Fruit Susceptibility Research Articles

Fungitoxic role of endogenous eugenol in the hybrid grapevine cultivar Baco blanc resistant to <i>Botrytis cinerea</i>

Eugenol (2-methoxy-4-(2-propenyl)-phenol), widely spread in various plants, notably clove, basil and bay, is a well-known antifungal and antibiotic molecule that is abundant in the hybrid grapevine cultivar Baco blanc (Vitis vinifera × Vitis riparia × Vitis labrusca). This variety, created by François Baco (19th century), is confirmed in this study as highly resistant to Botrytis cinerea by comparing fruit rot incidence and severity with two Vitis vinifera cultivars: Folle Blanche and Ugni Blanc. According to two major antibiosis modes of action, i.e., direct or volatile, this study demonstrated the efficiency of eugenol in vitro by also investigating precisely the effect on B. cinerea of small concentrations of eugenol, 3 to 4 ppm, corresponding to IC10. Moreover, the vapour-inhibiting effect was shown to be highly powerful. The total eugenol concentration peaked at the veraison stage, exceeding 1000 μg×kg-1 in the skin of Baco blanc berry under our conditions. At this point, leaf removal in the bunch zone induced a significant increase in eugenol (32 %), from 1118 to 1478 μg×kg-1, which was also associated with a significant decrease in B. cinerea infection in the vineyard. Thus, for the first time, eugenol, as an endogenous molecule of Baco blanc, was clearly demonstrated to be an inducible compound in the vineyard. Furthermore, significant intravarietal variability in eugenol concentrations according to the Baco blanc clone was demonstrated to be associated with significant differences in fruit susceptibility to the plant pathogen assessed in biotests. Interestingly, in keeping with fruit ontogenic resistance, a significant negative correlation was established between the technological maturity of berries and the total eugenol content in the berry skin. Finally, the time-progress study of the two biochemical forms of eugenol (bound vs. free eugenol) allowed us to hypothesise the effectiveness against the plant pathogen of some precursor forms of eugenol, and the corresponding biochemical structures are currently being investigated. Thus, eugenol appears to be a key biochemical marker of ontogenic resistance in the hybrid cultivar Baco blanc.

Open field trials of food-grade gum in California and Oregon as a behavioral control for Drosophila suzukii Matsumura (Diptera: Drosophilidae).

The invasion of Drosophila suzukii, spotted-wing drosophila, across Europe and the US has led to economic losses for berry and cherry growers, and increased insecticide applications to protect fruit from damage. Commercial production relies heavily on unsustainable use of conventional toxic insecticides. Non-toxic insecticide strategies are necessary to alleviate the disadvantages and non-target impacts of toxic conventional insecticides and improve Integrated Pest Management (IPM). A novel food-grade gum deployed on dispenser pads (GUM dispensers) was evaluated to mitigate D. suzukii crop damage in five commercial crops and nine locations. Trials were conducted at a rate of 124 dispensers per hectare in cherry, wine grape, blueberry, raspberry, and blackberry in California and Oregon, USA during 2019 and 2020. The majority of trials with the food-grade gum resulted in a reduction of D. suzukii egg laying in susceptible fruit. In some cases, such damage was reduced by up to 78%. Overall, results from our meta-analysis showed highly significant differences between GUM treatments and the untreated control. Modeling simulations suggest a synergistic reduction of D. suzukii damage when used in combination with Spinosad (Entrust SC) insecticide. These data illustrate commercial value of this tool as a sustainable alternative to manage D. suzukii populations within a systems approach.

