Showing papers in "Journal of the American Society for Horticultural Science in 2003"

Yield Responses of a Mature Olive Orchard to Water Deficits

Abstract: Irrigation is one of the most important means of increasing olive oil production but little information exists on the responses of olive to variable water supply. Five different irrigation strategies, full irrigation, rain fed, and three defi cit irrigation treatments were compared from 1996 to 1999, in Cordoba, southern Spain, to characterize the response of a mature olive (Olea europaea L. 'Picualʼ) orchard to irrigation. Crop evapotranspiration (ETc) varied from less than 500 mm in the rain fed to ≈900 mm under full irrigation. The defi cit irrigation treatments had ETc values that ranged from 60% to 80% of full ETc depending on the year and treatment. Water relations, and oil content and trunk growth measure- ments allowed for the interpretation of yield responses to water defi cits. In a defi cit irrigation treatment that concentrated all its ETc defi cit in the summer, stem water potential (Ψx) decreased to -7 MPa but recovered quickly in the fall, while in the treatment that applied the same ET defi cit progressively, Ψx was never below -3.8 MPa. Minimum Ψx in the rain fed treatment reached -8 MPa. Yield (Y) responses as a function of ETc were calculated for biennial yield data, given the alternate bearing habit of the olive; the equation are: Y = -16.84 + 0.063 ET -0.035 × 10-3 ET2, and Y = -2.78 + 0.011 ET - 0.006 × 10-3 ET2, for fruit and oil production respectively, with responses to ET defi cits being similar for sustained and regulated defi cit irrigation. The yield response to a defi cit treatment that was fully irrigated during the bearing year and rain fed in the nonbearing year, was less favorable than that observed in the other two defi cit treatments. The olive (Olea europaea L.) is, among fruit trees, an important source of both fruit and edible oil. Increased appreciation of olive oil as part of the Mediterranean diet (International Olive Oil Council, 2001) has raised olive oil prices, leading to an important increase in new plantings in many world areas. Additionally, there have been trends to intensify olive production, primarily via high-density plantings and irrigation. Because olive has been traditionally a rain-fed crop in the Mediterranean region, little information exists on its irrigation requirements, and even less on the responses to variations in irrigation water supply (Orgaz and Fereres, 1997). New irrigation developments are under close scrutiny at present and the economic advantages of shifting olive plantations from traditional rain fed to irrigation must be clearly demonstrated before new water is allocated for irrigation. Many olive growing regions suffer chronic water shortages and increased competition from other sectors for the available water resources (Fereres and Cena, 1997). A basic tool to assess the value of irrigation water is the crop water production function (Vaux and Pruitt, 1983). Crop biomass and yield are linearly related to evapotranspiration (ET) but the relations with applied irrigation water are usually curvi- linear (Stewart and Hagan, 1973). Sometimes, nonlinear relations between yield and ET have been observed (i.e., cotton; Orgaz et al., 1992). It is important to characterize the production function of olive, a crop that has a reputation of being drought resistant. If the response to variation in ET is nonlinear, optimal ET levels can be defi ned for different oil and water prices and defi cit irrigation programs to achieve such ET levels could be formulated. Reports on the responses of olive yield to variable amounts of applied water differ according to different sources. Lavee et al.

Kaolin Particle Film Applications Can Increase Photosynthesis and Water Use Efficiency of `Ruby Red' Grapefruit Leaves

