HortJ

A major challenge in terms of commercializing 1-methylclopropene (1-MCP) to extend the storage life and control physiological disorders in European pears is that it irreversibly inhibits fruit ripening in some cultivars, particularly flesh softening that is necessary for optimal consumption quality. In this study, we examined the effect of 1-MCP pretreatments on fruit ripening and associated transcriptomic changes in ‘La France’ (Pyrus communis L.) pears during storage at 20°C and 5°C. Compared to non-treated controls, 1-MCP pretreatment suppressed fruit respiration and ethylene production rates, and markedly delayed flesh softening. Normal ripening (ethylene production and flesh softening to eating quality firmness) was observed in 1-MCP treated fruit after 42 d at 20°C, and 112 d at 5°C. Subsequent RNA-Seq analysis revealed that 6,427 genes, including those associated with ethylene biosynthesis (ACS1, ACS1b, ACO1, and ACO2), cell wall degrading enzymes (PG3, β-GAL, EG, and EXP1), and transcription factors (AGL18 and NAC29) were up- or down-regulated in non-treated fruit both at 20°C and 5°C. The expression patterns of these genes were disrupted by 1-MCP pretreatment, but up- or down-regulation was also observed when ethylene was detected in 1-MCP-treated fruit. Together, these findings demonstrate the potential for practical use of 1-MCP to extend storage life in ‘La France’ pears given that (i) a single application markedly extended storage life to 56 d at 20°C and 112 d at 5°C, and (ii) treated fruit could regain their softening capacity, thus eliminating previous irreversible ripening blockage concerns.

Young coconut shell cracking is a significant problem reported during trimming and polishing. By studying the shell structure, fruit development, pressure inside the shell (internal pressure) of young fruits, dissolved carbon dioxide in the coconut water and cracking incidence, as well as postharvest treatments to manipulate the pressure and carbon dioxide concentration, it was revealed that cracking depended on the physical property of the shell and the internal pressure. Cracking was principally found on the large carpel where the shell was the thinnest. The growing area presenting a high cracking incidence was found to have fruits with a thinner shell than fruits from a nearby area. The younger fruits had a weaker, thinner shell and high internal pressure. Once the fruits were 28 weeks old, the internal pressure dropped to slightly above atmospheric pressure. The level of internal pressure did not depend on rainfall or growing area. However, postharvest heating, dipping in water and exposure to carbon dioxide increased the internal pressure. To reduce shell cracking incidence, it is recommended to delay harvesting to allow shell strengthening, delay the trimming and polishing processes to allow water loss from the fruit and reduce the internal pressure. Dipping fruit in an anti-browning solution should also be brief to avoid water absorption.

Limes (Citrus aurantifolia Swingle) have a short postharvest life. Therefore, effective treatments increasing storage life to lengthen the time that produce remains fresh is desirable. This study evaluated the effects of postharvest treatments of 1-methylcyclopropene (1-MCP), gibberellic acid (GA₃), and Aloe vera on lime storage life and fruit quality. The optimum individual treatments of 50% Aloe vera coating, 300 mL·L⁻¹ GA₃, and 750 nL·L⁻¹ 1-MCP were identified as most effective in extending lime postharvest life. Under ambient conditions (26.4 ± 1.0°C, 64.4 ± 7.4% RH), 1-MCP fumigation was the best treatment, increasing lime postharvest life to 28.2 days. The 1-MCP-treated fruit had a higher juice content than the control fruit. Also, soluble solid contents and titratable acidity were not significantly different, while ascorbic acid was lower than the control. Under cold room conditions (10.0 ± 0.3°C, 68.9 ± 12.4% RH), 1-MCP fumigation followed by Aloe vera coating was the best treatment, increasing lime storage life by 38.7 days. The longer storage time did reduce juice content in treated limes compared to untreated fruit. However, the treatment did not affect the soluble solid contents, titratable acidity, or ascorbic acid level. In conclusion, for optimum postharvest life in limes stored under ambient conditions, fumigation with 1-MCP is best. While for limes stored in cold rooms, a cotreatment of 1-MCP fumigation followed by Aloe vera coating maximizes postharvest life.

