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Variation in antioxidant activity (AA), total phenolic content (TPH), and total anthocyanin content (ACY) was examined in 1998 and 1999 in fruit of 52 (49 blue-fruited and 3 pink-fruited) genotypes from a blueberry breeding population. The species ancestry included Vaccinium corymbosum L. (northern highbush blueberry), V. angustifolium Ait. (lowbush blueberry), V. constablaei Gray (mountain highbush blueberry), V. ashei Reade (rabbiteye blueberry), and V. myrtilloides Michx. (lowbush blueberry). Using a methyl linoleate oxidation assay (MeLO) on acidified methanolic extracts of the berries, a 5-fold variation was found in AA in 1998 and a 3-fold variation in 1999 among the blue-fruited genotypes. Analyses of variance (ANOVA) revealed variation among genotypes (P < 0.0001) in single and combined years, regardless of inclusion of pink-fruited selections and adjustment for berry size. While mean AA of all genotypes did not change between the 2 years, ranking of some genotypes for AA changed significantly between 1998 and 1999. Of the 10 genotypes that demonstrated the highest AA in 1998, four were among the 10 genotypes that demonstrated highest AA in 1999. Similarly, of the 15 genotypes with the highest AA, 10 were the same both years. As with AA, mean TPH of all genotypes did not change between years and ANOVA demonstrated genotypic variation regardless of adjustment for berry size/weight or exclusion of pink-fruited selections. Changes in genotype rank occurred between years. The difference in TPH between lowest- and highest-ranking blue-fruited genotypes was ≈2.6-fold in both 1998 and 1999. Seven of the 10 highest-ranking genotypes were the same both years and TPH correlated with AA (r = 0.92, P < 0.01) on a genotype mean basis for combined years. ACY correlated less well with AA (r = 0.73, P < 0.01 for combined years). When genotypes were categorized into six groups according to species ancestry, V. myrtilloides and V. constablaei × V. ashei crosses ranked highest and second highest, respectively, for AA in both years. The groups comprised of V. corymbosum genotypes, V. angustifolium genotypes, and those with both V. corymbosum and V. angustifolium in their lineage were indistinguishable from each other. Samples from some of the genotypes were analyzed for oxygen radical absorbance capacity and ferric-reducing antioxidant power, and these aqueous-based antioxidant assays correlated well with the lipid emulsion-based MeLO (all r ≥ 0.90, P < 0.01). The three antioxidant assays may be equally useful for screening in a blueberry breeding program and the choice of assay may depend on the goal of the program and the resources available.

We evaluated regional variation in the Delta Absorbance Meter® index of absorbance difference (I_AD) as a measure of harvest maturity and for predicting the occurrence of storage disorders in ‘McIntosh’ apples [Malus ×sylvestris (L.) var. domestica (Borkh.) Mansf.] in 2016 and ‘Honeycrisp’ apples in 2016 and 2017. Apples were grown in Maine (ME), Minnesota (MN), and Ontario (ON), and they were harvested from one orchard in each region, and two to three times each year, followed by cold storage at 0.5 °C for 2 months in 2016 and 4 months in 2017. In 2016, ‘Honeycrisp’ I_AD values were similar in ME and ON, but lower than in MN. In 2017, I_AD was greater in ME than in the other two regions during the first harvest, and it similar to MN in the latter two harvests and lower in ON than in the other regions. In ‘Honeycrisp’ apples, I_AD was more strongly related to starch pattern index (SPI), internal ethylene concentration, and fruit peel blush than to chlorophyll or soluble solids concentration. Soft scald incidence (SSI) of ‘Honeycrisp’ fruit was greater in ME than in MN and ON in both years. In ME, SSI was related to I_AD at harvest in both years, but with an inverse relationship with the first harvest and a positive relationship in the second harvest. A positive relationship also occurred in ON in 2017. SSI was not related to I_AD at harvest in MN in both years and ON in 2016. Regional similarities in patterns of change in ‘Honeycrisp’ fruit I_AD were not consistent from year to year, and this indicates that a single I_AD standard should not be used to assess fruit maturity in different regions. In ‘McIntosh’, I_AD values were variable among the three regions and were not related to other maturity indicators. I_AD was not useful for measuring maturity in ‘McIntosh’ apples, but it was weakly related to core browning incidence.

It has been reported that 90-day old fruit of rin mutant tomato plants treated with nutrient solution containing 1 g EDTA/L attain 98% red coloration of untreated wild-type fruit. We grew rin plants in sand and watered with half-strength Hoagland's solution until flowering. After flowering, plants were watered until run-off daily with full-strength Hoagland's solution (control), full-strength Hoagland's solution with 135 μ M or 2.5 mM Na₂EDTA, or full-strength Hoagland's solution lacking calcium. We did not observe any red fruit or measure any differences in ethylene production or soluble polyuronides content. Analyses of pericarp ion content indicated that fruit from plants treated with 2.5 mM Na₂EDTA had higher concentrations of sodium and manganese than control fruit. Fruit from plants treated with solution lacking calcium developed blossom end rot and had less calcium and iron than control fruit.

