Redhaven Peach Research Articles

Early performance of several Prunus interspecific hybrid rootstocks for Redhaven peach in southern Ontario

A multi-year orchard experiment was established to measure the performance of Rootpac®-R, Rootpac®-20, Rootpac®-40, and Rootpac®-70 rootstocks using ‘Redhaven’ peach (Prunus persica var. persica) as the scion, compared with the ‘Bailey’ peach seedling rootstock, the current industry standard. Tree survival after five years was 79% on Rootpac-40, whereas the remaining rootstocks showed no tree mortality. Tree vigour and canopy height and width were influenced by rootstock genotype beginning the year of planting in 2016. For the first five years of production, Rootpac-70 consistently produced the largest trees based on truck cross-sectional area (TCSA) and by year five, all rootstocks produced trees with similar TCSAs, except for Rootpac-70, which was 38% larger than Bailey. By year five, cumulative yields were greatest on Rootpac-70, which were 10% higher than Bailey; cumulative yields of Rootpac-R, Rootpac-20, and Rootpac-30 were 98%, 89%, and 84% that of Bailey, respectively. Cumulative yield efficiency was significantly influenced by rootstock although the magnitude of the differences was small and likely of insignificant commercial importance. Rootpac-40 consistently produced the largest fruit. These results are only reflective of the orchard establishment years and additional data are required before peach producers can make fully informed decisions concerning the rootstocks evaluated in this study for their orchard systems. However, at this juncture, all the Rootpac rootstocks evaluated in this study are likely to impart excessive vigour to be used in a higher density system and offer little advantage over Bailey.

Effects of Various Irrigation Regimes on Soil Water Balance, Yield, and Fruit Quality of Drip-Irrigated Peach Trees

The aim of this research was to determine the amount of irrigation water, irrigation interval, and water consumption that gave the greatest yield, to determine the effect of irrigation on fruit quality characteristics, and to investigate variations in soil moisture in Redhaven peaches irrigated by drip irrigation in the Aegean region of Turkey. The study was performed in 2003 and 2004 on split plots in randomized blocks with three replications. Main treatments were 3 and 6 days between irrigations, and subtreatments comprised four different pan coefficients (Kp1.25, Kp1.00, Kp0.75, and Kp0.50). According to the 2-year averages of peach yields, the effect on yield of the amount of irrigation water was found to be significant (p<0.01), but the effect of the irrigation interval was found not to be significant. Total yield varied between 5,966 and 16,340 kg ha-1, and marketable yield between 5,349 and 14,164 kg ha-1, according to irrigation treatments. A maximum average yield of 14,101 kg ha-1 was obtained...

Quality of nectarine and peach nectars as affected by lye-peeling and storage

Abstract This study was focused on nectarine and peach nectars, with the aim to evaluate different quality indices at the time of production and to devise a predictive model for quality variation during storage at 23 and 37 °C. Nectars were produced from the Elegant Lady and Redhaven peach varieties and from the Stark Red Gold nectarine variety, from both peeled and unpeeled fruits. The effects of processing on antioxidant contents, antioxidant activity and colour were evaluated. At the time of production, β-carotene ranged from 0.52 to 0.79 mg/kg, hydroxycinnamic acids (chlorogenic and neochlorogenic) from 34 to 73 mg/kg, catechin from 0 to 24 mg/kg, quercetin 3-O-glycosides from 3.9 to 12.7 mg/kg, and cyanidin 3-O-glucoside from 0 to 9.4 mg/kg. Within the same variety, carotenoid and phenolic contents were lower in the nectars obtained from peeled fruits than in those obtained from unpeeled fruits. However, as ascorbic acid was adjusted to a level of 300 mg/kg during blending, which is far higher than the observed levels of phenolics and carotenoids, it mainly accounted for nectar radical-scavenging activity towards the 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl radical, which on average was 1.8 mmoles Trolox equivalents/kg. The colour of nectars was improved by processing lye-peeled fruits at room temperature, whatever the variety used; i.e., this process decreased the redness index, a∗, and increased the lightness index, L∗, and yellowness index, b∗, with respect to the traditional process. During storage, ascorbic acid degraded by following pseudo-first order kinetics, with the same rate constant for all nectars. The colorimetric parameters a∗, L∗, and b∗ varied following pseudo-zero order kinetics, with the same rate constant in all the nectars. Therefore, the better the colour after processing, the better it remained during storage. These results were validated by an independent process carried out with the Springebelle peach variety. From the kinetic models defined, which can be applied to the nectars whatever the variety and process used, it was demonstrated that an increase in storage temperature from 23 to 37 °C caused a 3.5-fold increase in the rate constant for ascorbic acid degradation and a 4-fold increase in the rate constants for a∗ and L∗ variations.