Xylem Functionality Is Not a Direct Indicator of Apple Preharvest Fruit Drop

Apple (Malus ×domestica) growers can incur significant economic losses when fruit drop before they can be harvested [preharvest fruit drop (PFD)]. In some years and cultivars, more than 30% of potential yield can be lost. Growers frequently apply plant bioregulators to reduce PFD, either via delay in maturity [aminoethoxyvinylglycine (AVG), 1-methylcycolpropene] or via inhibition in production of cell hydrolysis enzymes in the fruit pedicel [naphthalene acetic acid (NAA)]. Finding a physiological indicator of PFD would allow growers to assess the susceptibility of fruit to PFD. Due to its lignification, xylem is believed to be the last tissue to break down in the fruit pedicel, leading to PFD. To determine whether loss in xylem functionality can be used as an indicator of PFD potential, studies were conducted in 2020 and 2021 with ‘Red Delicious’ treated with AVG (132 µL·L−1), NAA (10 µL·L−1), and an ethylene-producing compound [ethephon (150 µL·L−1 in 2020, 200 µL·L−1 in 2021)] to generate a range of PFD potentials. Xylem functionality was assessed in the fruit cortex. Internal ethylene content (IEC), fruit maturity indices, and PFD rates were quantified weekly throughout the harvest period. Expression of genes encoding for cell hydrolysis enzymes (MdEG1 and MdPG2) was quantified to relate xylem functionality to fruit abscission mechanisms. In 2020 and 2021, AVG reduced PFD compared with the untreated control by decreasing IEC. Although ethephon did not result in higher PFD than untreated fruit, NAA reduced PFD in 2020 but not 2021. For all treatments in both years, there was a linear decrease in xylem functionality throughout the measurement period. Cumulative PFD exponentially decreased as xylem functionality neared zero and the climacteric rise in ethylene began. Concurrent with the rise in IEC and PFD was an increase in the expression of MdEG1 and MdPG2 in the fruit pedicel of the control compared with AVG-treated fruit. AVG-treated fruit lost xylem functionality at a similar rate to the untreated control but had lower expression of MdEG1 and MdPG2. These results indicate that xylem functionality is not a sole direct indicator of PFD. The concurrent increase in PFD and expression of MdEG1/MdPG2 supports previous research indicating that these two genes may serve as potential markers for PFD.

Influence of Fruit Wounding on Subsequent Monilinia laxa Infection of Nectarines

Despite the fact that brown rot is the most economically important disease in stone fruits, the relationship between mechanical stress and infection has never been explored. Thus, to explore this connection, we carried out four experiments linking nectarine wounding and M. laxa infection. First, we evaluated a possible systemic reaction of the fruit to wounding that could impact the M. laxa infection. Afterward, we study the impact of the fruit in the environment on M. laxa colonies grown in vitro. Subsequently, we tested the disease susceptibility of fruits inoculated with M. laxa placed in the same environment as wounded fruits. Finally, in the fourth experiment, the effect of wounding on the subsequent fruit infections was evaluated at three fruit stages. As a result, we observed that there was no evidence of a fruit systemic reaction to wounding and M. laxa infection. In the study related to the impact of the fruit in the environment of M. laxa, the findings suggest that M. laxa “perceived” the fruit’s presence, resulting in accelerated in vitro growth. Moreover, the presence of wounded fruits in the box increased the susceptibility to brown rot. Inoculated fruits showed a delayed and reduced infection 7 h after being wounded, during the second stage of fruit development (15–19 weeks after full bloom). Moreover, a red reaction associated with inoculation was detected immediately after the fruits were wounded. Nine phenolic compounds exclusively related to the red areas were extracted, while six other compounds were present in higher proportions. These compounds may be actively involved in plant–pathogen interactions and the activation of metabolic pathways involved in nectarine susceptibility/resistance to M. laxa.

Colletotrichum infections during flower development and fruit ripening in four olive cultivars

Olive anthracnose, caused by Colletotrichum, is an important disease in olive-growing regions, with the most destructive symptoms being fruit rot and blossom blight. Susceptibility of fruit to Colletotrichum increases with maturity, but differences between cultivars and Colletotrichum species have been reported, still information on flower susceptibility during development is scarce. The susceptibility of the olive cultivars Arbequina, Coratina, Frantoio and Picual was evaluated during flower development and fruit maturity to Colletotrichum acutatum s.s., C. nymphaeae, C. fioriniae, C. theobromicola and C. alienum. Susceptibility to anthracnose begins in early stages during flower development and increases during blossoming. Flowers of Arbequina, Coratina and Picual were susceptible, whereas those of Frantoio were moderately susceptible. Green fruit developed less anthracnose than mature fruit. At the green fruit stage, Arbequina and Frantoio were the most susceptible, Coratina was intermediate, and Picual was moderately susceptible, while no differences were found among the cultivars at mature fruit stages. No mayor differences were found among the Colletotrichum species with exception of C. theobromicola, which caused greatest severity at the green fruit stage. Future research should focus on developing anthracnose management strategies to minimize the disease progress from early stages of flower development and fruit ripening, especially in the most susceptible olive cultivars.

