Showing papers in "Journal of the American Society for Horticultural Science in 1990"

Comparison of extraction methods for the rapid determination of essential oil content and composition of basil

Abstract: Essential oils were extracted from leaves, flowers, and stems of Ocimum basilicurn, O. kilimandschar icum, and O. micranthum by solvent extraction, hydrodistillation, and steam distillation for essential oil content and the oil analyzed by GC and GC/MS for composition. While the yield of essential oil was consistently higher from steam distillation than hydrodistillation, a similar number of compounds was recovered from both hydrodistillation and steam distillation. Though the relative concentration of the major constituents was similar by both methods, the absolute amounts were higher with steam distillation. Essential oil content and composition varied by plant species and plant part. Essential oil content was highest in flowers for O. basilicum and in leaves for O. micranthum. No significant differences were observed in essential oil yield and relative concentration of major constituents using fresh or dry samples and using samples from 75 g to 10 g of dry plant tissue. While minor differences between hydrodis- tillation and steam distillation were observed, both methods resulted in high yields and good recovery of essential oil constituents. Hydrodistillation is a more-rapid and simpler technique than steam and permits the extraction of essential oil where steam is not accessible. Essential oils are a diverse group of natural products that are important sources of aromatic and flavoring chemicals in food, industrial, and pharmaceutical products. Essential oils are largely composed of terpenes and aromatic polypropanoid compounds derived from the acetate-mevalonic acid and the shikimic acid pathways, respectively. Essential oil composition of plants var- ies and is due to genetic and environmental factors that influence genetic expression (Bernath, 1986). The essential oil content of plant tissue also varies with developmental stage (Burbott and Loomis, 1967), and can vary by extraction methods (Guenther, 1972).

Enzyme Polymorphism in Mango

Abstract: Forty-one (Mangifera indica L.) cultivars were characterized electrophoretically using the isozyme systems aconitase, isocitrate dehydrogenase, leucine aminopeptidase, phosphoglucose isomerase, phosphoglucomutase, and triosephosphate isomerase. The outcross origin of some of the mango cultivars was supported by the isozymic banding patterns. Reported parentage of some other cultivars was not consistent with their isozymic banding patterns.

Prestorage heat treatment as a means of improving poststorage quality of apples.

Abstract: Additional index words. Malus domestics, color, firmness, acidity, soluble solids concentration, ethylene, respiration Abstract. The benefits conferred by a prestorage heat treatment on poststorage quality of apples (Malus domestics Borkh.) were measured on 'Anna', a non-storing early cultivar, and 'Granny Smith', a long-storing late cultivar. The major benefit was a decrease in rate of apple softening, both during OC storage and during simulated shelf life at 20C. Soluble solids concentration was not affected by heat treatment, but titratable acidity was reduced. Ethylene production after heat treatment and storage was similar to or higher than that of control apples, but respiration was lower. The optimum temperature and time combination for prestorage treatment of both cultivars was 4 days at 38C. High temperatures have been reported to inhibit ripening of many-fruits "(Mitchell, 1986). If held for too long above 35C, fruit will fail to ripen normally when returned to lower temper- atures. However, pears and apples have been reported to ripen normally if held at 40C for up to 6 days and then returned to 20C (Maxie et al., 1974; Liu, 1978). Liu examined ripeness indices of four cultivars of apples after 2 or 4 days at 40C and found that, compared to control, the heat treatment lowered titratable acidity, retained firmness, and had no effect on soluble solids concentration (SSC). Porritt and Lidster (1978) reported similar changes after storage of heat-treated apples. We have examined this prestorage treatment on 'Anna' apples, a non- scoring early cultivar, and 'Granny Smith,' a long-storing late cultivar. We determined how long the effects persisted in stored apples by examining their rate of ripening, ethylene production, and respiration after various durations of storage. We also de-

Tolerance of `Valencia' Oranges to Controlled Atmospheres, as Determined by Physiological Responses and Quality Attributes

Abstract: Valencia' oranges (Citrus sinensis (L.) Osbeck) tolerated up to 20 days of exposure to 0.5%, 0.25%, or 0.02% O2, at 5 or 10C followed by holding in air at 5C for 7 days without any detrimental effects on external and internal appearance. Oranges stored in 0.5%, 0.25%, or 0.02% O2 had lower respiration rates, but higher resistance to CO, diffusion and higher ethanol evolution rates than those stored in air at 10C. Similar, but less pronounced, effects of the low O2 atmospheres were observed at O and SC. Respiration rates, internal CO 2 concentrations, and ethanol evolution rates were generally higher at 10C than at 0C, while resistance to CO 2 diffusion was lower at the higher temperature. 'Valencia' oranges kept in 60% CO2 at 5C for 5 to 14 days followed by holding in air at 5C for 7 days developed slight to severe injury that was characterized by skin browning and lowered external appearance scores. Juice color, soluble solids content, pH, titratable acidity, and ascorbic acid content were not significantly influenced by either the low O2 or the high CO2 treatments. However, these treatments increased ethanol and acetaldehyde contents, which correlated with the decrease in flavor score of the fruits. Ethanol content of the oranges transferred to air following low 0 2 treatment correlated with CO2 production rate of the fruits at the transfer temperature and was related to ethanol evolution and probably production rates after the transfer. Long-term storage of oranges in controlled atmospheres (CA) is not recommended because CA has little or no advantage for extending the storage life of the fruits (Hatton and Cubbedge, 1977a). Low O2 or high (CO2 atmospheres stimulated accumu- lation of ethanol, acetaldehyde, and several other volatile com- pounds in oranges (Davis et al., 1973; Norman and Craft, 1971; Pesis and Avissar, 1989) and increased activity of pyruvic de- carboxylase (EC 4.1.1.1) and alcohol dehydrogenase (EC 1.1,1.1) (Davis et al., 1973). CA storage delayed skin degreening and extended storage life of limes and lemons (Hatton and Cub- bedge, 1977a; Hatton and Reeder, 1969). Prestorage treatments with 10% to 40% CO2 in air reduced chilling injury and stem- end rind breakdown of grapefruits (Hatton and Cubbedge, 1977b; Hatton et al., 1975). Although oranges can not tolerate long-term storage in CA conditions, the fruits may tolerate a short period of exposure to low O2 and/or high CO2 atmospheres. In recent years, there has been an increased interest in studying the responses of fresh fruits and vegetables to short-term exposure to O 2 levels at or below 1% and CO2 levels at or above 50% because these at- mospheres may be effective as a quarantine treatment for post- harvest insect control (Aharoni et al., 1979; Benshoter, 1987; Lidster et al., 1981, 1984; Soderstrom and Brandl, 1987). CA treatment can be used for quarantine procedure only when they can effectively kill the insects of concern without detrimental effects on quality attributes of the fresh commodities. In this study, we investigated the effects of short-term ex- posures to O 2 levels at or below 0.5% and CO2 level at 60% at 0, 5, and 10C on postharvest physiology and quality attributes of 'Valencia' oranges to determine their tolerance to these treat- ments, which may be used for postharvest insect control.

Seasonal Fluctuations of Some Enzymes Relating to Sucrose and Sorbitol Metabolism in Peach Fruit

Abstract: Sugar levels and composition were determined in developing 'Hakuto' peach (Prunus persica Batsch var. vulgaris Maxim.) fruit. Glucose and fructose in nearly equal amounts were the predominant sugars detected during the early stage of development. Sucrose subsequently began to accumulate and was the predominant sugar in mature fruit. Sorbitol remained at a low level throughout development. The large increase in the amount of sucrose was accompanied by a rapid increase in sucrose synthase (EC 2.4.1.13) activity. Sucrose phosphate synthase (EC 2.4.1.14) was also detected in flesh extracts, but the activities were low throughout development. Acid invertase (EC 3.2.1.26) activity was highest in young fruit and declined with development. Activity, however, increased again at a later stage of development. Peach fruit contained appreciable sorbitol oxidase activity, while other sorbitol-related enzymes were barely detectable, suggesting that transported sorbitol was predominantly converted to glucose. These results suggest that the supply of glucose and fructose depends on acid invertase and sorbitol oxidase, and that accumulation of sucrose depends on-sucrose synthase.

