Brief Summary of Minutes of Annual Meeting

Detailed minutes of the meeting are attached.

Objective 1 Prestorage delays in cooling were evaluated for efficacy and consistency in preventing soft scald in Honeycrisp apples. Fruit harvested in late September were stored at 1 °C immediately or after 1 to 5 days at 15-18 °C. Occurrence of disorders was assessed after several months in storage; soft scald and soggy breakdown were not always distinguishable. Five-day delayed cooling prevented soft scald in two of the four years in which it was severe. Soft scald incidence was low in one year. An increase in bitter pit with delayed cooling occurred in only one year [ME]. Crop load had a dramatic effect on postharvest quality of Honeycrisp apples. As crop load was reduced, fruit increased in size, were redder in color, and had greater firmness and soluble solids content [NS]. Skin punctures were a major source of storage decay in Honeycrisp apples and dipping the fruit also contributed. Recommendations to industry are to clip the peduncle when harvesting and keep the fruit dry between harvest and storage [NS]. CA storage of Honeycrisp apples grown in Nova Scotia does not promote storage disorders and retains harvest-like quality. Using HarvestWatch chlorophyll fluorescence monitoring, the fruit can be stored at 0.5 to 0.8 kPa O2 with 1 kPa CO2 [NS]. Holding Honeycrisp apples at least 7 days at 20 °C (delayed cooling) prior to storage controlled soft scald, but soggy breakdown was still noted in fruit from some orchards in some years. Non-destructive methods such as magnetic resonance imaging are being sought to detect fruit susceptible to internal breakdown and eliminate them from the packing line [NS]. Ambrosia apples transported from British Columbia to Ontario maintained excellent quality during 3 months of CA storage (1.2% O2 + 1.5% CO2 at 0.5 or 3 °C), with <1 ppm internal ethylene concentration (IEC), 17.5 lb firmness, little greasiness, and very few storage disorders. However, stem punctures and bruising could be of concern. Fruit treated with 1-MCP retained up to 4 lbs more firmness than control fruit. After 6 months in CA storage, Ambrosia apples held at 0.5 °C had greater firmness (16.9 vs. 16.6 lb) and lower SSC (16.2 vs. 16.7%) and malic acid (0.2 vs. 0.3%) compared with those stored at 3 °C. There was no effect of storage temperature on IEC and greasiness after 6 months of CA storage. Ambrosia apples stored in CA for 6 months had excellent quality with very few storage disorders and little decay [ON]. Early harvest, no cooling delay, 1-MCP treatment, and CA storage (CA1: 2.5% O2 + 2.5% CO2 or CA2: 1.5% O2 + 1.2% CO2) at 0.5 °C for 3 months all improved firmness and acidity retention, and reduced IEC and greasiness, in Ontario-grown Ambrosia apples. More storage disorders and rots were noted in Ontario Ambrosia than in fruit from B.C. There was higher incidence of flesh browning (up to 58%) and soft scald (4.9%) in apples from the earlier harvest, with no cooling delay, no 1-MCP, and air storage at 0.5 °C. Storage rots were also greater in apples held at 0.5 °C rather than 3 °C (20.9% vs 8.6%), with some rot likely the result of secondary infection of scalded tissue. These results suggest that Ambrosia apples are chilling sensitive [ON]. Ambrosia apples stored for 6 months had higher incidences of greasiness, flesh browning, core browning, CO2 injury, soft scald, lenticel damage, and rots than those stored for 3 months. Early harvest, no cooling delay, 1 MCP treatment, and storage at 0.5 °C all improved fruit firmness after 6 months of CA1 storage. There was higher incidence of flesh browning in apples from the earlier harvest, with no cooling delay, no 1-MCP, and stored in CA at 0.5 °C. Incidence of soft scald was highest in fruit from the second harvest, with no cooling delay and stored in CA at 3 °C. Storage rots were also greater in apples from the second harvest [ON]. Browning potential was evaluated for fresh-cut slices of several new apple varieties including Ambrosia, Aurora Golden Gala, Galarina, Gold Rush, Honeycrisp, Eden, and Quebec selection 'yellow.' Fruit were grown in Ontario, British Columbia, and Quebec. The two selections from Quebec (Eden and yellow) showed the least browning, with ratings of slight to none. There was no consistent influence of growing region on the degree of browning, and Ambrosia slices responded similarly to post-cutting treatments