Postharvest Disease Development on Southern Highbush Blueberry Fruit in Relation to Berry Flesh Type and Harvest Method

Postharvest decay, incited by various fungal pathogens, is a major concern in most blueberry production areas of the United States. Because the risk of infection is increased by fruit bruising, which in turn is increased by machine-harvesting, it has been difficult to harvest fruit from the early-maturing but soft-textured southern highbush blueberries (SHB) mechanically for the fresh market. This could change fundamentally with the recent development of SHB genotypes with crisp-textured ("crispy") berries, i.e., fruit with qualitatively firmer flesh and/or more resistant skin. Four replicate row sections of two or three SHB genotypes having crispy fruit and three with conventional fruit were either hand- or machine-harvested at a commercial blueberry farm in northern Florida in April 2009 and May 2010. Harvested fruit were sorted, packed, and placed in cold storage (2°C) for up to 3 weeks. Average counts of aerobic bacteria, total yeasts and molds, coliforms, and Escherichia coli on fruit samples before the cold storage period were below commercial tolerance levels in most cases. In both years, natural disease incidence after cold storage was lowest for hand-harvested crispy fruit and highest for machine-harvested conventional fruit. Interestingly, machine-harvested crispy fruit had the same or lower disease incidence as hand-harvested conventional fruit. Across all treatments, natural postharvest disease incidence was inversely related to fruit firmness, with firmness values >220 g/mm associated with low disease. In separate experiments, samples from the 0-day cold storage period were inoculated at the stem end with Alternaria alternata, Botrytis cinerea, or Colletotrichum acutatum, and disease incidence was assessed after 7 days in a cold room followed by 60 to 72 h at room temperature. In response to artificial inoculation, less disease developed on crispy berries. No significant effect of harvest method was observed, except for A. alternata inoculation in 2009, when hand-harvested fruit developed a lower level of disease than machine-harvested fruit. Taken together, this study suggests that mechanical harvesting of SHB cultivars with crisp-textured berries is feasible from a postharvest pathology perspective.

Postharvest variation in apple (Malus x domestica Borkh.) Flavonoids following harvest, storage, and 1-MCP treatment

The impact of 1-methylcyclopropene (1-MCP) on the synthesis and retention of flavonoid compounds during storage and ripening of red Delicious (Malus x domestica Borkh.) apples was investigated. Numerous anthocyanins, flavonols, flavan-3-ols, and a hydroxycinnamic acid from three different fruit harvest maturities were monitored after a 120 day storage and 1 week shelf life period using high-performance liquid chromatography/diode array detector analysis. The total flavonoid concentration was 5% greater in fruit treated with 1-MCP, whereas chlorogenic acid levels were 24% lower. All compounds analyzed increased in concentration during fruit harvest; however, the anthocyanins generally declined after storage, while chlorogenic acid levels increased. 1-MCP treatment resulted in the retention of anthocyanins in the latter stages of storage but did not affect the flavonols and flavan-3-ols. Chlorogenic acid biosynthesis from early and optimal fruit harvest maturities was greatly inhibited by 1-MCP during storage and the 1 week shelf life period. However, 1-MCP did not affect chlorogenic acid concentrations in late-harvested fruit. Results suggest that 1-MCP may inhibit the activity of phenylalanine ammonia-lyase and subsequent biosynthesis of flavonoid compounds. However, because very little postharvest biosynthesis of flavonoids occurs in apples, 1-MCP treatment may be useful for maintaining some of the intrinsic flavonoid levels of red Delicious apples, if applied at the proper harvest maturity.

Short-term exposures of fish to perfluorooctane sulfonate: acute effects on fatty acyl-coa oxidase activity, oxidative stress, and circulating sex steroids

This study investigated the effects of exposure to waterborne perfluorooctane sulfonate (PFOS) on oxidative stress and reproductive endpoints in fish. Exposures utilized species commonly used in toxicological testing, including the fathead minnow (Pimephales promelas) and rainbow trout (Oncorhynchus mykiss), as well as relatively insensitive taxa such as creek chub (Semotilus atromaculatus), spottail shiner (Notropis hudsonius), and white sucker (Catostomus commersoni). In all fish species, short-term (14-28 d) exposure to PFOS produced only modest mortality at concentrations consistent with environmental spill scenarios. However, PFOS consistently increased hepatic fatty acyl-CoA oxidase activity and increased oxidative damage, as quantified using the 2-thiobarbituric acid-reactive substances assay. Plasma testosterone, 11-ketotestosterone, and 17beta-estradiol titers were often elevated with PFOS exposure. Vitellogenin, the egg yolk precursor protein, was occasionally altered in the plasma with PFOS exposure, but responses varied with maturity. Oviposition frequency and egg deposition in fathead minnow were not significantly impaired with PFOS exposure, despite a trend toward progressive impairment with increasing exposure concentrations. Although short-term PFOS exposure produced significant impacts on biochemical and reproductive endpoints in fish at concentrations consistent with environmental spills, the impact of long-term exposure to environmentally relevant concentrations of PFOS is unclear.

Oxidative stress and bioindicators of reproductive function in pulp and paper mill effluent exposed white sucker

This study investigates oxidative stress and bioindicators of reproductive function in wild white sucker (Catostomus commersoni) collected from environments receiving pulp and paper mill effluent discharges in northern Ontario. Samples were collected over an eight-year period adjacent to three pulp and paper mills using a variety of processing and bleaching techniques. Fish collected downstream of pulp and paper mills within the Moose River basin exhibited elevated hepatic and gonadal 2-thiobarbituric acid reactive substances (TBARS), the presence of which is indicative of oxidative stress in these tissues. Within the Jackfish Bay system, exposure to pulp and paper mill effluent did not elevate hepatic or gonadal TBARS. Hepatic cytochrome P4501A activity (CYP1A) and fatty acyl-CoA oxidase (FAO) activities were frequently increased in livers of Moose River basin fish exposed to pulp and paper mill effluent, while lower activities of both enzymes were found within fish from the Jackfish Bay system. This suggests that oxidative stress may be related to CYP1A and FAO activities. Within the Moose River system, increases in measures of oxidative stress (TBARS, FAO) were generally coincident with decreased levels of 17 beta-estradiol; however, testosterone was often lower in Jackfish Bay system fish without any commensurate changes in oxidative stress. The suite of reproductive and oxidative stress parameters measured in this study varied between seasons and mills suggesting responses to effluent are dynamic and effects are complicated by different receiving environments. The relationship between gonad size, gonadal oxidative stress, and circulating plasma steroids remains unclear.