Environment Influences Anatomy of Stomata and Epidermal Cells in Tissue-cultured Rosa multiflora

Abstract: The surface structure of rose (Rosa multiflora L. CV. Montse) leaves formed in vitro under several envi- ronmental conditions (light level, relative humidity) and with various growth regulator treatments was studied by light and scanning electron microscopy. The epidermis from leaves developed in cultures grown under a higher light level and a lower relative humidity (80 µmol·s -1 ·m -2 and 75% RH) than the conditions used in commercial labora- tories (25 µmol·s -1 ·m -2 and 100% RH) showed anatomical modifications of the epicuticular wax, stomata, and epidermal cells similar to that of greenhouse-grown plant leaves. These results indicate that cultured plantlets can resemble greenhouse-grown plants under modified environmental conditions. In vitro pretreatment will reduce trans- plant losses and shorten the acclimatization period in the greenhouse. The survival and growth of in vitro plantlets is still problem- atic for some crops. Reduced cuticle development, abnormal stomatal function (Brainerd and Fuchigami, 1981; Fuchigami et al,, 1981) and poorly developed vascular systems (Fabbri and Bartolini, 1985; Grout and Aston, 1977; Leshem, 1983; Ziv et al., 1981) are suggested causes for the susceptibility of plantlets to water stress during acclimatization. Gradual hardening-off with periods of decreasing humidity are necessary for plantlets to survive the transition from culture to the greenhouse or the field. Despite elaborate and time-consuming acclimatization protocols using humidity tents and/or intermittent mist, signif- icant losses are often incurred, particularly in dicotyledonous woody species (Wardle et al., 1983) and herbaceous plants sus- ceptible to vitrification; e.g., Dianthus (Ziv et al., 1981) and Cynara scolymus (unpublished data). Hardening-off plantlets in vitro, by reducing the humidity (Maene, 1985; Maene and Debergh, 1987; Vanderschaeghe and Debergh, 1987) and increasing the irradiance, might reduce losses because the plantlets would be less fragile when removed from culture. The present study was undertaken to determine if en- vironmental changes in the culture container could improve the quality of in vitro plantlets before transplanting to greenhouse conditions.

Postharvest Ethanol Buildup and Off-flavor in 'Murcott' Tangerine Fruits

Abstract: “. Britex and Zivdar, water-based polyethylene waxes, were applied in commercial and experimental formulations as spray coating, a single dip, or double dips on ‘Murcott’ tangerine (Citrus reticulate Blanco) fruits. Postharvest waxing of ‘Murcott’ tangerine reduced weight loss but affected the sensory characteristics of the fruit. Charges in fruit weight loss and juice composition occurred in the waxed fruits after 4 weeks of storage at 5C plus 1 week of simulated retail handling at 17C. Changes quality. ‘Murcott’ is a hybrid tangerine cultivar that has been grown in Israel for almost 15 years. The fruit is flat (oblate) with a yellowish peel and a firm texture. The flesh is tender, very sweet and juicy, and has a very rich flavor. Harvested fruit, however, especially those that are waxed, develop off-flavors regardless of rootstock origin, maturity at harvest, or storage conditions (Cohen et al., 1985). Newhall and Grierson (1955) emphasized the necessity of wax coating citrus to impart a high gloss to the skin and to prevent water loss and shrinkage, thus prolonging the marketing life of fresh fruit. However, Davis et al. (1967, 1973) showed that waxing various citrus fruit cultivars affects respiration and composition of the internal atmosphere, leading to the development of distinct off-flavors. In studies of physiological changes occurring in citrus fruits during storage, ethanol was found to be the volatile component undergoing the greatest change (Davis and Chace, 1969). Ethanol buildup and off-flavors in juice were found after multiple coatings of either water- or solvent-solub le waxes were applied to oranges. These detrimental effects emphasize the dangers of overtaxing (Davis and Hoffmann, 1973). The aim of this study was to determine whether various wax formulations, either those already in use commercially or those experimentally produced for coating ‘easy-to-peel” fruits, differ in their influence on physiological, chemical, and sensory characteristics of ‘Murcott’ tangerines during storage and simulated retail handling (shelf-life).

Calcium-mediated postharvest changes in texture and cell wall structure and composition in golden delicious apples

Abstract: Changes in texture, cell wall structure and composition during storage of Ca-treated and untreated 'Golden Delicious' apple fruit (Malus domestics Borkh.) were investigated. The cell wall region of Ca-treated fruit showed no swelling during storage and cell-to-cell contact was maintained, whereas regions of the middle lamella in untreated tissue stained lightly, appeared distended, and eventually separated. In control fruit, microfibril orientation was lost in distended regions of the cell wall, especially in the outer wall region adjacent to the middle lamella. Furthermore, the middle lamella was fenestrated and in some cases was completely degraded. These changes during storage of control fruit were accompanied by a decrease in arabinose and galactose moieties of the cell wall and an increase in soluble pectin. Calcium treatment of fruit inhibited solubilization of polyuronide and arabinose moieties and reduced the loss in galactose content during storage. Tensile strength and firmness were positively correlated to Ca content of the fruit cortex. Excessive tensile stress caused tissue failure in control fruit when cells of the cortical tissue separated at the middle lamella. In contrast, cylinders of Ca-treated fruit fractured through cortical cell walls.

Salt Effects on Growth and Ion Uptake of Pistachio Rootstock Seedlings

Abstract: The degree of salt resistance of Pistacia spp. grown in the western United States is not adequately known. This study evaluated seedling growth and ion uptake characteristics of two Pistacia spp. and one hybrid in outdoor lysimeters for two seasons. After 12 weeks, seedling stem elongation of P. atlantica Desf., P. terebinthus L. (three selections), and P. integerrima Stewart × atlantica (referred to as Gold II) was reduced by an average of 33% at soil solution salinity of 12.6 dS·m -1 (or 8.0 dS·m -1 in the saturation extract). Gold II was the most vigorous genotype and produced the greatest biomass in control and high-salt solutions. Decreases in root and stem growth (average of all seedlings combined) occurred at soil solution salinity of 13.8 dS·m -1 (or 8.7 dS·m -1 in the saturation extract). Increasing salinity resulted in a higher root to stem ratio, which was most pronounced in P. terebinthus. Comparatively small but significant differences in leaf Na and Cl concentrations between species and selections occurred. All species limited Na transport to leaf tissue up to 125 meq Na/liter in soil solution, storing the greatest amount in roots. Chloride concentrations on a dry-weight basis were substantially higher in leaves than in roots. Increasing salinity did not affect leaf K and Mg concentration s, whereas Ca was significantly reduced. Leaf Na and Cl concentration s of P. atlantica and P. terebinthus had significant correlation with Na and Cl concentration s in soil solutions (r = + 0.83 to + 0.94). Domestic cultivation of pistachio, P. vera L., began in Cal- ifornia and has recently increased in Arizona, southern New Mexico, and far west Texas. These areas are frequently affected by high salinity, and pistachio, which has been described as salt-tolerant (Sepaskhah and Maftoun, 1981; Behboudian et al., 1986), is potentially an alternative to salt-sensitive pecan (Carya illinoensis (Wangenh.) C. Koch.) or almond (Prunus amygdalus Batsch). P. atlantica, P. terebinthus, and P. integerrima are the major rootstock of the domestic pistachio industry. How- ever, the responses of these species to salinity in southwestern growing conditions have not been adequately studied. Most in- vestigations have been made in a greenhouse environment and confined to P. vera scion cultivars not grown in the United States (Parsa and Karimian, 1975; Sepaskhah and Maftoun, 1981, 1982; Sepaskhah et al., 1985). These studies have demonstrated that growth rates of P. vera cultivars decrease with increasing NaCl concentration in culture solutions and that a positive cor- relation exists between Na as well as Cl concentrations in plant tissue and in the culture solutions. Although direct evidence is yet to be determined, some believe that Cl and possibly Na may cause specific ion effects in pistachio. Sepaskhah and Maftoun (1982), for instance, have suggested that differential salt sen- sitivity of P. vera cultivars may be related to the degree of Na and Cl accumulation in the plant. Scorching of bearing 'Ker-

Foliar application of calcium chloride delays postharvest ripening of strawberry.

Abstract: Additional index words. Fragaria × ananassa, storage, calcium Abstract. Effects of CaCl2 preharvest treatment on postharvest strawberry (Fragaria × ananassa) ripening and gray mold development were assessed. Two experiments were carried out in 1987 on two sites. In the first experiment, the effects of rate of application of CaCl 2 and degree of fruit maturity at treatment were studied with the conventional cultivar Kent. In the second experiment, the influence of concentration and frequency of application of CaCl 2 was investigated with day-neutral 'Tribute'. Calcium treatment caused a significant increase in fruit and leaf Ca contents, which were closely correlated. The degree of fruit maturity at application and the frequency of treatment did not affect Ca concentration in the tissues. Several maturity criteria were measured during fruit storage in air at 4C. Anthocyanin and free-sugar contents and tissue electrical conductivity increased, while titratable acidity and firmness decreased. In both experiments, Ca treatment delayed ripening and gray mold development. The delay increased with increasing Ca concentration . The importance of Ca in, the regulation of fruit ripening and vegetable maturation is well established (Ferguson, 1984; Poo- vaiah, 1986). Studies on leaf senescence (Ferguson, 1984; Poo- vaiah and Leopold, 1973) and fruit ripening (Poovaiah, 1986) show that tissue Ca content often infuences various senescence characteristics, e.g., protein and chlorophyll content (Poovaiah and Leopold, 1973) or rate of respiration (Bangerth et al., 1972). Calcium has been applied before and after harvest to prevent physiological disorders and to delay ripening of various fruits (Poovaiah, 1986). Most Ca entering the tissues accumulates in cell walls and membranes that are thought to be sites of its antisenescence action (Glenn et al., 1988). There has been ex- tensive research on the use of Ca to delay ripening of various fruits (Paliyath et al., 1984; Richardson and Al-Alani, 1982; Tingwa and Young, 1974), but little attention has been given to strawberry, a fruit with a short shelf life and highly suscep- tible to mold (Eaves and Leefe, 1962; Maas, 1971). The present study shows that foliar application of Ca may have beneficial effects on strawberry fruit storage by delaying ripening and development of gray mold (Botrytis cinerea ).

