Mature Green Research Articles

Effect of ethylene on mRNA abundance of three β-galactosidase genes in wild type and mutant tomato fruit

Recent studies indicate that β-galactosidases may play an important role in fruit development and ripening. The temporal expression patterns of a recently discovered family of tomato β-galactosidase (TBG) genes suggest that accumulation of some TBG mRNAs may be regulated by ethylene. Because of the dramatic changes in mRNA abundance patterns that TBG4, TBG5 and TBG6 exhibit at the onset of fruit ripening (when ethylene production begins), we analyzed the effects of ethylene exposure on expression of these genes at 35 days after pollination (Mature Green) in wild type and three tomato ripening-impaired mutants: ripening inhibitor (rin), non ripening (nor) and Never ripe (Nr). RNA gel blot analysis showed that 48 h of ethylene treatment increased accumulation of TBG4 mRNA up to 20-fold, except in the nor mutant, suggesting that the NOR gene product is required for ethylene up-regulation of TBG4. Experiments in which fruit were exposed to ethylene for either 2 or 24 h indicated that the observed TBG4 up-regulation is an indirect response to the ethylene treatment, rather than a primary (or direct) response. Ethylene treatment caused the levels of TBG5 mRNA to decrease 63–93% in wild type and mutant fruit at the Mature Green stage, but had no effect after the onset of ripening. Ethylene dramatically decreased the mRNA abundance of TBG6 in wild type and all mutants at the Mature Green stage. It was shown previously that the TBG4-encoded enzyme has β-galactosidase and exo-galactanase activity. In order to elucidate its potential cell wall modifying activity, the TBG5-encoded enzyme was expressed in yeast. β-Galactosidase and exo-galactanase activity of the TBG5-encoded enzyme were confirmed through a quantified release of galactosyl residues from p-nitrophenyl-β-d-galactopyranoside and from tomato fruit cell wall fractions containing β(1→4)-d-galactan, respectively. The TBG6-encoded product was not successfully expressed in yeast. We present a summary of the potential function of the TBGs studied here and their mRNA accumulation in relation to the climacteric production of ethylene in tomato fruit.

Biochemistry of fruit ripening of guava (Psidium guajava L.): compositional and enzymatic changes.

Changes in chemical composition and the activities of hydrolytic enzymes during four different stages of maturity, viz. mature green (MG), color turning (CT), ripe (R), and overripe (OR), have been studied in guava fruits cv. Banarsi Surkha. Chlorophyll content decreased while carotenoid content increased during ripening. Starch content decreased with concomitant increase in alcohol-soluble sugars. Cellulose, hemicellulose, and lignin also decreased up to ripe stage, while pectin continued to decrease up to OR stage. PG (polygalacturonase) and cellulase exhibited progressive increase in activity throughout ripening, whereas pectin methyl esterase (PME) activity increased up to CT stage and decreased at R stage. The activities of alpha-amylase and beta-amylase decreased significantly with ripening. The most notable metabolic changes occurred between MG and CT stage, implying that for improved postharvest handling, guava fruits may be harvested at CT stage.

Application of CP-MAS and liquid-like solid-state NMR experiments for the study of the ripening-associated cell wall changes in tomato

13C and 1H NMR spectra of an ethanol insoluble material (EIM) prepared from the pericarp of mature-green (MG) and red-ripe (RR) tomato fruits were acquired in ‘liquid-like’ and cross-polarisation with dipolar decoupling and magic angle spinning (CPMAS) conditions using the same triple resonance probe. Such a strategy allowed acquisitions of various NMR experiments aimed at detecting compositional differences as well as distinguishing differences in molecular mobility for various constituent polysaccharides related with the two ripening stages. Increase of the proton dipolar decoupling power levels from 3 to 50–55 kHz during single pulse 13C acquisition, led to more intense signals for pectic and hemicellulosic polysaccharides. This behaviour was interpreted as reflecting motional restrictions of these polysaccharides inside the porous cell wall network. Measurements of the proton rotating frame relaxation times T 1ρ in the ‘liquid-like’ conditions and of the proton transverse relaxation times T 2 from CPMAS spectra, revealed changes in mobilities for some pectic polysaccharides in relation with ripening, particularly for the H1 and H5 protons of α-1,5 arabinan (Ara) side chains of rhamnogalacturonans. These data are discussed in relation with known pectic modifications occurring during ripening and associated with the tomato fruit softening.