The effect of short-term anoxic treatment prior to storage at ambient and cool temperatures on pericarp browning, fruit quality, secondary metabolites, antioxidant activity, and the browning enzyme of litchi (Litchi chinensis Sonn.) cv. Hong Huey were investigated. Litchi fruit were exposed to anoxic conditions for 6, 12, 18 and 24 h before storage at 28 ± 2°C for 5 days, or at 7 ± 2°C for 14 days. Anoxic treatment resulted in significantly decreases in electrical conductivity, weight loss, browning index, while maintaining the total soluble solids (TSS) and delaying increases in polyphenol oxidase (PPO) and peroxidase (POD) activities compared with control fruit. Furthermore, anoxic treatment increased litchi pericarp methanol extract antioxidant capacity, as measured by free-radical scavenging activity. This is associated with greater amounts of ascorbic acid, anthocyanins, and phenolic/flavonoid components as compared with control fruit. Additionally, anoxic treatment considerably delayed litchi fruit pericarp browning. This suggests that with adequate short-term anoxia duration, an enhanced non-enzymatic antioxidant process may directly or indirectly delay litchi pericarp browning. Thus, a short anoxic treatment enables harvested litchi quality to be sustained at ambient and cool temperatures. This non-chemical and inexpensive treatment deserves further development and application, especially in commercial distribution systems where cooling is insufficient.

Abiu is a tropical fruit with many beneficial bioactive compounds. However, its economic value is limited by a short shelf life and rapid browning. This study evaluated the effect of ascorbic acid on extending abiu fruit shelf life during storage. The fruit was soaked in ascorbic acid solutions of 0 mM (control), 5 mM (AA5), and 10 mM (AA10) for 10 minutes, air-dried, then stored in an ambient room (28 ± 1°C and 80 ± 5% RH) for 12 days. The results indicated that the 10 mM exogenous ascorbic acid treatment increased abiu fruit shelf life up to 12 days, nine days longer than the control. Abiu fruit, after the AA10 treatment, underwent a 1.4-fold lower weight loss than the control. In addition, on day 12 of storage, the browning of fruit with the AA10 treatment were 8 and 11% on the peel and pulp, respectively. The climacteric peak of abiu fruit in the AA10 treatment occurred on day 8 of storage, three days later than the control. The AA10 treatment also maintained vitamin C content and fruit firmness. Thus, the AA10 treatment effectively extended shelf life and maintained abiu fruit quality.

Pineapples (Ananas comosus (L.) Merr.) are harvested throughout the year, with acid and soluble solid contents varying with season. However, there is a lack of knowledge about the relationship between the acid and soluble solid content and climatic factors. To investigate these relationships, we analyzed the acid and soluble solid content records of a large number of fruit harvested over 15 years from three production areas in Japan. Over the warm period (June to September) pineapple acid content was low, while over the cool period (December to April) it was high, regardless of the cultivar. Soluble solid contents were highest in June and lowest between September and March. Acid content at harvest inversely correlated with the temperature immediately before harvest, and the relationship modelled linearly with the mean temperature over the 10 or 20 days before harvest as a variable. The acid content of ‘N67-10’ is highly dependent on temperature, while that of ‘Okinou P17’ is stable regardless of temperature. The soluble solid content was affected by temperature over longer periods than the acid content and was modelled using a quadratic equation with the mean temperature over the 70–120 days before harvest as a variable. The approximate curve of soluble solid content peaked around 23°C. The majority of ‘Okinou P17’ fruit yielded a soluble solid content of > 15 °Brix over a wide temperature range (≥ 19°C), while the temperature at which most ‘N67-10’ fruit had soluble solid of > 15 °Brix was limited to a narrow range (22–23°C). Although the coefficients of both model equations were significant for all cultivars, the R² of soluble solid content was smaller than that of acid content. These results contribute to understanding the relationship between acid and soluble solid content and temperature.

The pineapple (Ananas comosus (L.) Merr.) is an economically important tropical fruit crop. In this study, we performed quantitative trait locus (QTL) analysis using 168 individuals of the F₁ population of ‘Yugafu’ × ‘Yonekura’ for 15 traits: leaf color (L*, a*, b*), harvest day, crown number, slip number, stem shoot number, sucker number, fruit weight, fruit height, fruit diameter, fruit shell color, soluble solid content, acidity, and ascorbic acid content. The constructed single-nucleotide polymorphism (SNP)-based genetic linkage map consisted of a total genetic distance of 2,595 cM with 3,123 loci, including 22,330 SNPs across 25 chromosomes. QTL analysis detected 13 QTLs for 9 traits: leaf color a*, harvest day, fruit weight, fruit height, fruit diameter, fruit shell color, soluble solid content, acidity, and ascorbic acid content. The causative gene for each QTL was predicted with two genes identified as candidate genes. The AcCCD4 gene on Aco3.3C08 was the predicted causative gene for the shell color QTL, which negatively controls shell color by carotenoid degradation. The Myb domain protein-encoding gene on Aco3.3C02 was the predicted causative gene for shell color and leaf color a* QTL, which positively regulates anthocyanin accumulation. The QTL and gene information provided here contributes to future marker-assisted selection for fruit quality.

