Cold tolerance was measured midwinter in a New Hampshire, USA, orchard collection of 33 peach and nectarine cultivars over 3 years using natural and artificial freezing methods. Flower bud survival and xylem and cambium hardiness were based on the inflection point from nonlinear regression, as well as comparisons of injury at about −20 °C. Flower bud hardiness was greatest in ‘BuenOs’, ‘Contender’, ‘Cresthaven’, ‘Redhaven’, and ‘Scarlet Rose’. The lowest hardiness occurred in ‘Brigantine’, ‘Desiree’, ‘Emeraude’, ‘Evelynn’, ‘Galaxy’, ‘Glenglo’, ‘Jade’, ‘PF5D’, ‘PF23’, ‘Silverglo’, ‘Spring Snow’, and ‘Sugar May’. Other cultivars had either intermediate or inconsistent year-to-year bud hardiness. Bud hardiness in 2021 was weakly correlated with bud hardiness in 2023, but neither were correlated with bud mortality in 2022 after a severe freeze. Cambial hardiness in one year was not correlated with hardiness in other years. ‘August Rose’, ‘BuenOs’, ‘Cresthaven’, ‘Desiree’, and ‘Silverglo’ had the hardiest cambium which was consistent from year to year. Xylem hardiness was greatest in ‘BuenOs’, ‘Contender’, ‘Desiree’, ‘John Boy’, ‘PF17’, ‘Redhaven’, ‘Silvergem’, and ‘TangOs’. Xylem injury was significantly correlated across years indicating that this tissue responds more consistently to midwinter freezing temperatures than flower buds and cambium.

In northern temperate zones, peach trees are vulnerable to cold temperature injury in the fall, particularly as climate change prolongs warm weather in the fall and potentially delays the onset of cold acclimation. Four experiments evaluated how cold acclimation of flower buds and shoot phloem, cambium, and xylem is affected by exposure to varying temperatures in the fall. One-year-old peach shoots from trees grown in Maine, USA, were collected from October through November, exposed to 1, 3, or 6 days of low, high, and freezing temperatures, and subjected to stepwise controlled freezing to about −30 °C. Injury was visually quantified as oxidative browning of flower buds and shoot tissues. High temperature exposure, even of a single day, decreased cold tolerance of flower buds and shoot tissues until late November, when high temperatures only minimally decreased cold hardiness. In mid-November, increasing the duration of high temperature exposure from 1 to 3 days decreased cambium and phloem hardiness, but hardiness in flower buds was not further decreased by the longer duration of 3 days. By late November, hardiness in flower buds, cambium, and phloem was less responsive to high temperature, and was increased by prior exposure to 6 days of freezing. After high temperature, xylem lost hardiness to a small degree in mid-October and late November, but in mid-November this occurred in only one experiment. In this study, deacclimation during high temperature in the fall was greater in cambium and phloem than in flower buds and at times greater than in xylem.

'MN80', a cross between 'Honeycrisp' and 'Liberty', a newly-released apple sold under the Triumph trademark, is meant to be marketed primarily to home gardeners and small-scale commercial orchards. It was selected for release based on its fruits' resistance to apple scab, thus requiring less spraying than scab-susceptible cultivars. The quality of 'MN80' fruit from two growing locations over multiple years was assessed at harvest and after storage for four months at 0-1 degrees C and 4-5 degrees C. Mean firmness of Wisconsin-grown 'MN80' fruit decreased as harvest week increased, but mean fruit fresh weight and total soluble solids concentration (SSC) remained the same over harvest time, which was also observed for ME-grown fruit. Fruit stored at 4-5 degrees C exhibited more shrivel and loss of firmness than fruit stored at 0-1 degrees C. Percentages of fruit showing internal browning and soft scald in storage increased with harvest date for ME-grown fruit in 2019 but not 2021. Consumer sensory panels evaluating newly-harvested fruit liked 'Honeycrisp' and Maine-grown 'MN80' fruit best, followed by Wisconsin-grown 'MN80' fruit, then 'Cortland' fruit. However, after 4 months of storage, Maine-grown 'MN80' fruit had the highest overall liking scores of all the stored cultivars. Mean sensory attribute scores of Maine- and Wisconsingrown 'MN80' fruit changed little with storage, whereas stored 'Honeycrisp' and 'Cortland' had lower scores than newly-harvested fruit. For all cultivars, storage temperature had no effect on sensory attribute scores. These data suggest that 'MN80' fruit retain characteristics that appeal to consumers between harvest and 4-5 months of cold storage.