The color of red potato tubers is due to an accumulation of anthocyanins in periderm and peripheral cortex tissues. The objective of this study was to characterize changes in anthocyanin content and tuber surface color during tuber development. Using the red tuber-producing potato (Solanum tuberosum L.) cultivar Norland, we observed that chroma (intensity of redness) and anthocyanin content per unit of surface area of greenhouse-grown tubers decreased as tuber weight increased. There was no increase in hue (tint) during the same developmental periods. Using high-performance liquid chromatography (HPLC), we determined that pelargonidin and peonidin are the major anthocyanidins (aglycones of anthocyanins) in the tuber periderm. Northern blot analyses indicated that steady-state mRNA levels of dihydroflavonol reductase (DFR), an anthocyanin biosynthetic enzyme, continued throughout tuber development. These results suggest that anthocyanins are synthesized throughout tuber development, and that cell division and/or enlargement contribute to a decline in chroma and anthocyanin concentration.

During postharvest storage, apple [Malus pumila P. Mill.] fruit softens and its texture changes noticeably, with adverse effects on fruit quality. These changes are a result of degradation of the cell wall and middle lamella. Enzymes that cause changes in the cell walls have been characterized, but temporal distribution of their activities and their molecular regulation during storage is not well understood. ‘Honeycrisp’ fruit does not soften significantly during storage in contrast to fruit from ‘Macoun’, which softens significantly during storage. Contrasting phenotypes of ‘Honeycrisp’ and ‘Macoun’ were analyzed for changes in transcript levels of four cell-wall–modifying genes in fresh and 3-month-stored fruit from both cultivars. A suppression-subtractive hybridization experiment identified 15 cDNAs differentially expressed in fresh or 3-month-stored ‘Macoun’ fruit. Transcript levels of these 15 cDNAs were further quantified by quantitative real-time polymerase chain reaction (qRT-PCR) in fresh and 3-month-stored fruit from both ‘Macoun’ and ‘Honeycrisp’. The combination of a late increase in MdEXPA2 and decreased levels of MdPG and MdAFase1 transcript levels in ‘Honeycrisp’ fruit during storage may lead to its nonsoftening phenotype. Three cDNAs, potentially important for postharvest changes in apple fruit were also identified based on their different expression patterns in fresh and 3-month-stored ‘Macoun’ and ‘Honeycrisp’ fruit.

Dietary antioxidants may have a role in preventing some of the chronic diseases in humans resulting from free radical oxidation of lipids and other cellular components. Blueberries (Vaccinium L. sp.) are considered one of the best fresh fruit sources of antioxidants, and there is the potential to increase the antioxidant activity further through breeding. Thus, the variability of fruit antioxidant activity (AA) was examined among a set of 16 highbush and interspecific hybrid cultivars grown at locations in Minnesota (MN), Michigan (MI), and Oregon (OR) over 2 years (1998 and 1999) to determine effects of genotype, year, and location. Nine cultivars were common to all three locations in both years. Antioxidant activity, total phenolic content (TPH), and total anthocyanin content (ACY), were determined in triplicate samples from each genotype. Cultivars differed significantly (P ≤ 0.05) in AA, TPH, and ACY both within and over locations. The single location mean AA for all cultivars changed significantly between the 2 years in OR and in MI, while the single location mean for TPH differed between the 2 years in MN and MI. Changes in cultivar rank were significant for AA, TPH, and ACY between years within each location. Significant changes in rank for TPH and ACY were also noted between pairs of locations as well. Pearson's correlation for AA (based on cultivar means) appeared highest between MN and OR (r = 0.90) and MN and MI (r = 0.69) in 1998; correlations between locations for the combined years were 0.74 for MN and OR, 0.55 for MN and MI and 0.45 for MI and OR. For the group of nine cultivars, AA correlated well with TPH within each location, with r ranging from 0.67 to 0.95 for data from individual and combined years. Correlation of AA with ACY at each location was lower than that for AA with TPH, in both individual and combined years. This study demonstrates significant genotype× environment interaction for AA in blueberry.

