Fruit Susceptibility Research Articles

Patulin Mycotoxin in Mango and Orange Fruits, Juices, Pulps, and Jams Marketed in Pakistan.

The objective of the study was to explore the incidence of patulin (PAT) mycotoxin in mango and orange fruits and derived products marketed in Pakistan. A total of 274 samples, including 70 mango fruits, 63 mango-based products (juices, pulp, and jam), 77 orange fruits, and 64 orange-based products, were collected. PAT was determined by reverse-phase high-performance liquid chromatography (HPLC) with UV-Vis detector (276 nm). Linear detector response was observed (R2 > 0.99), the limit of detection (LOD) was 5 µg/kg and recovery percentage was 97.4%. The incidence of PAT in mango samples was 61.7%, and the concentration ranged from <LOD to 6415 µg/kg with a mean of 110.9 µg/kg. Our results showed the high susceptibility of mango fruits to patulin, and it was observed that decayed mango fruits were most contaminated with PAT. Among the mango samples, PAT concentration was higher in fruits than in processed products such as mango juice, pulp, and jam. Toxin incidence in orange samples was 52.5% with concentrations from <LOD to 61 µg/kg and a mean of 6.3 µg/kg. As much as 29 samples of mango (21.8%) contained PAT concentration above the regulatory limit (50 µg/kg), whereas there was only one exceeding orange sample (0.7%). Our results show that PAT seems to be a problem in fruits, juices, and derived solid products, especially from mango, and needs surveillance on regular basis.

Changes in Winter Squash Fruit Exocarp Structure Associated with Age-Related Resistance to Phytophthora capsici.

Phytophthora capsici is a destructive pathogen of cucurbits that causes root, crown, and fruit rot. Winter squash (Cucurbita spp.) production is limited by this pathogen in Michigan and other U.S. growing regions. Age-related resistance (ARR) to P. capsici occurs in C. moschata fruit but is negated by wounding. This study aimed to determine whether structural barriers to infection exist in the intact exocarp of maturing fruit exhibiting ARR. Five C. moschata cultivars were evaluated for resistance to P. capsici 10, 14, 16, 18, and 21 days postpollination (dpp). Scanning electron microscopy imaging of Chieftain butternut fruit exocarp of susceptible fruit at 7 dpp and resistant fruit at 14 and 21 dpp revealed significant increases in cuticle and epidermal thicknesses as fruit aged. P. capsici hyphae penetrated susceptible fruit at 7 dpp directly from the surface or through wounds before 6 h postinoculation (hpi) and completely degraded the fruit cell wall within 48 hpi. Resistant fruit remained unaffected at 14 and 21 dpp. The high correlation between the formation of a thickened cuticle and epidermis in maturing winter squash fruit and resistance to P. capsici indicates the presence of a structural barrier to P. capsici as the fruit matures.

Bruise Damage of Pomegranate during Long-term Cold Storage: Susceptibility to Bruising and Changes in Textural Properties of Fruit

ABSTRACT This study evaluated the bruise susceptibility of pomegranate fruit and textural properties of impact bruised fruit during long-term storage. Pomegranate fruit were stored at 5ºC and 85% relative humidity for 90 d. Impact tests were performed by dropping fruit from three drop heights (20, 40, and 60 cm) onto a flat hard surface to obtain different impact energy levels. The energy absorbed at impact, bruise volume (BV, mm3), bruise area (BA, mm2) and bruise susceptibility (BS, mm3/mJ) of pomegranate fruit were determined at 30 d interval for each impact dropped fruit. Textural properties for whole bruised and control (non-bruised) cold-stored fruit were carried out at 14 d intervals to determine the mechanical strength based on compression, cutting and puncture resistance tests. Based on impact tests, the increase in BV and BA of pomegranate fruit with increased drop heights and duration of cold storage were found significant (p < .05) during the first 2 months of storage and then decreased in the last month of storage time. Pearson correlations indicated a strong linear relationship between the increase in both BV and BA with an increase in impact energy throughout the 90 d storage period. Fruit puncture resistance and whole fruit cutting force, cutting energy and power as well as fruit compression strength properties; firmness, and related textural properties increased with higher impact bruising and prolonged storage. The results obtained in this study demonstrate that long-term storage, indeed, influenced the susceptibility of pomegranate fruit to bruise, and altered fruit texture.