Apples are typically spot picked according to color and, therefore, indirectly according to canopy light exposure that affects fruit peel anthocyanins. We studied how interior and exterior canopy positions influenced fruit maturity and storage disorder incidence in 'Honeycrisp' apples grown in Maine (ME) USA, Minnesota (MN) USA and Ontario (ON) Canada, and harvested two to three times. Harvest maturity was more advanced in exterior compared with interior fruit. In both ME and ON, index of absorbance difference (I-AD) was higher for interior fruit compared to exterior fruit. Starch pattern index (SPI) was lower in interior fruit in ME and ON during the first harvest, but not the later harvests, and not in MN where starch breakdown was advanced. Internal ethylene concentration (IEC) at harvest, measured in ON only, was lower in interior fruit during the first harvest, but no difference occurred between the two positions in the latter two harvests. After four months of cold storage plus 1- and 7-d shelf tests, IEC (measured in ON only) was lower in exterior fruit. In all three sites, soft scald, soggy breakdown and bitter pit incidence did not vary between the canopy positions. Fruit were not conditioned to 10 degrees C and stored at 0.5 degrees C to allow for full development of chilling injury disorders. Canopy position altered fruit maturation and quality with no significant effect on soft scald or bitter pit.

The goal of this research was to evaluate resistance of apple rootstocks to late winter deacclimation during a 2-day exposure to warm temperatures in Maine. We measured the cold temperature tolerance of xylem, phloem, and cambium from 0 to −40 °C in 1- and 2-year-old shoot pieces from apple rootstock cultivars and advanced selections ‘M.9 T337’ (M.9), ‘M.7 EMLA’ (M.7), ‘Budagovsky 9’ (B.9), ‘Geneva® 41’ (G.41), ‘Geneva 30’ (G.30), ‘Geneva 935’ (G.935), ‘Geneva 814’ (G.814), G.4013, G.5257, and Vineland 6 (V.6) after a 2-day exposure to warm (22 °C) or cold (2 to 4 °C) temperatures. Injury was measured on a 0 to 10 rating scale based on percentage of discolored cross-sectional xylem and phloem, and cambial length and circumference with brown discoloration, with 0 indicating no browning and 10 indicating browning in the entire tissue. Injury was also measured as intensity of browning on a scale of 0 (no browning) to 5 (dark brown to black). The weighted averages of the two ratings were used to calculate an index of browning. Genotypic variation occurred in the degree of deacclimation, which ranged from none to as much as 15 °C loss in hardiness. Two genotypes, ‘G.41’ and ‘M.9’, showed little change in hardiness in both years they were tested. Two genotypes, G.4013 and ‘G.814’, lost substantial hardiness in both years and may be vulnerable to late winter freeze-thaw events, but were among the hardiest before deacclimation. ‘G.935’ and G.5257 showed a small loss of hardiness, whereas ‘B.9’ lost hardiness in the cambium, but not the xylem, and V.6 lost hardiness after warm exposure, but showed almost no injury at temperatures as cold as −35 °C. The loss of hardiness of these four genotypes that were tested in only one year should be verified with additional testing because of the potential for yearly variation.

Various factors, including environment, maturity, weather, and cultivars are known to impact the profile and concentration of phenolic phytochemicals in plums. Major anthocyanins and neochlorogenic acids were quantified in fruit among four cultivars (Methley, Obilnya, Shiro and Vanier) of Asian plum, Prunus salicina, at the partial-ripe and tree-ripe stages of maturity in 2014 and 2015. Anthocyanin concentration was greater with the later stage of maturity in every cultivar except 'Shiro' which did not have detectable anthocyanins. 'Obilnya' had the greatest anthocyanin concentration, followed by 'Methley' and 'Vanier'. Anthocyanin concentration was greater in 2015 than in 2014 in 'Methley' and 'Obilnya', but in 'Vanier', it was greater in 2014 in tree-ripe fruit. Cyanidin 3-O-glucoside and cyanidin 3-O-rutinoside were detected in three cultivars, but their relative concentrations varied. Cyanidin 3-O-glucoside was predominant in 'Methley' in both years and in 'Vanier' partial-ripe fruit in both years, but cyanidin 3-O-rutinoside was the predominant anthocyanin in 'Obilnya' in both years and in 'Vanier' tree-ripe fruit only in 2014. Cyanidin 3-O-galactoside occurred in only 'Methley' and 'Obilnya' and was generally less than 25% of the total concentration. Large year-to-year variation in neochlorogenic acid, the predominant hydroxycinnamic acid (HCA), occurred in 'Shiro' and 'Vanier' fruit, but variation due to maturity was small in all four cultivars. Total phenolic concentration (TPC) was measured by the Folin-Ciocalteu method and antioxidant activity (AOA) by DPPH assay in only 2015. TPC was greater in tree-ripe than in partial-ripe plums of every cutlivar. The relationship between TPC and AOA was curvilinear indicating a reduction in slope as TPC increased.

