Preclimacteric Stage Research Articles

Role of calcium and heat treatments in alleviating physiological changes induced by mechanical damage in plum

Plum (Prunus salicina Lindl. cv. Blackstar) fruit were harvested at the pre-climacteric stage of ripeness. After being treated with calcium (calcium chloride at 1 mM) or heat at 45 °C (hot water dip immersion for 10 min), fruit were mechanically damaged at three equatorial zones with a given force of 50 N and then held at 20 °C under controlled conditions. Results revealed that both treatments led to a reduction of the mechanical damage, and in turn alleviated the physiological responses that occurred in mechanically damaged plums. A reduction of “wound-induced” ethylene and respiration rates, which were detected just a few hours following mechanical damage, was observed for treated plums. During storage, mechanical damage advanced the climacteric ethylene and respiration peaks, while a delay in those plums previously treated either with calcium or heat was found. Thereafter, control plums exhibited an accumulation of free spermidine and abscisic acid in mechanically damaged flesh, which could be considered a physiological response to mechanical stress. These changes were minimised in calcium- and heat-treated damaged plums, indicating that these treatments would induce a significant resistance to mechanical damage in plum.

Temporary Relationship Between C2 H4 Evolution and C2 H4 Recptor Genes

`Granny Smith' apples were stored at 1 °C, 5 °C and 20 °C, then treated at the preclimacteric stage with 2 ppm MCP, various O2 concentrations, and MCP + low O2. All the treatments greatly retarded the onset of the C2 H4 climacteric, and hence ripening. MCP + low O2 was much more effective than were the applications of MCP and low O2 singly. Even at 20 °C, 4.04 kPa O2 inhibited the rise in C2 H4 evolution for 145 d. Neither low O2 nor MCP inhibited the System 1 C2 H4 evolution. The suppression of the climacteric rise in C2 H4 evolution was accompanied by a strong inhibition of the accumulation of ERS1 C2 H4 receptor and ACS transcripts. On the other hand, ETR1 receptor was constitutively expressed. When climacteric fruits were treated with MCP, and with low O2 + MCP the rate of C2 H4 evolution decreased sharply. This occurred simultaneously with a decrease in ERS1 mRNA. Moreover, the decrease in ERS1 mRNA paralleled the decrease in C2 H4 evolution. The data thus indicate that the initiation and sustainment of the C2 H4 climacteric requires the presence of functional C2 H4 receptors. The expression of ETR2 and ERS2 is also under investigation.

STORAGE OF MANGO FRUITS CV. ROSA TREATED WITH CALCIUM CHLORIDE AFTER HARVEST AT DIFFERENT MATURITY STAGES

The aim of this research was to evaluate the conservation of mango (Mangifera indica L.) cv. Rosa, at different maturity stages, treated with calcium chloride after harvest. Fruits were harvested from an orchard in Areia, Paraiba State, Brazil, at the mature-green (green-yellowish) and pre-climacteric (yellow-greenish) maturity stages. Calcium chloride (CaCl 2 ) was applied by 15-cm deep fruit immersion during two hours in solutions containing 0.0 (control); 4.0; and 8.0 %. Fruits were stored at 10 ± 1 °C and 85% RH during 20 days, followed by a 5-day storage at room temperature (24 + 2 °C). Fruit firmness, weight loss, skin color (scores 1 to 7), external and internal appearances (scores 1 to 6), total soluble solids (TSS), and total titratable acidity (TTA) were evaluated. Calcium chloride was notably more effective when applied to pre-climacteric fruits. However, fruits treated with 4.0 % CaCl 2 showed fruits presented skin black spot, soaked areas, and decay especially pre-climacteric mangoes. As compared to controls, 8.0 % CaCl 2 treatment provided a five-day increase in shelf-life of mature-green 'Rosa' mango stored at 10 ± 1 °C. Upon transference to room temperature, 8.0% CaCl 2 provided lowest weight losses, while maintaining TSS, TTA, fruit firmness, and best internal and external appearances, even though, no significant delay on skin color development was detected.