Identification of volatile compounds from fruits aroma and citrus essential oils and their effect on oviposition of Ceratitis capitata (Diptera: Tephritidae).

Ceratitis capitata (Wiedemann), also known as the Mediterranean fruit fly, is one of the most serious pests for several fresh fruit commodities causing extensive fruit losses worldwide. The response of C. capitata adults to fruit and nonfruit volatiles has been extensively studied. However, the linkage between fruit volatiles and the female ovipositional choice has not been fully elucidated. The present study focused on identifying the volatile organic compounds emitted by detached intact fresh fruits (oranges, lemons, bergamots, and apples) and citrus essential oils and evaluate their effect on Mediterranean fruit fly oviposition. There were more than 130 and 45 volatiles compounds detected in fruits odors and citrus essential oils, respectively. The volatile profile of fruits was dominated either from terpenes and terpenoids or from esters of butanoic, hexanoic, and octanoic acids while limonene was by far the most abundant compound in all citrus essential oils. Oviposition of C. capitata was strongly affected by volatiles emanated from both intact fruit and the citrus essential oils. Regarding the volatiles of the intact fruits, the odor of sweet orange elicited strong oviposition responses to females, while bergamot had the least stimulatory effect on oviposition. Bergamot oil also elicited the least oviposition stimulation compared to sweet orange and lemon essential oils. Our discussion elaborates on the role of fruit volatiles on host finding behavior and fruit susceptibility to C. capitata infestation and includes possible practical implication of the above findings.

Investigation of pectolytic and PR genes expression, quality and phytochemical contents in organic and non-organic table grapes at harvest and during storage

The demand for organic table grapes is increasing worldwide. However, comprehensive information of quality parameters and phytochemical compounds in organically grown fruit remain unclear. Furthermore, table grapes are perishable and postharvest quality retention and waste prevention is very important. In this study we have compared the differences between organic and non-organic table grapes in terms of phytochemical compounds and quality parameters as well as the changes in the expression levels of pathogen related and lytic genes during storage. Organic fruit showed higher levels of phenolics, flavonoids, caffeic acid, hydrogen peroxide, protein content, antioxidant and anti-stress enzymes and total antioxidant activities at harvest and during storage. Although, the expression levels of polygalactronases, pectin methyl esterase, chitinase and glucanase genes was lower in organically grown table grapes at harvest, but the expression of all these genes was significantly increased during cold storage. After 60 days of cold storage the expression levels of pectin methyl esterase, chitinase and glucanase genes was significantly higher than the conventionally grown grape berries in organic ones. The highest expression of polygalacturonase was recorded in organic samples after 30 days of storage. There was no significant difference between the two types of table grapes for decay extension and tissue deterioration rate. The results of this study indicate that due to higher levels of phytochemicals and antioxidant compounds the organic table grapes have a higher nutritional quality. Furthermore, the increase in PR and pectolytic genes expression levels is enough for decreasing the fruit susceptibility to decay pathogens and enhancing the postharvest life of organic grapes.

Differences in Lipid Metabolism, Polar Metabolites, and Phenolics in Persea americana under Two Storage Conditions

Harvested avocado fruits can be potentially exposed both to pre- and post-harvest factors that may influence the susceptibility of fruit to quality loss. Regular air (RA) storage consists of approximately 78% nitrogen, 21% oxygen, 0.3% carbon dioxide, and smaller amounts of some other gasses. A controlled atmosphere (CA) is a changed atmosphere that is used to delay respiration and reduce fungal and physiological deterioration, and it is an appropriate and practical technology for prolonging the shelf life and maintaining the quality of fruits on a large scale. An experiment was conducted by collecting fruits from two different avocado orchards (Bartolillo and Quilhuica) during two harvest seasons based on dry matter content and two subsequent years. The current study was designed to investigate the changes in polar metabolites, phenolic compounds, and fatty acids in the skin of Hass avocados stored under two distinct conditions. Bartolillo orchard fruits were mostly correlated to linoleic and oleic acid as important variables. For Quilhuica, fruits were mostly correlated with palmitoleic, palmitic, and oleic acids. Phenolic content increased at the beginning of storage and decreased at the end of storage for one orchard and contrarily for others, indicating that the result was dependent on the orchard and storage condition. Serine, glutaric acid, xylitol and D-mannitol were the polar metabolites that most correlated with fruits of the Quilhuica orchard while ß-sitosterol and gluconic were related to fruits of the Bartolillo orchard. The differences in fatty acids, polar metabolites and phenolics were dependent on orchard and storage conditions.