We evaluated regional variation in the Delta Absorbance Meter® index of absorbance difference (IAD) 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’ IAD values were similar in ME and ON, but lower than in MN. In 2017, IAD 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, IAD 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 IAD 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 IAD at harvest in MN in both years and ON in 2016. Regional similarities in patterns of change in ‘Honeycrisp’ fruit IAD were not consistent from year to year, and this indicates that a single IAD standard should not be used to assess fruit maturity in different regions. In ‘McIntosh’, IAD values were variable among the three regions and were not related to other maturity indicators. IAD was not useful for measuring maturity in ‘McIntosh’ apples, but it was weakly related to core browning incidence.

Plant growth and development , Plant growth and development , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

To identify genotypes of apple ( Malus × domestica ) rootstock with vulnerability to low temperature, we measured the low temperature tolerance of xylem, phloem and cambium in 2-year-old shoot pieces from cultivars Budagovsky 9 (B.9), M.7 EMLA (M.7), M.9 EMLA (M.9), Geneva ® 41 (G.41), Geneva 30 (G.30), Geneva 214 (G.214), Geneva 814 (G.814), and Geneva 935 (G.935), as well as six advanced selections in the Geneva (G.) series and three in the Vineland (V.) series. From Oct. 2013 to Apr. 2014, injury was measured as a 0–10 rating based on percentage of discolored cross-sectional xylem and phloem, and cambial length and circumference with brown discoloration, with 0 indicating no browning and 10 indicating browning in the entire tissue. From Oct. 2014 to Apr. 2015, injury was measured as xylem, phloem and cambium browning using a similar rating scale that accounted for both the percentage of browned tissues and the intensity of browning. Following exposure to −35 to −40 °C, many genotypes, including ‘M.7’, ‘M.9’, ‘G.935’, G.4011, G.4292, G.5087, and V.5, had only partial xylem injury in the fall, whereas others, ‘M.7’, ‘G.41’, ‘G.214’, and G.4011, had more extensive xylem browning at −30 °C and colder. ‘G.30’ had moderate to severe xylem browning at −15 to −19 °C. In late October of both years, G.4013 exhibited severe phloem browning at relatively high temperatures, but accrued additional hardiness by Nov. 2014, whereas genotypes ‘B.9’, ‘M.9’, ‘G.30’, and ‘G.41’ developed considerable phloem hardiness by late October with no additional increase in hardiness in November. Geneva and Vineland genotypes exhibited a low degree of susceptibility to injury at −35 to −40 °C in Jan. 2014 and Mar. 2015. Shoot hardiness in Apr. 2014 and 2015 was highly variable between the 2 years, with severe browning of xylem and cambium at −40 °C in every genotype sampled in Apr. 2014, but not in Apr. 2015. ‘M.9’ and G.3902 appeared to be the least vulnerable to injury in April, whereas ‘G.30’, ‘G.41’, ‘G.814’, G.4292, and G.5257 seem more likely to suffer injury in spring. ‘G.30’ had tender xylem in both fall and spring, G.4013 had the least hardy cambium and phloem in fall, and G.5257 the least hardy cambium in the spring. These genotypes are vulnerable to damaging temperatures during fall acclimation and spring deacclimation.

Fruit quality and consumer acceptance were measured in 14 plum cultivars. In 2015, six cultivars of asian plum ( Prunus salicina ) and one cultivar of american plum ( Prunus americana ) were harvested partially ripe and tree-ripe. In 2016, three types of plums, asian, american, and european ( Prunus domestica ), were harvested tree-ripe. Within most cultivars in 2015, partially ripe fruit were rated as highly as tree-ripe fruit using a hedonic rating from 1 to 9 with 1 being dislike extremely and 9 being like extremely. ‘Obilnya’ and ‘Abundance’ were rated higher than ‘Shiro’ and ‘Methley’ at both stages of ripeness and higher than ‘Vanier’ at the partially ripe stage. ‘Early Golden’ and ‘Spring Satin’ were rated higher than ‘Shiro’ and ‘Methley’ at the tree-ripe stage. In 2016, seven cultivars (Obilnya, Kahinta, Superior, Toka, Castleton, Early Italian, and Rosy Gage) were scored at the desired consumer acceptance level. ‘Shiro’ and ‘Caçak’s Best’ received overall acceptability scores below the level of acceptability. Plum type had minimal effect on scores for texture, sweetness, sourness, and overall liking. European cultivars received lower color scores than american and asian plums. Soluble solids concentration (SSC) ranged from 6.7% to 13.6% in asian plums, from 14.8% to 19.8% in american plums, and from 15.3% to 22.1% in european plums. Overall consumer acceptance of american and european cultivars was as good as for asian cultivars.

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.

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.