EFFECT OF FRUIT DROPPING ON POSTHARVEST QUALITY OF MANGO ‘ROSA’ AT TWO MATURITY STAGES

The aim of this research work was to evaluate the effect of fruit dropping from the tree on postharvest conservation of mango fruit (Mangifera indica L.) cv. Rosa, in the green-yellowish (mature-green) and yellow-greenish (pre-climacteric maturity stages. The treatments were: fruits dropped from an average height of 5-m and the control (mango harvested using a 6-m rod provided with a 20x40-cm cloth basket at the end), for each maturity stage. Mangoes of each treatment were kept at room temperature (24 ± 2 °C). Fruit weight loss, total soluble solids (TSS), total titratable acidity (TTA), skin color, and external and internal appearances were evaluated. As measured by external appearance, mango harvested in yellow-greenish maturation stage was much more affected by dropping. For green-yellowish fruits, the symptoms resulting from dropping were impaired or uneven ripening, followed by decay. For yellow-greenish mango fruits, the impacts resulted in an accentuated rate of weight loss, darkened skin, pulp browning, fungi infection, and soaked areas. Skin black spots were observed in dropped yellow-greenish fruits four days after harvesting, paralleled by an increased pulp's TTA, and presence of fermentative off-flavor. Dropping mango cv. Rosa from the tree reduced the shelf life by about four days for yellow-greenish, as compared with green-yellowish non-dropped fruits. Fruit dropping resulted in acceleration of the senescence process, mainly for mango harvested at pre-climacteric, yellow-greenish maturity stage.

INFLUENCE OF 1-METHYLCYCLOPROPENE ON POSTHARVEST CONSERVATION OF EXOTIC MANGO CULTIVARS

The aim of this research work was to evaluate the influence of 1-methylcyclopropene (1-MCP) on postharvest conservation of exotic mango (Mangifera indica L.) fruits CVs 'Rosa', 'Jasmim', and 'Espada', harvested as mature-green and pre-climacteric maturity stages, from an orchard in Areia, Paraiba State, Brazil. Fruits, from each cultivar and maturity stage, were treated in sealed (90 x 60 - cm2) chambers with 100 ppb 1-MCP for 24 hr. Fruits were stored at room temperature (23 ± 1 °C) and 80 % RH during 16 days. Fruit weight loss, total soluble solids (TSS), total titratable acidity (TTA), skin color (1-7 scale), and external appearance (1-5 scale), were evaluated. The results show that 1-MCP was capable of delaying ethylene-induced ripening processes for all mango cultivars tested. Mature-green 'Rosa' and 'Espada' mangoes treated with 1-MCP presented lower weight losses, while maintaining TSS, TTA, and better external appearances. For 'Jasmim' cultivar, by the end of evaluation period, better external appearance was more evident for pre-climacteric fruits.

Ripening and quality of 'Laetitia' plums following harvest and cold storage as affected by inhibition of ethylene action

The inhibition of ethylene action by 1-methylcyclopropene (1-MCP) extends shelf and storage life of many climacteric fruits. However, 1-MCP appears to have limited effects on stone fruit depending on specie and cultivar. The effects of 1-MCP on ripening and quality of 'Laetitia' plums were determined during ripening at 23ºC following harvest and cold storage. Japanese plums (Prunus salicina, cv. Laetitia) were harvested at mature pre-climacteric stage, cooled to 2ºC within 36 hours of harvest and then treated with 0, 0.05, 0.10, 0.50 or 1.00 muL L-1 of 1-MCP at 1°C for 24 hours. Following treatment, fruits were either held at 23ºC for 16 days or stored at 1ºC for 50 days. Fruits were removed from cold storage at 10-day intervals and allowed to ripe at 23°C for five days. A delay of climacteric respiration and ethylene production by 1-MCP treatment during ripening following harvest and cold storage was associated to a slow rate of fruit softening. 1-MCP treatment also delayed the loss of titratable acidity and changes of flesh and skin color, whereas it had little or no effect on soluble solids content. 1-MCP effects were concentration- and storage duration-dependent and, generally, a saturation fruit response to 1-MCP occurred between 0.5 and 1.0 muL L-1. During ripening, 1-MCP treated fruits attained quality similar to that of controls. Results indicated that 1-MCP treatment may extend shelf life (23ºC) and storage life (1ºC) of 'Laetitia' plums by approximately six and 20 days, respectively.