Compositional and enzymatic changes in guava (Psidium guajava L.) fruits during ripening

Changes in chemical composition and hydrolytic enzyme activities in guava fruits cv. Lucknow-49 have been reported at four different stages of maturity, viz., mature green (MG), color turning (CT), ripe (R) and over ripe (OR). Chlorophyll content decreased, while carotenoid content increased with advancement of ripening. Starch content decreased with concomitant increase in alcohol soluble sugars. The cell wall constituents viz., cellulose, hemicellulose, and lignin decreased up to R stage, while the pectin content decreased throughout up to OR stage. Among the cell wall hydrolyzing enzymes, polygalacturonase (PG) and cellulase exhibited progressive increase in activity throughout ripening, while pectin methyl esterase (PME) activity increased up to CT stage and then decreased up to OR stage. The maximum increase in the activities of cell wall hydrolysing enzymes was observed between MG and CT stages. The activities of starch hydrolyzing enzymes, α-amylase and β-amylase decreased significantly with advancement of ripening. These changes in the activities of hydrolyzing enzymes could be considered good indicators of ripening in guava.

Aroma Volatiles of Mature-green and Tree-ripe `Tommy Atkins' Mangoes after Controlled Atmosphere vs. Air Storage

To determine the effects of fruit maturity, storage temperature, and controlled atmosphere (CA) on aroma volatiles, mature-green (MG) and tree-ripe (TR) `Tommy Atkins' mangoes (Mangifera indica L.) were stored for 21 days in air or in CA (5% O2 plus 10% or 25% CO2). The MG fruit were stored at 12 °C and the TR fruit at either 8 or 12 °C. Homogenized mesocarp tissue from fruit that had ripened for 2 days in air at 20 °C after the 21-day storage period was used for aroma volatile analysis. The TR mangoes produced much higher levels of all aroma volatiles except hexanal than did MG fruit. Both MG and TR mangoes stored in 25% CO2 tended to have lower terpene (especially p-cymene) and hexanal concentrations than did those stored in 10% CO2 and air-stored fruit. Acetaldehyde and ethanol levels tended to be higher in TR mangoes from 25% CO2 than in those from 10% CO2 or air storage, especially at 8 °C. Inhibition of volatile production by 25% CO2 was greater in MG than in TR mangoes, and at 8 °C compared to 12 °C for TR fruit. However, aroma volatile levels in TR mangoes from the 25% CO2 treatment were in all cases equal to or greater than those in MG fruit treatments. The results suggest that properly selected atmospheres, which prolong mango shelf life by slowing ripening processes, can allow TR mangoes to be stored or shipped without sacrificing their superior aroma quality.

Irradiation, Stage of Maturity at Harvest, and Storage Temperature during Ripening Affect Papaya Fruit Quality

Solo-type papaya (Carica papaya L.) fruit at the mature green (MG) or one-quarter yellow (QY) stage of maturity were imported through the Port of Miami, Fla., and either irradiated (0.675 kGy) or not irradiated. Fruit condition and quality attributes were determined after ripening to the edible ripe stage at 25 °C before and after storage for 7 days at 10, 12, or 15 °C. The incidence and severity of peel scald was increased by irradiation regardless of storage and ripening regime; however, the degree of severity was dependent on fruit maturity at irradiation. Irradiated QY fruit tended to have the most serious incidence and severity of scald. Mature green fruit ripened at 25 °C without storage had the lowest incidence of fruit with hard areas in the pulp (“lumpy” fruit). The QY fruit generally were second only to irradiated MG fruit stored at 10 °C in incidence of lumpiness. Anthracnose sp. decay and stem-end-rots affected 53% of all fruit. The least decay occurred on fruit ripened at 25 °C without storage, regardless of fruit maturity, and the most decay occurred on QY fruit with or without irradiation. Fruit ripened at 25 °C without storage had more palatable pulp (5.5 N) at the edible ripe stage than did fruit held in storage and then ripened. The effect of fruit maturity or irradiation dose on fruit firmness, however, was dependent on the storage temperature. Mature green fruit ripened at 25 °C lost less weight than did those stored at cold temperatures prior to ripening. We recommend that importers obtain fruit with only a slight break in ground color, and distribute them as rapidly as possible, while maintaining transit/storage temperatures at or above 15 °C with or without exposure to irradiation.