Validation of a Warning System to Control Brown Rot in Peach and Nectarine

Monilinia spp. is the main pathogen that affects stone fruit, causing significant production losses, especially in seasons with favorable climatic conditions for disease development. Currently, the standard practices for controlling this disease are by means of spray programs of synthetic fungicides. Fungicide applications using treatment schedules imply an increase in the number of applications; however, the applications are justified considering the real risk of Monilinia spp. infection. Consequently, fruit surface contains a higher number and concentration of residues, but not better control of the disease. From previous studies, the epidemiology of Monilinia spp. was deeply studied in one of the main stone fruit regions of Europe, the ‘Valle del Ebro’, and an epidemiological model was developed to describe the brown rot epidemic pattern in this area. After that, a warning system for fungicide applications in the field was elaborated that included the main factors to be considered as fruit susceptibility, the presence of inoculum in the field, and climatological factors (temperature, leaf wetness, rainfall, or their interaction). In the present study, we present data of the warning system validation during six seasons in 38 fields of peaches and nectarines of the ‘Valle del Ebro’. The results indicated that the incidence of disease caused by Monilinia spp., recorded in the field and postharvest, was similar in both plot evaluations and the calendar and warning systems. However, the disease level was higher in late varieties (3.2% and 9.3% of infected fruit recorded in the field and in postharvest, respectively) in comparison with earlier varieties (0.6% and 3.1% of infected fruit recorded in the field and in postharvest, respectively). In general, the strategy applied (the calendar or warning system) did not affect the disease level recorded. However, when fungicide treatments were applied following the warning system, the treatment reductions were higher than 50% in 96% of the trials in early varieties; meanwhile, in late varieties, this level of reduction was obtained in 77% of trials. Our data encourage the use of the proposed warning system as an effective strategy to control Monilinia spp. in peaches and nectarines, reducing the number of chemical treatments applied in the field with a high level of efficacy.

Radiação e condições de temperatura pré colheita determinam a suscetibilidade dos frutos do tomate a danos causados pelo frio pós-colheita

ABSTRACT The aim of this work was to improve the understanding about the relationship between solar radiation and temperature exposure during crop and tomato fruit susceptibility to postharvest chilling injury. Two preharvest treatments were applied: direct sunlight exposed plants (Ex) and shaded plants (Sh). After harvest, fruit were stored at 10⁰C and 4⁰C for ten days. Then, fruit were removed from the chambers and stored at room temperature for four days. Several determinations were carried out: total mineral and calcium content, fruit quality and postharvest parameters, ions leakage and thiobarbituric acid reactive species content and chilling injury index (CII). Ex fruit had higher values of chilling injury index than the Sh fruit, and at the same time, fruit under 4⁰C storage treatment presented a more marked damage than those stored at 10⁰C, demonstrating that accumulated radiation in the field, as a result of a higher solar radiation exposure, is a critical factor affecting postharvest chilling injury susceptibility. The lower calcium content in the Ex fruit could be one of the causes of their response to chilling.