Quality improvement and extension of shelf life by 1-methylcyclopropene in plum as affected by ripening stage at harvest

Plum ( Prunus domestica L. cv. ‘President’) fruits were harvested at two pre-climacteric stages of ripeness (stage 1 and stage 2), and then treated with 1-methylcyclopropene (1-MCP) at two doses (0.3 and 0.5 μl l −1) followed by 1, 2, 3, 4 and 5 weeks of cold storage and their respective 7 days of shelf life at 20 °C. Both 1-MCP doses were effective in terms of ethylene inhibition during shelf life after cold storage, for both ripening stages. Similarly, lower weight losses, delayed colour changes, reduced softening rate and diminished ripening index were found in 1-MCP treated plums than in controls at both stages of ripeness. Hence, during cold storage and shelf life, the efficacy of 1-MCP on ethylene production, weight loss, pulp firmness and ripening index was dose-dependent, while for colour and respiration rate the dose-dependence was only found during shelf life. The storability of 1-MCP treated plums could be extended up to 4 weeks of cold storage plus 7 days at 20 °C, and only up to 1 week of cold storage plus 7 days at 20 °C for controls. Then, 1-MCP is an effective tool for quality improvement and extension of shelf life in plums, and fruit might be harvested in stage 2 of ripening, at which the most desirable organoleptic attributes had been developed on tree.

Electronic nose as a non-destructive tool to evaluate the optimal harvest date of apples

An electronic nose (E-nose) has been evaluated for use as a tool to predict the optimal harvest date of apples (Malus domestica Borkh.). The volatiles of ‘Jonagold’ and ‘Braeburn’ apples were assessed during the preclimacteric stage for two consecutive harvest years by means of an E-nose. A principal component data analysis indicated the presence of both a year and cultivar effect. Partial least square (PLS) models were constructed based on data of both harvest years. The cultivar effect made it difficult to build accurate and robust models for the two cultivars together. As a consequence, calibration models were constructed based on data of 2 years, but for each cultivar separately. The prediction of maturity, according to the Streif Index, showed a cross-validation correlation of 0.89 and 0.92 for ‘Jonagold’ and ‘Braeburn’ fruit, respectively. The calibration models for the prediction of the maturity, defined as the number of days before commercial harvest had a validation correlation of 0.91 for ‘Jonagold’ and 0.84 for ‘Braeburn’ fruit. Individual quality characteristics (soluble solids, acidity, starch and firmness) were predicted reasonably well. The calibration model for soluble solids content resulted in a consistent validation correlation over the results over 2 years (0.76 and 0.77). The starch and firmness were predicted with a validation correlation between 0.72 and 0.80. The prediction of the total acidity was poor (validation correlation of 0.66 and 0.69). It was also demonstrated that the type of validation influences the model prediction performance. Care should be taken when interpreting and using the models to predict the optimal harvest date for other years and cultivars.

SOFTENING AND BIOCHEMICAL CHANGES OF SAPOTE MAMEY FRUIT (POUTERIA SAPOTA) AT DIFFERENT DEVELOPMENT AND RIPENING STAGES

We investigated some of the physicochemical and biochemical factors associated with flesh softening of sapote mamey fruit during development and ripening. The activities of pectinmethylesterase (PME), polygalacturonase (PG) and β-galactosidase (β-GAL) enzymes were measured in fruits harvested at different development stages, and postharvest in two production seasons. The textural changes were most noticeable at the preclimacteric stage in ripening fruit. The water-soluble pectin (WSP) increased at a different rate than firmness decreased. No correlation between PG or PME activity and changes in firmness was observed in ripening fruits, though a low correlation was seen between β-GAL activity and softening in climacteric stage. Greatest loss of firmness occurred in climacteric stage. Fruit pulp softening was not dependent on a single enzyme activity.