410 Interactive Effects of Harvest Maturity, Controlled Atmosphere, and Surface Coatings on Mango (Mangifera indica L.) Flavor Quality

Mango fruit, cv. Tommy Atkins, were harvested from two grove sites in south Florida at mature green (MG) and tree ripe (TR) maturities. The fruit were either coated with one of two coatings (NS = Nature Seal® 4000, a polysaccharide coating, or CW = carnauba wax) or left uncoated (control) and stored in humidified air or held in a controlled atmosphere (CA = 5% O2 plus 25% CO2) at 12 °C for 21 days followed by 2 days in air at 20 °C. There were 12 fruit for each treatment/maturity stage combination replicated by grove site. After storage, the pulp was homogenized for later consumer or descriptive panel analysis. Measurements for total soluble solids (SS), pH, titratable acidity (TA), and flavor volatile compounds were also made. TR-harvested fruit were sweeter and generally more aromatic than MG-fruit as determined by sensory and/or chemical analysis. NS-coated fruit were more sour, bitter, and astringent compared to controls and CA-treated fruit. NS-coated fruit received lower overall consumer scores than CW-coated fruit, but were not different from controls or CA-treated fruit. This was reflected also in descriptive panel ratings. There were no differences based on storage treatment for SS, pH, or TA; however, NS-coated fruit were higher in acetaldehyde, methanol and ethanol compared to control or CA-treated fruit. Correlation and regression analysis showed significant relationships between sensory and chemical data.

Carambola Quality after Ethylene and Cold Treatments and Storage

Carambolas (Averrhoa carambola L.) must be treated with an approved insect quarantine procedure such as cold treatment before shipment to certain markets. Condition and quality of mature-green (MG) and slightly yellow (SY) fruit were determined after they were: 1) treated with ethylene at 0.1 ml·L-1 for 48 hours (C2H4), 2) subjected to cold treatment (CT) at 1 °C for 15 days, and 3) held in storage at 5 °C for 7 days plus 3 days at 15 °C. Ethylene-treated fruit were softer and yellowness was enhanced compared with non-C2H4-treated fruit. MG fruit were firmer and lost more mass following CT and storage than SY fruit. C2H4 treatment increased the severity of peel scald, stem-end breakdown (SEB), and fin browning but had no effect on pitting. CT increased the severity of scald and pitting, and the severity of SEB, but did not affect fin browning. Peel scald, pitting, SEB, and fin browning were more severe in MG than in SY fruit at the final evaluation. C2H4-treated fruit had lower total soluble solids concentration, higher titratable acidity and pH, and a less preferred flavor and texture than control fruit. We conclude that carambola fruit should be selected at harvest at the slight-yellow stage (3% to 25% of surface area) instead of at the mature-green stage. Fruit to be cold-stored should not be C2H4 treated due to enhanced mold development and severity of SEB.