Standardizing Methods for Evaluating the Chilling Requirements to Break Dormancy in Seeds and Buds (Including Geophytes): Introduction to the Workshop

Many plants and/or organs require chilling to break their dormancy (Coville, 1920; Doorenbos, 1953; Nienstaedt, 1967). Generally, the optimum temperature is between 0° and 10 °C (Coville, 1920; Doorenbos, 1953; Nienstaedt, 1967). Temperatures required may be continuous, sequential or alternating. The establishment of appropriate protocols for breaking dormancy will permit comparisons between laboratories and produce more effective treatments for commercial use. Romberger (1963) has identified three phases of dormancy: 1) correlative inhibition, 2) rest, and 3) quiescence. Correlative inhibition occurs when buds do not grow because of inhibitory effects caused by apical dominance or lateral dominance (Samish 1954). This period has also been referred to as “Summer Dormancy” (Doorenbos, 1953). The rest phase, also called “Winter Dormancy” (Doorenbos, 1953), occurs when a bud does not grow because of the effects of an internal factor within the bud (Doorenbos, 1953). Quiescence, “Imposed Dormancy” (Doorenbos, 1953), refers to the condition when bud growth is inhibited because of unfavorable environmental conditions (Samish, 1954). Lang (1987) referred to these three phases of dormancy as “Ecodormancy” (correlative inhibition), “Endodormancy” (rest), and “Paradormancy” (quiescence). The termination of the endodormancy (rest) period in temperate plant organs of various species requires a period of chilling (Coville, 1920; Doorenbos, 1953; Nienstaedt, 1967). The duration of the chilling period and the temperature required to overcome endodormnacy (rest) are genetically controlled (Bennett, 1950; Nakasu et al., 1982; Nooden and Weber, 1978; Samish, 1954; Sherman et al., 1977). The prerequisite of the chilling period for the termination of endodormancy (rest) was first observed by Knight (1801) and subsequently studied by many researchers (Chandler et al., 1937; Coville, 1920; Molish, 1908). The effective chilling period ranges from 250 to 1000 hours (Samish, 1954; Vegis, 1964). Erez and Lavee (1971) indicated in peach trees, 5 °C is the optimum temperature to satisfy the chilling requirement. Fluctuating temperature has been proposed to be more effective in satisfying the chilling requirements of deciduous fruit trees (Erez at al., 1979; Lyr et al., 1970; Samish and Lavee, 1962). However, Lavender and Cleary (1974) found that fluctuating temperatures under natural conditions were less effective in overcoming chilling requirements than a constant temperature in many coniferous species. In addition, chilling requirements may vary with age for a given plant species (Nienstaedt, 1966) and variation within species also occurs (Sharik and Barnes, 1976). Scalabrelli and Couvillon (1986) found that terminal buds required less chilling temperatures than the lateral buds of ‘Redhaven peach. Long photoperiods may partially compensate for the chilling requirement in many plant species (Garber, 1983; Nienstaedt, 1966; Olmested, 1951). They postulated that low temperature and photoperiod are not entirely independent since long daylengths could partially compensate for insufficient chilling. A continuous 24-h photoperiod can break dormancy in many plant species (Downs and Borthwick, 1956; Kawase, 1961; Wareing, 1956), while a continuous dark photoperiod will cause budbreak of trees only after their chilling requirements have been satisfied (Wareing, 1956). Artificial breaking of endodormancy (rest) period has been practiced since the early 1900s (Doorenbos, 1953). Early methods used to force spring-flowering shrubs were: injury (Jost, 1893), acetylene (Johanssen, 1896), ether (Johanssen, 1900), electric current (Bos, 1907), and warm water bath (Molisch, 1908, 1909). Dormancy-breaking treatments were also used on temperate fruit trees grown in warm regions of the world which lacked sufficient chilling temperature to overcome rest naturally (Black, 1952). The amount and time of application of dormancy breaking agents, depends on the stage of physiological growth and genetic makeup of the plants (Erez, 1987; Fuchigami and Nee, 1987). Black (1952) indicated that most dormancy-breaking treatments should be applied at the sublethal (near-lethal) levels in order to be effective. Workshop Papers and Authors