regardless of where the fruit were grown. [ON]. Apple fruit from 184 lines of the Core Collection maintained at the USDA Apple Germplasm Repository in Geneva, NY were assessed for patterns in volatile ester formation. Cluster analysis indicated that some precursors for ester biosynthesis are co-regulated while others appear to be independently regulated [MI]. Objective 2 Pre-storage treatment for 10 days with ultra-low oxygen (ca. 0.3-0.7%) at 20 °C in either a flow-through or closed system controlled superficial scald and bitter pit in Granny Smith apples subsequently stored up to 8 months in air at 0 °C. By comparison, 1-MCP treatment prevented scald but gave only a small reduction in the incidence of bitter pit [CA]. Low-O2 storage is a reliable alternative to chemical drench treatments for control of superficial scald. However, to avoid injury and disorders induced by CA storage, the lowest acceptable O2 concentration must be established. This threshold O2 level can be determined with chlorophyll fluorescence using HarvestWatch sensor technology. Recently this technology was shown to effectively control scald and maintain fruit quality in organic Delicious and Cortland apples. Its commercial adoption continues, with over 800 sensors now in use worldwide, but primarily in apple storages in Europe [NS]. Effects of fruit maturity, storage duration, 1-MCP treatment, iron or calcium salts, and peel tissue mineral content on lenticel breakdown (LB) in Gala apples were evaluated. More mature fruit had a higher risk of LB, whereas time in storage, pre-storage treatment with 1-MCP, contact with iron or calcium ions, and peel mineral content did not affect the incidence of LB. A system using dye infusion did not predict the risk of LB, whereas a system using soap/detergent gave a good correlation with packing line prediction of LB [WA]. A model for prediction of scald susceptibility in Anjou pears placed in long-term cold storage was developed using accumulated cool growing temperatures in eight orchards. When tested the model did not adequately predict the risk of scald development [WA]. Timing and concentration of bin drenching of Anjou pears with Ethoxyquin at harvest were varied to establish a protocol that will prevent scald development in long-term cold storage without chemical burn. When unrinsed fruit were stored long term, chemical burn from Ethoxyquin was excessive at levels that controlled scald [WA]. The application of Ethoxyquin using thermofogging was tested at one concentration in a storage room containing fruit from four orchards to find if this technique would provide effective scald control without chemical burn. Chemical burn was limited to fruit on the top layer in the top bins, but scald was not completely controlled [WA]. Responses of Bartlett and Anjou pears to storage at less than 1 kPa O2 varied between lots and with storage duration. Incidence of core browning, senescent scald, and internal breakdown were reduced by storage at 0.5 kPa O2. Anjou fruit stored at 0.4 kPa O2 did not develop scald, and degreened and softened more slowly than fruit stored at 1.5 kPa O2, but two lots developed peel speckling. Increasing O2 to 1.5 kPa during storage did not consistently prevent development of speckling [USDA-WA]. Ethyl formate fumigation was shown to have good potential for use as a quarantine treatment for bean thrips in navel oranges. When fully developed, this treatment will assure continued access to the Australian market for California citrus [CA]. Muscodor albus, a fungus produced by AgraQuest, Inc. (Davis, CA), is very effective at controlling postharvest fungal and bacterial organisms, including E. coli and Listeria, by producing a cocktail of volatile compounds. The fungus is very active and effective at 20 °C in both air and CA storage, but does not thrive below 5 °C, and thus efficacy as a biocontrol agent declines and varies with the pathogen. The reduced activity at low temperatures is probably not insurmountable, but the distributor is not presently seeking regulatory approval for postharvest applications [NS]. A selective agar medium, DG-18-P, was used to assess densities of Penicillium expansum in orchard soils and on apple fruit at harvest. Soil samples from major apple production regions in New York State were assayed. Results of this research and prior work indicate that contaminated harvest bins, and not freshly harvested fruit or soil on