Modified Atmosphere Packaging Minimizes Increases in Putrescine and Abscisic Acid Levels Caused by Chilling Injury in Pepper Fruit

Bell pepper fruit (Capsicum annuum L. cv. Lamuyo) at two stages of maturity, mature green (MG) and mature red (MR), were stored at 2 and 10 °C to investigate physiological changes resulting from chilling injury. The MG fruit showed evidence of chilling injury (surface pitting) when stored at 2 °C, while MR fruit were unaffected by cold. At the same time, differences in the evolution of plant regulators were detected: In chilling-sensitive MG peppers, ethylene evolution and levels of 1-aminocyclopropane-1-carboxylic acid (ACC), putrescine (Put), and abscisic acid (ABA) rose significantly during storage, while in MG fruits stored at 10 °C and MR fruit stored at both 2 and 10 °C the values were low and no changes were observed. Spermidine (Spmd) content remained low in fruits at both maturity stages and at both temperatures. Chilling injury was reduced in MG fruits stored at 2 °C when modified atmosphere packaging (MAP) was used, particularly with the less permeable film. MAP also led to less pronounced inc...

Changes of Ethylene Evolution, ACC Content, Ethylene Forming Enzyme Activity and Respiration in Fruits of Highbush Blueberry.

Summary We measured ethylene evolution, ACC content, ethylene forming enzyme (EFE) activity, and respiration in highbush blueberry (Vaccinium corymbosum L.) from flowering to harvest to assess the role of ethylene in the processes. Cultivars used were 'Collins' (early maturing), 'Berkeley' (mid-season), and 'Dixi' (late maturing). Ethylene evolution increased at both petal-fall and maturation stages, and was higher in the early stage than in the late stage. Ethylene at petal fall was produced by the calyx and ovary parts, but not the corolla. This indicates that ethylene evolution in flowering is correlated with pollination or fertilization or both. Ethylene evolution rate in the maturation stage was high between the blue pink (BP) peel color in 'Collins', and mature green (MG) stage in 'Berkeley', and green pink (GP) stage in 'Dixi'. Ethylene evolution was higher for 'Collins' than for the others in both years and higher in 1995 than in 1994. The pattern of EFE activity was not similar to that of ethylene evolution except in 'Collins'. Therefore, the correlation between ethylene evolution and EFE activity in the maturation stage was different with each cultivar. Berry ACC content was high at GP stage in three cultivars before ethylene evolution increased.

Physical Characteristics of Mature Green and Ripe Tomato Fruit Tissue of Normal and Firm Genotypes

Tissue firmness of ripe tomatoes is controlled by cell wall integrity of the fruit tissue and by the enzymatic softening that normally occurs during ripening. This study was conducted to determine the physical characteristics of cells and tissues of mature green (MG) and ripe fruit that might account for differences in firmness between `Rutgers' (normal), `Flora-Dade' (Firm), and two mutant lines called high-pigment (T4065 hp) and dark-green (T4099 dg), both of which possess extra firm fruit. Fruit samples were tested for resistance to a force applied to whole fruit and to sections of the pericarp tissue and by stress-relaxation analysis. Determinations were also made of cell density and cell wall content within the pericarp tissue. Fruit of mutant lines had firmer tissue than either `Rutgers' or `Flora-Dade' at MG or ripe. Whole fruit compression measurements showed that T4099 dg was firmer than T4065 hp or `Rutgers' at MG and firmer than `Flora-Dade' and `Rutgers' when ripe. Whole fruit of `Flora-Dade' were significantly firmer than `Rutgers' at MG and ripe. Firmness measured by compressive strength also showed that mutant lines had firmer pericarp tissue than the wild types at both MG and ripe stages. Stress-relaxation analysis showed that MG fruit of T4099 dg had greater tissue elasticity than `Rutgers' or `Flora-Dade'. Ripe fruit of both mutant lines had more tissue elasticity than wild types. There were no apparent differences among the genotypes due to tissue relaxation. From these analyses, tissue elasticity appears to be a significant parameter in determining tissue firmness in the tomato genotypes used in this study. Firmness and textural quality of ripe tomatoes appeared to be dependent on elasticity of the pericarp tissue and on the level of enzymatic softening during ripening.