Abstract: Effects of foliar sprays of a kaolin clay particle film (Surround WP) on leaf temperature (Tlf), net gas exchange, chlorophyll fluorescence and water relations of sun-exposed leaves on field-grown grapefruit trees (Citrus paradisi L.) were studied during Summer and Fall 2001. Trees were sprayed twice a week for 3 weeks with aqueous suspensions of kaolin (Surround) at 60 g·L -1 . Physiological effects of kaolin application were most prominent around midday on warm sunny days than in mornings, evenings or cloudy days. Kaolin sprays increased leaf whiteness (62%), reduced midday leaf temperature (Tlf; ≈3 °C) and leaf to air vapor pressure differences (VPD; ≈20%) compared to water-sprayed control leaves. Midday reductions in Tlf and VPD were accompanied by increased stomatal conductance (gs) and net CO2 assimilation rates (ACO2) of kaolin sprayed leaves, suggesting that gs might have limited ACO2 in water-sprayed control leaves. Midday photoinhibition of photosynthesis was 30% lower in kaolin-sprayed leaves than in control leaves. Midday water use efficiency (WUE) of kaolin-sprayed leaves was 25% higher than that of control leaves. However, leaf transpiration and whole-tree water use were not affected by kaolin film sprays. Increased WUE was therefore, due to higher ACO2. Leaf intercellular CO2 partial pressures (Ci) were similar in control and kaolin-sprayed leaves indicating that stomatal conductance was not the major cause of reduced ACO2. These results demonstrate that kaolin sprays could potentially increase grapefruit leaf carbon uptake efficiency under high radiation and temperature stress.

Phenolic acid content and composition of eggplant fruit in a germplasm core subset

Abstract: ADDITIONAL INDEX WORDS. germplasm evaluation, hydroxycinnamic acids, phytonutrient, Solanaceae, Solanum melongena ABSTRACT. Eggplant (Solanum melongena L.) is ranked among the top ten vegetables in terms of oxygen radical absorbance capacity due to its fruitʼs phenolic constituents. Several potential health promoting effects have been ascribed to plant phenolic phytochemicals. We report here a fi rst evaluation of phenolic acid constituents in eggplant fruit from acces- sions in the USDA eggplant core subset. The core subset includes 101 accessions of the cultivated eggplant, S. melongena, and 14 accessions representing four related eggplant species, S. aethiopicum L., S. anguivi Lam., S. incanum L., and S. macrocarpon L. Signifi cant differences in phenolic acid content and composition were evident among the fi ve eggplant species and among genotypes within species. Fourteen compounds separated by HPLC, that were present in many but not all accessions, were identifi ed or tentatively identifi ed as hydroxycinnamic acid (HCA) derivatives based on HPLC elution times, UV absorbance spectra, ES--MS mass spectra, and in some cases proton NMR data. These phenolics were grouped into fi ve classes: chlorogenic acid isomers, isochlorogenic acid isomers, hydroxycinnamic acid amide conjugates, unidentifi ed caffeic acid conjugates, and acetylated chlorogenic acid isomers. Among S. melongena accessions, there was a nearly 20-fold range in total HCA content. Total HCA content in S. aethiopicum and S. macrocarpon was low relative to S. melongena. A S. anguivi accession had the highest HCA content among core subset accessions. Chlorogenic acid isomers ranged from 63.4% to 96% of total HCAs in most core accessions. Two atypical accessions, S. anguivi PI 319855 and S. incanum PI500922, exhibited strikingly different HCA conjugate profi les, which differed from those of all other core subset accessions by the presence of several unique phenolic compounds. Our fi ndings on eggplant fruit phenolic content provide opportunities to improve eggplant fruit quality and nutritive value. The cultivated eggplant (Solanum melongena L.), also known as aubergine, brinjal, or Guinea squash, is a species of consider- able economic importance in many parts of the world including Asia, Africa, and the subtropics of India and Central America. It is particularly important in India, China and southeast Asia. Related eggplant allies are also grown. These include S. aethiopicum, S. anomalum, S. macrocarpon, S. incanum, S. nigrum, S. gilo and S. duplosinuatum grown in Africa; S. muricatum, S. quitoense, S. piliferum and S. topiro in Central and South America; and S blumei, S. indicum, S. macrocarpon, S. nigrum and S. torvum in southeast Asia (Swarup, 1995). Current evidence suggests that eggplant is native to India, with secondary centers of diversity in other parts of southeast Asia and China (Swarup, 1995). Eggplant exhibits wide diversity in growth habit, vegetative characters, and fl oral morphology, and produces fruit with many different shapes, sizes, and colors, depending on the cultivar. The oblong to elongate-shaped purple/black eggplant is used world- wide, but other varieties that differ in color, size, and shape are also known. Eggplant genetic resources have been assessed for resistance against the most serious diseases and pests that affect crop production. Analogous detailed assessments of eggplant nutri- ent composition are lacking. Characterization of eggplant phenolic compounds has been limited to studies of fruit development and postharvest storage or on the role of these compounds as substrates for polyphenol oxidase in the enzymatic browning of cut or injured tissue (Esteban et al., 1989, 1992; Flick et al., 1978).