Pesticide residues in strawberry fruits cultivated under integrated pest management and conventional systems in Cundinamarca (Colombia)

Due to the high susceptibility of strawberry fruits to the attack of pests and diseases, a large amount of pesticides is applied during the crop cycle and harvest period. The inadequate use of these substances can generate residuals in agricultural products, which, through intake, pose a risk to human health. The objective of this study was to determine and compare the pesticide residues in strawberry fruits from two different production systems, distributed in the main producing areas of the Cundinamarca Department (Colombia). Eight samples of strawberry crops were collected in four producer municipalities (Guasca, Facatativa, Mosquera and Sibate), two to compare different systems (conventional production vs. production based on the Integrated Pest Management, IPM). Samples at a concentration of 394 molecules were examined by liquid and gas spectrometry. Fisher's exact test was used to determine the association between crop practices and the residual level in fruits. Twenty two different molecules were detected for the samples analyzed, with 37 detection events, of which eight were reported in IPM production systems and 29 in conventional producers. Results revealed a total of two molecules at excessive concentrations after Colombian regulations. Significant differences were found between the two production systems. This is attributable to the producers´ lack of knowledge and understanding about conventional management in Good Agricultural Practices, and the concepts of pesticide restriction period and residuality.

Improving Fruit Coloration, Quality Attributes, and Phenolics Content in ‘Rainier’ and ‘Bing’ Cherries by Gibberellic Acid Combined with Homobrassinolide

The purpose of this work was to evaluate the potential of gibberellic acid (GA3) combined with homobrassinolide (HBR) treatment to improve fruit anthocyanin content, to maintain high-quality properties, to reduce susceptibility to physiological disorders, and to retard the development of bioactive compounds in yellow-fleshed ‘Rainier’ and red-fleshed ‘Bing’ sweet cherries. Application of 1, 5, and 10 mg L−1 HBR once at straw color did not affect anthocyanin accumulation in ‘Rainier’, but 5 or 10 mg L−1 HBR application elevated anthocyanin content in ‘Bing’. No significant differences were observed in fruit size, soluble solids content (SSC), titratable acidity, or surface pitting between the control and HBR treatments in either cultivar after 4 weeks of storage at 0 °C; however, low rates of stem browning and decay were noted in HBR treatments. A single application of GA3 resulted in firmer fruit. Spraying HBR and GA3 to cherries effectively recovered anthocyanin synthesis and increased the levels of phenolics and SSC. Moreover, in combination, these compounds reduced stem browning and pitting development. In conclusion, pre-harvest application of 10 mg L−1 GA3 combined with 5 mg L−1 HBR had a potential to retain the normal skin color development and phenolics synthesis, to increase SSC accumulation, and to reduce fruit susceptibility to disorders in mid-season sweet cherry.

Potential host fruits for Drosophila suzukii: olfactory and oviposition preferences and suitability for development

AbstractDrosophila suzukii (Matsumura) (Diptera: Drosophilidae), the spotted wing drosophila, is a pest endemic to Southeast Asia that invaded the Americas and Europe in 2008. In contrast to most of its congeners, D. suzukii possesses a serrated ovipositor that allows it to lay eggs in unwounded commercial fruits, resulting in severe revenue losses for the industry. The purpose of this study was to determine the susceptibility of known host fruits, including cherry, strawberry, blueberry, and grape, and potential host fruits, such as banana and apple, to attack by D. suzukii. Based on the responses to volatile cues offered in a six‐choice olfactometer, the preference of female D. suzukii was ranked in the following order: strawberry = cherry &gt; banana = apple = blueberry = grape, but in no‐choice and choice oviposition tests, the preferences were ranked as follows: cherry &gt; strawberry = blueberry &gt; grape = banana &gt; apple. Furthermore, we reconfirmed that D. suzukii mainly targets rotten fruit for feeding and ripe fruit for oviposition, and females preferred fruits with intensive mechanical damage. Based on developmental parameters, apple was the least suitable host. This study has implications for the control of D. suzukii, especially in mixed fruit orchards, by providing a promising avenue for exploiting behaviour‐based control tools and emphasizing the importance of phenology in host fruit susceptibility.

Diurnal Harvest Cycle and Sap Composition Affect Under-Skin Browning in 'Honey Gold' Mango Fruit.