Differential expression of seven alpha-expansin genes during growth and ripening of pear fruit.

Seven cDNAs, designated PcExp1 to PcExp7, encoding expansin homologues, were isolated from mature pear fruit and their expression profiles were investigated in ripening fruit and other tissues, and in response to ethylene. Accumulation of PcExp2, -3, -5 and -6 mRNA increased markedly with fruit softening and then declined at the over-ripe stage. Treatment of fruit at an early ripening stage with 1-methylcyclopropene (MCP), an inhibitor of ethylene action, suppressed ethylene biosynthesis, fruit softening and the accumulation of the expansin mRNAs. Conversely, propylene treatment at the preclimacteric stage induced accumulation of the same four expansin genes, as well as ethylene production and fruit softening. The expression patterns correlated with alteration in the rate and extent of fruit softening. The abundance of PcExp1 mRNA increased at the late expanding phase of fruit development and further increased during ripening, whereas PcExp4 mRNA levels were constant throughout fruit growth and ripening. The MCP and propylene treatments had little effect on PcExp1 and PcExp4 expression. PcExp7 was expressed in young but not mature fruit. PcExp4 and PcExp6 mRNA was also detected in flowers. The accumulation of PcExp4, -5, -6 and -7 mRNA was more abundant in young growing tissues, but not in fully expanded tissues, suggesting roles for these genes in cell expansion. These results demonstrate that characteristically, multiple expansin genes show differential expression and hormonal regulation during pear fruit development and at least six expansins show overlapping expression during ripening.

バナナ果実の追熟中におけるＮＡＤＰ依存型イソクエン酸脱水素酵素活性の変化

The changes in activity of NADP-linked isocitrate dehydrogenase (NADP-IDH, EC 1.1.1.42) of banana fruit (Musa spp. [AAA group, Cavendish subgroup]) during postharvest ripening were investigated. The activity of NADP-IDH in the flesh of mature green fruit was low during the preclimacteric stage at 20°C. However, the enzyme activity in fruit treated with propylene increased during ripening to more than twice that of the control. The contents of pyruvate and 2-oxoglutarate also increased in propylene treated fruit. The increase in 2-oxoglutarate is attributed to the rise in NADP-IDH activity because they both coincided with the increase of respiration rate during postharvest ripening. Hence, NADP-IDH is considered to play an important role in the postharvest ripening of banana fruit.

Cloning of an auxin-responsive 1-aminocyclopropane-1-carboxylate synthase gene ( CMe-ACS2) from melon and the expression of ACS genes in etiolated melon seedlings and melon fruits

Two cDNA fragments (pCMe-ACS2 and 3) encoding auxin-responsive 1-aminocyclopropane-1-carboxylate synthase (ACS; EC.4.4.1.14) have been isolated from melon, and the expression patterns of the genes in etiolated melon seedlings and melon fruit have been determined by RT-PCR analysis. The deduced amino acid sequences of pCMe-ACS2 and 3 were homologous to those of AT-ACS6 and 4, which were auxin-responsive ACS genes of Arabidopsis. Both CMe-ACS2 and 3 were auxin-responsive ACS genes and their expressions in roots and hypocotyls were induced by treatment with indole acetic acid (IAA, 100 μM). The mRNA level of CMe-ACS2 in the fruit increased after pollination. Those of both CMe-ACS2 and 3 temporarily increased in the mesocarp tissues at the preclimacteric stage (from day 3 to day 5 after harvest) during ripening, while that of CMe-ACS3 was lower than that of CMe-ACS2. The increase in the mRNA level of CMe-ACS1 (wound- and ripening-induced gene, T. Miki, M. Yamamoto, N. Nakagawa, O. Ogura, H. Mori, H. Imaseki, T. Sato, Nucleotide sequence of a cDNA for 1-aminocyclopropane-1-carboxylate synthase from melon fruits, Plant Physiol. 107 (1995) 297–298.) in the mesocarp tissue was not observed until 5 days after harvest. A genomic DNA encoding CMe-ACS2 was isolated and its nucleotide sequence was determined. Nucleotide sequences resembling the auxin-responsive elements (AuxRE) D1 and D4 (the TGTCTC element) in the GH3 gene from soybean, and the auxin-responsive domain (AuxRD) B in PS-IAA4/5 from pea were found in the 5′-flanking region of the CMe-ACS2 gene.