Fruit susceptibility and critical period for protection of Persian lime against citrus canker with copper sprays

Fruit susceptibility and critical period for protection of Persian lime against citrus canker with copper sprays

Analysis of the collision-damage susceptibility of sweet cherry related to environment temperature: A numerical simulating method

Sweet cherry is extremely susceptible to collision damage during post-harvest handling. Fruit-to-rigid surface and fruit-to-fruit collision systems were modeled by the dynamic FE method and the sweet cherry model included three parts: exocarp, mesocarp, and pit. A fruit-to-rigid surface horizontal collision testbed was newly developed to validate the prediction accuracy of the fruit FE model. It was found that the fruit model inputting the average elastic moduli and failure stress of the fruit tissues can reproduce the experimental maximum impact force and contact time in the compression stage with the relative error of 1.58 and 1.87%, respectively. Three mathematical models were proven to be capable of quantitatively assessing the internal damage degree of sweet cherry by three independent variables: collision type, initial fruit velocity, and environment temperature. This study shows an effective numerical simulation approach for objectively predicting the horizontal collision-damage susceptibility of sweet cherry and other fresh fruit in postharvest damage-prevention strategy analysis. • • Fruit FE model can reproduce two collision experimental mechanical parameters. • • Fruit damage volume increased nonlinearly with the collision contact time. • • The velocity change of the local tissue in fruit during collision was presented. • • The degree of fruit collision damage can be predicted by the obtained models. • • Collision type was the most key factor affecting the fruit damage susceptibility.

Xylem functionality controlling blossom-end rot incidence in transgenic ALC::NCED tomato plants

Fruit susceptibility to the physiological disorder known as blossom-end rot (BER) is an important limitation in tomato production. Abscisic acid (ABA) is known to reduce leaf transpiration, which can enhance plant water use efficiency (WUE), as well as increase fruit xylem functionality, Ca2+ uptake and oxidative stress defenses, which has been suggested to reduce BER incidence. However, the role of ABA on most of these factors determining fruit susceptibility to BER remains poorly understood. ABA production is mainly regulated by the expression of 9-cis-epoxycarotenoid dioxygenase (NCED) genes. Manipulation of NCED gene expression by the alcohol inducible promoter (ALC) could be an alternative approach to stimulate ABA production and its beneficial effects on inhibiting BER incidence. The objectives of this study were to use ALC::NCED transgenic tomato plants to decrease BER incidence and investigate which mechanisms were involved in BER. In this study, two transgenic tomato lines (1 and 2) were developed with the ALC::NCED construct. This construct allows the inducible activation of the ALC promoter by treating the plants with ethanol vapor that drives NCED expression and ABA synthesis. According to the results, after full bloom, weekly spraying transgenic plants with ethanol (2%) decreased BER incidence in both transgenic lines, compared to the wild type ‘New Yorker’ plants. The transgenic line 1 had higher NCED expression in response to ethanol than the transgenic line 2 and wild type ‘New Yorker’. At 15 and 30 days after pollination, transgenic lines 1 and 2 had higher number of functional xylem vessels which helped to increase Ca2+ concentration in the distal end of the fruit, compared to the wild type fruit. In response to higher NCED expression, WUE and antioxidant content in leaves and fruit were higher in both transgenic lines, compared to the wild type, helping to explain the lower BER incidence. Therefore, our study shows that stimulating NCED expression with an inducible system increases the number of functional xylems and Ca2+ uptake into the fruit, improving plant WUE and reducing BER incidence.

Susceptibility of apple fruits from selected cultivars to the Colletotrichum acutatum species complex

The pathogenicity of five isolates of Colletotrichum acutatum species complex (CASC) was tested on artificially injured apple fruits of the cultivar ‘Golden Delicious’ under laboratory conditions. Then, ten apple cultivars were tested for their relative susceptibility to CASC. Differences in the pathogenicity of the CASC isolates were confirmed in the test. The highest degree of pathogenicity was showed by the isolates from the strawberry and DCSBPM J1 from the apple. No cultivars were resistant to the pathogen. The disease incidence ranged from 57.5% to 100%. The individual cultivars showed different susceptibility to the tested isolates. The cultivars ‘Braeburn’, ‘Jonagold’ and ‘Rubinola’ showed the least susceptibility to the pathogen, while the cultivars ‘Jonagored’ and ‘Otava’ were recorded as the most susceptible to CASC. All the tested isolates were confirmed, by the conventional PCR method, to belong to CASC. The sequences of isolates DCSBPM J1 and DCSBPM 1209 were deposited in the GenBank.

