ABSTRACT Autophagy, a cellular degradation pathway, and the phytohormone ethylene function in plant development, senescence, and stress responses. However, the manner of their interaction is mostly unknown. We reasoned that this may be revealed by studying autophagy in a climacteric fruit ripening context, for which ethylene is crucial. During ripening, fruits undergo softening, color change, toxic compound degradation, volatile production, and sugar assembly by fine-tuning synthesis and degradation of their cellular content. For autophagy activity assessment, we analyzed autophagy-related 8 (ATG8) lipidation and GFP-ATG8-labeled autophagosome flux in tomato fruit cells. Autophagy activity increased sharply from ripening initiation, climaxed at its middle stage, and declined towards its end, resembling ethylene production dynamics. Silencing the core-autophagy genes SlATG2 , SlATG7 , and SlATG4 separately in mature fruits resulted in early ethylene production and ripening onset, which was abrogated by 1-methylcyclopropene (1-MCP), an ethylene signaling inhibitor. Beyond ripening, Arabidopsis atg5 and atg7 mutant seedlings exhibited elevated ethylene production and sensitivity to 1-Aminocyclopropane 1-carboxylic acid (ACC), ethylenès precursor, which induces autophagy. This research demonstrates that autophagy limits tomato fruit ripening via a general role in ethylene restriction, opening the path for a mechanistic understanding of autophagy-ethylene crosstalk and harnessing autophagy for fruit shelf-life extension.

Acorn squash are a conveniently sized, inexpensive, nutritious vegetable, but the fruit quality of traditional cultivars is often unsatisfactory. New, sweet-tasting acorn squash were developed recently, but data on their fruit development and storability are limited. Our objective was to monitor the physical, carbohydrate, and antioxidant contents of 'Table Confection' sweet acorn squash fruits over the course of their development and after cold storage. Fruits were harvested at intervals spanning 15 to 60 days past anthesis (dpa) and assessed for various quality components. Maximum weight and dry matter content were attained at 40 dpa but 60-dpa fruits were firmer, with higher total soluble solids (TSS) (60 dpa: 18%; 40 dpa: 9%), sucrose, and antioxidant contents, and a more intense fruit-flesh colour. After long-term cold storage at either 10 degrees C-RH 70% or 15 degrees C-RH 95%, the fruits that had been harvested at 40 dpa had greatly increased TSS (17%), sucrose content, and flesh-colour intensity, but lost as much as 13% of their weight. The results indicate that if premature harvesting is forced by production or marketing considerations, sweet acorn squash can achieve high quality during cold storage, but at the expense of weight loss in accordance with the duration of storage.

Acorn squash (Cucurbita pepo) have been a familiar item at produce stands for decades in the United States and Canada, but little known or appreciated elsewhere. Following the breeding and development of sweet-fleshed acorn squash in Israel and its commercial introduction in 2007, acorn squash became a high-priced, popular produce item there. Scarcity of supply in winter has led to attempts to fill the consumer demand by using available protected cultivation infrastructure in the relatively mild area of southwestern Israel for production. Such production has proven feasible but it was not determined whether it would be preferable to allow the plants to simply grow sprawling on the ground or vertically, using trellises to train the plants to grow erect. Two sweet acorn squash hybrid cultivars differing in fruit size were compared, growing on the ground or on trellises, for yield, quality, and storability of the fruits. The hybrids bore fully ripe fruits from December through February, producing 56% higher yields when trellised rather than when allowed to grow on the ground. The fruits of trellised plants of both hybrids were more uniformly black-green and firmer than those of ground-grown plants. Their dry matter content at harvest and after 78 days of storage was very high, averaging 28% and 25%, respectively. Total soluble solids content of the fruit flesh from trellised plants was 19% at harvest and an extraordinary 20% after storage at 10°C, 70% RH. The fruit flesh of trellised plants was also more highly colored and had higher carotenoid, ascorbate, and anti-oxidant contents. Overall, trellising of sweet acorn squash during the winter under protected cultivation resulted in significantly higher yields and the finest fruit quality.