FT-IR spectroscopic determination of the degree of esterification of cell wall pectins from stored peaches and correlation to textural changes

The FT-IR spectroscopic study of peach cell walls revealed the existence of two peaks absorbing at 1749 and 1630 cm −1 assigned, respectively, to the absorption of the esterified and non-esterified carboxyl groups of the pectin molecules. A linear relationship between the degree of esterification [(number of esterified carboxylic groups/number of total carboxylic groups)×100] and the ratio of the area underneath the peak at 1749 cm −1 over the sum of the areas underneath the two peaks, at 1749 and 1630 cm −1, was established using the FT-IR spectra of standard compounds. The use of the 2nd derivative and curve-fitting techniques allowed the elimination of spectral interferences from other cell wall components. The degree of esterification (D.E.) of pectins from Redhaven peaches immediately after harvest and during storage was evaluated from FT-IR data. During storage at 0°C, the D.E. remained practically constant up to 35 days. During storage at higher temperatures it decreased approaching a final value — the same for all temperatures. This value was reached after 22 days of storage at 5°C, 15 days at 15°C and after only 6 days at 20°C. The changes in the degree of esterification during storage correlated well to fruit firmness.

Orchard Performance of Seedling and Clonal Rootstocks for Peach on a Severe Peach Tree Short-life Site

Thirteen rootstocks grafted with Redhaven peach were established on a severe peach tree short-life (PTSL) site in central Georgia. Most rootstocks tested were peach seedling types: Lovell, Nemaguard, Guardian (BY520-9), BY520-8, Boone County, Bailey and two `Tennessee Natural' selections. A seedling plum rootstock, St. Julian, was also used. Clonal type rootstocks included a peach × almond hybrid, GF677; plum, GF43 and Damas 1869; and a plum hybrid, GF655-2. Trees on Guardian displayed the best survival with only 20% mortality due to PTSL, through 7 years. In contrast, 40% of trees on Lovell succumbed to PTSL. Currently, Lovell is the recommended rootstock for PTSL-prone sites. Other rootstocks ranged from 50% to 100% mortality due to PTSL. Trees on Guardian displayed significantly higher vigor through the first 4 years following planting compared to trees on Lovell. Furthermore, trees on Guardian produced significantly greater yields than those on Lovell, in all but 1 year. Rootstock effects on tree survival, vigor, bloom and harvest dates, fruit yield and size, and suckering will be discussed.

DAMAGE LOSS COST CURVES FOR PEACH IMPACT BRUISING1

ABSTRACTFor the design of protective packaging for the distribution of fresh market peaches, it is important to determine the damage loss cost curve. This curve combines data on the frequency of drops in distribution as a function of drop height with the likelihood of losses occurring from damage resulting from impacts from specific drop heights. For fresh market peaches, externally visible bruises are the impact damage producing losses. In this study peaches of six cultivars were dropped onto a steel plate from heights in the range 8–38 cm. They were visually examined externally and internally for bruises and for fiber tears. Results were combined with data from a previous study covering the overlapping range of 31–91 cm. and used to calculate the damage loss cost curves for Redhaven peaches and for the composite of the six cultivars. The curves predict worst case losses in the 95% range for packages designed to protect against drops of 16 cm or less. Worst case losses decrease steadily with package designs ranging up to 46 cm where losses are in the 10–20% range.