Hydrophilic Polymers— Their Response to Soil Amendments and Effect on Properties of a Soilless Potting Mix

Abstract: The levels of hydration of several hydrophilic polymers (hydrogels) varied greatly. Starch-based polymers had the fastest rate of hydration (<2 hours), followed by a propenoate-propenamide copolymer. Polyacrylamide materials required 4 to 8 hours to become fully hydrated. Maximum water retention in distilled water varied from 400 to 57 g of water per gram of dry material. All hydrogels retained less water in the presence of metal ions or fertilizers in the soaking solution, with substances releasing Fe +2 being the most detrimental. After exposure to fertilizers and ions, the water-holding capacity of a polyacrylamide with a high degree of cross linkage, but not that of hydrogels of the other structures, was fully recovered by subsequently soaking in distilled water. Pots amended with a polyacrylamide polymer but without Micromax (a micronutrient source) reached maximum water retention after six irrigations, while those with Micromax required 10 irrigations to reach peak water retention. The amounts of water being held in pots decreased after repeated fertilization. Medium volume increased with increasing levels of the polyacrylamide Supersorb C (0, 2, 4, or 6 g/pot). Micromax incorporated in medium amended with Supersorb C caused a depression in volume. Medium bulk density, total water retention, and water retention per unit volume of medium were increased by the incorporation of the hydrogel, regardless of the presence of Micromax. Noncapillary porosity measured at container capacity in medium amended with Micromax progressively decreased as the amount of hydrogel increased, but remained unchanged in medium without Micromax. Repeated drying and dehydration of the medium resulted in reduced water retention and increased noncapillary pore space.

Ripening of Mangos Following Low-temperature Storage

Abstract: The effects of harvest maturity of mangos (Mangifera indica L.) on storage tinder various low-temperature regimes and the influence of storage on quality development during subsequent ripening at higher temperatures were investigated. The capacity for storage of mango fruit depended on harvest maturity, storage temperature, and the time of harvest within the season. Development of peel and pulp color, soluble solids concentration, pH, and softening in 'Amelie', 'Tommy Atkins', and 'Keitt' mangos occurred progressively during storage for up to 21 days at 12C. Based on the level of ripening change that occurred during 12C storage, immature fruit showed superior storage capacity than fruit harvested at more-advanced stages of physiological maturity. On transfer to ripening temperatures (25C); however, immature fruit failed to develop full ripeness characteristics. Mature and half-mature fruit underwent limited ripening during storage at 12C, the extent of which increased with progressive harvests during the season. Ripening changes during storage for 21 days were less at 8 and 10C than at 12C. Chilling injury, as indicated by inhibition of ripening, was found at all harvest stored at 8C, and in early season harvests stored at 10C. Fruit from mid- and late-season harvests stored better at 10 than at 12C, with no apparent signs of chilling injury. Flavor of mangos ripened after low-temperature storage was less acceptable than of those ripened immediately after harvest. Suggestions are made for maximizing storage potential by controlling harvest maturity and storage temperature for progressive harvests throughout the season. Mangos are judged as luxury items on the markets of most temperatures may be a cultivar effect, and may also be related industrialized countries, although a reduction in price, together to, the stage of harvest maturity and ripeness of the mangos when with improved and consistent quality, likely could result in in- placed in storage. creased consumption. The high cost of mangos in importing Harvest in the fully mature, firm, green, pre-climacteric stage countries is due primarily to airfreight charges, but air transport does have the advantage of speed over sea transport. Sea trans-

Heat Shock Response in Field-grown, Ripening Papaya Fruit

Abstract: papaya Abstract. Mesocarp softening during papaya (Carica papaya L.) ripening was impaired by heating at 42C for 30 min followed by 49C for 70 min, with areas of the flesh failing to soften. Disruption of the softening process varied with stage of ripeness and harvest date. The respiratory climacteric and ethylene production were higher and occurred 2 days sooner in the injured fruit than in the noninjured fruit that had been exposed to 49C for only 30 min. Skin degreening and internal carotenoid synthesis were unaffected by the heat treatments. Exposure of ripening fruit to either 42C for 4 hr or 38 to 42C for 1 hr followed by 3 hr at 22C resulted in the development of thermotolerance to exposure to the otherwise injurious heat treatment of 49C for 70 min. Four stainable polypeptide bands increased and seven declined in single-dimensional acrylamide gels following incubation of fruit at the nondamaging temperature of 38C for 2 hr. Three polypeptides showed marked increases when polysomal RNA was translated. These polypeptides had apparent molecular weights of 17, 18, and 70 kDa. Proteins with molecular weights of 46, 54, and 63 kDa had slight increases after heat treatment. The levels of these polypeptides peaked 2 hr after heat treatment and declined within 24 hr. The amount of these polypeptides in the unheated control varied with the batch of fruit. The concen- tration of three translated polypeptides, with apparent molecular weights of 26, 37, and 46 kDa, declined. Other polypeptides continued to be translated during and after holding papayas for 2 hr at 38C.

Fertilizer salts reduce hydration of polyacrylamide gels and affect physical properties of gel-amended container media.

Abstract: Hydration of three commercial hydrophilic polyacrylamide gels in deionized water ranged from 340 to 420 g per gram of gel. Hydration was progressively inhibited by fertilizer salt concentrations from 0 to 20 meq·liter -1 . Hydration of the gels in the presence of divalent cations (Ca 2+ and Mg 2+ ) and monovalent cations (K+ and NH4 + ) at 20 meq·liter -1 was reduced to ≈10% ≈10% and 20% of maximum, respectively. The valence of the accompanying anion did not affect hydration. Gel hydration was unaffected by urea over the range of 2 to 20 m M. Sequential rinses of the hydrated gels with deionized water completely reversed the inhibition due to the monovalent, but not the divalent, cations. The electroconductivity (EC) of the external solution increased during gel hydration. In the presence of fertilizer salts, the physical properties of a 2 redwood sawdust : 1 sand (v/v) container mix were unaffected by hydrophilic gel additions of 1.2 and 2.4 kg·m -3 (1 × and 2 × the recommended rate, respectively). Hydrogels may have value as a soil amendment to improve water-holding capacity because these gels can hold up to 1500 times their weight in pure water (Johnson, 1984a). Polyacryl- amide gel added to coarse sand at a rate of 2 g·kg -1 increased

Respiration and C2H4 production in various harvested crops held in CO2-enriched atmospheres.