Genetic variability in the susceptibility of immature peach fruit to Monilinia laxa is associated with surface conductance but not stomatal density

Monilinia laxa is a fungus that causes brown rot in stone fruit. Immature green fruits in the first stage of fruit development (stage I) are generally susceptible. To investigate the relationship between the physical characteristics of immature fruit and susceptibility to M. laxa, we characterized the progeny, derived from a clone of wild peach (Prunus davidiana) crossed with two commercial nectarines (Prunus persica) varieties, through laboratory infection, transpiration monitoring and stomata counting. Two types of fruit infections were observed - ‘classic’ brown rot and ‘clear spot’ symptoms - which have not previously been described in the literature. The number and density of stomata did not explain the observed variability of infection in the progeny. However, surface conductance was positively correlated with infection level. This study provides experimental evidence partially linking physical fruit characteristics to brown rot infection at the immature fruit stage. The role of delayed cuticle deposition in susceptibility to brown rot of immature fruit is discussed.

1-Methylcyclopropene differentially regulates metabolic responses in the stem-end and calyx-end flesh tissues of ‘Empire’ apple during long-term controlled atmosphere storage

Firm flesh browning, a postharvest disorder of ‘Empire’ apples, can develop during controlled atmosphere (CA) storage. The disorder is initiated in tissues at the stem-end tissue and progressively develops through the calyx-end region of fruit. The susceptibility of fruit to the disorder can be provoked by the application of 1-methylcyclopropene (1-MCP) prior to storage. To gain a better understanding of the metabolic changes associated with disorder development, we coupled metabolic profiling with measures of flesh tissue color in partial least squares-discriminant analysis (PLS-DA) to determine changes in metabolic profile occurring in stem and calyx tissues of untreated and 1-MCP treated fruit during CA storage. Flesh tissues were less light (L*) in the stem-end tissues than in the calyx-end tissues and to a greater extent in 1-MCP treated than untreated fruit. Reduction in L* in 1-MCP treated fruit corresponded to metabolic divergence between stem-end and calyx-end tissues. Furthermore, tissues of 1-MCP treated fruit had lower levels of volatile aromatic compounds (VACs), but less so in the stem-end tissues than in the calyx-end tissues. The levels of most amino acids and VACs were higher in the stem-end tissues of 1-MCP treated fruit than in untreated fruit. Of the VACs, methanol, acetaldehyde and ethanol concentrations were much greater in the stem-end tissues than in the calyx-end tissues of untreated fruit but reduced by 1-MCP treatment, irrespective of tissues. In summary, metabolic profiling indicates that 1-MCP treatment induces greater physiological changes in the stem-end tissues than in the calyx-end ones under hypoxic storage condition. While the underlying metabolic processes that result in firm flesh browning remain to be elucidated, the accumulation of small molecule compounds, such as amino acids, in the stem-end tissues suggests that 1-MCP affects ethylene related pathways in this region to a greater extent, and may be associated with higher incidence of flesh browning during long-term CA storage.

Emission of volatile organic compounds during nectarine-Monilinia laxa interaction and its relationship with fruit susceptibility to brown rot

Fruit volatile organic compounds (VOCs) can be emitted by stone fruit in response to biotic stress. One of the main fungal diseases of stone fruit is brown rot, caused by species of Monilinia spp. Hence, we aimed to reveal the most relevant VOCs that participate either in resistance or susceptibility to Monilinia laxa in nectarines. To this aim, we analyzed the VOCs emitted by two developmental stages (immature, one month before harvest; mature, commercial harvest) of two nectarine cultivars, with different susceptibility to M. laxa. Furthermore, we also determined the VOCs profile of M. laxa grown in in vitro culture media based on peach juice. Results elucidated 34 VOCs whose production pattern was different among samples (control and inoculated of both stages and cultivars), being 13 VOCs also emitted by M. laxa culture. A hierarchical analysis and a multivariate analysis exhibited the variations in the VOCs profile of all samples according to their susceptibility to M. laxa, and the suitability of the model to predict the M. laxa disease (91.94% of the total variation). In general, results highlighted i) a group of VOCs, positively correlated with M. laxa disease, that were emitted by visual M. laxa symptomatic tissues (e.g., aldehyde (E,E)− 2,6-nonadienal) and also by M. laxa itself (e.g., terpenoids alpha-muurolene and (E)-beta-ionone), and ii) a group of VOCs, negatively correlated with brown rot disease, that were emitted by tissues with no visual M. laxa symptoms (e.g., ketone butyrolactone and aldehyde (E)− 2-decenal) and also by M. laxa itself (e.g., aldehyde decanal), suggesting an antifungal role of these compounds. Therefore, this study provides putative potential VOCs that not only will help to improve the knowledge of brown rot development on nectarines, but also provides target volatiles that may serve as potential brown rot control compounds.