Under-skin browning (USB) is an unsightly physiological disorder that afflicts ‘Honey Gold’ mango fruit. Under-skin browning symptoms develop after harvest upon the interaction of physical abrasion and physiological chilling stresses. Less understood preharvest and/or harvest factors may also influence fruit susceptibility to USB. In this study, we examined the impact of harvest time during the diurnal cycle and fruit sap components on USB development. Fruits were harvested at 4- to 6-h intervals, lightly abraded with sandpaper to simulate vibration damage during refrigerated road transport, held at 12 ± 1°C for 6 days, transported to the research facilities and ripened before USB assessment. Spurt and ooze sap from the fruit were collected at each harvest time. The samples were separated and analysed by gas chromatography–mass spectrometry. Fruit harvested at 10:00, 14:00 and 18:00 h had 3- to 5-fold higher incidence of USB than did those picked at 22:00, 2:00 and 6:00 h. Sap concentrations of the key aroma volatile compounds 2-carene, 3-carene, α-terpinene, p-cymene, limonene and α-terpinolene were higher for fruit harvested at 14:00 h compared to those picked at other times. In the fruits harvested in the afternoon, abraded skin treated with spurt sap sampled at 14:00 h had 14.3- and 29.0-fold higher incidence and severity, respectively, of induced browning than did those treated with sap collected at 6:00 h. The results showed that fruit harvested in the afternoon were more susceptible to USB than those picked at night or in early morning. The diurnal variation in fruit sensitivity was evidently associated with specific compositional differences in sap phytotoxicity. Topical application to the fruit skin of pure terpinolene and limonene resulted in induced USB damage, whereas pure carene and distilled water did not. Microscopy examination showed that while skin damage caused by pure terpinolene and limonene was not identical to USB per se, similarities suggested that sap components cause USB under inductive commercial conditions. Considered collectively, these findings suggest that night and early morning harvesting will reduce USB and thus improve the postharvest quality of Honey Gold mango fruit.

Susceptibility of apple fruits (Malus x domestica Borkh.) to the postharvest pathogen Colletotrichum fioriniae: cultivar differences and correlation with fruit ripening characteristics

Colletotrichum spp. infections are an increasing threat to the fruit production industry worldwide, as a postharvest disease. Gaining knowledge on the susceptibility of apple fruit cultivars to Colletotrichum species is essential for specific breeding programs aiming to decrease the disease susceptibility of commercial apple cultivars. We investigated fruit susceptibility of nine apple cultivars at harvest and after storage, and studied the relationship of the susceptibility with fruit ripening characteristics. An accurate artificial inoculation technique, by wounding and injecting the spore suspension, was used to consistently follow-up the relative susceptibility symptoms of fruits. The nine apple cultivars studied, cvs. Pinova, Nicoter, Nicogreen, Golden Delicious, Gala, Elstar, Jonathan, Idared and Topaz, showed clear differences in susceptibility to C. fioriniae, main species causing problems in Europe, based on lesion expansion growth rate data. Cultivar Nicoter and Nicogreen were evaluated as less susceptible cultivars, while cv. Golden Delicious and cv. Pinova were classified as high susceptible cultivars. After three months of storage all fruit cultivars showed a higher susceptibility than at harvest. We further explored the link between fruit ripening characteristics and postharvest pathogen developments. Results showed significant higher Brix, ethylene production and respiration and significantly lower firmness and titratable acids after storage, with the extent of these changes being cultivar dependent. The ripening parameters respiration and Brix had a positive and the firmness a negative correlation with the lesion expansion growth rate of C. fioriniae after artificial wound inoculations. These experiments help to give a better insight in the susceptibility of different cultivars. Moreover, our data support the hypothesis that the extent of the necrotrophic fungal development depends on the fruit ripening stage.

Induced expression of the Fragaria × ananassa Rapid alkalinization factor-33-like gene decreases anthracnose ontogenic resistance of unripe strawberry fruit stages.