Abstract: The respiration rate (O2 uptake) and the rate of C2H4. production were measured before, during, and after 24 hours of treatment with 60% CO2 (20% O2) in 18 kinds of fruits and vegetables by use of an automated system connected to a microcomputer. High CO2 decreased respiration only in climacteric fruit and broccoli, which were producing C2H4. Ethylene production decreased with CO, treatment of peaches, tomatoes, and broccoli, but that of bananas increased. In five nonclimacteric fruits (three citrus species, grapes, and Japanese pears) and several vegetables (carrots, onions, cauliflower, and cabbage), in which C2H4 production was not detected, high CO2 affected respiration little, if at all. When eggplants, cucumbers, podded peas, spinach, and lettuce were treated with high CO 2, C2H4 production began and respiration increased. These results indicate that the respiratory responses of harvested horticultural crops to high CO2 might be mediated by the effects of CO2 on the action and/or synthesis of C2H4. There have been many studies of the storage of fruit and vegetables since the report of Kidd and West (1927) concerning the beneficial effects of high CO2/low O2 storage (controlled atmosphere, CA). Since CO2 is a product of respiration, it would be expected that respiration rate would decrease as CO2 concentration in the atmosphere increases (Hewer, 1987). Succinic acid accumulates and the activities of enzymes involved in its metabolism decrease in several fruits stored in high CO2, which is indirect evidence for this possibility (Biale, 1960; Kader, 1986). Carbon dioxide inhibits C2H4. action competitively and helps regulate C2H4 biosynthesis (Burg and Burg, 1967). Therefore, some of the benefits of storage in a high-CO2 atmosphere arise when C2H4 production or C2H4-mediated reaction is inhibited (Herner, 1987). It is not well-known how high CO, affects respiration and C2H4 synthesis; these two may be related (Sisler and Wood, 1988). The manner in which horticultural commodities respond to CO2 depends on the nature of the commodity and on the concentration and length of exposure to the gas (Herner, 1987). Although CO2 concentrations > 5% to 10% should be avoided in long-term storage, short-term exposure to very high CO2 (20% to 100’%) has beneficial effects on the storage life of some harvested commodities (Herner, 1987; Higashio et al., 1980). Using an automated microcomputer system for the measurement of O2 uptake, we determined that respiratory responses to high CO2 differed among horticultural crops and among developmental stages (Kubo et al., 1989a, 1989b). In these studies, however, the effects of high CO2 levels on C2H 4 production were not measured. The present study was designed to examine the effects of 60% CO2 in the presence of 20% 02 on the respiratory activity and C2H4 production in various horticultural crops. for publication 8 Jan. 1990. The cost of publishing this paper was n part by the payment of page charges. Under postal regulations, this refore must be hereby marked advertisement solely to indicate this r. Soc. Hort. Sci. 115(6):975-978. 1990. Materials and Methods Eighteen kinds of horticultural crops (Table 1) were used for the high-CO2 treatments. All plant material was obtained from a commercial market in Okayama, Japan. Treatment conditions. Plant material weighing =1 kg was placed in a respiration chamber (5.5 liter). Air was passed through the chamber for 12 hr, followed by a gas mixture of 60% CO2 ± 0.001%, 20% O2 ± 0.001%, and 20% N2 ± 0.001% for 24 hr, and by air for another 24 hr. The gas flow rate was 100 ml·min -1 and the chamber was at 25 ± lC. Measurement of respiration and C2H4 production. Both O2 uptake and C2H4 production were measured using an automated system connected to a microcomputer. The details of this system were described previously (Inaba et al., 1989). Briefly, the system consisted of a gas flow system, three gas chromatography (GC), a microcomputer, and interface. Two GCS, equipped with a thermal conductivity detector and molecular sieve 5A and Porapack Q column, were used for measurement of O2, CO2, and N2. N2 was used as an internal standard to improve the accuracy of measurement of 02. Another GC, with a flame ionization detector and activated alumina column, was used for measurement of C2H4. All operations, including gas sample injection, were regulated by the microcomputer. The measurement of O2 and C2H4 could be reproduced with an accuracy of 0.01% and 0.1 ppm, respectively. Uptake and production were measured every 3 hr during the experimental period. All measurements were repeated at least three times per treatment.

Physiological and Quality Responses of `Bartlett' Pears to Reduced O2 and Enhanced CO2 Levels and Storage Temperature

Abstract: Bartlett' pears (Pyrus communis L.) tolerated up to 10 days of exposure to atmospheres containing 1.0%, 0.5%, or 0.25% O2 at 0, 5, or 10C without any detrimental effects on their quality attributes. The fruits also tolerated 4 to 6 days of exposure to air enriched with 20%, 50%, or 80% CO2 at the three temperatures. The beneficial effects of exposures to the O2-reduced or CO2-enriched atmospheres included reduction of respiration and ethylene production rates and retardation of skin yellowing and flesh softening. While 1.0% or 0.5% O 2 and 20% CO2 did not increase ethanol and acetaldehyde contents, 0.25% O2 slightly increased and 50% or 80% CO2 dramatically increased the contents of these two volatiles in juice of the fruits. The effects of low O 2 or high CO2 on the above attributes generally became more pronounced at the higher temperatures. The low O2 or high CO2 treatments did not significantly affect either soluble solids content or titratable acidity. Low O 2 did not influence, but high CO2 slightly increased pH of the fruits. There have been many studies of controlled-at mosphere (CA) storage of fresh fruits and vegetables, but these have largely evaluated the responses of the commodities to moderately low O2 (2% to 3%) and/or high CO2 ( ≤ 5%) levels over long-term storage. In recent years, there has been increased interest in studying the responses of fruits and vegetables to short-term exposure to O 2 levels ≤ 1% and CO2 levels ≥ 20%. Such at- mospheres may be effective as a quarantine treatment for insect control in fresh fruits and vegetables (Aharoni et al., 1979; Lidster et al., 1981, 1984; Soderstrom and Brandl, 1987; Sod- erstrom et al., 1986). Exposure of 'Granny Smith' apples to O 2 levels ≤ 0.5% for 9 days has been reported to have beneficial effects in scald control and in delay of fruit softening and loss of greenness (Little et al., 1982). Nichols and Patterson (1987) showed that short-term storage of 'Delicious' apples to 0.5% or 0.75% O 2 maintained fruit firmness and increased ethanol content. Yoshi- da et al. (1986) reported that storage of 'Bartlett' pears in 1% O2 for 4 months reduced ethylene production rate and retained higher levels of organic acids. Claypool (1969, 1973) showed that low-O2 atmospheres (0.5% to 1%) prolonged storage life and caused no injury to 'Bartlett' pears. Long-term storage of 'd'Anjou' pears in 1.0% O2 maintained higher dessert quality and higher contents of amino acids and organic acids than stor- age in air, and prevented scald disorder and internal brown core (Chen and Mellenthin, 1982, Chen et al., 1981; Mellenthin et al., 1980). Couey and Wright (1977) reported that short-term exposure of 'd'Anjou' pears to 12% CO2 for 14 days before storage re- duced stem decay and scuffing, improved flavor retention, and retarded softening after either regular or CA storage. Similarly, prestorage high CO2 (10% to 20%) treatments for 10 to 15 days retained higher firmness, acidity, and flavor scores of 'Golden Delicious' apples (Couey and Olsen, 1977) and retarded soft-

Hydroxyquinoline citrate and low pH prevent vascular blockage in stems of cut rose flowers by reducing the number of bacteria.

Abstract: Stems of cut rose flowers (Rosa hybrids L., CVS. Sonia, Ilona, Polka, and Frisco) were held in a sodium hypochlorite solution and then placed in distilled water or in a buffer at pH 6.0. After 2 days, many bacteria were found in the basal end of the stems, even when the number of bacteria in the water was below the detection limit. The hydraulic conductance of 5-cm stem segments was reduced whenever the number of bacteria exceeded =10 6

Micropropagation of Members of the Cactaceae Subtribe Cactinae

Abstract: Micropropagation of 11 rare or endangered cacti species belonging to the subtribe Cactinae was achieved by rooting of proliferated axillary shoots. Shoot tip explants were obtained from seedlings of Escobaria missouriensis D.R. Hunt, E. robbinsorum (Earle) D.R. Hunt, Sclerocactus spinosior (Engelm.) Woodruff & L. Benson, and Toumeya papyracantha (Engelm.) Br. & Rose, and from mature plants of Mammillaria wrightii Engelm., Pediocactus bradyi L. Benson, P. despainii Welsh & Goodrich, P. knowltonii L. Benson, P. paradinei B.W. Benson, P. winkleri Heil, and S. mesae-verdae (Boissevain) L. Benson. Three or four species were used in each of a series of experiments investigating the effects of basal media and auxin and cytokinin types and concentrations on axillary shoot proliferation. Low or no auxin but moderate to high cytokinin concentrations were required for axillary shoot production. All species rooted spontaneously on hormone-free media; however, several species rooted better on media containing auxin. All species were re-established in the greenhouse. The propagation of native cacti is usually done with seed and rooted offshoots; however, conventional propagation methods are inadequate for those species that exhibit no to few offshoots, seed dormancy, low germination rates, self-sterility, slow growth, or that require many years to mature. These difficulties are compounded by the limited availability of species that are threat- ened with extinction.

Tolerance of Ten Lettuce Cultivars to High Temperature Combined with NaCl during Germination