bin runners, are the principal source of P. expansum inoculum [NY-G]. Evaluations of preharvest fungicide sprays for control of postharvest decay were conducted for a second year. Captan was most effective for reduction of viable P. expansum spores on the fruit surface at harvest, but the other fungicides tested (thiophanate-methyl, pyraclostrobin plus boscalid, and pyrimethanil) gave better suppression of decay when fruit were wound inoculated with spores at harvest. An unexpected result from one trial in a commercial orchard was that a preharvest spray with captan plus thiophanate-methyl reduced CO2 injury in Empire apples held in long-term CA storage [NY-G]. Objective 3 Effects of storage temperature, 1-MCP treatment, and low oxygen CA on the rate of ripening in Granny Smith apples were investigated. Surprisingly, in air control fruit onset of the ethylene climacteric occurred after 1 week at 1 °C and after 6 weeks at 18 °C. However, ethylene eventually rose to 3-fold higher levels at 18 °C vs. 1 °C. 1-MCP treatment inhibited ethylene production completely for 34 weeks at 1 °C, whereas at 18 °C ethylene began to rise after 14 weeks. Low O2 CA combined with 1-MCP treatment delayed the onset of ethylene production at 18 °C until 22 weeks. Storage at higher temperature accelerated chlorophyll loss. Ethylene evolution was temporally associated with expression of the ethylene receptor gene MdERS1 at both 18 °C and 1 °C [MD]. 1-MCP treatment and short-term low oxygen storage were evaluated for control of superficial scald in Cortland apples. Fruit were untreated or treated with 1-MCP and stored in air or 0.8% O2 CA for varying durations, followed by an increase in O2 to 2.5-2.8% after 2 to 4 weeks. 1-MCP or low O2 CA alone reduced scald after five months of storage, but combination of the two was more effective. An initial two weeks in 0.8% O2 was as effective as 3 or 4 weeks [ME]. 1-MCP treated Empire apples were more susceptible to external CO2 injury than untreated fruit when stored in 2.5 and 5%, but not 1%, CO2 (in 2% O2 CA). 1-MCP did not increase the period of highest susceptibility to injury during CA storage, the greatest sensitivity to injury being 0-3 weeks after harvest. However, when kept in air for up to 14 days before exposure to 5% CO2, sensitivity to injury decreased in untreated but not in 1-MCP-treated fruit. DPA treatment, even at low concentration, prevented CO2 injury. DPA treatment could be delayed for 4 days after 1-MCP treatment while fruit were exposed to 5% CO2 in air. In summary, 1-MCP enhances the risk of external CO2 injury, but injury can be prevented by at harvest treatment with DPA. In the absence of DPA treatment, handling procedures such as maintaining low CO2 levels in the storage atmosphere must be used [NY-I]. The effects of delayed applications of 1-MCP and DPA on subsequent incidence of superficial scald on apples were compared. Prompt treatment with 1-MCP after harvest was critical for substantial scald control. There also was variation among apple cvs. in the long-term efficacy of 1-MCP for scald control [NY-I]. Various storage regimes involving different concentrations of O2 and CO2 and a range of temperatures were evaluated with the goal of minimizing development of flesh browning in apple fruit. Warmer storage temperatures can increase this disorder in fruit that have been treated with 1-MCP. Flesh browning in stored fruit is a problem of critical importance to the New York apple industry and will be a priority for further research in the coming harvest season [NY-I]. Protocols aimed at ensuring predictable, adequate ripening of 1-MCP-treated Anjou pear fruit were evaluated. Pears treated with 300 nL/L 1-MCP at harvest were stored in CA with 0.5 kPa CO2 and up to 5 kPa O2. After 6 and 9 months at -1 °C plus 7 days at 20 °C, peel yellowing occurred with increasing O2 concentration but 1-MCP-treated fruit remained greener than controls. Post-storage softening increased with increased O2 concentration after 6 and 9 months. After 6 months, 1-MCP-treated fruit did not soften to 6 lbs or less in 7 days at 20 °C, whereas after 9 months, treated fruit stored at 3 or 5 kPa O2 softened to 3.8 and 3.4 lbs, respectively. In some cases, 1-MCP treatment prevented scald and reduced decay incidence [USDA-WA]. Treatment of Bartlett pears with a new sprayable formulation of 1-MCP prior to harvest reduced the rates of respiration, ethylene production, and