Involvement of ethylene in glutamate-mediated tomato fruit resistance to Alternaria alternata

Recent progress showed the potential of glutamate to regulate stress responses by affecting phytohormones homeostasis, but much remains to be explored. To decipher the role of ethylene in glutamate-induced resistance to Alternaria alternata, ethephon application, ethylene perception inhibitor (1-MCP) experiment and ethylene measurement were pursued. Concurrently, temporal alteration in ethylene biosynthesis and signaling pathways were transcriptionally analyzed in tomato fruit. Our data exhibited that ethylene conferred tomato fruit susceptibility rather than resistance to Alternaria alternata. The enhanced resistance in glutamate treatment was related to decreased ethylene production during the early stages of interaction, accompanied by lower expression levels of SlACS1, SlACS2 and SlACO1 relative to the control. Interestingly, 1-MCP induced amounts of resistance similar to that observed in glutamate treatment, while ethylene receptors (SlETR3 and SlETR4), mitogen-activated protein kinase SlMPK3 and ethylene response factor SlERF1 were down-regulated by glutamate during infection. Collectively, antagonizing the ethylene biosynthesis or signaling might play a pivotal role in glutamate-induced resistance to the necrotrophic pathogen Alternaria alternata.

The Occurrence of Aflatoxins in Date Palm (Phoenix dactylifera L.) Worldwide

Due to global warming, the risk of aflatoxins exposure through the consumption of contaminated food has increased. Aflatoxins pose serious health hazards to humans’ and animals’ health because of their carcinogenic, mutagenic, and teratogenic properties and their immunosuppressive effects. Aflatoxin contamination in various agricultural commodities has attracted much attention worldwide. Date palm fruits are among these important commodities that are vulnerable to fungal contamination and consequent aflatoxins production. Furthermore, dates are often consumed directly without any further processing, which may result in direct exposure to aflatoxins. Moreover, dates are the second dried fruits traded worldwide, which reflects the widespread consumption of dates due to their nutritive values in addition to religious and cultural values. Accordingly, this review summarizes and discusses the frequency and incidence of aflatoxin contamination in dates worldwide and outlines the analytical procedure for aflatoxin determination in dates for the first time. The susceptibility of date palm fruits to aflatoxins contamination has been documented at various levels in several regions. The findings urged the importance of conducting more comprehensive studies on aflatoxin occurrence and contamination levels in dates as a likely contributor to the dietary exposure to aflatoxins.

High inoculum of Monilinia fructicola is a threat to peach production in the tropics due to fruit susceptibility at all development stages

AbstractBrown rot is the main disease of stone fruits in Brazil, but the susceptibility of peaches to brown rot at different stages of development in the field has not been studied under subtropical conditions. This information is relevant to guide the management of the disease. The objective of this research was to determine the influence of inoculating peaches with Monilinia fructicola at different stages of development on the infection and progress of brown rot at postharvest. Two experiments were carried out: one ex vivo with two cultivars and the other in the field for two seasons. Peaches were inoculated at different sizes for both experiments. In the field, peaches were bagged to avoid natural infection, and M. fructicola inoculum was monitored. The ex vivo incidence of the disease was lower at pit hardening than at other fruit stages for both cultivars. The incidence of brown rot for peaches attached to the trees increased with fruit ripening. Conversely, the time for symptom expression was reduced according to peach diameter. Peaches inoculated with a diameter smaller than 2 cm showed a lower incidence of brown rot and longer periods for disease expression than fruit inoculated near harvest. In conclusion, in areas with high inoculum in the orchard, a common condition in the subtropics, the grower must prevent infection at all stages of fruit development, thus avoiding losses during marketing.