Many studies of apple (Malus ×domestica Borkh.) softening have been done using cultivars that eventually become mealy. We wanted to determine whether observations in these studies would be seen in a cultivar that maintains its crispness. In this paper, we compared the texture, ultrastructure, and some physiological parameters of Honeycrisp, an apple cultivar introduced in 1991 by the Minnesota Agricultural Experiment Station, with its parents and Delicious. Sensory evaluations and instrumental texture measurements showed that `Honeycrisp' maintained a crisp texture from harvest through 6 months of cold storage, whereas its parents, `Macoun' and `Honeygold', softened over the same time period. Turgor potential, cell wall composition, and ultrastructural comparisons of the fruit were made. Cell turgor potentials of `Honeycrisp' and `Delicious' were similar and greater than those of `Macoun' and `Honeygold', and clearly correlated with firmness. There were no differences in cell wall neutral sugar composition, except for arabinose, which was not highly correlated with crispness. `Honeycrisp' fruit maintained cell wall integrity after 6 months of storage, while cell walls of `Macoun' and `Honeygold' deteriorated. These data show that it is important to compare more than one cultivar when studying crispness. Honeycrisp is a cultivar that maintains its crispness through long storage without controlled atmosphere conditions. After 6 months of storage, this crispness can be attributed to a maintenance of high turgor potential and cell wall integrity.

Shading has been used to produce high-quality lettuce (Lactuca sativa) in locations where production conditions are not optimal for this cool-season crop. To learn what additional benefits shading provides if heat-tolerant cultivars are used and to understand the effects of shading on growth, sensory quality, chemical content, and transcriptome profile on heat-tolerant lettuce, we grew two romaine lettuce cultivars with and without shading using 50% black shadecloth in 2018 and 2019. Shading reduced plant leaf temperatures, lettuce head fresh weights, glucose and total sugars content, and sweetness, but not bitterness, whereas it increased lettuce chlorophyll b content compared with unshaded controls. Transcriptome analyses identified genes predominantly involved in chlorophyll biosynthesis, photosynthesis, and carbohydrate metabolism as upregulated in unshaded controls compared with shaded treatments. For the tested cultivars, which were bred to withstand high growing temperatures, it may be preferable to grow them under unshaded conditions to avoid increased infrastructure costs and obtain lettuce deemed sweeter than if shaded.

Multiple types of flesh browning can occur as storage disorders in ‘Honeycrisp’ apple (Malus ×domestica Borkh.) fruit. Predicting its occurrence is hindered by differing definitions of the types of browning, incomplete understanding of their etiologies, and difficulty in assessing harvest maturity of ‘Honeycrisp’ fruit. In 2013, of ‘Honeycrisp’ fruit grown, harvested over multiple weeks, and stored in Maine, Minnesota, Ontario, and Quebec, only the Quebec fruit developed diffuse flesh browning. A detailed comparison showed that the Quebec fruit differed in size, but not in other quality attributes, from fruit of the other locations. The Quebec fruit experienced lower temperatures during active fruit growth and were increasing in cell size up to harvest. Analyses of climate data from 2009 to 2015 indicated that accumulated growing degree-days (GDD) 50–60 day after full bloom (DAFB) could account for 31% of the variation in diffuse flesh browning, and seasonal GDD <500 are associated with a greater likelihood of injury. Fruit that exhibited diffuse flesh browning had higher magnesium and lower fructose levels than unaffected fruit. As these measurements were made after browning was assessed, the timing of the onset of these characteristics in relation to browning cannot be determined.

Soft scald is an apple (Malus ×domestica Borkh.) fruit disorder that appears in response to cold storage after about 2–8 weeks. It appears as a ribbon of dark tissue on the peel of the fruit, with occasional browning into the flesh. Several apple cultivars are susceptible to it, including Honeycrisp. The objectives of this study were to examine the cellular microstructure of fruit exhibiting soft scald and determine if any aspect of the peel microstructure at harvest could be indicative of future soft scald incidence. Light and electron microscopy were used to examine the peel microstructure of ‘Honeycrisp’ fruit that were unaffected or affected by soft scald. Tissue with soft scald had brown pigmented epidermal and hypodermal cells, whereas unaffected fruit peel epidermal cells were unpigmented. Cuticular wax of unaffected peel had upright wax platelets or clumps of wax, but peel surfaces with soft scald exhibited flattened granules and were more fragile than that of unaffected fruit. Epidermal cells of fruit with soft scald were more disorganized than that of unaffected fruit. Light microscopy was used to examine peels of ‘Honeycrisp’ fruit from four growing locations and fruit from a ‘Honeycrisp’ breeding population at harvest. ‘Honeycrisp’ and ‘Honeycrisp’ progeny fruit were also stored at 0 °C for 8 weeks and scored for soft scald incidence. Cross-sections of unaffected peel of stored ‘Honeycrisp’ fruit looked similar to that of freshly harvested fruit. No significant correlations were found between soft scald incidence and measured microstructural attributes of ‘Honeycrisp’ fruit at harvest, suggesting that peel microstructure cannot be used to predict possible soft scald incidence after storage.