Lipid Changes in Mature-green Tomatoes during Ripening, during Chilling, and after Rewarming subsequent to Chilling

Lipid composition and pigment content were determined in pericarp of `Pik Red' tomatoes (Lycopersicon esculentum Mill.) that were harvested when mature-green (MG) then ripened for 1 or 14 days at 20C, chilled for 11 or 21 days at 2C, or chilled for 21 days and transferred to 20C for 4 days (rewarmed). During ripening, chlorophyll fell below a detectable level, carotenes increased 100-fold, phospholipids (PLs) dropped ≈20%, and galactolipids (GLs) dropped ≈35%. Fatty-acid unsaturation decreased slightly. Steryl esters (SEs), more than free sterols (FSs) and steryl glycosides (SGs), increased at the expense of acylated steryl glycosides (ASGs), and in all four steryl lipids, the stigmasterol: sitosterol ratio rose dramatically, whereas the level of isofucosterol fell sharply. During chilling, chlorophyll declined ≈40% and carotenes ≈60%. PL content did not change, whereas GL fell ≈15%. Fatty-acid unsaturation increased slightly. FS, much more than SG and SE, increased at the expense of ASG. The stigmasterol: sitosterol ratio changed little in ASG, SG, and SE but declined in FS. Isofucosterol increased in FS and SE. Rewarming had little effect on the levels of chlorophyll, carotenes, or PL levels, but caused GL to fall another ≈15%. Fatty-acid unsaturation decreased slightly in GL and ASG. The distribution of total sterol in ASG, SG, FS, and SE changed dramatically, yielding proportions close to those in unchilled MG fruit. Also, 4 days after rewarming, the stigmasterol: sitosterol ratio had increased sharply, particularly in FS and SE, and there was a further rise in isofucosterol in all four steryl lipids. These results indicate that chloroplast damage occurs during chilling, but PL-rich cell membranes are not degraded, even upon rewarming. Changes in sterol composition and conjugation during chilling and after rewarming could result in membrane dysfunction.

Ripening Stage Affects the Chilling Sensitivity of Greenhouse-grown Peppers

Greenhouse-grown `Bison' and `Doria' peppers (Capsicum annuum L.) were harvested when mature green (MG) (>95% surface green) or ripe (>95% of surface red or yellow). Both cultivars responded similarly to temperature and neither exhibited chilling injury (CI), as indicated by surface pitting, after storage at 13C for 1 or 2 weeks. Ripe peppers showed no CI when held at 1C for 1 or 2 weeks, while MG peppers exhibited CI after these treatments. Exposing MG peppers to 1C for 3 days caused CI and stimulated C2H4 (12.3x) and CO2 production (2.5x). In contrast, a similar exposure of ripe peppers did not cause CI but stimulated C2H4 (6.5x) and CO2 production (1.4x). It seems that CO2 and C2H4 production was stimulated by exposure to 1C, not necessarily by CI development. Our data question the physiological significance of elevated CO2 and C2H4 production in CI development. The observed tolerance of ripe peppers to 1C suggests that ripe greenhouse-grown peppers can be stored at temperatures lower than those currently recommended for bell peppers.

Changes in fluorescent lipid peroxidation products of room-ripened and vine-ripened tomato fruits in relation to other ripening parameters

The changes in ripening parameters and in lipid peroxidation products such as aldehydes, malondialdehyde (MDA), and fluorescent compounds (FCs), were examined at different maturity stages of tomato fruits during ripening on the vine. These changes were compared with the corresponding changes occurring in room-ripened tomato fruits, harvested at the mature green (MG) stage and stored at 12 or 22°C. Some of the harvested fruits were treated with 600 μl l −1 ethylene for 2 days prior to their storage at 22°C. Except for aldehydes and MDA, all changes in the other parameters observed with vine-ripened fruits, were enhanced in room-ripened fruits stored at 22°C or treated with ethylene. However, in contrast with fruits stored at 22°C, the ripening pattern of fruits stored at 12°C resembled that of vine-ripened fruits. These results suggest that the slow ripening rate during storage at 12°C reflects the rates of natural ripening occurring on the vine. Among the lipid peroxidative processes assayed, accumulation of FCs proved to be a more sensitive parameter than accumulation of aldehydes and MDA for assessing the extent of lipid oxidation during tomato fruit ripening.