SummaryRapid alkalinization factor (RALF) genes encode for ubiquitous small peptides that stimulate apoplastic alkalinization through interaction with malectin‐like receptor kinase. RALF peptides may act as negative regulators of plant immune response, inhibiting the formation of the signal receptor complex for immune activation. Recently RALF homologues were identified in different fungal pathogen genomes contributing to host infection ability. Here, FaRALF‐33‐like gene expression was evaluated in strawberry fruits inoculated with Colletotrichum acutatum, Botrytis cinerea, or Penicillium expansum after 24 and 48 h post‐infection. To investigate the role of FaRALF‐33‐like in strawberry susceptibility, transient transformation was used to overexpress it in white unripe fruits and silence it in red ripe fruits. Agroinfiltrated fruits were inoculated with C. acutatum and expression, and histological analysis of infection were performed. Silencing of FaRALF‐33‐like expression in C. acutatum‐inoculated red fruits led to a delay in fruit colonization by the fungal pathogen, and infected tissues showed less penetrated infective hyphae than in wild‐type fruits. In contrast, C. acutatum‐inoculated white unripe fruits overexpressing the FaRALF‐33‐like gene decreased the ontogenic resistance of these fruits, leading to the appearance of disease symptoms and penetrated subcuticular hyphae, normally absent in white unripe fruits. The different response of transfected strawberry fruits to C. acutatum supports the hypothesis that the FaRALF‐33‐like gene plays an important role in the susceptibility of fruits to the fungal pathogen C. acutatum.

The Survival of Mediterranean Fruit Fly (Diptera: Tephritidae) Over Winter in Western Australia.

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) is one of the most economically important pest insects of fruit crops worldwide. Mediterranean fruit fly can cause up to 100% crop loss in susceptible fruit. In order to formulate best management practices, it is critical to understand how Mediterranean fruit fly overwinters in a given geographical location and bridge the gap between autumn and spring populations. In this study, we evaluated the overwintering potential of Mediterranean fruit fly immature and adult stages in two locations in Perth Hills, Western Australia. We also monitored wild adult Mediterranean fruit fly populations for 2 yr. Adults were present year-round with captures very low in winter to early spring relative to summer and autumn. Field experiments revealed that immature stages in apples (eggs/first instar) and soil (pupae) remained viable in winter, emerging as adults at the onset of warmer weather in spring. In field cages, adults survived 72-110 d, and female laid viable eggs when offered citrus fruit, though only 1-6% eggs survived to emerge as adults. Adults survived longer in field cages when offered live citrus branch. The findings suggest that all Mediterranean fruit fly life stages can survive through mild winter, and surviving adults, eggs in the fruit and/or pupae in the soil are the sources of new population that affect the deciduous fruit crops in Perth. We recommend that Mediterranean fruit fly monitoring is required year-round and control strategies be deployed in spring. Furthermore, we recommend removal of fallen fruit particularly apple and other winter fruit such as citrus.

Assessing Preharvest Field Temperature and At-harvest Fruit Quality for Prediction of Soft Scald Risk of ‘Honeycrisp’ Apple Fruit during Cold Storage

‘Honeycrisp’ apple is susceptible to the postharvest chilling disorder soft scald that renders fruit unmarketable. Reducing or preventing this disorder is an important component of ‘Honeycrisp’ postharvest management. In commercial settings, advanced fruit maturity and orchard history contribute to an estimation of soft scald susceptibility, but additional at-harvest information indicative of soft scald risk would enable better management decisions. In this study, we obtained fruit from commercial orchards for 3 successive years, and assessed field growing degree days (GDD), field chilling hours (CH), and fruit quality metrics at harvest, followed by soft scald incidence assessment at 12 weeks of cold storage. The analyses indicated starch index, soluble solids content (SSC), internal ethylene concentration, titratable acidity (TA), peel background color, firmness, GDD, or CH do not reliably indicate fruit susceptibility to soft scald. However, SSC and TA were elevated in fruit that later developed soft scald, and a higher number of GDD also sometimes preceded soft scald, which is consistent with advanced fruit maturity that can enhance soft scald risk. Overall, results suggest that other tools may be required to accurately predict postharvest soft scald on a quality control laboratory scale. The statistical analyses applied to the present study would have utility for assessing other soft scald prediction tools or markers.