CYCLES IN GAS EXCHANGE OF PEACH IN GREENHOUSE.

Observations from the field experiments on peach (Prunus persica) over the past 7 years suggested a possibility of regular cycles in single leaf gas exchanges (SLGE). The purpose of this research was to study SLGE of peach under the controlled photosynthetic light using metal halide lamps in the greenhouse to determine if such cycle existed. Eighteen trees of Redhaven peach, 6 each on Lovell, Nemaguard, and Wildpeach rootstocks grown in 30 L plastic containers, which were arranged on 2 benches 6 feet below the metal halide lamps. Two leaves per tree were selected 5 feet below the individually controlled lamps. Lights were turned on 30 minutes prior to observations for PAR, leaf temperature, transpiration, stomatal conductance, and photosynthesis measurements. Using a portable (LI-6000) photosynthesis system, SLGE were recorded on the same leaves daily from 0900 to 1100 h for 3 weeks starting on 1 July 1992. Though fluctuating natural light caused minor variations in PAR, it was always above the saturation point. Light did not affect leaf temperature. No distinct cyclic pattern for any of the measured SLGE parameters was observed. Rootstock significantly affected photosynthesis; trees budded on Lovell had higher rate than on Wildpeach. It is concluded that the likely cycles in the SLGE data from field studies may not be real but have resulted from the environment.

CHANGES IN ORGANIC ACIDS AND OTHER COMPOSITIONAL AND PHYSIOLOGICAL ATTRIBUTES OF PEACHES DUE TO CHILLING INJURY.

Babygold 5 (BG5) and Redhaven (RDH) peaches at maturity 4 were held at 2.3°C for 0, 2 and 4 weeks. After each cold storage treatment half of the fruit sample was evaluated; the other half was ripened for 8 days at 21°C and respiration was measured daily. The evaluations on both samples were for malic, citric and quinic acids, titratable acidity (TA), soluble solids (SS) and flesh firmness. Malic acid in ripened BG5 and RDH Fruits increased relative to their unripened counterpart over the cold storage time; citric acid increased in BG5, decreased in RDH; quinic acid decreased in both cultivars; TA increased; SS decreased in BG5, did not change in RDH; flesh firmness increased in BG5, did not change in RDH. Respiratory rate increased with cold storge time in both cultivars. Overall, BG5 showed more susceptibility to chilling than RDH.

SHORT-LIFE AND NON-SHORT-LIFE SOIL RATIO AND ROOT TYPE AFFECT PEACH TREE SURVIVAL IN FIELD MICROPLOT

A planting of 90 Redhaven peach (Prunus persica (L) Batsch) trees either budded to Lovell and Nemaguard rootstocks or on their own roots, was established in spring 1984 using in-ground 55-gallon microplots. Planting soils (top soil, not B and C layers) prepared in five ratios by mixing soils from peach tree short life (PTSL) and non-PTSL (NPSL) sites (100% PTSL, 75% PTSL + 25% NPSL, 50% of each, 25% PTSL + 75% NPSL, and 100% NPSL) as main plots, were replicated 3 times. Two trees per rootstock were randomized within main plots. The planting was maintained using conventional cultural practices. Observations for tree survival were recorded in December each year. During this investigation, both soil mix and root types significantly affected tree survival, which was consistently the highest in 100% NPSL and the lowest in 100% PTSL soil. Effects of other soil combinations were intermediate; however, greater tree mortality was associated with increased ratio of PTSL soil. Trees on Lovell roots invariably survived the best followed by those on Nemaguard roots and the lowest when on their own roots. As early as in fourth leaf, &gt;55% of the own-rooted trees died compared to &lt; 10% on either rootstock.