Changes of Endogenous Jasmonic Acid and Methyl Jasmonate in Apples and Sweet Cherries during Fruit Development

Trans-jasmonic acid (JA), cis-JA, and trans-methyl jasmonate (MeJA) were quantified in pulp and seeds of `Tsugaru' apple [Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.] and `Satohnishiki' sweet cherry (Prunus avium L.). Trans-JA and cis-JA showed similar changes during development in both types of fruit. JA concentration was high in the early growth stages of apple pulp development, decreased with days after full bloom (DAFB), and then increased again during maturation. There was an initial decrease in concentration of MeJA in apple pulp, followed by a general increase towards harvest. Concentrations of JA and MeJA in the pulp of sweet cherry were high during early growth stages, then decreased towards harvest. PDJ treatment at 104 DAFB (preclimacteric stage) increased endogenous abscisic acid concentration and anthocyanin concentration at 122 and 131 DAFB (maturation stages) in apple. JA concentration in apple seeds was also high in the early growth stages, then decreased, and finally peaked at harvest. MeJA concentration in apple seeds increased towards harvest. In the seeds of sweet cherry, JA and MeJA concentrations generally increased until harvest. In both types of fruit, concentrations of JA and MeJA in the seeds were higher than those of pulp. On a dry weight basis, changes in concentration in the seeds preceded those in the pulp. These results demonstrate that relatively high amounts of JA and MeJA are associated with young developing fruit. These substances may have a role in regulation of fruit growth at early growth stages, though this has not been demonstrated. Chemical name used: n-propyl dihydrojasmonate (PDJ).

Changes in Abscisic Acid Levels, Ethylene Biosynthesis, and Protein Patterns during Fruit Maturation of `Granny Smith' Apples

Endogenous ABA, free and conjugated ACC concentrations, ethylene-forming capacity (EFC), and presence of ACC oxidase (ACO) and ACC synthase (ACS) proteins were monitored during the preharvest maturation period of `Granny Smith' apple fruit (Malus sylvestris L. Mill. var. domestica (Borkh.) Mansf. `Granny Smith'). Total proteins from peel and pulp tissues were also extracted at different maturity stages and separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis, providing evidence of differential protein accumulation during fruit development. Endogenous ABA concentration in the peel tissue was higher than in pulp, the highest level occurring ≈2 months before commercial harvest. In the pulp tissue, concomitant increases in ACC and ABA concentrations were observed, preceded by a peak in EFC. However, no ACO or ripening-related ACS proteins were detectable throughout the period considered, suggesting that very low levels of both enzymes are present during the preclimacteric stage of `Granny Smith' apples. A hypothesis on the possible interaction between ABA and ethylene during maturation of `Granny Smith' apples is proposed. Chemical names used: abscisic acid (ABA); 1-aminocyclopropane-1-carboxylic acid (ACC).

Characterization of ethylene biosynthesis associated with ripening in banana fruit.