Oxygen Radical Absorbing Capacity, Anthocyanin and Phenolic Content of Highbush Blueberries (Vaccinium corymbosum L.) during Ripening and Storage

Abstract: The antioxidant properties of blueberries have been examined only in ripe fruit, although fruit of different maturities are used in processed food products. In this study, highbush blueberry cultivars Bergitta, Bluegold, and Nelson highbush blueberry fruit at different stages of ripeness were examined to characterize differences in oxygen radical absorbing capacity (ORAC) and the phenolic components responsible for ORAC. Underripe fruit at different stages of maturity were also stored at 20 °C for up to 8 days to assess changes in ORAC and phenolic content. Antho- cyanin content was substantially higher in fruit of more advanced stages of ripeness. In contrast, the phenolic content and ORAC were lower in the riper fruit. Anthocyanins continued to form during storage, although rate of pigment formation declined after about 4 days. Less anthocyanin pigment was formed in the less ripe fruit. After 8 days of storage, the anthocyanin content of fruit harvested 5% to 50% or 50% to 95% blue exceeded that of ripe fruit. Up to 60% of the total phenolic content could be accounted for by anthocyanins. ORAC was positively correlated with total phenolic content (R2 = 0.78), but not with anthocyanin content. Reports of the human health benefits of dietary antioxidants

Physiological Responses of Pepper to Salinity and Drought

Abstract: Production of vegetable crops can be limited by saline irrigation water. The variability of crop salt tolerance under different environmental conditions requires species-specific and environment-specific field evaluations of salt tolerance. Data on field performances of vegetable crops grown on soils that have been irrigated with saline water for many years are lacking. In this study we analyzed the long-term effect of irrigation with saline water on soil properties and on responses of field-grown pepper (Capsicum annuum L.) plants in these soils. Yield, gas exchanges, water relations, and solute accumula- tion were measured in plants grown under three different irrigation treatments: a nonsalinized control (ECw = 0.5 dS·m -1 ) and two concentrations of commercial sea salt, corresponding to ECw of 4.4 and 8.5 dS·m -1 , respectively. In addition, a nonwatered drought stress treatment was included. Irrigation water with an EC of 4.4 dS·m -1 resulted in 46% reduction in plant dry weight (leaves plus stem) and 25% reduction in marketable yield. Increasing the electrical conductivity of the irrigation water to 8.5 dS·m -1 caused a 34% reduction in plant dry weight and a 58% reduction in marketable yield. Leaf and root cellular turgor and net CO2 assimilation rates of leaves in salt-stressed plants decreased along with a reduction in leaf area and dry matter accumulation. High concentrations of Na + and Cl - in the irrigation water did not significantly alter the level of K + in leaves and fruit. In contrast, drought stressed plants had higher concentrations of leaf K + compared to well watered control plants. These results indicate that Na + and K + may play similar roles in maintaining cellular turgor under salinity and drought stress, respectively. The regulation of ion loading to the shoots was most likely functionally associated with physiological modifications of the root/shoot ratio that was substantially smaller in salinized vs. drought stressed plants. From an agronomic perspective, irrigation with moderately saline water (4.4 dS·m -1 ) it is recommendable, compared to no irrigation, to obtain an acceptable marketable yield in the specific environment considered.