Phenological asynchrony between the fruit fly Anastrepha fraterculus and early maturing peach cultivars could contribute to pesticide use reduction

Phenological asynchrony between fruit crops and pests consists of a discrepancy between the period of fruit susceptibility and that of high pest abundance in the orchards. Therefore, it may be used for reducing pesticide applications. We assayed the potential phenological asynchrony between peach cultivars with different growing cycles and the Anastrepha fraterculus (Diptera: Tephritidae). To this end, we assessed fruit infestation by A. fraterculus at harvest for one growing season (2012-2013) in early, average and late maturing peach cultivars. Moreover, the fruit infestation was checked for non-cultivated native and non-cultivated wild exotic plant hosts around the peach orchards of the experimental area during 2013 and 2014. In addition, we monitored A. fraterculus abundance weekly during three consecutive growing seasons, S1 (2011-2012), S2 (2012-2013) and S3 (2013-2014), to assess phenological asynchrony between peach cultivars and A. fraterculus. In particular, we checked the influence of meteorological variables on A. fraterculus abundance, and tested if A. fraterculus abundance at the time when fruits are susceptible differed among cultivars. Eventually we discuss the possibility of sustainable management of peach in southern Brazil. This study constitutes a first assessment of the periods of crop vulnerability and pest presence in peach orchards in South of Brazil and provides necessary information for taking advantage of the phenological asynchrony phenomenon for this pest-crop association.

Investigating the involvement of ABA, ABA catabolites and cytokinins in the susceptibility of 'Nules Clementine' mandarin to rind breakdown disorder.

'Nules Clementine' mandarin was used to investigate the potential involvement of endogenous plant hormones in mediating citrus fruit susceptibility to rind breakdown disorder (RBD). The effect of light exposure (namely canopy position and bagging treatments) on the endogenous concentration of ABA, 7'-hydroxy-abscisic acid (7-OH-ABA), ABA-glucose ester (ABA-GE) and dihydrophaseic acid (DPA), and t-zeatin was tested using four preharvest treatments: outside, outside bagged, inside and inside bagged. Phytohormones concentration was evaluated during nine weeks of postharvest storage at 8°C. The shaded fruit inside the canopy had the highest RBD score (0.88) at the end of postharvest storage, while sun-exposed fruit had the lowest score (0.12). Before storage, ABA concentration was lowest (462.8µg kg-1 ) for inside fruit, and highest in outside bagged fruit (680.5µg kg-1 ). Although ABA concentration suddenly increased from the third week, reaching a maximum concentration of 580 µg kg-1 at week 6 in fruit from inside position, it generally reduced 1.6-fold ranging from 240.52 to 480.65 µg kg-1 throughout storage. The increase of 7-OH-ABA was more prominent in fruit from inside canopy. Overall, the concentration of ABA-GE increased three-fold with storage time. DPA concentration of bagged fruit from inside canopy position was significantly higher compared to outside fruit. The lower ABA-GE and higher DPA concentration in inside bagged fruit throughout storage also coincided with higher RBD. The strong positive correlations between 7-OH-ABA, DPA and RBD incidence demonstrated that these ABA catabolites could be used as biomarkers for fruit susceptibility to the disorder. © 2019 Society of Chemical Industry.

Depression of Fungal Polygalacturonase Activity in Solanum lycopersicum Contributes to Antagonistic Yeast-Mediated Fruit Immunity to Botrytis.

The acquisition of susceptibility to necrotrophy over the course of ripening is one of the critical factors limiting shelf life. In this study, phytopathology and molecular biology were employed to explore the roles of pectinase in fruit susceptibility and ripening. Solanum lycopersicum fruit softened dramatically from entirely green to 50% red, which was accompanied by a continuously high expressed SlPG2 gene. The necrotrophic fungus Botrytis cinerea further activated the expression of SlPGs and SlPMEs to accelerate cell wall disassembly, while most of the polygalacturonase inhibitor proteins encoding genes expression were postponed in ripe fruit following the pathogen attack. Pectin induced the antagonistic yeast to secrete pectinolytic enzymes to increase fruit resistance against gray mold. The activities of pathogenic pectinase of B. cinerea were correspondingly depressed in the pectin-inducible yeast enzyme elicited ripe fruit. These data suggest that pectinase is a molecular target for regulation of disease resistance during fruit ripening.

