Brief Summary of Minutes of Annual Meeting

Biochemical factors associated with Pink Lady apple internal browning disorder showed that there were no difference in polyphenoloxidase activity between apples stored in air and flesh browning damaged and undamaged apples stored in CA. Flesh browning damaged apples had lower Ca⁺² concentrations than undamaged apples stored in the same CA conditions [CA]. DPA-treated Honeycrisp apples had higher soft scald incidence at 1.5ºC and lower incidence at 4.5ºC, compared to fruit with no DPA treatment. The incidence of soft scald was highest in Honeycrisp apples held in controlled atmosphere (CA) and treated with 1-MCP, and lowest in those treated with DPA and held in air storage [ON] Bitter pit, soft scald and soggy breakdown have impacted profitability of Honeycrisp apple. Factors associated with occurrence of these disorders have been identified and information on calcium spray, storage temperatures and postharvest handling treatments has been provided to the industry. A pre-storage delay treatment has been developed to reduce incidences of soggy breakdown and soft scald, although bitter pit incidence may be aggravated if fruit are not grown with sufficient calcium inputs [NY-I]. Eight new cultivars of highbush blueberries in Southern California were evaluated for soluble solids, titratable acidity, total phenolics, total anthocyanins, and FRAP. Overall quality scores were best for Misty, Emerald and Sharpblue [CA]. Grammu Smith (scald-sensitive cultivar) apples contained larger quantities of alpha-farnesene and conjugated trienols than did Gala (scald-resistant cultivar) apples. The initiation of the climacteric regulated both scald development and alpha-farnesene and conjugated trienol contents. The combined application of 1-MCP + 1.5% O₂ prevented the initiation of ethylene climacteric for 100 days and suppressed the increase in alpha-farnesene content. Scald symptoms occurred on Granny Smith apples only when they were stored at 1 and 5ºC and not when they were stored at 10 and 20ºC. The expression of MGR1 and FPPS does not control alpha-farnesene biosynthesis because treatments that enhanced the accumulation of their transcripts strongly inhibited alpha-farnesene content. The initiation of ethylene climacteric plays a crucial role in scald development [MD]. Volatile aroma production was higher in Golden Delicious and Fuji apples treated with soybean oil 21 days before harvest. Oil treatment improved retention of flavor impact alcohols in apples held in prolonged CA storage. Flavor regeneration capacity of apples was improved by late season soybean oil application. No apparent phytotoxicity has been observed over a two-season period, and none of the oil treatments negatively influenced storability of the fruit. It is possible for growers to use a late-season organic soybean oil spray to combat pests as well as improve the quality of the fruit [WA]. A risk model has been developed based on weather data observed during July and August to forecast apple disorders [ON, QC]. Postharvest decay of Golden Delicious apples was completely eliminated when the fruit were treated with a combination of two antagonists (yeast biocontrol agents) and sodium bicarbonate and stored in CA (1.4% O₂, 3% CO₂). The antagonists alone reduced decay and sodium bicarbonate increased the effectiveness of each antagonist. Storage under CA conditions also increased the effectiveness of each antagonist, alone or in combination. The goal of this research is to combine alternative methods of control to provide an effective substitute for synthetic pesticides [MD-USDA]. One of the antagonists tested for control of postharvest decay in intact apples (Metschnikowia pulcherrima) was found to be effective in reducing the populations of several foodborne human pathogens on fresh-cut apple slices [MD-USDA]. Radio frequency (RF) heating is a promising quarantine treatment for persimmon and guava fruit if the initial fruit quality and maturity is at optimum levels. However, RF does not appear promising as a treatment for passion fruit or longan [CA, WA]. Complete control of all life stages of grape mealybug, western flower thrips, omnivorous leafrollers and Pacific spider mites without negatively affecting the quality of the grapes could be achieved with a pre-treatment of 6%CO₂ + 1% SO₂ for 30 