softening after up to 6 months of air storage at 1 °C. 1-MCP treated fruit took 1 to 3 days longer than the controls to ripen at 20 °C after storage. Best results were obtained with fruit harvested one week after treatment with 56 mg/L of the 1-MCP formulation [CA]. Ethylene production, firmness loss, and color change (green to yellow) were inhibited or delayed in Bartlett pears sprayed preharvest with a new formulation of 1-MCP. These effects were more pronounced in late harvested fruit. Fruit drop was inhibited; only 1-MCP sprayed pears remained on the trees after 2 weeks (consequently these fruit increased in size). Pears from the optimum harvest treated with 1-MCP postharvest were of similar quality to those sprayed with 1-MCP preharvest. 1 MCP-treated (pre or postharvest) pears had much lower incidence and less severe senescent scald, core breakdown, and storage rots than non-treated-fruit. 1-MCP improved the quality of Bartlett pears in all years of study, thus there appears to be great potential for commercial and industry benefits [ON]. Impact of ethylene and CO2 on the efficacy of 1-MCP in delaying ripening of Bartlett pears was investigated. Pears were treated with 0 or 300 ppb 1-MCP in the presence of up to 1000 µL/L ethylene or up to 4 kPa CO2. Ethylene at >1 µL/L was sufficient to abolish the effects of 1-MCP, and CO2 levels of 2 or 4 kPa during 1-MCP treatment reduced the efficacy. Thus, low ethylene and moderately high CO2 levels during 1-MCP treatment of fruit at harvest can compromise effectiveness of 1-MCP [USDA-WA]. Exposure of partially ripe bananas (stages 2 and 3) to 1-MCP at 100-300 ppb for 6 hours at 14 °C can be a useful supplement to temperature management in extending the yellow-life of bananas [CA]. Shiro plums treated with 1-MCP were firmer, retained green color longer and turned yellow-gold more slowly than non-treated fruit. 1-MCP reduced ethylene production during holding at 22 °C, and treated fruit had lower CO2 production. The latter effect was more consistent in fruit from the second harvest. Similar results over three years show that 1-MCP can maintain the quality of Shiro plums for longer storage and marketing periods than are currently possible [ON]. 1-MCP-treated Redhaven peaches had slightly higher firmness values and less peel blush than non-treated fruit. There were no clear effects of 1-MCP on respiration, ethylene production, soluble solids concentration, or chilling injury incidence. Results were similar to those from last year, and show that there is little benefit to using 1-MCP on Redhaven peaches [ON]. 1-MCP-treated Fantasia nectarines were firmer and produced less CO2 than those not treated. There was no significant effect of 1-MCP on ethylene production, soluble solids, or color. 1-MCP improved firmness retention in Fantasia nectarines each year, but effects on other quality attributes were not consistent, suggesting that factors such as growing conditions or crop load influence the efficacy of 1-MCP [ON]. 1-MCP treatment of greenhouse tomatoes on a commercial scale was investigated. Pallets of cherry tomatoes and tomatoes on vine (TOV) packaged in clam shells (12-oz and 2-lb, respectively) were untreated or treated with 1-MCP (500 ppm for 12 h at 53 °F) and evaluated for quality over several weeks. This period included transport from Mexico, subsequent storage (~55 °F), and simulated marketing periods at room temperature. 1-MCP slowed ripening of both cherry tomatoes and TOVs, extending shelf life by several days. In cherry tomatoes, 1-MCP reduced shrivel and weight loss, delayed firmness and acidity loss, and slowed deep red color development. Similarly, in TOV's 1-MCP reduced weight and firmness loss, delayed sugar and acidity loss, slowed deep red color development, and also reduced shrivel and maintained sepal freshness for 3 days at room temperature. 