We investigated the characteristics of ethylene biosynthesis associated with ripening in banana (Musa sp. [AAA group, Cavendish subgroup] cv Grand Nain) fruit. MA-ACS1 encoding 1-aminocyclopropane-1-carboxylic acid (ACC) synthase in banana fruit was the gene related to the ripening process and was inducible by exogenous ethylene. At the onset of the climacteric period in naturally ripened fruit, ethylene production increased greatly, with a sharp peak concomitant with an increase in the accumulation of MA-ACS1 mRNA, and then decreased rapidly. At the onset of ripening, the in vivo ACC oxidase activity was enhanced greatly, followed by an immediate and rapid decrease. Expression of the MA-ACO1 gene encoding banana ACC oxidase was detectable at the preclimacteric stage, increased when ripening commenced, and then remained high throughout the later ripening stage despite of a rapid reduction in the ACC oxidase activity. This discrepancy between enzyme activity and gene expression of ACC oxidase could be, at least in part, due to reduced contents of ascorbate and iron, cofactors for the enzyme, during ripening. Addition of these cofactors to the incubation medium greatly stimulated the in vivo ACC oxidase activity during late ripening stages. The results suggest that ethylene production in banana fruit is regulated by transcription of MA-ACS1 until climacteric rise and by reduction of ACC oxidase activity possibly through limited in situ availability of its cofactors once ripening has commenced, which in turn characterizes the sharp peak of ethylene production.

POTENTIAL FOR IMPROVEMENT OF MANGO SKIN COLOUR DURING STORAGE

External fruit colour is a major determinant of consumer appeal in mango. Mangoes are generally harvested at the hard, green preclimacteric stage, with ripening occurring after harvest. The optimum ripening temperature for cv. Kensington Pride, the main Australian mango cultivar, is 18-24°C. These conditions generally allow parallel skin yellowing and flesh softening. Prolonged mango storage (e.g. at 13°C) or ripening at 30°C desynchronises these two ripening processes, so that fruit generally soften but retain some of the green skin colour. In addition, some mango cultivars develop a red blush prior to harvest but this is often limited by reduced fruit exposure to light due to shading during growth, subtropical seasonal haze and too high temperatures. Therefore, there is a need for a postharvest method to improve mango skin colour. To test the potential for postharvest illumination to improve mango skin colour at ripe fruits of cvs. Kensington Pride and Tommy Atkins at commercial maturity were exposed soon after harvest to cool-white fluorescent illumination at 13°C and 20°C (temperatures recommended for mango storage and ripening in Australia, respectively). Two levels of photon fluency rate (135 μmol/m 2 .s and 175 μmol/m 2 .s) were tested. In both cultivars the response to illumination was greater at 20°C than at 13°C. Both levels of illumination provided similar improvements in skin colour at ripe. Illumination of 'Kensington Pride' for 5 and 48 hrs at both low and high light intensity, resulted in significantly more yellow and red colour on the skin at ripe. Low intensity light exposure for 1 hr was not effective. Twenty four hours illumination of 'Tommy Atkins' fruit with low intensity illumination increased both the yellow and red colour of the skin at ripe.

Expression of ACC Synthase and ACC Oxidase Genes in Melons Harvested at Different Stages of Maturity.

Melon (Cucumis melo L.) fruits vary in ethylene production rates, depending on the cultivar, which can affect the storability of the fruits. To understand these differences at both the biochemical and molecular levels, two popular cultivars, 'Andes' and 'Earl's Favourite' were used ; these cultivars produce relatively high and low amounts of ethylene, respectively. Ethylene biosynthetic activity in the peel, mesocarp and placenta of 'Earl's Favourite' fruits harvested at different stages of maturity remained low even at the commercial harvest maturity (CHM), and ethylene production in the intact fruit was also low. In 'Andes', 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (ACS) activity and ACC content in the mesocarp and placenta and ethylene production in intact fruit increased drastically at CHM. Northern blot analysis using mRNA extracted from the respective tissues of fruits at different stages of maturity indicated that CMe-ACS1 mRNA accumulated in the mesocarp and placenta of 'Andes' at CHM, whereas in 'Earl's Favourite' there was no accumulation in any of the tissues at all maturities. In ACC oxidase (ACO) genes, mRNA for ACO1 accumulated in the mesocarp and placenta of both cultivars at CHM, and that for ACO2 was almost constitutively expressed. Ethylene, exogenously applied to fruits at the preclimacteric stage, slightly induced CMe-ACS1 mRNA accumulation in 'Andes' but not in 'Earl's Favourite' fruits, whereas wounding induced CMe-ACS1 transcripts accumulation in both cultivars. The accumulation of ACO1 mRNA in the two cultivars was greatly stimulated by ethylene and wounding treatments. When 'Andes' fruit at climacteric stage were treated with 1-methylcyclopropene (MCP), an inhibitor of ethylene action, transcripts for CMe-ACS1, ACO1 and ACO2 were barely detectable. These results suggest that the difference in the ethylene-forming capability between the two cultivars may result from the expression of CMe-ACS1 mRNA during natural fruit ripening and in response to exogenous ethylene.