ESTABLISHMENT OF A REDHAVEN PEACH ORCHARD WITH Pratylenchus penetrans-INFESTED AND NONINFESTED ROOTSTOCKS IN A FUMIGATED AND NONFUMIGATED NIAGARA SOIL

Redhaven peach (Prunus persica (L.) Batsch) trees, grafted on the rootstocks Bailey, Siberian C, or Harrow Blood, with roots free of, or infested by, root-lesion nematodes (Pratylenchus penetrans) were planted in fumigated or P. penetrans-infested Vineland fine sandy loam at Jordan Station, Ontario. Tree growth and soil nematode population densities were monitored for 6 yr. In general, fumigation suppressed soil populations of P. penetrans during the first 4 yr, whereas no consistent nematode control was obtained through the use of nematode-free rootstock. The rootstock Siberian C supported larger numbers of P. penetrans than the other two rootstocks throughout the experiment, whereas Bailey favored the build-up of the pin nematode (Paratylenchus projectus). Tree diameter of nematode-free rootstock was greatest in the first 3 yr only; soil fumigation alone increased growth during the first year only. Tree mortality tended to be lowest in fumigated soil planted to clean rootstocks. Harrow Blood showed the highest mortality; Siberian C the lowest. The data suggest that only nematode-free peach trees should be planted. Orchards should be fumigated if P. penetrans exceeds 800 kg−1 of soil and/or when there is a history of replant failure on a light-textured soil.Key words: Prunus persica, pin nematode, Paratylenchus projectus, replant problem, rootstocks, fumigation

Fruit thinning of peach trees (Prunus persica(L.) Batsch.): the effect of paclobutrazol on fruit drop and shoot growth

SummaryPaclobutrazol (2000 mg l−1) was tested as a fruit thinning agent for cvs Redhaven and Sudanell-1 peach trees. Foliar sprays were applied at three different stages of fruit development: G or petal fall; H or shuck-off; and the beginning of pit-hardening, and compared to trees either hand-thinned or left unthinned. No effect on fruit drop or crop load was observed on Redhaven, but some abscission of fruits occurred on the Sudanell-1 trees treated with paclobutrazol at stages G and H. Shoot growth of both cultivars was inhibited by the two latter applications; this effect was greater in Redhaven, which also showed a reduction in trunk girth increment. In the year after treatments no effect on cropping was observed, but shoot growth was promoted on the trees treated with paclobutrazol in comparison with trees either hand-thinned or left unthinned in the previous year.

SEASONAL VARIATION IN CAMBIAL ELECTRICAL RESISTANCE AND ITS RELATION TO GROWTH IN TWO CULTIVARS OF PEACH

Seasonal trends in cambial electrical resistance (CER) of Loring and Redhaven peach trees (Prunus persica (L.) Batsch) were monitored with the use of a Shigometer. Three readings were taken on the main trunk of each tree periodically from early June 1981 through early December 1982. Individual records were maintained for each tree. One increment core was also taken from the trunk of each tree in late November 1982. The data suggested a relationship between CER and the onset of dormancy and a multiple regression analysis demonstrated a significant correlation between CER and growth, cultivar, and a growth-cultivar interaction (R2 = 0.61).Key words: Prunus persica, dormancy, growth, electrical resistance, peach