1-MCP had no effect on the incidence of decay [ON]. Sorption of 1-MCP by non-target oak bin materials was shown to be significant and efficacy of 1-MCP treatments of apple fruit was reduced when treatment levels were below 600 ppb [MI]. Absorption of 1-MCP by packaging materials was found to reduce its efficacy in maintaining apple fruit quality during cold storage. Corrugated cardboard reduced the effectiveness of 1-MCP when applied as a gas at sub-saturating levels. This negative effect was most pronounced when the fruit were encased in plastic liners within corrugated boxes [MI]. Trials were continued to determine the efficacy of new postharvest fungicides in reducing storage rots. Results were consistent with those from previous trials and documented the effectiveness of both pyrimethanil and fludioxonil [NY-G]. Objective 4 Optimal harvest maturity and postharvest quality of fruit from eight strains of Gala apple including Brookfield, Buckeye, Crimson, Galaxy, Gale, Pacific, Royal, and Ultra were found to be similar. The patterns of decline in fruit firmness and titratable acidity, and increase in soluble solids content with advancing harvest maturity were closely similar for fruit of all strains [CA]. Enzyme activities of polygalacturonase, ²-galactosidase, and arabinofuranosidase were measured in fruit of different apple genotypes at 2 week intervals from harvest to 8 weeks in air storage at 0 ÚC. Analyses of fruit of three genotypes that remain crisp in storage, Honeycrisp, MN1702, and one of their progeny, showed no correlating pattern of enzyme activities. Hence, changes in activity of these cell wall hydrolases alone cannot explain why some apple fruit stay crisp during storage [MN]. A test of 26 apple genotypes showed a strong correlation between the Golden Delicious-type expansin allele and fruit softening. Fruit of 19 genotypes softened during storage, and all had the Golden Delicious allele. Fruit of 7 genotypes stayed crisp during storage, and these all had the Granny Smith-type expansin allele. Thus, expansin may have a key role in determining texture of pome fruit [MN]. Work required to break cylinders of fruit from various apple genotypes, including Honeycrisp progeny, was measured at harvest and after 4 months of storage in air at 0 ÚC. One of the Honeycrisp progeny studied was MN1914, recently released by the Minnesota Experiment Station. Significant changes in work values during storage are indicative of softening. Test results suggested that maintenance of crispness in stored fruit may be a heritable trait [MN]. A prototype firmness tester developed by the USDA agricultural engineering program at Michigan State was evaluated for its ability to discriminate between treatments resulting in differences in apple fruit firmness. The experimental bioyield tester was more sensitive and gave more consistent results than the conventional Magness-Taylor firmness tester [MI]. A mathematical model was developed with the intent that it be a user-friendly decision support tool for designing modified atmosphere (MA) packages of fruits and vegetables. Input of data describing respiratory response to temperature and a single assumption regarding the K1/2 yielded a robust model suitable for designing MA packages [MI]. Physical qualities, antioxidant contents and activity, and antiproliferation activity were evaluated for Jewel strawberry fruit harvested at the white tip and red ripe maturity stages and stored in 65 or 95% RH at 3 or 10 °C for 12 days. Overall quality and firmness declined more rapidly in red ripe than in white tip stage fruit, and decreased more rapidly at 10 °C than at 3 °C. Anthocyanins increased more rapidly at 10 °C than at 3 °C in white tip fruit. The initial anthocyanin levels in red ripe fruit were about 5-fold greater than those in white tip fruit, but declined during storage. Total flavonoid and phenolic contents, and total antioxidant activity were higher in white tip than in red ripe fruit. Changes in total antioxidant activity were correlated with total flavonoids and phenolics, but not anthocyanins or ascorbic acid. Fruit quality was correlated with firmness and color attributes, total flavonoid and phenolic concentrations, and antioxidant activity. Strawberry extract at 50 mg/mL inhibited HepG2 cell proliferation about 80%. EC50 values were not affected by maturity at harvest or storage temperature [NY-I]. In a study with USDA-ARS, Winter Haven, FL, imported mangos from Mexico, Ecuador, Brazil, and Peru were evaluated for their range of vitamin C, beta-carotene, and gallotannin contents. Fruit of the 5 varieties most commonly imported into the U.S. were shipped to Lane, OK and ripened at 20-25 °C prior to sampling. Vitamin C ranged from 20-30 mg/100 g for Hayden, Tommy Atkins, Keitt, and Kent, and was >100 mg/100 g for Ataulfo, a cv. grown only in Mexico. Samples were saponified and carotenoids determined in hexane extracts. Violaxanthin and beta-carotene were the most abundant carotenoids. Beta-carotene