Abstract: Water that may contain salt often is used to cool soil to help overcome high-temperature inhibition of lettuce germination. This study was done to determine how lettuce cultivars differ in their germination response to high temperature and NaCl. Ten lettuce (Lactuca sativa L.) cultivars (Grand Rapids, Climax, Coolguard, Empire, Great Lakes 659-700, Mesa 659, Salinas, Vanguard 75, Red Coach 74, and Wintersupreme) were germinated at 20, 25, 30, or 35C with 0.0, - 0.3, - 0.6, - 0.9, - 1.2, or - 1.5 MPa NaCl. With no NaCl, germination percentages and rates decreased significantly at 35C for all cultivars except 'Salinas', which decreased at 30C. With higher concen- trations of NaCl, decreases in germination percentages and rates were observed at lower temperatures. Cultivar differences in response to temperature were present with no NaCl but became larger in the presence of NaCl. 'Great Lakes 659-700' and 'Mesa 659' were most sensitive to high temperature and salt. 'Coolguard' and 'Empire' were most tolerant to high temperature and salt, with some tolerance also present in 'Grand Rapids' and 'Vanguard 75'. Relative tolerance of cultivars to NaCl as shown by germination percentages and rates was consistent with growth of roots. Lettuce seed germination is inhibited by soil temperatures in excess of 25 to 32C, depending on the cultivar (Borthwick and Robbins, 1928; Gray, 1975; Thompson et al., 1979). These temperatures often are exceeded when lettuce is planted during late August or September for winter production in southwestern states, such as Arizona and California (Valdes and Bradford, 1987). Germination often is poor, resulting in nonuniform stand establishment and subsequent variability in maturity at harvest (Gray, 1975; Krause, 1980; Wurr and Fellows, 1983). In an attempt to overcome this problem, growers frequently keep the soil surface moist until stands are established. Although this practice helps reduce soil temperature, salts dissolved in the irrigation water also are applied to the soil surface. Much irri- gation water in southwestern states measures around 0.0 to - 0.3 MPa, although some measures as high as - 0.6 MPa (Dutt and McCreary, 1970). Salts in the upper few centimeters of the soil may be as high as 14 mmhos·cm -1 (J. M. C., unpublished). We found no studies in the literature considering differences in response of lettuce cultivars to combinations of high temper- ature and salt. Some studies dealt with response of lettuce to salt only. Lettuce is moderately sensitive to salt relative to other species (Maas and Hoffman, 1977), with some researchers re- porting differences in sensitivity among cultivars (Pasternak et al., 1986; Shannon and McCreight, 1984; Shannon et al., 1983) and others reporting no differences (Ayers et al., 1951). How- ever, seedlings frequently were started with fresh water and treated with salt solutions later. In some studies, seeds of var- ious lettuce cultivars were imbibed in salt solutions, although Seeds of 'Grand Rapids', 'Climax', 'Coolguard', 'Empire', 'Great Lakes 659-700', 'Mesa 659', 'Salinas', 'Vanguard 75', 'Red Coach 74', and 'Wintersupreme' lettuce were obtained from Asgrow Seed Co. (Kalamazoo, Mich.), SunSeeds (Hol- lister, Calif.), and Quali-Sel Seed (Salinas, Calif.). All are crisphead types except 'Grand Rapids', which is a leaf type. Aqueous solutions of NaCl were prepared to obtain osmotic potentials of 0.0, -0.3, -0.6, -0.9, - 1.2, or - 1.5 MPa (0.0, 3.5,7.1, 10.6, 14.2, or 17.7 g·liter -1

Apple Thinning by Photosynthetic Inhibition

Abstract: Shading (92%) of ‘Redchief Delicious’ apple (Malus domestics Borkh.) trees for 10-day periods from 10 to 20, 15 to 25, 20 to 30, and 25 to 35 days after full bloom (DAFB) caused greater fruit abscission than shading from 5 to 15, 30 to 40, 35 to 45, or 47 to 57 DAFB. Fruit 8 to 33 mm in diameter (10 to 30 DAFB) were very sensitive to 10 days of shade, even though fruit sizes of 6 to 12 mm are considered the most sensitive to chemical thinners. In a second test, shading for 3 days caused fruit thinning; 5 days of shade in the periods 18 to 23, 23 to 28, and 28 to 33 DAFB caused greater thinning than 11 to 16 or 33 to 38 DAFB. Shading reduced photosynthesis (Pn) to about onethird that of noncovered trees. Terbacil (50 mg·liter) + X-77 surfactant (1250 mg·liter) applied with a handpump sprayer 5, 10, or 15 DAFB greatly reduced fruit set and caused some leaf yellowing, particularly in the earliest treatments. Terbacil reduced Pn by more than 90% at 72 hours after application. Shoot growth of trees defruited by shade or terbacil was equivalent to defruited or deblossomed trees; ethephon (1500 mg·liter) inhibited tree growth and defruited trees. No terbacil residues were dectected in fruit at harvest from applications made 5, 15, 20, 25, or 30 DAFB. Eleven of 12 photosynthesis-inhibiting herbicides were also found to thin ‘Redchief Delicious’ apple trees. Shading caused more thinning than terbacil at the later applications, which may reflect poorer absorption and/or lesser photosynthetic inhibition than when terbacil was applied to older leaves. Spur ‘Delicious’ strains of apple normally set heavy crops and are difficult to thin adequately with currently available thinning agents (Byers, 1978; Byers et al., 1982; Herrera-Aguirre and Unrath,, 1980; Unrath, 1978, 1981). High rates of naphthaleneacetic acid (NAA) or naphthaleneacetamide (NAD) may cause many dwarfed (pygmy) fruit (Byers, 1978; Byers et al., 1982; Rogers and Thompson, 1969; Rogers and Williams, 1977; Unrath 1978, 1981). Carbaryl plus lower rates of NAA (5 mg·liter) have given excellent results in some years, but have caused serious overthinning and/or pygmy fruit development in others (Byers, 1978; Byers et al., 1982; Rogers and Williams, 1977). Combinations of ethephon plus carbaryl have overand underthinned in some tests (Byers et al., 1982; unpublished data), but thinned adequately in others (Herrera-Aguirre and Unrath, 1980; Unrath, 1978). Shading of apple or peach limbs or spraying trees with chemical photosynthetic inhibitors can induce fruit abscission (Byers et al., 1984, 1985; DelValle et al., 1985) without pygmy fruit development in ‘Delicious’ (Byers et al., 1985). Terbacil, but not shading, has caused leaf injury in some experiments, parfor publication 9 Feb. 1987. We thank Ciba-Geigy, Dupont, BASF, Chemical companies for supply of various photosynthetic inhibitors ron Chemical for X-77 surfactant; Sharon Myers, Raymond Myers, Ramsey, Dept. of Statistics, VPI & SU, for statistical assistance and The cost of publishing this paper was defrayed in part by the payment harges. Under postal regulations, this paper therefore must be hereby dvertisement solely to indicate this fact. of Horticulture. Research Assistant. of Biochemistry. ral Manager. titularly when applied dilute with a hand-pump sprayer (Byers et al., 1984, 1985; DelValle et al., 1985). The objectives of these experiments were: 1) to explore several chemical classes of photosynthetic inhibitors for apple thinning activity and degree of leaf injury, 2) to determine the most sensitive period when photosynthetic inhibition would cause apple thinning, and 3) to determine the effect of terbacil or shading on photosynthetic activity of apple leaves at rates that cause thinning. Materials and Methods Several studies were conducted in 1985 and 1986 on 5and 6-year-old ‘Redchief Delicious’/MM.111 trees located near Winchester, Va. These trees set a heavy crop in the fourth season and required much hand-thinning. All experiments were laid out in randomized complete-block designs. Each treatment was applied to whole, single-tree plots within six replicate blocks, except where indicated. Blocks were consecutively oriented within tree rows. Spray treatments were applied with a 5-liter stainless steel hand-pump to the point of drip. Full bloom occurred 19 Apr. 1985 and 22 Apr. 1986. Experiments 1, 2, and 3. Twelve photosynthesis-inhibiting chemicals used in these experiments are listed in Table 1. In 1985, 11 of these inhibitors were applied to four trees each in a randomized block design (Expt. 1), but, because of rain, a second experiment (Expt. 2) was conducted to retest those materials that may not have had sufficient time to dry before the rain (propazine, dipropetryn, metribuzin, bentazon). In 1986, 12 inhibitors were applied as described above (Expt. 3), but rates were adjusted based on leaf injury and thinning responses J. Amer. Soc. Hort. Sci. 115(1):14-19. 1990. observed in 1985. The surfactant X-77 at 0.0125% (v/v) was added to all treatments in both years. When significant injury occurred in an experiment, injury was rated from 0 to 10 (0 = no injury, 4 = heavy interveinal yellowing, 5 = interveinal necrotic leaves, 10 = complete defoliation and twig injury or death). Experiment 4. Black polypropylene shade material (92% shade) (E.C. Geiger, Harleysville, Pa.) was used to enclose whole trees for 10-day periods in the intervals 5 to 15, 10 to 20, 15 to 25, 20 to 30, 25 to 35, 30 to 40, 35 to 45, and 47 to 57 DAFB. The shade material measured 90% shade on an overcast day, but, when placed at an angle to the sun draped over the tree, 95% shade was measured using a LI-COR Model LI-85 light meter with a quantum sensor (Lincoln, Neb.). Terbacil (50 mg·liter ) + X-77 (2500 mg·liter), applied at 5, 10, 15, 20, 25, 30, 35, or 40 DAFB, was also compared to shade, carbaryl (900 mg·liter) + NAA (10 mg·liter) + a nonphytotoxic, highly refined paraffinic, 70-sec superior oil (2500 mg·liter ), ethephon (1500 mg·liter), hand-defruited, handdeblossomed, and hand-thinned trees. At harvest, 2.5-kg samples of fruit were collected from terbacil-sprayed trees 5, 15, 20, 25, or 30 DAFB and were analyzed for residues using standard liquid chromatographic methods described by Pease et al. (1978). Fruit per tree was counted between 30 and 61 DAFB and was expressed as fruit per square centimeter of trunk crosssectional area (TCSA). A 10-fruit sample was collected from each tree near harvest and sized with a band-type caliper. Fruit color was estimated as a percentage of fruit surface showing red and fruit firmness was determined with a Magness–Taylor penetrometer (D. Ballauf, Washington, D. C.) with an ll-mmdiameter tip. Soluble solids concentration (SSC) was determined by use of a Labeco refractometer (Laboratory Equipment Co., San Francisco) from a composite juice sample from the 10 fruits noted. The average shoot length of the five longest terminal shoots (four scaffolds plus central leader) on each tree was measured the following dormant season and expressed as a percentage of the control. Trunk circumference of each tree was measured 30 J. Amer. Soc. Hort. Sci. 115(1):14-19. 1990. cm above the soil on 1 May 1985 and in Dec. 1985. The increment in diameter for the 1985 season was calculated and expressed as a percentage of that of the control. Return bloom was rated from 0 to 10 (0 = no bloom, 4 = enough for full crop, 10 = all spurs flowering). A 5-kg sample of fruit was collected from trees treated with 50 mg·liter 1 terbacil + X-77 15 DAFB. Terbacil residue analysis of fruit collected at harvest was conducted according to Pease et al. (1978). Detection levels in fruit tissues were 0.01 mg·liter , with a 67% recovery rate in controlled samples. Experiment 5. Shade material (92%) was used to enclose six whole trees for either 1, 3, 5, or 7 days 13 to 14, 12 to 15, 11 to 16, and 10 to 17 DAFB, respectively. In addition, shade material was used to enclose six trees for 5 days 18 to 23, 23 to 28, 28 to 33, or 33 to 38 DAFB. Nonthinned and handthinned controls were also included for comparison. Fruit diameter, average shoot length, and trunk diameters were taken as in Expt. 4. Experiment 6. Net photosynthesis (Pn) was measured in the field with a portable ADC (Analytical Development Co., supplied by P.K. Morgan Instruments, Andover, Mass.) LCA-2 infrared CO2 analyzer (LCA-2) equipped with a Parkinson leaf chamber (P.K. Morgan Instruments) that exposed 6.25 cm of leaf to sunlight. Only bright, cloudless days were chosen for Pn measurements, which were taken between 10:00 AM and 1:00 PM and consecutively by block. Photosynthesis of three leaves on each of two trees treated with terbacil 0, 2, 24, 72, or 120 hr previously were measured at 20 DAFB. Experiment 7. Photosynthesis of trees that were shaded with polypropylene shadecloth 5 to 15 or 10 to 20 DAFB and of nonshaded trees was measured with shade either on or off the trees at 20 DAFB (three leaves on each of two trees for each treatment). All data were averaged for each single-tree replicate before performing LSD (0 = 0.05), Duncan’s multiple range procedure (0.05), or regression analysis. General Linear Model (GLM) procedures of the Statistical Analysis System (SAS) program package (SAS Institute, 1982) were used for analysis of variance.