The pericarp is the predominant tissue determining the structural characteristics of most fruits. However, the molecular and genetic mechanisms controlling pericarp development remain only partially understood. Previous studies have identified that CLASS-II KNOX genes regulate fruit size, shape, and maturation in Arabidopsis thaliana and Solanum lycopersicum. Here we characterized the roles of the S. lycopersicum CLASS-II KNOX (TKN-II) genes in pericarp development via a detailed histological, anatomical, and karyotypical analysis of TKN-II gene clade mRNA-knockdown (35S:amiR-TKN-II) fruits. We identify that 35S:amiR-TKN-II pericarps contain more cells around their equatorial perimeter and fewer cell layers than the control. In addition, the cell sizes but not the ploidy levels of these pericarps were dramatically reduced. Further, we demonstrate that fruit shape and pericarp layer number phenotypes of the 35S:amiR-TKN-II fruits can be overridden by the procera mutant, known to induce a constitutive response to the plant hormone gibberellin. However, neither the procera mutation nor exogenous gibberellin application can fully rescue the reduced pericarp width and cell size phenotype of 35S:amiR-TKN-II pericarps. Our findings establish that TKN-II genes regulate tomato fruit anatomy, acting via gibberellin to control fruit shape but utilizing a gibberellin-independent pathway to control the size of pericarp cells. Tomato CLASS-II KNOXgenes regulate fruit and pericarp anatomy via both gibberellin-dependent and independent pathways.

Fruits can be divided into dry and fleshy types. Dry fruits mature through senescence and fleshy fruits through ripening. Previous studies have indicated that partially common molecular networks could govern fruit maturation in these different fruit types. However, the nature of such networks remains obscure. CLASS-II KNOX genes were shown to regulate the senescence of the Arabidopsis (Arabidopsis thaliana) dry fruits, the siliques, but their roles in fleshy-fruit development are unknown. Here, we investigated the roles of the tomato (Solanum lycopersicum) CLASS-II KNOX (TKN-II) genes in fleshy fruit ripening using knockout alleles of individual genes and an artificial microRNA line (35S:amiR-TKN-II) simultaneously targeting all genes. 35S:amiR-TKN-II plants, as well as a subset of tkn-II single and double mutants, have smaller fruits. Strikingly, the 35S:amiR-TKN-II and tknII3 tknII7/+ fruits showed early ripening of the locular domain while their pericarp ripening was stalled. Further examination of the ripening marker-gene RIPENING INHIBITOR (RIN) expression and 35S:amiR-TKN-II rin-1 mutant fruits suggested that TKN-II genes arrest RIN activity at the locular domain and promote it in the pericarp. These findings imply that CLASS-II KNOX genes redundantly coordinate maturation in both dry and fleshy fruits. In tomato, these genes also control spatial patterns of fruit ripening, utilizing differential regulation of RIN activity at different fruit domains.

Storage at low temperatures is a common practice to prolong postharvest life of fruit and vegetables with a minimal negative impact on human/environmental health. Storage at low temperatures, however, can be restricted due to produce susceptibility to non-freezing chilling temperatures, when injuries such as physiological disorders and decays may result in unmarketable produce. We have investigated tomato fruit response to postharvest chilling stress in a recombinant inbred line (RIL) population developed from a cross between a chilling-sensitive cultivated tomato (Solanum lycopersicum L.) breeding line and a chilling-tolerant inbred accession of the tomato wild species S. pimpinellifolium L. Screening of the fruit of 148 RILs under cold storage (1.5°C) indicated presence of significant variations in chilling tolerance, manifested by varying degrees of fruit injury. Two extremely contrasting groups of RILs were identified, chilling-tolerant and chilling-sensitive RILs. The RILs in the two groups were further investigated under chilling stress conditions, and several physiological parameters, including weight loss, chlorophyll fluorescence parameters Fv/Fm, and Performance Index (PI), were determined to be efficient markers for identifying response to chilling stress in postharvest fruit. The Fv/Fm values reflected the physiological damages endured by the fruit after cold storage, and PI was a sensitive marker for early changes in photosystem II function. These two parameters were early indicators of chilling response before occurrence of visible chilling injuries. Antioxidant activities and ascorbic acid content were significantly higher in the chilling-tolerant than the chilling-sensitive lines. Further, the expression of C-repeat/DREB binding factors (CBFs) genes swiftly changed within 1-hr of fruit exposure to the chilling temperature, and the SlCBF1 transcript level was generally higher in the chilling-tolerant than chilling-sensitive lines after 2-hr exposure to the low temperature. This research demonstrates the presence of potential genetic variation in fruit chilling tolerance in the tomato RIL population. Further investigation of the RIL population is underway to better understand the genetic, physiological, and biochemical mechanisms involved in postharvest fruit chilling tolerance in tomato.