was 5 (Tommy), 7 (Haden), 10 (Keitt), 17 (Kent) and 26 (Ataulfo) mg/kg. Differences in phytonutrient content were more pronounced among the five varieties than in any single variety grown in different countries [USDA-OK]. Grafting rootstocks of pathogen or cold-resistant cucurbits to watermelon has been done for centuries in Asia, but has only recently been tested in the U.S. In a study with Syngenta, it was found that fruit from grafted plants of 3 rootstocks and 3 watermelon cvs. had 20-50% more lycopene than fruit from control plants. Also, one watermelon variety exhibited a 100% increase in lycopene content when grown in California rather than in Florida [USDA-OK]. When included in an experimental diet fed to Zucker Diabetic Fatty rats, watermelon pomace, which contains lycopene, citrulline, and arginine, delayed adverse cardiovascular events. Control animals were fed a normal diet, and three other groups were maintained on diets supplemented with pectin, lycopene, or arginine. The arginine supplement gave results similar to those with pomace. Rats fed pomace or arginine diets had more aortic flexibility, gained less weight, and had lower blood glucose compared with animals on the other three diets [USDA-OK]. Objective 5 Consistent with the diverse botanical origins of boysenberry, raspberry and blueberry, fruit softening-related changes in cell wall pectin and cellulose-hemicellulose polysaccharide networks differ among these berries [CA]. The actions of tomato fruit polygalacturonase and expansin contribute to ripening-associated fruit softening and increased fruit susceptibility to pathogens like Botrytis cinerea [CA]. A combination of objective color (Hue angle) of the peel and firmness of the pulp can be used to accurately determine physiological development (ripeness) stage of bananas [CA]. The plant hormones gibberellin (GA) and abscisic acid (ABA) had opposite effects on tomato fruit susceptibility to blossom end rot. GA treatments started at 2 weeks post-anthesis increased fruit cell membrane permeability and subsequent development of the disorder, whereas ABA decreased membrane permeability and the incidence of blossom end rot. Compared with GA-treated fruit and water controls, ABA-treated fruit and fruit treated with a GA inhibitor (Apogee) had a higher number of functional xylem vessels [CA]. Expression of genes involved in flavonoid metabolism, ethylene production, and a-farnesene synthesis was compared in tissue from scalded and non-scalded sides of Anjou pears ripened 1-5 days at 20 °C after long-term air storage at -1 °C. Generally, expression was greater in tissue where scald developed. Polyphenol oxidase (PPO) transcript increased in scalded tissue but disappeared in non-scalded tissue, suggesting a role of PPO in the browning reactions resulting in scald symptoms [CA]. A study of the biophysical properties of Honeycrisp apples that may pre-dispose the fruit to soft scald and internal breakdown disorders was initiated. One goal of this work is to develop a non-destructive technique appropriate for industry use to detect fruit susceptibility to these disorders [NS]. A slow-drying method used on wine grapes after harvest improves sugar content, red color and flavor. Promising results were obtained using chlorophyll fluorescence changes as a biosensor to monitor water loss in grapes and thus determine when they had lost the desired 20-25% of their initial water content. The physiological basis of the relationship between chlorophyll fluorescence and water loss is being investigated [NS]. Full-length cDNAs were cloned for three apple ethylene response factor genes expressed in fruit tissues, MdERF1, MdERF3, and MdERF4. Based on Arabidopsis ERF classification, the apple ERF genes are members of subfamilies 1b, 2a, and 10. MdERF1 is most closely related to AtERF110, followed by ABR1 and AtERF108. Expression of AtERF108 increases more than 30-fold in response to Botrytis cinerea, the highest level of induction among six ERF genes tested from group 10. MdERF3 is closely related to the Arabidopsis gene RAP2.4, which has not yet been functionally analyzed, and MdERF4 is most similar to four RAP2.10 genes of Arabidopsis, none of which has been characterized. Thus, MdERF1 is currently the most promising gene with respect to a role in the response to B. cinerea infection and expression studies are in progress [OR-C]. Postharvest expression of defense-related