Quality and cell wall components of anna and granny smith apples treated with heat, calcium, and ethylene

Abstract: Anna' and 'Granny Smith' apples (Malus domestics Borkh.) that were held at 38C for 4 days before storage at 0C not only were firmer than controls upon removal from storage, but also softened more slowly during shelf life at 17C. Skin yellowing and loss of acidity attendant upon the heat treatment were not prevented by dipping fruit in 2% CaCl2 before heating. Both heat-treated and control fruit softened at the same rate upon exposure to ethylene at 100 µl·liter -1 upon removal from storage. The insoluble pectin content of cortical tissues was higher in heat-treated fruit than in controls after 10 days at 17C, while soluble pectin levels were lower. Arabinose and xylose levels were lower in cell walls from heat-treated cortical tissue, but the treatment had no effect on loss of galactose residues during shelf life. Previous researchers have noted that heating apples at 38C for 4 to 6 days after harvest retarded or inhibited fruit softening while maintaining most other aspects of storage quality (Liu, 1978; Porritt and Lidster, 1978). The exception was a slight yellowing of the skin and a decrease in titratable acidity in comparison with unheated fruit. Calcium treatments also extend the storage life of apples, primarily by reducing the rate of metabolic activity (Bangerth et al., 1972}, thus reducing senes- cence phenomena such as fruit softening, yellowing, and loss of acidity (Ferguson; 1984; Glenn et al., 1988). Since uptake of Ca by pear cells was specifically enhanced by heating cells at 38C (Klein and Ferguson, 1987), we endeavored to determine if heating Ca-treated apples could synergistically inhibit loss of fruit firmness in storage, without associated problems of acid loss and skin yellowing. The specific objectives of this research were to increase the effectiveness of postharvest Ca dips by use of a heat treatment, while simultaneously counteracting the disadvantages of heat treatment alone (loss of acidity and yellowing). Since heat treat- ment inhibits ethylene production by apples (Klein, 1989), we investigated whether softening could be reinduced by exposing heat-treated fruit to ethylene at 100 µl·liter -1 upon removal from storage. We also studied whether the decrease in apple fruit softening after a prestorage heat treatment is due to changes in the neutral sugar and pectin composition of the cell wall in cortical tissue.

Response to Selection and Associated Changes in Genetic Variance for Soluble Solids and Titratable Acids Contents in Strawberries

Abstract: Parental potential, or breeding value, was evaluated for strawberry (Fragaria × ananassa Duch.) genotypes selected for high, intermediate, or low phenotypic expression of soluble solids content (SSC) and titratable acid content (TA). Progeny means and genetic variance parameters were estimated using seedlings from 40 crosses among these selections, conducted in two factorial sets. Selection response for breeding value was detected for SSC in the upward direction and for TA in both upward and downward directions. Populations created by divergent selection of parents followed by intermating expressed additive genetic variances 2.3 and 9.3 times larger than those estimated for ap- propriate controls for SSC and TA, respectively. For TA, the response to selection for breeding value was consistent with results for genotypic selection reported earlier. The significant selection response in breeding value obtained for SSC differed from the results of previous clonal tests that had detected no significant genotypic selection response. These results, together with previous assessments, suggest that cumulative genetic gain can be obtained for both SSC and TA. However, gain for SSC will be contingent on selection under conditions that approximate commercial treatment; this will not be necessary for TA, as expression for this trait is stable across test location and cultural treatments. Strawberry flavor is conditioned in part by the balance be- tween SSC and TA expressed in ripe fruit (Sweeney et al., 1970). Genetic variation for SSC and TA in strawberry can be exploited by selection and propagation of 'specific genotypes and by choice of appropriate' parents and control of cross combi- nations. When genetic effects are large and mostly additive, both genotypic values and breeding values are predictable from the performance of individual seedling phenotypes. However, if dominance effects are large, the correspondence between gen- otypic value and breeding value will be low and clonal perform- ance may be a poor predictor of parental value. The effectiveness of mass selection in detecting superior parents and genotypes for SSC and TA depends on the mode of inheritance for genes that condition these traits. The study reported here is the third "in a series aimed at un- derstanding the inheritance of SSC and TA in strawberries and deriving selection strategies for developing cultivars with im- proved flavor. Broad-sense heritabilities (H*) and narrow-sense heritabilities (h*) were estimated in an earlier study, using seed- lings from controlled crosses among genotypes representative of current advanced-generation germplasm (Shaw et aI., 1987). Results from this initial genetic survey demonstrated large dom- inance effects for SSC (h 2

Storage temperature and ethylene influence on ripening of papaya fruit

Abstract: The temperature and ethylene response of ripening papaya fruit (Carica papaya L. CV. Sunset) was deter- mined with and without 14 days of storage at 10C. Temperatures at or higher than 30C adversely affected the quality of the ripe papaya. Papayas held at 32.5C for 10 days failed to ripen normally, as evidenced by poor color development, abnormal softening, surface pitting, and an occasional off-flavor. Skin yellowing, fruit softening, and flesh color of papayas exhibited a quadratic response to ripening time within the temperature range of 22.5 to 27.5C. Flesh color development of nonstored fruit did not change significantly during the first 6 days at ripening temperatures, then rapidly increased. Fruit stored for 14 days at 10C exhibited faster ripening rates (e.g., degreening and softening and no delay in flesh color development) than nonstored fruit when removed to other ripening temperatures (17.5 to 32.5 C). Problems of weight loss and development of external abnormalities were more significant at temperatures higher than 27.5C. The optimal temperature range was found to be between 22.5 and 27.5C, with fruit taking 10 to 18 days to reach full skin yellowing from color break, whether or not fruit was stored at 10C. Exogenously applied ethylene (=100 µl·liter -1 ) stimulated the rate of fruit ripening, as measured by more uniform skin yellowing and rate of flesh softening whether or not the fruit were stored for 14 days at 10C. Ethylene did not ripen immature papayas completely in terms of skin and flesh color development. The outer portion of the flesh of ethylene-trea ted fruit had a faster rate of ripening, as indicated by carotenoid development and softening rate, while the same area of the flesh was still pale white in nonethylene-treated fruit. Ethylene reduced the coefficient of variation for skin color, softening rate, and flesh color development in treated fruit. Ethylene increased the rate of skin degreening and hastened the rate of carotenoid development and softening in the outer mesocarp, while having little effect on the inner mesocarp.