CELL WALL COMPOSITION AND SYNTHETIC CAPACITY OF THE PERICARP OF RIPENING `JACKPOT' TOMATO

Discs from outer pericarp of mature green (MG) and light red (LR) tomatoes were incubated with 13C6-glucose as precursor to cell wall constituents, to determine biosynthetic capacity of the outer 2mm (including cuticle) and adjacent inner 2mm of tissue. Cell wall material was fractionated into pectic and hemicellulosic classes by sequential extraction, and alditol acetates and partially-methylated alditol acetates were prepared. Neutral sugars (NS), glycosidic linkage compositions and incorporation of label were determined by GC-FID and GC-MS. Rhamnose, arabinose and galactose accounted for ca. 90% of both labeled and total NS in the pectic fractions (sugar ratios within ripeness stage were the same for labeled and total NS). Xylose and glucose accounted for ca. 70% of both labeled and total NS in the hemicellulosic fraction (sugar ratios within ripeness stage were different between labeled and total NS). In the crude cell wall, galactose and glucose contents were significantly higher in the inner than in outer tissues for both MG and LR tomatoes. Loss of galactose during ripening was higher from outer tissues. These results show compositional differences between inner and outer tissues, and suggest that ripening-related wall synthesis may give rise to pectic polymers similar in NS composition to existing polysaccharides, and hemicellulosic polymers which may differ in composition.

Sensitivity of Tomatoes at Mature-green and Breaker Ripeness Stages to Internal Bruising

Internal bruising (IB) caused by handling impacts results in disruption of normal ripening in tomato (Lycopersicon esculentum Mill.) locular gel. It was selected as an injury indicator to investigate the effect of drop height (O, 10, 20, 30 cm) onto an unpadded surface and number of impacts (one or two) for three tomato cultivars. For mature-green (MG) tomatoes, significant incidence of IB (5% to 45%) was found in all cultivars for single drops on opposite sides of fruits from 20 cm; two drops on the same location from 20 cm caused 20% to 30% IB. Breaker-stage (BR) tomatoes were more sensitive to impacts than MG. Single drops from 10 cm on opposite sides of BR fruits caused 15% to 73% IB, depending on cultivar. Two drops on a single location from 10 cm caused 50% to 68% IB. `Sunny' was less susceptible to IB than `Solar Set' or `Cobia' (formerly NVH-4459).

Molecular Cloning of Tomato Pectin Methylesterase Gene and its Expression in Rutgers, Ripening Inhibitor, Nonripening, and Never Ripe Tomato Fruits

We have purified pectin methylesterase (PME; EC 3.1.11) from mature green (MG) tomato (Lycopersicon esculentum Mill. cv Rutgers) pericarp to an apparent homogeneity, raised antibodies to the purified protein, and isolated a PME cDNA clone from a lambdagtll expression library constructed from MG pericarp poly(A)(+) RNA. Based on DNA sequencing, the PME cDNA clone isolated in the present study is different from that cloned earlier from cv Ailsa Craig (J Ray et al. [1989] Eur J Biochem 174:119-124). PME antibodies and the cDNA clone are used to determine changes in PME gene expression in developing fruits from normally ripening cv Rutgers and ripening-impaired mutants ripening inhibitor (rin), nonripening (nor), and never ripe (Nr). In Rutgers, PME mRNA is first detected in 15-day-old fruit, reaches a steady-state maximum between 30-day-old fruit and MG stage, and declines thereafter. PME activity is first detectable at day 10 and gradually increases until the turning stage. The increase in PME activity parallels an increase in PME protein; however, the levels of PME protein continue to increase beyond the turning stage while PME activity begins to decline. Patterns of PME gene expression in nor and Nr fruits are similar to the normally ripening cv Rutgers. However, the rin mutation has a considerable effect on PME gene expression in tomato fruits. PME RNA is not detectable in rin fruits older than 45 days and PME activity and protein begin showing a decline at the same time. Even though PME activity levels comparable to 25-day-old fruit were found in root tissue of normal plants, PME protein and mRNA are not detected in vegetative tissues using PME antibodies and cDNA as probes. Our data suggest that PME expression in tomato pericarp is highly regulated during fruit development and that mRNA synthesis and stability, protein stability, and delayed protein synthesis influence the level of PME activity in developing fruits.