and ethylene-inducible genes in mature wild type and ACS-suppressed trangenic Greensleeves apple fruit was evaluated by RT-PCR. Climacteric ethylene was produced in wild-type fruit, whereas ACS-suppressed apples produced almost none. ACS transcript increased in concert with ethylene production in controls and was undetected in transgenic apples. In contrast, ACO was constantly expressed in both untransformed and ACS-silenced fruit. Patterns of lipoxygenase (LOX) and polygalacturonase inhibitor protein (PGIP) gene expression were similar in the two apple genotypes, and thus it appears neither gene is controlled by ethylene. Although chitinase is a pathogenesis-related (PR) protein that can be induced by ethylene, chitinase genes were not expressed in ripening apples [OR-C, CA]. Gene expression associated with branched-chain volatile ester formation in apple fruit was analyzed. A microarray was constructed with approximately 200 known and 10,000 unknown gene products. Expression analysis revealed close to 700 gene products of potential interest and these were sequenced. A putative alpha-keto decarboxylase may be involved in degradation of the transamination precursor/product of isoleucine to form branched-chain alcohol precursors for ester biosynthesis [MI]. Gene sequences from apple were subjected to bioinformatic analysis to identify genes with potential roles in transcriptional regulation, biosynthesis of or response to hormones, aroma production, cell wall metabolism, flowering, and abscission. A microarray representing 2,200 apple genes was designed and is now available through Combimatrix Corp. This experimental system will allow parallel analysis of the activity of thousands of key genes in developmental processes such as apple fruit ripening, senescence, and abscission [MI]. Approximately 100 apple lines representing several wild species and many cvs. of Malus domestica were evaluated for timing of fruit drop relative to fruit internal ethylene concentration. Among both M. domestica cvs. and wild species, accessions were noted that failed to abscise fruit at the end of the season. This trait was not clearly associated with lack of ethylene production in the fruit, presence of dysfunctional ACS alleles, or a block in fruit ripening, and therefore it is most likely controlled by an abscission-specific mechanism downstream from ethylene signaling [MI]. Quercetin, a flavonoid known to inhibit growth of cultured human tumor cells, is present in apple fruit at variable concentration. Quercetin is also implicated in resistance of apple trees to fire blight. It has been shown that introducing a copy of a petunia chalcone isomerase gene into tomato increased the level of quercetin 60-fold. Using PCR primers designed on the basis of reported MdCHI gene fragments, two 95% identical 800-bp cDNAs encoding chalcone isomerase were cloned from the Golden Delicious and Galaxy apple cvs. Transformation of Galaxy apple with the cultivar-specific MdCHI cDNA driven by a strong constitutive promoter (CaMV35S) is currently in progress [NY-G]. Effects of 1-MCP on ethylene and polyamine metabolism and associated gene expression in ripening tomato fruit were investigated. The ethylene and polyamine biosynthetic pathways share S-adenosylmethionine as a common intermediate. 1-MCP delayed ripening for 8 days, similarly delaying ethylene production and expression of ACS and some ethylene receptor genes, but not ACO. Overall, analyses of changes in free and bound polyamines, and expression of genes involved in their metabolism, indicated that polyamines are not directly associated with the delay in tomato fruit ripening after 1-MCP treatment but they may prolong the fully-ripe stage before fruit senesce [NY-I]. Metabolic profiling of Granny Smith apples irradiated with UV-white light at harvest for up to 48 h and stored 6 months in air at 0 °C showed that this treatment induced changes in amino acid, organic acid, sugar, and pectin metabolism. Metabolic flux data indicated that key components of fruit quality were affected by the pre-storage irradiation, including ethylene synthesis, acid metabolism, and degradation of the middle lamella. The results suggest an important influence of preharvest light conditions on the post-storage metabolome [USDA-WA]. Braeburn apples untreated or treated with 1-MCP and stored at 1 °C in CA (1 kPa O2, 3 kPa CO2) for up to 6 months developed internal browning and cavities, whereas fruit stored in air or treated with diphenylamine (DPA), alone or in combination with 1-MCP, were free of these disorders. CA storage influenced the levels of DPA and DPA derivatives. A possible link between a-farnesene metabolism and disorder development was also indicated [USDA-WA]. Certain apple cultivars develop a greasy feel when overripe and 1-MCP treatment can reduce greasiness. In a 3-year study, Royal Gala apples treated with 1-MCP at 1.0 µL/L and stored at -1 °C for up to 6 months were evaluated for internal ethylene concentration, and epicuticular wax morphology and composition. 