Cytokinin treatment modifies litchi fruit pericarp anatomy leading to reduced susceptibility to post-harvest pericarp browning

Litchi (Litchi chinensis Sonn.) is a subtropical fruit known for its attractive red pericarp color, semi-translucent white aril and unique flavor and aroma. Rapid post-harvest pericarp browning strictly limits litchi fruit marketing. In the current research, we hypothesized that modification of litchi fruit pericarp anatomy by hormone application may reduce fruit susceptibility to post-harvest pericarp browning. In this context, we hypothesized that cytokinin treatment, known to induce cell division, may yield fruit with thicker pericarp and reduced susceptibility for fruit surface micro-crack formation, water loss and post-harvest pericarp browning. Exogenous cytokinin treatment was applied at different stages along the course of litchi fruit development and the effect on fruit pericarp anatomy, fruit maturation and postharvest pericarp browning was investigated. Interestingly, cytokinin treatment, applied 4 weeks after full female bloom (WFB), during the phase of pericarp cell division, led to mature fruit with thicker pericarp, reduced rate of post-harvest water loss and reduced susceptibility to post-harvest pericarp browning, as compared to non-treated control fruit. Histological sections ascribe the difference in pericarp anatomy to increased cell proliferation in the parenchymatic tissue and the highly-lignified brachysclereid cell layer. In contrast, exogenous cytokinin treatment applied 7 WFB, following the phase of pericarp cell division, significantly increased epidermal-cell proliferation but had no significant effect on overall fruit pericarp thickness and only minor affect on post-harvest water loss or pericarp browning. Interestingly, the late cytokinin treatment also significantly postponed fruit maturation-associated anthocyanin accumulation and chlorophyll degradation, as previously reported, but had no effect on other parameters of fruit maturation, like total soluble sugars and total titratable acids typically modified during aril maturation. In conclusion, exogenous cytokinin treatment at different stages in fruit development differentially modifies litchi fruit pericarp anatomy by induction of cell-type specific cell proliferation. Early cytokinin treatment during the phase of pericarp cell division may prolong litchi fruit storage by reducing fruit susceptibility to post-harvest water loss and pericarp browning.

Prevalence of mistletoes in fruit and timber trees in the wet and intermediate zone of Sri Lanka

A survey was conducted to identify the parasitic plant species occurring in timber and fruit trees during November 2015 to April 2017, in 15 Districts of Wet and Intermediate Zones of Sri Lanka using two stage stratified random sampling scheme. The parasitic plants on fruit and timber trees were identified by comparing them with the specimen in National Herbarium, Peradeniya. Host plant species were taxonomically identified after consultation of botanical experts and using species identification keys. Correlation between parameters were made using SAS software. Mistletoes infested in varying degrees in 27 perennial fruit and 20 timber tree species in different cropping systems. Dendrophthoe falcata, D. neilgherrensis, Scurrulla cordifolia, Viscum articulatum, Taxillus incanus, and V. orientale were the mistletoes species infested in fruit trees; whereas, D. falcata, D. neilgherrensis, S. cordifolia, S. parasitica, V. articulatum and V. orientale were found in timber species. D. falcata was the most predominent parasitic plant in both fruit and timber trees. Mangifera indica and Albizia odoratissima were the most susceptible host fruit and timber species, respectively. The study indicated that further studies are required on the increased occurrence of parasitic plants, their effects on host plants and development of control measures.

High Humidity and Age-Dependent Fruit Susceptibility Promote Development of Trichothecium Black Spot on Apple.

Fruit bagging is a widely used orchard practice in China. Trichothecium black spot (TBS) is a disease highly associated with the fruit bagging. In this study, we characterized in vitro factors affecting the causal agent, Trichothecium roseum, and TBS development and infection histology on field-bagged apple fruit in situ. Under in vitro conditions, conidial germination required exogenous nutrients, and the germination rate was significantly promoted by high humidity, a condition mimicking the bag microenvironment. Germ tubes penetrated fruit via natural openings including stomata, lenticels, and surface cracks. To determine the chronology of infection by T. roseum, 'Fuji' fruit were inoculated in the field at different developmental stages. The earliest infection occurred 60 days after full bloom (dafb), and disease incidence increased as fruit maturity advanced. At harvest time (165 dafb), lesions on more recently inoculated fruit (105 dafb, 150 dafb) were larger than lesions from fruit inoculated on earlier dates. Histological observation showed that infection of younger fruit elicited stronger host lignification responses restricting lesion development. Taken together, our results support the hypothesis that high humidity in sealed bags and increased susceptibility associated with advancing fruit maturity are key factors promoting T. roseum infection and TBS symptom development on bagged apple fruit.