Acorn squash (Cucurbita pepo) is an important vegetable in the United States and Canada and is known for its nutritional content and long storage life. A breeding program in Israel for acorn squash produced several cultivars that are now commercially available. The fruits of the Israeli cultivars have high sugar content (12-18% total soluble solids) and a black-green rind with a yellow-orange flesh. Current agricultural practices in Israel call for growing acorn squash plants prostrate, in an open field. However, experimental trellised growth of acorn squash in greenhouses covered with 50 mesh nets enables a long growing season during the winter, by providing protection against viruses transmitted by insects. Trellising vs. prostrate growth efficiently uses the limited protected space and promotes high plant productivity. In addition, fruit quality is improved in trellised squash. Trellised squash fruits are uniformly colored rather than having an orange section where they touch the ground and are less prone to insect damage. Nevertheless, the long growth period during the wet season promotes a high incidence of fungal rots that develop on decaying plant parts. An initial inoculum of molds from the field represents a major complication for long-term storage of the harvested squash, resulting in a significant produce loss. In this study, the application of precise steam treatments was evaluated for improving the storability of trellised acorn squash fruits produced in netted greenhouses during two consecutive seasons. Our results indicate that the steam postharvest treatment can reduce fruit decay incidence with a minimal effect on fruit quality.

For decades, heat treatments have been known to reduce or eliminate decay-causing agents and slow the physiological deterioration of freshly harvested fruits and vegetables. For years, fungicides and pesticides have been used to control fungi on freshly harvested fruits and vegetables. However, these chemicals can contaminate the environment and be hazardous to those who consume fresh produce. Therefore, heat treatments, lasting only minutes or up to several days, have been developed to control insects and pathogenic fungi on fresh produce after harvest. In the 1990s, hot water rinsing and brushing (HWRB) technology to clean and disinfect fresh produce at relatively high temperatures (50 to 62 °C) for seconds (12–20 s) was developed at the Volcani Institute in Israel. This technology has been improved over time and is currently used commercially on several crops in Israel and elsewhere. This article discusses the development of this prestorage technology, from 1996 to 2006, and describes the effects of HWRB on the internal and external characteristics of fruits and vegetables, as well as the possible mode of action of this technology, as examined in the literature published since 1996.

This work evaluated the efficacies of different coatings: chitosan, gelatin and chitosan-gelatin applied layer-by-layer (LbL); for maintaining the quality of sweet peppers that were stored for 3 weeks at a sub-optimal temperature (1.5 °C) and at an optimal storage temperature (7 °C). After the cold-storage period, fruits were kept under marketing conditions (21 °C) for 3 more days. An edible chitosan coating (2%) effectively alleviated chilling injury and the incidence of decay, and also preserved the nutritional quality of sweet peppers that were kept for 3 weeks at 1.5 °C plus 3 more days at 21 °C. The chitosan coating was more effective than the two other coatings. All three coating treatments significantly reduced external CO2 production, as compared to uncoated control fruit. Storage temperatures did not significantly affect external CO2 production, although CO2 production was slightly higher at 1.5 °C. The chitosan coating exhibited good CO2 gas permeability properties and the peppers coated with that material had lower respiration rates than those in the other two experimental treatments or the control. From a practical point of view, chitosan coating could replace the plastic bags previously found to alleviate chilling injury in peppers that are stored at 1.5 °C as a quarantine treatment.

Yellow sweet peppers (Capsicum annuum L. cv. Dinamo) are generally more susceptible than red sweet peppers to physiological and pathological deterioration after harvest. Yellow peppers also fetch higher prices at market. In this study, we examined the external and nutritional quality attributes of yellow pepper fruits stored at suboptimal temperatures of 1.5 and 4 °C for 3 weeks, followed by a 3-day shelf-life simulation. Notably, yellow peppers kept in plastic (Xtend®, Stepac, Tefen, Israel) bags at 4 °C maintained their external quality just as well as peppers stored at the optimum temperature of 7 °C. In addition, nutrient content (namely ascorbic acid) and total phenolic and hydrophilic antioxidant contents were not reduced when the peppers were kept at suboptimal storage temperatures of 4 or 1.5 °C in Xtend® plastic packaging. Thus, the external and nutritional qualities of yellow pepper fruits can be preserved at suboptimal temperatures of 4 °C with Xtend® plastic packaging. This is particularly significant in light of the fact that storage at such temperatures is sometimes used as a quarantine method to eliminate pests on produce imported into Israel.