minutes at 68ºF (20ºC) followed by fumigation with 4.7% ethyl formate at 68ºF and 18-21 days at 36ºF (2ºC) [CA]. Concentrations of headspace volatiles, including trans-2-hexenal, varied substantially among blueberry fruit from 10 cultivars exhibiting a broad range of resistance/susceptibility to decay by Colletotrichum acutatum (anthracnose). Aromatic volatiles decreased rapidly in most cultivars during 5 days of storage at 20°C, and C. acutatum infection prior to storage had no effect on either volatile profiles or concentrations throughout storage. Production of aromatic volatiles in blueberry fruit is not inducible by C. acutatum infection and does not contribute to disease resistance against Anthracnose Ripe Rot [MD-USDA]. A selective agar medium was developed for enumerating Penicillium populations in orchard soils and is being used to determine the relative importance of inoculum from orchards as compared to inoculum that recycles on bins or in apple storages [NY-G]. A survey of 19 apple packinghouses revealed that 14 of 25 water flumes in these packinghouses had detectable populations of Penicillium spores in the water 13 of the 25 flumes also contained coliform bacteria [NY-G]. 1-MCP treatment (1 ppm; 18 h at 20°C) maintained the quality of Golden Delicious apples stored in air at 1°C for up to 5 months when applied <36 h after fruit had entered the climacteric, but was ineffective when applied to fruit 3 to 7 days into the climacteric. Apples treated in the orchard with ReTain could be stored 3 to 4 weeks after harvest in a preclimacteric state and still respond well to 1-MCP treatment. Fruit not treated with ReTain entered the climacteric 2 to 5 days after harvest while those treated with ReTain took 4 to 5 weeks. This study demonstrated that preharvest treatment of apples with ReTain greatly extends the time after harvest in which 1 MCP treatment is beneficial [MD-USDA]. 1-MCP applied to partially ripened dAnjou pears (after on-set of climacteric) slowed the softening and extended the shelf life. Pears could not ripen properly if 300 ppm of 1-MCP were applied. The applicable dosage of 1-MCP for dAnjou pears is somewhere between 20 and 30 ppm, in which pears ripened regularly. However, this dosage had very limited effect on the control of superficial scald [OR]. Shiro Plums, Fantasia Nectarines, Bartlett pears, and Bosc pears treated with 1-MCP were firmer and had less CO2 production, ethylene, and hydrophobic volatiles (aroma, flavour) than those not treated with 1-MCP [ON]. 1-MCP treated persimmon fruit retained firmness much better than the untreated fruit after the holding period at 20ºC [CA]. Soybean oil application significantly increased the mean volatile and aldehyde emission as well as hexanal and 2-hexenal levels of Golden Delicious apples measured immediately after CA storage. Soybean oil application improved regeneration capacities of straight chain esters and increased the emission of branched chain ester 2-metyl-butyl acetate [WA]. Postharvest fungicide trials showed that fludioxonil, pyrimethanil, and a mixture of pyraclostrobin plus boscolid were all very effective for controlling blue mold and gray mold on wound-inoculated apples [NY-G]. Wound-inoculated fruit treated with 1-MCP and held in cold air storage for 90 days had a higher incidence of blue-mold decay than fruit that was stored without 1-MCP treatment [NY-G]. Thiabendazole, fludioxonil, pyrimethanil, and a mixture of pyraclostrobin plus boscolid all reduced blue mold decay by more than 70% in wound-inoculated apples even when fungicides were applied 96 hr after inoculation, but Penbotec was the most effective [NY-G]. In order to develop crisp apples, breeders may want to look for apple fruit with a relatively small average number of cells. Crispness maintenance, like that found in Honeycrisp, is probably heritable. Cell number in apples was positively correlated to change in crispness and change in fracture force during storage. Cell wall phenolics were found to be irrelevant to apple fruit texture. [MN]. The combined application of 2 ppm 1-MCP + 1.5% O₂ suppresses the induction of ethylene climacteric in fruits kept at either 6.5ºC or 1ºC. 1-MCP is more effective in retarding the climacteric ethylene rise than is 1.5% O₂. The inhibition of the induction of the ethylene climacteric is reflected in the changes