Surface Color Changes of Tomato and Other Solanaceous Fruit during Chilling

Chilling of mature-green (MG) tomato fruit (Lycopersicon esculentum Mill. and related species) was investigated to determine the effect of chilling stress on surface color during low-temperature storage. Color measurements were made with a tristimulus calorimeter (L, a, b values), and data were analyzed by multivariate analysis of variance and canonical variates analysis. Changes in surface color of MG fruit during chilling were not correlated overall with relative chilling sensitivity of cultivars/lines; however, within standard and cherry types, chilling-tolerant fruit changed surface color more during chilling than chilling-sensitive fruit when fruit were picked early in the season. Early harvests were less chilling-sensitive than late harvests. The number of hours below 15.6C in the 200 hours before harvest was positively correlated with postharvest chilling sensitivity. A high vs. ambient relative humidity during storage did not affect chilling-induced percent change in color. Tobacco mosaic virus resistance led to less and Verticillium albo-strum Reinke & Berthier resistance led to more chilling-induced color change. There was no effect from resistances to Fusarium oxysporum Schlechtend f. sp. lycopersici (Sacc.) W.C. Snyder & H.N. Hans, alternaria stem canker (Alternaria solani Sorauer), anthracnose [Colletotrichun coccodes (Wallr.) S.J. Hughes], root-knot nematode (Meloidogyne hapla Chitwood), Phytophthora infestans (Mont.) deBary, or Stemphylium botryosum f. sp. lycopersici Rotem, Cohen, & Wahl. Our results show harvest date had an effect on chilling-induced changes in surface-color in MG fruit.

Surface Topology of Chilling Injury of Tomato Fruit

Chilling-injury symptoms on the surface of eight cultivars or lines of tomato (Lycopersicon esculentum Mill.) fruit were mapped with respect to subtending locules. Mature-green (MG) fruit were chilled at SC for 10 to 25 days and then ripened to red ripe at 20C. Mature-green fruit showed a major portion of injury over subtending locules and on the stem end. The location of injury corresponded with the regions that were the last to ripen. The injuries of immature-green (IG) fruit treated in a similar manner were different from those of MG fruit both in appearance and in distribution.

CORRELATION AMONG CHANGES IN THE NUCLEAR MAGNETIC RESONANCE IMAGE OF RIPENING TOMATO FRUIT AND OTHER RIPENING PARAMETERS

Tomato fruit undergo an orderly series of physiological and morphological changes as they progress from mature-green (MG) to red-ripe. Fruit are commercially harvested at the MG stage, a stage which often encompasses fruit of varying degrees of maturity. The ability to predict the time required for MG fruit to ripen would reduce variability in experiments and could be commercially used to pack fruit that would ripen uniformly. Nuclear magnetic resonance (NMR) imaging can nondestructively measure internal changes associated with plant growth and developmental. In this study, NMR images were taken of freshly harvested tomato fruit (Lycopersicum esculentum cv. Castlemart) at different stages of maturity and ripeness. Measurements were also made of the stage of ripeness, rate of respiration and ethylene production, lycopene and chlorophyll content, density of the pericarp wall, and condition of locular tissue. NMR images showed substantial charges in the pericarp wall and locular tissue during maturation and ripening of tomato fruit. However, it was difficult to objectively evaluate these visual changes with other ripening parameters. For example, increased lightness and graininess of the pericarp wall image was associated with a decrease in wall density; while lightening of the locular image was associated with tissue liquefacation. Use of NMR imaging in studies of tomato fruit ripening will be discussed.