This study examined the effects of stem-pruning and fruit-thinning on the yield of marketable watermelon fruit (>5 kg) and watermelon quality after four days of postharvest storage at 22 °C (marketing simulation). We examined the fruits from non-grafted and grafted plants (TZ and Nurit rootstocks) for two consecutive years. Grafting increased the number of marketable fruit per m2. The weight of the average marketable fruit was increased by pruning, but was not affected by thinning or by the choice of rootstock. The level of total soluble solids was higher among fruits from Nurit rootstock. Flesh texture was improved by grafting, but was not affected by thinning or pruning. Thinning improved the taste of the fruit significantly better than stem-pruning did. Grafting (both rootstocks) was associated with crispier fruits. The fruits from Nurit-grafted plants tasted best. The combination of grafting + fruit-thinning increased the fruit lycopene content. The highest levels of vitamin C were found among the fruit from Nurit-grafted plants and the pruned + Nurit-grafted plants, in particular. Overall, fruit quality was affected mainly by grafting onto Nurit rootstock in combination with fruit-thinning and less by stem-pruning. However, not all internal and nutritional quality parameters were significantly affected by the grafting + fruit-thinning treatment.

Acorn squash (Cucurbita pepo) is a familiar fruit vegetable in North America, appreciated for its attractive appearance, good flavor, nutritional content and long storage life. A breeding program in Israel has produced three new acorn squash hybrids of enhanced sweetness and flavor. Presently, we evaluated productivity, quality, and storability of these new cultivars in fall plantings. The plants were grown trellised, in an insect-proof greenhouse, for fruit production during the winter to meet consumer demand. The plants were highly productive and bore fruits of superb quality, but there was a high incidence of fungal rots during postharvest cold storage. Pre-treating the fruits with hot water brushing and rinsing before storage was found effective in reducing rot incidence of the fruits stored at 15 °C, but only for one cultivar. Storing the fruits at 10 °C with reduced humidity (Rh 70%) enabled a 3-month shelf life with significantly reduced fruit-rot incidence and minimal effect on fruit quality of all three cultivars. Storage at 20 °C with reduced humidity was suitable for a 1-month period. These protocols for prolonging storage life will help attain controlled, gradual year-round marketing of quality acorn squash at uniform, reasonable price levels for farmers and consumers, and could facilitate overseas export.

SummaryPeppers are rich in health‐promoting phytochemicals, which are involved in the defence mechanisms against cancer. To select a lead variety of pepper with anti‐proliferative activity against colon cancer cells and liver cancer cells, high antioxidant activity, and high concentrations of capsaicin, flavonoids and phenolics, we compared these attributes in nine different pepper accessions belonging to Capsicum annuum and C. chinense. Quality parameters such as weight loss and total soluble solids content were tested as well. The different parameters were determined immediately after harvest and after prolonged storage and marketing simulation. A significant variation of these traits was detected among the accessions. C. chinense line 1745 had the highest antioxidant activity, the highest levels of capsaicin and flavonoids, a high and specific anti‐cancer activity, and the lowest weight loss level during postharvest storage. It is proposed that line 1745 has potential for use as a source for health‐promoting traits and should be further evaluated for use as a nutraceutical for the prevention and treatment of colon and liver cancers.

The aim of this research was to evaluate postharvest cherry tomato (Solanum lycopersicum (L.) Mill.) yield and fruit quality as affected by grafting and irrigation water quality in the desert region of Israel. Tomato plants (scion cv. Lorka) were grafted onto 3 commercial tomato rootstocks (Resistar, Beaufort and TRS2) and were irrigated with 2 water qualities: fresh water (electrical conductivity (EC)-1.6 dS m−1) and salty water (EC-4.0 dS m−1). Fresh water significantly increased fruit yield by an average of 17% and fruit size, regardless of plant grafting and rootstock, but there were no significant differences in fruit size between the water treatments. However, salty water, but not grafting, significantly improved several quality parameters of fruit stored for 12 d at 12 °C followed by 2 d at 20 °C in simulated sea transport of produce from Israel to Europe and marketing. Fruit harvested from plants irrigated with salty water showed higher sweetness, sourness and, especially, better general taste, and significantly reduced off-flavor, compared with those irrigated with fresh water. The combination of ‘Lorka’ on ‘Resistar’ rootstock and resulted in the best external, internal, and sensory quality parameters at the end of storability and marketing simulation, while the lowest-quality parameters were in fruit harvested from ‘Lorka’ on ‘Beaufort’ rootstock.