Peach and apple thinning by shading and photosynthetic inhibition

SummaryShading cv Biscoe peach scaffold limbs 30–40, 35–45 and 40–50 days after full bloom (AFB) caused greater fruit abscission than shading from 15–25, 20–30, 25–35 or 50–60 days AFB. Terbacil, applied to peach limbs at 400 ppm thinned fruit at a similar timing as shading (35 and 40 days AFB). Whole tree airblast sprays of terbacil (300 ppm) applied 35 days AFB to cv Redhaven peach trees induced fruit abscission, but c. 25 % of the leaves showed marginal yellowing at harvest. Flower buds were produced at the nodes of leaves bearing symptoms. Shading of cv Starkrimson Delicious limbs from 16–26 days AFB caused significant fruit abscission. Shading 6–16, 26–36 and 36–46 days AFB did not induce fruit drop. Terbacil (400 ppm) applied to limbs at 6 and 16 days AFB significantly reduced fruit set, but applications 26 and 36 days AFB were ineffective. Whole tree airblast applications of terbacil (200 ppm) defruited spur cv Delicious trees when applied 16 days AFB. Limb treatments of terbacil at rates twice those of the airblast treatments caused much less fruit abscission. No leaf symptoms were observed with the airblast treatments (200 ppm), but some yellowing of leaves occurred on the limb treatments that were applied with a hand sprayer to the point of drip at 400 ppm. Apple and peach fruit from shaded or terbacil-thinned limbs or trees were similar or larger than from hand thinned.

Control of Green Peach Aphid and Peach Twig Borer, 1983

Abstract A 4-year-old orchard of Nectared, Ruby Grande, Harko nectarines and Early Redhaven and Elberta peaches was used in this test. Replicated four-tree blocks of each variety were used for both treatments and the check. Treatments were applied on 31 Mar. All plots were sprayed to the point of drip (400 to 500 gal/acre) with handguns at 400 to 500 lb/in2 . Evaluation was made by counting number of colonies for green peach aphid and the number of wilted terminals per tree for the peach twig borer.

Peach, Lesser Peach Tree Borer Control, 1979 and 1980

Abstract A 15-yr-old block of Sunqueen and Red Haven peaches was used in these tests. The objective of the 1979 experiment was to determine the effects of timing and interval between applications on the performance of Thiodan. The objective in 1980 was to compare the effectiveness of several insecticides for lesser borer control. In each year, 10 trees arranged in a randomized block design were used for each treatment. Sprays were applied to the trunk and scaffold limbs with a hydraulic sprayer equipped with a hand-gun and operated at 250 pst. Trees were sprayed until the bark, and especially old borer injuries, were thoroughly soaked, which required approximately 4 gallons of spray per tree. The timing of sprays coincided with the emergence of 1st generation moths, as measured by pupal case counts and pheromone trap catches. Timing of applications in 1979 using Thiodan 50WP 0.75 lb Al/100 gal is given in Table I; application dates in 1980 were Jun 6 and 26. The treatment effectiveness was determined by weekly counts of pupal cases, which was indicative of the number of larvae and pupae able to complete their development in the treated trees (1980) and the successful establishment and completion of development by the generation following treatment (1979, 1980). Pupal cases were removed as counted.

Characterization and Partial Purification of Aldose-6-phosphate Reductase (Alditol-6-Phosphate:NADP 1-Oxidoreductase) from Apple Leaves

Aldose-6-phosphate reductase (alditol 6-phosphate:NADP 1-oxidoreductase) was isolated and characterized from mature apple leaves (Malus domestica cv. Starkrimson). The enzyme was purified 79-fold. The enzyme catalyzed the following reversible reaction: d-glucose 6-phosphate + NADPH + H(+) right arrow over left arrow d-sorbitol 6-phosphate + NADP(+). No activity was detected when NAD(+) was substituted for NADP(+) or when NADH was substituted for NADPH. The enzyme reduced d-galactose 6-phosphate at a higher rate than d-glucose 6-phosphate. d-Mannose 6-phosphate and 2-deoxy-d-glucose 6-phosphate were reduced at low rates. d-Glucose 1-phosphate, d-fructose 6-phosphate, d-ribose 5-phosphate, d-glucose, and sorbitol did not serve as substrates. The pH optimum for both d-sorbitol 6-phosphate oxidation and d-glucose 6-phosphate reduction was 9.5. The K(m) values for d-sorbitol 6-phosphate oxidation and d-glucose 6-phosphate reduction were 3.9 and 20 millimolar, respectively. AgNO(3) (0.1 millimolar) and p-chloromercuribenzoate (1.0 millimolar) completely inhibited the enzyme.Aldose-6-phosphate reductase activity was also detected in mature leaves from Golden Delicious and Antonovka apples (Malus domestica), Conference and Bartlett pears (Pyrus communis), Redhaven peach (Prunus persica), and Perfection apricot (Prunus armeniaca). This suggests that the enzyme has a wide distribution and plays an important role in sorbitol synthesis.