Application of 1-MCP and propylene to identify ethylene-dependent ripening processes in mature banana fruit

Mature green bananas (Musa sp., AAA group, Cavendish subgroup, cultivar `Williams') were treated with 1-methylcyclopropene (1-MCP) at a preclimacteric stage and at intervals of 6, 12 and 24 h after propylene treatment (HAPT) to initiate ripening. The fruit were then allowed to ripen in air or propylene. Ethylene production, respiration rates, peel colour and total volatiles production were monitored during ripening. 1-MCP significantly delayed the onset and affected the rate and magnitude of several physiological responses. Application of 1-MCP at a preclimacteric stage or 6 and 12 HAPT delayed onset of the ethylene and respiratory climacterics, peel degreening and total volatiles production. Application of 1-MCP 24 HAPT after autocatalytic ethylene had commenced did not inhibit development of the ethylene and respiratory climacterics, but delayed colour development and total volatiles production. In all cases, when 1-MCP treated fruit did produce ethylene, rates of production were significantly enhanced, whilst rates of respiration were always lower. Onset of total volatiles production was delayed and the rates were lower in all 1-MCP treated fruit. Degreening of the peel was significantly delayed and disrupted by 1-MCP. The results show that these ripening related processes, once engaged with autocatalytic ethylene production, become partially independent of further ethylene action. Some possible reasons for the failure of 1-MCP treated fruit to ripen normally are discussed.

Influence of Storage Period on the Postharvest Characteristics of Five Mango (Mangifera indica L.) Cultivars

Five mangos cultivars (Mangifera indica L., `Palmer', `Keitt', `Spring Field', `Kent', and `Anderson') were harvested at the preclimacteric stage. Fruits were selected for study that were uniform and free of visual defects and stored for 18 days at 10 °C, 90% to 95 % RH. Fruits were evaluated every 3 days for pulp and peel color, total soluble solids, titratable acidity, ascorbic acid content, and total and reducing sugars. Pulp and peel color parameters (lightness, hue, and chroma) were significantly different among cultivars. The soluble solids content, ascorbic acid, and starch content changed significantly during storage and were significantly different among cultivars. Total and reducing sugars content did not change significantly after 10 days of storage. Results of this study indicated that these five mango cultivars have good storage potential.

Effects of Heat Treatment on Postharvest Quality of Mango Fruits

Mango fruits (Mangifera indica L.) were harvested at the preclimacteric stage. Fruits were immersed in 38, 42, 46, 50, and 54°C heated water for 30, 60, and 45 min prior to storage at 5°C for 2, 4, or 6 weeks in carton boxes. After storage, they were kept at 20°C. Fruits were evaluated for pulp color, total soluble solids, titrable acidity, ß-carotene content, reducing sugars and visible symptoms of chilling injury. Heated water had no significant effect on pulp color parameters (lightness, hue, and chroma). Soluble solids concentration, ß-carotene content and reducing sugars were higher in heated than in nonheated fruit after ripening. The chilling index was three-fold lower in treated than nontreated fruit. During storage and after removal at 20°C, hot-water-treated fruits ripened faster than nontreated fruits. Results of this study indicate that mango tolerance to chilling temperatures may increase after prestorage heat treatments.