Grafting of vegetable plants is done primarily to reduce the potential for damage caused by soil-borne diseases. Most of the watermelons (Citrullus) grown in the Mediterranean Basin, including in Israel, are grafted, mainly on interspecific hybrid pumpkin (Cucurbita) rootstocks. Biblical law (Leviticus 19:19) does not allow intergeneric grafting, so in recent years, great efforts have been made in Israel to find or breed watermelon rootstocks. Both interspecific and intergeneric grafting can have negative or positive effects on fruit yield and quality after harvest. The inconsistencies in fruit quality and shelf-life parameters can be attributed to differences in production environments. However, many farmers are grafting and planting the same rootstock-scion combination all over the country, regardless of local soil, water, and climactic conditions. We studied the effect of similar rootstock-scion combinations on watermelon yield and fruit quality in three regions of Israel differing in soil type and altitude. Fruit-quality parameters were evaluated after 4 days at 21 °C (local marketing simulation). Fruit quality was significantly affected, mainly by the growing region, based on factorial analysis, but also by rootstock-scion combination, regardless of rootstock vigor. Therefore, the best rootstock-scion combination needs to be found and adopted for each growing region. Grafting was essential for watermelon crop survival in contaminated soils and improved both plant performance and postharvest fruit quality, but was not a factor in non-contaminated soils.

There are gaps in our knowledge of the effects of irrigation water quality and amount on yield and postharvest quality of pepper fruit (Capsicum annuum L.). We studied the effects of water quality and quantity treatments on pepper fruits during subsequent simulated storage and shelf-life. Total yield decreased with increasing water salinity, but export-quality yield was not significantly different in fruits irrigated with water of either 1.6 or 2.8 dS/m, but there was a 30–35% reduction in export-quality yield following use of water at 4.5 dS/m. Water quantity hardly affected either total or export-quality yield. Water quality but not quantity significantly affected fruit weight loss after 14 days at 7 °C plus three days at 20 °C; irrigation with water at 2.8 dS/m gave the least weight loss. Fruits were significantly firmer after irrigation with good-quality water than with salty water. The saltier the water, the higher was the sugar content. Vitamin C content was not affected by water quality or quantity, but water quality significantly affected antioxidant (AOX) content. The highest AOX activity was found with commercial quality water, the lowest with salty water. Pepper yield benefited by irrigation with fresh water (1.6 dS/m) and was not affected by water quantity, but post-storage fruit quality was maintained better after use of moderately-saline water (2.8 dS/m). Thus, irrigation water with salinity not exceeding 2.8 dS/m will not impair postharvest quality, although the yield will be reduced at this salinity level.

Acorn squash fruits (Cucurbita pepo L.) are very sweet and are an excellent source of nutrients and vitamins. Very little information is available about their optimal storage temperature or how to extend their shelf life. The present goal was to elucidate the best storage temperature of this fruit, and to evaluate hot water rinsing and brushing (HWRB) technology to maintain fruit quality for several months. The optimal storage temperature was found to be 15 °C. However, treating the fruits with HWRB at 54 °C for 15 s and then storing them at 15 °C significantly maintained fruit quality for 3.5 months, as indicated by higher fruit firmness, lower decay incidence, and improved retention of green skin color.

Molecular markers linked to QTLs controlling post-harvest fruit water loss in pepper may be utilized to accelerate breeding for improved shelf life and inhibit over-ripening before harvest.

We investigated the survival of Mediterranean fruit fly (Medfly) larval stages on yellow peppers stored for 21 d in cold environments (1.5, 4 and 7 degrees C), and the differences in larval mortality rates of Medflies exposed to 1.5 degrees C storage environments between yellow and red peppers. In addition, we investigated the effect of packing yellow peppers and exposing them to cold environments for 21 d on the quality of the fruits. The aim of the study was to investigate packing and shipping post-harvest protocols as a preliminary investigation to explore cold environments as a system to assure the export of quality peppers with low risks of surviving Medfly immature stages. This exploratory study showed that storing yellow peppers for 21 d in lined boxes (20-mm-thick macroperforated Xtend film) at 1.5 and 4 degrees C protected the quality of the fruit, and precluded the survival of Medfly eggs and larval stages (L1, L2 and L3). In contrast, peppers stored at 7 degrees C for 21 d did not completely kill immature stages of the Medfly. In addition, the study showed that Medfly larval stages exposed to 1.5 degrees C environments on yellow and red peppers have different tolerances to cold. Sensitivity to cold in red pepper was higher than in yellow for all larval stages. In addition, sensitivity to cold between larval stages varied between yellow and red peppers: for yellow, sensitivity preceded as follows L1 > L2 > L3, while in red peppers it was L2 > L1 > L3. Abilities to accumulate lipids and protein by feeding Medfly larvae suggest that palatability and nutrition may be partially responsible for the differences in cold tolerance. (C) 2016 Elsevier B.V. All rights reserved.