Comparison of AFLPs, RAPD Markers, and Isozymes for Diversity Assessment of Garlic and Detection of Putative Duplicates in Germplasm Collections

Abstract: Garlic (Allium sativum L.) is an asexually propagated crop that displays much morphological diversity. Studies which have assessed garlic diversity with isozymes and randomly amplified polymorphic DNA (RAPD) markers generally agreed with the morphological observations but sometimes failed to discriminate clones. To discriminate among closely related garlic clones in more detail, we introduced amplified fragment-length polymorphism (AFLPs) to evaluate the genetic diversity and phenetic relatedness of 45 garlic clones and three A. longicuspis clones and we compared AFLP results with RAPD markers and isozymes. Three AFLP primer combinations generated a total of 183 polymorphic fragments. Although similarities between the clusters were low (≥0.30), some clones within the clusters were very similar (>0.95) with AFLP analysis. Sixteen clones represented only six different banding patterns, within which they shared 100% polymorphic AFLPs and RAPD markers, and likely are duplicates. In agreement with the results of other investigators, A. longicuspis and A. sativum clones were clustered together with no clear separation, suggesting these species are not genetically or specifically distinct. The topology of AFLP, RAPD, and isozyme dendrograms were similar, but RAPD and isozyme dendrograms reflected less and much less polymorphism, respectively. Comparison of unweighted pair group method with arithmetic averaging (UPGMA) dendrograms of AFLP, RAPD, and isozyme cluster analyses using the Mantel test indicated a correlation of 0.96, 0.55, and 0.57 between AFLP and RAPD, AFLP and isozyme, and RAPD and isozyme, respectively. Polymorphic AFLPs are abundant in garlic and demonstrated genetic diversity among closely related clones which could not be differentiated with RAPD markers and isozymes. Therefore, AFLP is an additional tool for fingerprinting and detailed assessment of genetic relationships in garlic. longicuspis clones were discriminated morphologically from A. sativum clones by generally having exerted and purple anthers, higher flowering rate and seed production, and smaller bulbils in inflorescence (Etoh and Simon, 2002). The species have the same karyotype and A. sativum and A. longicuspis clones have been crossed successfully (Etoh, 1984; Pooler and Simon, 1994). Garlic has been propagated by vegetative means for centuries and the presence of many closely related or duplicated garlic clones is likely in germplasm collections. Large numbers of molecular markers are needed to discriminate closely related clones or to identify duplicates. One particularly useful tool to achieve this goal is amplified fragment-length polymorphism (AFLP), which could produce high multiplex informative mark- ers in a single reaction and, therefore, could generate sufficient markers to assess genetic diversity among garlic clones. AFLP is a PCR-based DNA fingerprinting technique (Vos et al., 1995) and like randomly amplified polymorphic DNA (RAPD), it generates primarily dominant markers. Neither AFLP nor RAPD require any probe or sequence information (Barker et al., 1999) and they can be applied to any species after some minor modifications. Isozymes, RAPD, and AFLP have been used extensively for determining genetic diversity and relatedness

Physiological Effects of Liquid Applications of a Seaweed Extract and a Humic Acid on Creeping Bentgrass