in texture. The inhibition of ethylene climacteric is reflected in the accumulation of ACS1 and ERS1 transcripts. The combined application of 1-MCP + 1.5% O₂ completely suppressed the expression of ACS1 and ERS1 genes [MA]. Phospholipase D (PLD) and lipoxygenase (LOX) have been implicated to play a role in ripening and senescence in mesocarp tissues of melons. Two cDNAs encoding a PLD± and a 13-LOX were cloned from Cucumis melo cv. Honey Brew, and their transcript levels in fruit mesocarp, floral, and vegetative tissues were determined by quantitative RT-PCR. Transcripts of both CmPLD±1 and CmLOX1 were most abundant in fruit mesocarp as well as root and flower tissues. The long-range goal of this work is to produce transgenic or hybrid melon lines bearing fruit with attenuated senescence and consequently longer shelf life [MD-USDA]. Apple peel had almost double the amount of total phenolic content than apple flesh. Empire apples had less than half of the total phenolic content in both the flesh and the peel than McIntosh and Delicious apples. The smaller amount of total phenolic content in Empire apples might be one of the reasons why Empire apples did not show scald disorder, because less phenol was available to be oxidized to form brown pigments [ON]. 1-MCP treatment temporarily delayed tomato fruit ripening for 8 days, similarly delaying ethylene production and the expression of ACC-synthase, and ethylene receptor genes (especially ETR4+5+6; less so ETR1+2, no effect on NR), though not on ACC-oxidase. The activity of the putrescine biosynthetic enzyme arginine decarboxylase was higher in treated fruit. Polyamines are not directly associated with a delay in tomato fruit ripening but may prolong the fully-ripe stage before the fruit tissues undergo senescence [NY-I]. The expression of the genes encoding alpha-farnesene synthase (AFS1) in the scald-resistant Idared and -susceptible Law Rome cultivars treated with 1-MCP has been studied. A sharp increase in AFS1 mRNA during the first weeks of storage preceded a proportional rise in alpha-farnesene and a subsequent increase in oxidation products (CTols). 1-MCP suppressed the increases in AFS1 transcript and alpha-farnesene early in storage. The inhibition of alpha-farnesene biosynthesis by 1-MCP is at the level of transcript abundance of AFS1, whereas heat treatment does not affect transcript abundance [NY-I, MD-USDA]. Very low ethylene producing transgenic apple lines have been identified that are suppressed for either ACS (ACC Synthase) or ACO (ACC Oxidase) expression. ACS suppressed lines show suppression of ACS mRNA accumulation, ACS enzymatic activity but display normal levels of ACO mRNA and enzyme. ACS/ACO suppressed lines have been identified that show no climacteric response (no autocatalytic ethylene production). Firmness, external color and titratable acidity are highly regulated by ethylene. Part of the pathway for accumulation of phenolics may be under ethylene regulation. ACS/ACO transgenic fruits that make very low ethylene are significantly suppressed in their capacity to make volatile esters, and this reduction is well correlated with a reduction in the activity of alcohol acyl transferase [CA]. PcAFS1, a gene encoding alpha-farnesene synthase (AFS) in scald-susceptible dAnjou pear fruit, was cloned using RT-PCR with primers based on apple AFS1 and RNA from peel tissue of pears cold-stored for 4-8 weeks. PcAFS1 expression in control fruit increased 4-fold over the first 3 months of air storage at -1°C, whereas in 1-MCP-treated (300 ppb; 6 h at 1°C) fruit the increase was delayed and diminished. Silencing of PCAFS1 will prove or disprove the hypothesis that alpha-farnesene and its oxidation products are directly involved in induction of superficial scald on dAnjou pear fruit [MD-USDA]. Treatments with 1-MCP retarded disease-related ethylene biosynthesis, but had little influence on disease progression. A mutant of Botrytis cinerea with a defect in the polygalacturonase gene Bcpg1 was less virulent on pear fruits, suggesting that pectin catabolism is important [OR]. Apples treated with FPT inhibitor does not lead to destruction of the FPT protein in the peel. Apparently farnesyl pyrophosphate (FPP) mediated signalling events are involved in the development of scald symptoms [WA].

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