Plant Regeneration of `Valencia' Sweet Orange, `Femminello' Lemon, and the Interspecific Somatic Hybrid following Protoplasm Fusion

Abstract: Protoplasm culture following the chemical fusion of 'Valencia' sweet orange (Citrus sinensis (L.) Osb.) protoplasts, isolated from an embryogenic suspension culture, with 'Femminello' lemon (Citrus limon (L.) Burro. f.) leaf protoplasts resulted in the regeneration of an interspecific allotetraploid somatic hybrid plant, two autotetraploid lemon plants, and diploid plants from both parents. The regeneration of plants from lemon leaf protoplasts is an example of protoplast-to -plant regeneration from non-nucellus-derived tissue for Citrus. Regenerated plants were classified according to leaf morphology, chromosome number, and analyses of phosphohexose isomerase (PHI), per- oxidase (PER), and 6-phosphoglucose dehydrogenase (PGD) zymograms. The somatic hybrid plant was vigorous, with leaves morphologically intermediate to the parents. The tetraploid lemon plants were similar to diploids, although less vigorous and with thicker leaves. The tetraploid lemon and somatic hybrid plants, if fertile, could be used in interploid sexual crosses to breed triploid seedless lemon cultivars with tolerance of mal secco disease from sweet orange. Further investigation of plant regeneration from leaf protoplasts could increase the number of totipotent Citrus clones amenable to somatic hybridization and genetic transformation experiments.

Association of Epicuticular Sugars with Aphid Resistance in Hybrids with Wild Tomato

Abstract: Behavioral studies have shown that aphid resistance in Lycopersicon pennellii (Corr.) D'Arcy is due to the presence of sugar esters in glandular exudate of the type IV trichomes. In this study, various methods for the estimation of epicuticular sugar ester concentrations were examined. There was a significant negative relationship between the concentration of sugar esters on the leaf and the level of potato aphid infestation in a segregating L. esculentum × L. pannellii F2 population. Selection for sugar ester accumulation should be an efficient selection technique for the aphid resistance of L. pennellii and other species that synthesize epicuticular sugar esters. The wild Peruvian tomato species (Lycopersicon pennellii (Corr.) D'Arcy) is a potential source of resistance to insects and other phytophagous pests of the cultivated tomato (L. esculen- tum Mill.) (de Ponti et al., 1975; Georgia and Sotirova, 1978; Gentile and Stoner, 1968a, 1968b; Gentile et al., 1968; Gentile et al., 1969; Goffreda et al., 1988; Juvik et al., 1982), Potato aphid (Macrosiphum euphorbiae Thomas) resistance in L. pen- nellii is related to the presence of glucose esters in type IV trichome exudate (Goffreda, 1988; Goffreda et al., 1989). The 2,3,4-tri-O-acylglucoses of L. pennellii are composed of C 4 to Cl2 fatty acids, including 2-methylpropanoic, 2-methylbutan - oic, 3-methylbutanoic, 8-methylnonano ic, n-decanoic, and n- dodecanoic acids (Burke et al., 1987). In laboratory bioassays, purified glucose esters significantly deter aphid settling at con- centrations as low as 25 µg·cm -2 ; at concentrations of 100 µm·cm -2

Modes of Inheritance of Photoperiodism in Fragaria

Abstract: Genetic analysis of day-neutral (photo-insensitive) cultivars and their derivatives hybridized to standard short-day clones of octoploid strawberries [Fragaria × ananassa Duchn., F. chiloensis (L.) Duchn., and F. virginiana glauca Staudt., x = 7, 2n = 56] revealed that photo-insensitivity is controlled by a single dominant allele of a Mendelian gene. The dominant genetic trait is expressed in hybrids with other Fragaria spp. Intergeneric hybrids of day-neutral Fragaria and short-day Potentilla glandulosa L. and P. fruticosa L. also express photo-insensitivity. The day-neutral genes in European perpetual flowering (photo-insensitive) diploid ‘Alpine’ F. vesca (2N = 14) apparently have evolved independently, since photo-insensitivity is recessive to photo-sensitivity. Native California diploid F. vesca have diverged considerably from European F. vesca. No photo-insensitive diploids have been found among them. Photo-sensitivity in native California F. vesca is controlled by three dominant genes. The origins of day-neutral cultivars of F. × ananassa and the classification of day-neutrality are discussed. Photoperiodism in flowering plants was first described in 1918 in short-day tobacco mutants (Garner and Allard, 1920). Subsequently, the angiosperms were classified as short-day (SD), long-day (LD), and photo-insensitive or day-neutral (DN), according to the daylight regime that induces flower bud initiation. The body of literature on photo-sensitivity in flowering plants indicates that the phenomenon is frequently controlled by a single gene or by very few genes or gene complexes (Chailakhyan, 1979; Skripchinsky, 1971; Bernier et al., 1981). Induction or repression of single genes or their products appears to act upon the meristematic tissue at the earliest stage of organogenesis and disrupt the regulation otherwise imposed by the interaction of genetic factors with environmental stimuli. This pattern apparently confers photo-insensitivity (Skripchinsky, 1971). In rice (Chandrartna, 1953, 1955), tetraploid sea island cotton (Gossypium barbadense; Lewis and Richmond, 1960), subterranean clover (Salisbury et al., 1987), Canadian wheat (Knott, 1986), sweet, pea (Ross and Murfet, 1985), and jute (Joshae and Thakare, 1986), photo-sensitivity is controlled by a dominant allele of a single gene. In contrast, day-length sensitivity is conferred by a recessive gene in okra (Wyatt, 1985), cucumber (Della and Peterson, 1984), and upland tetraploid cotton (G. hirsutum; Lewis and Richmond, 1957). Thus, in cotton, Lewis and Richmond (1957) concluded that day-neutrality evolved independently in the two species. The recessive allele of G. barbadense is not expressed in the genetic background of upland cotton (G. hirsutum). In a few cases, the inheritance of photoperiodism is more complicated. In pea (Ross and Murfet, 1986) and in some hexaploid wheat (Maystrenko and Aliev, 1986), two dominant alleles of two genes are involved. In sesame, three genes (Kotecha et al., 1975) are responsible for short-day sensitivity. Some investigators have implied that florigen and antiflorigen metaphoric substances have roles in perpetual flowering (Lang, 1984), while others believe that the elimination or exclusion of inhibitors causes day-neutrality (Ross and Morfet, 1986; Guttridge, 1959). In most investigations, pleiotropic effects, such as dwarfing and low yields, are observed. Other correlated effects caused by modifier genes, such as earliness, vernalization, d for publication 14 Feb. 1989. The cost of publishing this paper was in part by the payment of page charges. Under postal regulations, this erefore must be hereby marked advertisement solely to indicate this etc., have also been reported. Finally, some authors reported the induction of day-neutrality in sensitive plants by mutagens, such as X rays, while others have recovered spontaneous dayneutral mutants in populations of shortor long-day plants (Skripchinsky, 1971). Our study is devoted toward the elucidation of the inheritance of photoperiodism in Fragaria spp. Genetic evidence is presented to support the postulation that a dominant allele of a single Mendelian gene induces day-neutrality in the octoploids and that recessive alleles of one to three genes confer it in the diploids. Origins of the day-neutral Fragaria. European investigators discovered diploid “perpetual-flowering” (‘Alpine’) types as early as the 17th Century. Other perpetual-flowering clones have since been reported in Europe, e.g., ‘F. de Gaillon’, selected by Labaute in France in 1811 (Richardson, 1913-14) and ‘Baron Solemacher’, selected in Germany. Brown and Wareing (1965) concluded that a single recessive gene induced day-neutrality in short-day diploid European F. vesca. Studies suggest three independent sources of photo-insensitive octoploid cultivars (F. × ananassa). First, European ‘‘everbearing” (day-neutral = photo-insensitive) cultivars are derivatives of ‘Gloede’ seedlings introduced in France in 1866 (Richardson, 1913-14). Abbe Thivolet selected ‘St. Joseph’ in 1893 and later ‘St. Antoine de Padoue’. L. Gauthier hybridized ‘St. Antoine de Padoue’ with ‘Louis Gauthier’, a white-fruited berry, and selected ‘Merveille de France’, introducing it in 1904 (Darrow, 1966). Richardson (1913-14), in his pioneering study of perpetual flowering, used ‘St. Antoine de Padoue’ and its seedlings and ‘Laxton’s Perpetual’ hybridized to short-day ‘Bedford Champion’ (Richardson, 1913-14). The second original source of the day-neutral octoploid strawberry was probably a chance seedling or a clonal mutation of ‘Bismark’ found in New York by S. Cooper. He selected dayneutral ‘Pan American’ in 1898 (Darrow, 1966). Later, H. Rockhill, in 1904, crossed this cultivar with ‘Dunlap’ to obtain ‘Progressive’, from which he bred ‘Rockhill’ (Fig. 1, top left). The third major synthesis of day-neutral plants was reported by Bringhurst and Voth (1980). They collected late-fruited F. virginiana glauca plants from the Wasatch mountains near Salt Lake City, Utah, in 1954 and selected day-neutral plants among the offspring of the first backcross hybrids to short-day parents and introduced three new day-neutral cultivars in 1979; ‘Aptos’, ‘Hecker’, and ‘Brighton’ (Fig. 1, lower left); ‘Fern’ (Fig. 1, J. Amer. Soc. Hort. Sci. 115(1):146-152. 1990. top right) in 1983; ‘Selva’ in 1983 (Fig. 1, lower right); and ‘Muir’, ‘Mrak’, and ‘Yolo’ in 1988. Powers (1954) and Darrow (1937) had mentioned previously the possibility of F. Virginiana glauca as a potential source of the everbearing character. Materials and Methods Day-neutrality in diploid F. vesca (x = 7, 2N = 14). A dayneutral European vesca with the diagnostic electrophoretic genetic marker phosphoglucoseisomerase (EC 5.3.1.9) was hybridized with male-sterile short-day clones of F. vesca from Hecker Pass, Calif. The seeds were germinated in the greenhouse and plants were established in the field in 1986. Selected hybrids were selfed (F2) and crossed to ‘Alpine vesca’ (BC1). The offspring were planted and scored in the greenhouse 1 to 3 months after planting. Day-neutral plants flowered 6 to 8 weeks after germination. The same clone of ‘Alpine vesca’ was hybridized with a female F. chiloensis (8X) clone (CA Accession 1234 = CMC 1234), yielding vigorous semi-sterile pentaploid offspring. The chromosomes of hermaphroditic pentaploids of this cross were doubled with colchicine; a fully fertile decaploid was selfed, and the decaploid offspring were scored for photoperiodic reaction in Oct. 1988. Classification of day-neutral octoploid Fragaria. Many authors have classified day-neutrality on the basis of fruiting pattern, particularly for the late harvest data (Bringhurst et al., 1989). Some have used variation in growth habits and flowering (Nicoll and Galletta, 1987). In this report, four identification criteria were used: 1) Flowering of mother and runner plants in the nursery during the summer and fall. J. Amer. Soc. Hort. Sci. 115(1):146-152. 1990. 2) Germination of seeds and establishment of seedlings in the fields in early spring and scoring them for flowering 3 to 5 months later, in midto late summer or early fall. 3) Continuous cycles of flowering during the second year on plants established in the field in the fall of the first year and subjected to the extreme heat of the summer in the Sacramento Valley, Calif. 4) Classification of the parents based on the flowering pattern of their seedlings, i.e., hybridizing the standard short-day F. chiloensis with the suspected heterozygous DN cultivars and rearing their offspring as described in category 2. Day-neutrality in breeding populations (1977, 1983, 1985, 1986, and 1987). Standard short-day (SD) and day-neutral (DN) cultivars and their derivatives were hybridized in the greenhouse in the late winter and spring of 1983 and 1985 through 1987. Seeds were germinated in July. Seedlings were transplanted once in the greenhouse and established in the field in late September in the Sacramento Valley (Winters, Calif.). Individual plants were scored as DN after the flowers and fruits appeared in July, August, or September of the 2nd year. The total population varied from 8000 to 14,000 plants each year. The 1977 seeds were germinated in Feb. 1978, planted in the field in Apr. 1978, and scored in June, July, August, and September of the same year. Diallel experiment, 1987. Four SD plus four DN clones were intercrossed in all combinations and 64 families were established in the field as explained above in two randomized blocks with six plants in each block and in two locations at Winters (Sacramento Valley) and at Watsonville, Calif. (Central Coast). The seedlings were scored for day-neutrality as described in the