Abstract: A variety of organic materials such as humic substances, seaweed extracts (SWE), organic matter, and amino acids are being used as fertilizer supplements in commercial turfgrass management. Among them, SWE and humic acid (HA) are widely used in various biostimulant product formulations. These compounds have been reported to contain phytohormones and osmoprotectants such as cytokinins, auxins, polyamines, and betaines. Manufacturer claims are that these products may supplement standard fertility programs by reducing mineral nutrient requirements while improving stress tolerance. There is a lack of season-long, fi eld-based evidence to support these claims. This study was conducted to investigate the infl uence of monthly fi eld applications of SWE, HA, and high and low seasonal fertilization regimes on the physiological health of fairway-height creeping bentgrass (Agrostis stolonifera L.). Plots were treated monthly with SWE at 16 mg·m -2 and HA (70% a.i.) at 38 mg·m -2 alone, or in combination, and were grown under low (20 kg·ha -1 /month) or high nitrogen (50 kg·ha -1 /month) fertilization regimes during 1996 and 1997. Endogenous anti- oxidant superoxide dismutase (SOD) activity, photochemical activity (PA), and turf quality were measured in July of each year. Superoxide dismutase activity was increased by 46% to 181%, accompanied by a PA increase of 9% to 18%, and improved visual quality of bentgrass in both years. There was no signifi cant fertilization × supplement interaction. Although not part of our original objectives, it was noted that signifi cantly less dollar spot (Sclerotinia homoeocarpa F.T. Bennett) disease incidence occurred in supplement-treated bentgrass. Our results indicate that increased SOD activity in July due to SWE and/or HA applications improved overall physiological health, irrespective of fertiliza- tion regime. This suggests that these compounds may be benefi cial supplements for reducing standard fertilizer and fungicide inputs, while maintaining adequate creeping bentgrass health. mic acid (HA) are two novel materials that have shown promise for protecting turfgrasses against oxidative stress. Much early work by Schmidt and collaborators focused on refi ning appropri- ate dilution rates of seaweed extracts and HA based on turfgrass responses such as leaf growth rate and senescence (Goatley and Schmidt, 1990), nutrient uptake (Yan, 1993), root mass (Nabati et al., 1994), and photochemical activity (Zhang, 1997). These studies have shown that certain rates of generic and commercial formulations of SWE and/or HA can improve turfgrass quality and resistance to environmental stresses such as drought (Zhang, 1997) and salinity (Nabati, et al., 1994). Further research indicated that improved stress resistance was associated with increases in anti- oxidant contents and activities (Zhang and Schmidt, 1997; Zhang and Schmidt, 1999, 2000b). All of these studies were conducted under uniform fertilization. Because the chemical components of SWE and HA have yet to be completely characterized and tested for specifi c activity, we do not currently understand the physiological or biochemical bases of SWE and/or HAʼs effects on antioxidants and other stress responses. However, information from other researchers has provided some clues as to constituents and possible modes of action. Fike et al. (2001) reported that SWE derived from A. no- dosum contains various compounds including amino acids and micronutrients; they also reported hormonal activity equivalent to 50 mg·L-1 kinetin. Additionally, auxin and cytokinins have been identifi ed and quantifi ed in SWE using GC-MS techniques (Crouch and Van Staden, 1993; Sanderson and Jameson, 1986; Sanderson et al., 1987; Senn, 1987). Lastly, three betaine forms have been quantifi ed in A. nodosum extracts (Blunden et al., 1986). Quarternary ammonium compounds such as the betaines are thought to play a pivotal role in plant cytoplasmic adjustment

Differentiation of race specific resistance to Phytophthora root rot and foliar blight in Capsicum annuum