24-Epibrassinolide Mechanisms Regulating Blossom-End Rot Development in Tomato Fruit

Blossom-end rot (BER) is a physiological disorder believed to be triggered by low Ca2+ content in the distal fruit tissue. However, many other factors can also determine fruit susceptibility to BER. It is possible that during fruit growth, Ca2+ imbalance can increase membrane leakiness, which may trigger the accumulation of reactive oxygen species, leading to cell death. Brassinosteroids are a class of plant hormones involved in stress defenses, specially increasing the activity of antioxidant enzymes and the accumulation of antioxidant compounds, such as ascorbic acid. The objective of this study was to understand the mechanisms by which 24-epibrassinolide (EBL) reduces fruit susceptibility to BER. Tomato plants ‘BRS Montese’ were cultivated in a greenhouse and were weekly sprayed with water (control) or EBL (0.01 µM) after full bloom. Plants and fruits were evaluated at 15 days after pollination (DAP). According to the results, EBL treatment inhibited BER development, increased fruit diameter, length, and fresh weight. EBL-treated fruit showed higher concentrations of soluble Ca2+ and lower concentrations of cell wall-bound Ca2+. EBL-treated fruit also had higher concentrations of ascorbic acid and lower concentrations of hydrogen peroxide, compared to water-treated fruit. EBL treatment increased the activity of the three main antioxidant enzymes known as ascorbate peroxidase, catalase, and superoxide dismutase. According to the results, EBL treatment maintained higher soluble Ca2+ and antioxidant capacity, reducing fruit susceptibility to BER.

Effect of hot water treatment on chilling injury incidence and antioxidative responses of mature green mume (Prunus mume) fruit during low temperature storage

Mume (Prunus mume Sieb. et Zucc.) fruit are harvested and consumed at the mature green stage and have a short storage life at ambient temperature. The current handling and storage temperatures, below 6 °C, extend the storage life to a week, but chilling injury (CI) occurs after a longer storage. A pre-storage hot water treatment, dipping ‘Nankou’ fruit in 45 °C water for 5 min, substantially reduced susceptibility of fruit to CI at 6 °C storage, and extended storage life for three-fold. This research was conducted to reveal the antioxidantive responses of fruit to pre-heat treatment and chilling storage. Hot water treatment inhibited the increases in malondialdehyde and hydrogen peroxide levels, and delayed the decreases in ascorbate contents and total antioxidant capacity levels compared with the control fruit during storage. The activities of antioxidant-related enzymes including ascorbate peroxidase and monodehydroascorbate reductase were higher in hot water treated fruit than in the control fruit during cold storage. These results indicate that the alleviation of CI in mature green fruit by hot water treatment might be due to the protection and enhancement of the antioxidant system by increased activity of related enzymes.

Incidence of blossom-end rot in elongated tomato fruit

Blossom-end rot (BER) is a physiological disorder that can affect 100% of the fruit crop depending on the genotype. Tomato varieties with elongated fruit usually have a greater susceptibility to BER than other varieties. To evaluate and identify the possible physiological and morphological characteristics related to the onset of BER development, four varieties of long-shape tomato fruit with different susceptibility to BER: ‘San Marzano,’ ‘Banana Legs,’ ‘Roma,’ and ‘Mini-Roma’ were examined. Our results show that ‘San Marzano’ and ‘Banana Legs’ (elongated fruit) had a higher incidence of BER and lower Ca2+ concentration in the distal fruit tissue. ‘San Marzano’ (the most elongated fruit) presented higher electrolyte leakage in the distal fruit tissue. By comparison, ‘Roma’ and ‘Mini-Roma’ (less elongated fruit) were less susceptible to BER and had a higher ratio for proximal/distal fruit Ca2+ and a lower distal cell-wall bound content of Ca2+. Additionally, xylem functionality (vessels transporting water and solutes) in the distal fruit tissue was also higher in these more-tolerant varieties. These results support the theory that total fruit content of Ca2+ is not the only factor determining fruit susceptibility to BER, but rather a balance between physiological and morphological factors that influence Ca2+ transport and allocation in the fruit.