Bud Dormancy Status, Frost Hardiness. Shoot Moisture Content, and Readiness of Black Spruce Container Seedlings for Frozen Storage

Abstract: Black spruce (Picea mariana (Mill) B S P) first-year seedlings were exposed to 8-hr photoperiods and warm temperatures (26C maximum, 15C minimum) and tested weekly to determine bud dormancy status, frost hardiness, shoot moisture content, and the amount of damage caused by a period of frozen storage ( - 3C) Bud dormancy status, frost hardiness, and shoot moisture content were all strongly correlated to the time of bud initiation Frost hardiness was low ( - 5 to - 75C) during the period of needle primordia initiation until week 3 (3 weeks after 100% bud initiation), but bud dormancy decreased linearly over this period, from 37 days to budbreak for seedlings sampled at week - 1 (1 week before 100% of the seedlings had initiated terminal buds) and placed under conditions favoring shoot elongation, to 14 days to budbreak for seedlings sampled on week 3 From week 5 to week 8, there was a strong (r 2 > 0999) linear correlation between frost hardiness and bud dormancy status Shoot moisture content declined linearly from 84% on week - 1 to 74% on week 8 (r 2 = 097), and shoot moisture content was correlated with both frost hardiness (r 2 = 087) and the percentage of seedlings that suffered needle damage in frozen storage (r 2 = 085) Bud dormancy status, measured as number of days to 50% budbreak, was curvilinearly correlated with seedling damage following frozen storage, whereas linear relationships with damage in storage were found for dor- mancy release index (r 2 = 092) and frost hardiness (r 2 = 085) The ability of tree seedlings to endure frozen storage without damage has been empirically related to shoot frost hardiness, bud dormancy status, and shoot moisture content (Ritchie, 1984, 1986; Glerum, 1976; Rossvall-Ahnebrink, 1977), where seed- lings that are most dormant or have exceeded critical levels of frost hardiness or shoot moisture content exhibit the best stor- ability These relationships have practical significance because they may enable the proper timing of tree seedling frozen stor- age to be predicted by the measurement of these variables Ex- amples of the use of such attributes for predicting readiness for storage of various species have been given (Ritchie, 1984, 1986; Ritchie et al, 1985; Tinus et al, 1986) The levels of frost hardiness, bud dormancy, and shoot mois- ture content required for damage-free frozen storage have been shown to vary among species and for different provenances within a species (Ritchie, 1984, 1986; Ritchie et al, 1985; Rossvall-Ahnebrink, 1977) Therefore, it is important that the relationships between these variables and frozen storage be in- vestigated for new species before the implementation of storage programs In Canada, nearly all container stock produced, ex- cept in British Columbia, is overwintered outside There is growing interest in the use of frozen storage for overwintering container stock because of the advantages it gives in reducing losses due to shoot desiccation, root freezing, disease, and ro- dents Further, seedlings held in storage possess high post-plant- ing stress resistance as a result of remaining dormant through the spring until planting The purpose of this paper is to describe the relationships between shoot frost hardiness, bud dormancy status, shoot moisture content, and success of frozen storage for l-year-old black spruce seedlings

Sucrose Metabolism in Ripening Muskmelon Fruit as Affected by Leaf Area

Abstract: Muskmelon (Cucumis melo L.) fruit lack a stored starch reserve and therefore depend on translocated photoassimilate from the leaf canopy for sugar accumulation during ripening. The influence of canopy photosynthesis on sucrose' accumulation within muskmelon fruit mesocarp was examined. Canopy photosynthetic activities were estimated in a sweet and a nonsweet genotype. Photosynthetic rate of the nonsweet genotype, on a per-plant basis, was only 56% of that of the sweet genotype. The effect of limiting leaf area of the sweet genotype on carbohydrate concentrations and sucrose metabolizing enzymes within the fruit was evaluated. A 50% reduction of leaf area 8 days before initiation of fruit sucrose accumulation resulted in canopy photosynthesis similar to that of the nonsweet genotype. Reduced photosynthetic activity resulted in slightly lower soluble-carbohydrate concentration in the fruit; however, fruit sucrose concentration was three times higher than that reported previously for the nonsweet genotype. The extent to which 'fruit sucrose phosphate synthase (SPS) activity increased during maturation was diminished by leaf removal. Acid invertase activity declined in all fruit in a similar manner irrespective of defoliation. A reduction of leaf area of a sweet genotype reduced sucrose accumulation within the fruit. Lower fruit sucrose concentration was associated with lower concentration of raffinose saccharides and lower SPS activity within the fruit. Additionally, insufficient assimilate supply was judged not to be the factor responsible for low sucrose accumulation in a nonsweet genotype. Sucrose concentration of muskmelon mesocarp is a major component of fruit quality. Sucrose accumulation is one of sev- eral processes generally associated with ripening that commence midway through fruit development and continue until maturity (Pratt, 1971). Hubbard et al. (1989) recently reported that most, if not all, of the sucrose accumulating in muskmelon fruit as they ripen on the plant is synthesized within the fruit by the enzyme su- crose phosphate synthase (SPS) (EC 2.4.1.14). In contrast to other reports of very low SPS activity in muskmelon fruit (Lin- gle and Dunlap, 1987), Hubbard et al. (1989) found SPS activity as high as 38 µmol·hr - 1 ·g -1 (fresh weight) in mature musk- melon mesocarp. Moreover, fruit SPS activity increased during development as sucrose concentration increased. Lower SPS activity in fruit of a nonsweet muskmelon genotype, as com- pared to a sweet genotype, provided additional evidence for control of sucrose synthesis by this enzyme within the fruit