ENZYMATIC BROWNING OF PEACHES: EFFECT OF GIBBERELLIC ACID AND ETHEPHON ON PHENOLIC COMPOUNDS AND POLYPHENOLOXIDASE ACTIVITY

ABSTRACTFoliar sprays of gibberellic acid and ethephon applied to Redhaven peach trees at 21 and 46 days after bloom caused a reduction of enzymatic browning in mature fruit tissue. A replicate from each treatment was analyzed by two‐dimensional thin‐layer chromatography and polyacrylamide disc gel electrophoresis. Twenty‐one polyphenolic compounds were separated. Eight were oxidized by PPO, and were tentatively identified as four chlorogenic acid isomers, three leucoanthocyanidins, and catechin. No differences in qualitative distributions of phenolic compounds were observed which would account for the inhibition of browning in peach tissue. Polyacrylamide disc gel electrophoresis of peach PPO preparations showed the presence of up to 11 multiple forms displaying activity toward catechol. The bands had different substrate specificities and were present in different amounts, but PPO from peaches treated 21 days after bloom appeared to have a catechol reactive band not present in untreated peaches or peaches treated 46 days after bloom. One band from peaches treated 46 days after bloom with 150 ppm ethephon appeared to have decreased substrate specificity toward pyrogallol. Crude PPO preparations from untreated fruit and fruit receiving the 46‐day treatments oxidized o‐dihydroxyphenols only, and the relative PPO activities varied with treatment. These PPO preparations exhibited two pH optima; pH 4.4 and 6.2 for untreated and GA‐treated peaches (46‐day treatment), and pH 4.4 and 6.6 for peaches treated with ethephon (75 or 1.50 ppm, 46‐day treatment). PPO from the treated peaches had a lower proportion of total activity at pH 4.4 than PPO from untreated peaches.

Purification and characterization of polyphenol oxidase in redhaven peaches

Polyphenol oxidase from Redhaven peaches ( Prunus persica BATSCH) was purified by column chromatography on, Phenyl Sepharose, ECTEOLA Cellulose, Hydroxylapatite, and benzoylated DEAF Sephadex. The partially purified enzyme showed two major bands on, disc gel electrophoresis when stained for polyphenol oxidase activities, proteins, glycoproteins, and lipoproteins. Thin layer isoelectric focusing data indicated a pI between p H 4.5 and 5.5. The purified enzyme was stable for two months in buffered 20 % sucrose, glycerol, or ethylene glycol solutions at −15°C. Digestion of the enzyme with carbohydrases and proteases generated new isoenzymic forms of the enzyme.

Carotenoid Changes in the Mesocarp of the Redhaven Peach (Prunus persica) during Ripening

Summary Changes in the carotenoid pattern of the mesocarp of the Redhaven peach ( Prunes persica ) were investigated during the maturation period. In the green fruit the ratio between the four basic chloroplast carotenoids: β-carotene, lutein, violaxanthin and neoxanthin was 1 : 1 :2 : 1 differing from that found in leaves. The total carotenoid content was low, varying between 5-9 ,ug/g fresh weight. During ripening the level of β-carotene, lutein and neoxanthin decreased gradually. Levels of violaxanthin followed an uncommon course rising to a maximum as the fruit reached the preclimacteric stage and then gradually decreasing until maturity. The pattern of carotenoids in the climacteric fruit was characterized by the presence of additional pigments such as phytofluene (10%), cryptoxanthin (15%), isolutein (8%) and zeaxanthin (7%). Comparison with carotenoid patterns of two other varieties of peach revealed striking differences in carotenoid metabolism during maturation.