The salak fruit (snake fruit) contains one to three seeds covered with an aril. The size of the fruit primarily depends on the number of seeds. Fruits with more seeds grow larger and attain higher commercial value in fresh markets owing to their superior appearance. In eastern Thailand, during the hot period in the early rainy season, the fruit set of salak decreases, which is empirically believed to be caused by high night temperatures. In this study, we pollinated and incubated salak spadices at various temperatures (18–36°C) to determine the optimal post-pollination temperature range needed to produce valuable fruits. Chronological pollen-tube elongation in the pistil and development of the early embryo and endosperm were then observed anatomically, followed by fruit-set estimation. At ≤ 21°C, pollen-tube elongation was limited. At 24–27°C, although elongation was slow, pollen tubes attained embryo sacs in > 60% of florets within 36 h after pollination. Pollen tubes elongated fastest at 30–33°C and attained embryo sacs within 12 h after pollination. At 36°C, the difference in the elongation speed tended to be higher among the pistils. The percentages of ovules with developing embryos were the highest at 27°C at 48 h after pollination; zygote and early embryos were observed in 10.8% and 55.9% of the ovules, respectively, and the primary endosperm nucleus, dispersing endosperm nucleoplasm, and free endosperm nuclei were observed in 8.6%, 38.7%, and 19.4%, respectively. The second highest percentage was observed at 24°C. The percentages tended to decrease at 30°C and decreased significantly at ≥ 33°C. At ≥ 30°C, shriveled embryo sacs were observed. The estimated fruit-set percentage based on embryo development as the consequent fruit set was the highest (≈80%) at 27°C, while the second highest percentage (≈75%) was at 24°C. At ≥ 30°C, the estimated percentage decreased to less than half that at 27°C. Fruits containing three seeds were expected to grow in the range of 17.6–28.0% at ≤ 27°C. One- or two-seeded fruits were expected to grow at ≥ 30°C. Limited fruit set was expected at 36°C. Our results indicate that salak prefers relatively cool temperatures of approximately 25°C for the fertilization and set of valuable fruits.

‘Miyagawa-wase’ (Citrus unshiu Marcow.), an early-season citrus variety, is rich in multiple nutrients and widely consumed in Japan. In ‘Miyagawa-wase’, when the pulp reaches maturity and is ready to eat, the peel is still a greenish color because of the relatively high temperature in the harvest season. In this study, to improve the coloration of ‘Miyagawa-wase’ peel, we treated the fruit with 1-naphthaleneacetic acid (NAA) after harvest. The results showed that postharvest treatment with NAA was effective to induce chlorophyll degradation and carotenoid accumulation in ‘Miyagawa-wase’ peel during storage. In the NAA treatment, the reduction in the chlorophyll contents after harvest was in parallel with decreases in the expression of chlorophyll biosynthetic genes (CitGGDR, CitCHLH, CitCHL27, CitPORA, and CitCAO) and an increase in chlorophyll degradation gene CitPPH. The contents of the major carotenoids, β-cryptoxanthin and 9-cis-violaxanthin, were increased by the NAA treatment through upregulation of the expression of carotenoid biosynthetic genes (CitPSY, CitPDS, CitZDS, CitLCYb2, and CitHYb) after harvest. In addition, it was found that the positive effect on degreening in the NAA treatment was inhibited by the ethylene antagonist 1-MCP. In the combination treatment using NAA and 1-MCP, the total chlorophyll content was much higher, while the contents of β-cryptoxanthin and 9-cis-violaxanthin were lower compared with NAA treatment alone, indicating that the acceleration of degreening by NAA may be caused by ethylene. The results presented in this study suggest that postharvest NAA treatment is an effective method for improving the peel coloration in early-season citrus varieties.

Passion fruit (Passiflora edulis) is a tropical fruit that can be consumed fresh or processed. It is a typical respiratory climacteric fruit which is highly perishable because of the loss of water that causes dehydration and thus shrinkage, affecting the fruit appearance; in addition, some quality traits such as fruit weight, firmness and vitamin C content can also be influenced. Therefore, this fruit has a short shelf life. Storage in low temperatures has been assessed to extent the passion fruit shelf life remaining its fruit quality traits; however, information about the application of the hypobaric method in this fruit is null. The objective of this research was to evaluate the physical and chemical characteristics of the yellow and purple passion fruit under hypobaric storage conditions in low temperature. Results showed the hypobaric method had a positive effect in decreasing fruit weight loss, declining the loss of firmness, and reducing the degradation of vitamin C during the storage period. It decreased the evolution of ethylene which is positive to delay fruit senescence, and the production of CO₂. Finally, it was the only method which avoids the shrinkage completely in the purple passion fruits (‘Gulupa’, ‘Summer Queen’, and ‘Ruby Star’) and showed minor shrinkage in ‘POR1’ (yellow passion fruit). This method is considered as a promising technique to improve fruit storage.