1-MCP strongly inhibited ethylene production and delayed accumulation of wax constituents thought to be responsible for development of fruit greasiness. There was no clear correlation between wax morphology and the concentration of individual wax components [USDA-WA]. Relationships among a-farnesene synthesis and oxidation, ethylene production and perception, antioxidative enzyme activities, and superficial scald development in fruit of three apple cvs. were investigated at the biochemical and gene transcriptional levels. Scald-susceptible Cortland and Law Rome and scald-resistant Idared apples were untreated or treated with 1-MCP and stored in air at 0.5 °C. Separate blushed (red) and unblushed (green) peel tissue samples were taken at harvest and after up to 25 weeks of storage. Overall, the results indicated that a-farnesene synthesis is tightly regulated by ethylene and supported the proposed role of its conjugated trienol oxidation products in scald induction. However, gene transcription alone does not account for the big differences in ethylene and a-farnesene production among cvs. As well, the capacity to detoxify reactive oxygen species and/or alkoxy radicals appears to be greater in blushed than in unblushed peel tissue [NY-I, USDA-MD]. Conjugated triene (CT) oxidation products of a-farnesene are thought to induce development of superficial scald in apple and pear fruits. The major CT species in peel tissue of Anjou pears after 12-20 weeks of cold storage were shown to be the same pair of conjugated trienols (CTols) previously identified in hexane extracts of cold-stored Granny Smith apples, 3E and 3Z isomers of 3,7,11-trimethyldodeca-1,3,5,10-tetraen-7-ol. CTols likely arise from their 7-hydroperoxy analogs, which are produced during autoxidation of a-farnesene. The high level of accumulation in skin of scald-prone apple and pear fruits suggests that CTol production could be enzymatic. Two cDNAs encoding a glutathione peroxidase that may catalyze reduction of the 7-hydroperoxides to CTols have been cloned from Law Rome apple and Anjou pear [USDA-MD]. HPLC-DAD analysis of hexane extracts of peel tissue from cold-stored fruit of Granny Smith apple and Anjou pear revealed major and minor CT peaks, CT1 and CT2, the latter having a UV max at 281 nm. CT1 included the 3E and 3Z conjugated trienol isomers previously identified as the major in vivo oxidation products of a-farnesene. CT2 eluted just after CT1 and composed about 1012% of the total CTs. GC-MS and LC-MS analyses of CT2 indicated that this fraction includes isomers of 3,7,11-trimethyl-dodeca-2,4,6,10-tetraen-1-al and -1-ol. These CTs may arise as oxidation products of a-farnesene or farnesol. Previous reports showed a strong correlation between A281 nm in hexane extracts of cold-stored fruit and subsequent scald severity. Thus, the oxidation products in CT2 might serve as a catalyst for free radical reactions leading to scald development. [USDA-MD]. During ripening of tomato fruit, a marked increase in the stigmasterol : sitosterol ratio occurs in all four classes of sterol lipids (free, ester, glucoside, acylated glucoside). This increase is ripening-specific as it is minimal during maturation and aging of non-ripening mutant fruit. Unsaturation of the sterol side chain influences ordering of the lipid bilayer, and a high proportion of stigmasterol results in membrane leakiness. The gene encoding sterol 22-desaturase, a cytP450 enzyme that converts sitosterol to stigmasterol, was cloned from Rutgers tomato using primers based on the CYP710A7 cDNA sequence. Analysis of sterol 22-desaturase gene expression in fruit of wild-type and non-ripening mutant Rutgers lines, and RNAi silencing of the sterol 22-desaturase in Rutgers tomato, are in progress [USDA-MD].

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