ripening was confirmed in both attached and detached fruit. Using a continuous flow system to measure respiration rates of tomato fruit (Lycopersicon esculentum Mill. cvs. Counter and Sweet 100), a respiration rate increase of approximately 100% was observed during ripening whether fruit were detached from or attached to the vine. These results support the concept that tomato is a climacteric fruit. The contrast between results presented here and those presented recently on a cultivar of processing tomato (cv. Castlemart), may indicate a difference in climacteric behaviour among cultivars, or unrecognised flaws in the different methods of measuring CO2 evolution from tomato fruit.

Internal carbon dioxide and ethylene levels in ripening tomato fruit attached to or detached from the plant

The carbon dioxide and ethylene concentrations in tomato fruit (Lycopersicon esculentum cv. Castelmart) and their stage of ripeness (characteristic external color changes) were periodically measured in fruit attached to and detached from the plant. An external collection apparatus was attached to the surface of individual tomato fruit to permit non‐destructive sampling of internal gases. The concentration of carbon dioxide and ethylene in the collection apparatus reached 95% of the concentration in the fruit after 8 h. Gas samples were collected every 24 h. A characteristic climacteric surge in carbon dioxide (2‐fold) and ethylene (10‐fold) concentration occurred coincident with ripening of detached tomato fruit. Fruit attached to the plant exhibited a climacteric rise in ethylene (20‐fold) concentration during ripening, but only a linear increase in carbon dioxide concentration. The carbon dioxide concentration increases in attached fruit during ripening, but the increase is a continuation of the linear increase seen in both attached and detached fruit before ripening and does not exhibit the characteristic pattern normally associated with ripening climacteric fruit. In tomato fruit, it appears that a respiratory climacteric per se, which has been considered intrinsic to the ripening of certain fruit, may not be necessary for the ripening of “climacteric” fruit at all, but instead may be an artifact of using harvested fruit.

INTERNAL CARBON DIOXIDE AND ETHYLENE LEVELS IN TOMATO FRUIT RIPENING ATTACHED TO OR DETACHED FROM THE PLANT

The internal concentration of CO2 and C2H4 and the stage of ripeness was periodically measured in tomato fruit (Lycopersicon esculentum cv. Castelmart) attached to and detached from the plant. An external collection apparatus permitted nondestructive sampling of internal gases. The concentration of CO2 and C2H4 in the collection apparatus had equilibrated with the internal gas concentrations after 18 hr. A 20-fold increase in C2H4 during ripening of detached tomato fruit was paralleled by a 3-fold increase in CO2 concentration. Ripening attached fruit exhibited a 100-fold rise in C2H4 during ripening, but lacked a ripening associated climacteric rise in O02. CO2 did increase 2-fold in an erratic fashion during ripening of attached fruit, but the increase did not show any correspondence to increased C2H4 or ripening associated color changes. In tomato fruit, it appears that a CO2 climacteric per se, which has been considered an intrinsic quality of certain ripening fruit, may not be necessary for the ripening of “climacteric” fruit at all, but may instead be an artifact of using harvested fruit.

Ethylene evolution during ripening of detached tomato fruit: Its relation with polyamine metabolism

Ethylene and polyamine metabolism, both sharing a common precursor, S-adenosylmethionine (SAM), were investigated during detached tomato (Lycopersicon esculentum Mill. nothovar F1 “Lorena”) fruit ripening. Putrescine (PUT) was found to be the major polyamine in the fruits, always over 100 nmols/g FW, while spermidine (SPD) was between 7% and 3% of the level of PUT. Spermine (SPM) was not detected at any stage of ripening. The level of PUT and SPD, did not change significantly during ripening in spite of the almost continuous synthesis of 1-aminocyclopropane-1-carboxylic acid (ACC), the ethylene precursor, and only at the last stage of ripening was a drastic decrease in SPD content observed. The results obtained show that the onset of ACC synthesis and its accumulation within the tissue is not a consequence of a decrease in SPD synthesis.

The etiology of head rot disease of broccoli

Transmission and scanning electron microscope studies of broccoli florets affected by head rot, at various stages of disease development, strongly indicated a bacterial etiology for the disease. Nevertheless, the different species of bacteria isolated from diseased heads, using standard techniques, failed to reproduce symptoms in pathogenicity tests conducted in the glasshouse and in the field. However, a modified isolation technique, using broccoli heads showing incipient watersoaking symptoms, yielded a fluorescent pseudomonad which reproduced disease symptoms readily in glasshouse and field tests. On the basis of physiological and biochemical characters, the pathogenic bacterium was identified as a highly pectolytic pathovar of Pseudomonas marginalis. The bacterium also caused the rotting of potato, tomato and swede turnip slices, and also of intact and detached tomato fruit. However, it was not pathogenic on lettuce, parsnip or lucerne, and also failed to rot carrot slices.