Abstract: Despite extensive breeding efforts, no pepper (Capsicum annuum L. var. annuum) cultivars with universal resistance to phytophthora root rot and foliar blight (Phytophthora capsici Leon) have been commercially released. A reason for this limitation may be that physiological races exist within P. capsici, the causal agent of phytophthora root rot and phytophthora foliar blight. Physiological races are classified by the pathogen's reactions to a set of cultivars (host differential). In this study, 18 varieties of peppers were inoculated with 10 isolates of P. capsici for phytophthora root rot, and four isolates of P. capsici for phytophthora foliar blight. The isolates originated from pepper plants growing in New Mexico, New Jersey, Italy, Korea, and Turkey. For phytophthora root rot, nine of the 10 isolates were identified as different physiological races. The four isolates used in the phytophthora foliar blight study were all determined to be different races. The identification of physiological races within P. capsici has significant implication in breeding for phytophthora root rot and phytophthora foliar blight resistance. two susceptible varieties and confirmed the presence of a two- gene system for phytophthora root rot resistance. Criollo de Morelos-334 (CM334) an accession from Mexico is resistant to P. capsici (Guerrero and Laborde, 1980). Ortega et al. (1991) proposed that CM334 has three genes with multiple alleles that determine resistance. These results contradicted previous results by Guerrero and Laborde (1980), who stated two recessive genes provided resistance in CM334. Barksdale et al. (1984) found multiple genes were responsible for resistance to foliar blight and crown rot in pepper by using cultivars, Fyuco and P51, from Argentina and The Netherlands, respectively. Resistance to foliar blight and crown rot was treated as one disease syndrome in this research, not as two separate disease syndromes. Walker and Bosland (1999) found that two independent dominant genes, along with a dominant allele from a third independent gene, separately control resistance to foliar blight and root rot. There are several possible explanations for the conflicting evidence on the inheritance of resistance even when varieties of similar pedigrees are utilized. One explanation is that different parts of the pepper plant can become infected by P. capsici. Each plant part infected can be considered a separate disease syn- drome, i.e., root rot, foliar blight, and fruit blight. A second explanation, is that different genes control resistance to the different disease syndromes (Walker and Bosland, 1999). Walker and Bosland (1999) found that different genes were responsible for the inheritance of root rot resistance as compared to foliar blight resistance. Finally, Polach and Webster (1972) and Reifschneider et al. (1986) suggested that physiological races may exist within P. capsici. The objective of these experiments was to investigate the existence of physiological races within P. capsici. A host differ- ential utilizing several varieties of C. annuum that differed in resistance or susceptibility to P. capsici was chosen. Isolates of P. capsici originating from different geographical regions were selected to screen the host differential. Differences in the viru- lence of the isolates on specific hosts would confirm the existence of physiological races. Phytophthora capsici Leon. is a soilborne fungal pathogen of worldwide importance and is a major limiting factor in pepper (Capsicum annuum var. annuum) production (Bosland and Lindsey, 1991; Ristaino and Johnston, 1999). P. capsici is espe- cially difficult to control because it can cause multiple disease syndromes by infecting the roots, foliage, and fruits of pepper. Chemical control is limited and in most cases ineffective against phytophthora on pepper. Biological control of phytophthora has also been unsuccessful (Goldberg, 1995; Miller et al., 2002). The development of adapted phytophthora-resistant pepper cultivars is considered to be an essential approach to controlling phytophthora disease. Researchers have bred for phytophthora resistance in peppers for many years but none of the resistant cultivars have been reported to be resistant worldwide (Black and Berke, 1998; Ortega et al., 1995). This may be because the inheritance of resistance is not fully understood. The inheritance of resistance against phytophthora in pepper has been reported to be single-gene, two-gene, or multiple-gene systems (Barksdale et al., 1984; Guerrero and Laborde, 1980; Ortega et al., 1991; Reifschneider et al., 1992; Saini and Sharma, 1978; Smith et al., 1967; Walker and Bosland, 1999). Saini and Sharma (1978) reported that the bell pepper cultivar Waxy Globe carries a single dominant gene for resistance to phytophthora fruit rot. The inheritance of fruit rot resistance was confirmed by a backcross to the susceptible parent resulting in a 1:1 ratio for resistant to susceptible progeny. Both two-gene and multiple-gene systems have been reported for root rot and foliar blight. Smith et al. (1967) were the first to propose the two-gene system. Smith et al. (1967) developed F1, F2, F3, and BC1 populations from hybridiza- tion of three phytophthora-resistant lines and with the susceptible cultivar, Yolo Wonder. Their results indicate the presence of two independent, dominant genes determining resistance to phytophthora root rot. Reifschneider et al. (1992) used the resis- tant line CNPH148, a line derived from Criollo de Morelos, and

Leaf Anatomy and Stomatal Morphology of Greenhouse Roses Grown at Moderate or High Air Humidity

Abstract: Single node cuttings with one mature leaf were taken from Rosa ×hybrida ‘Baroness ̓and rooted in water culture. The plants were subjected to either 90% (high) or 70% (moderate) relative humidity (RH) in climate chambers. Single stem roses with intact roots were transferred to 40% (low) RH to investigate the stomatal response to water stress. Moderate RH plants showed decreasing leaf conductance from day 1 to day 3 during both light and dark phases, in contrast to high RH roses, which showed almost similar leaf conductances during the 3 days. Leaf samples were studied with a light microscope (LM) and a scanning electron microscope (SEM) to quantify morphological and structural changes. Epidermal imprints showed a signifi cantly higher number of stomata and longer stomata, as well as a wider stomatal apertures on roses grown at high RH. The high RH leaves showed a reduced density of vascular tissue and thinner leaves when compared to moderate RH leaves. Enlarged intercellular air-space (ICA) was found due to a reduced number of spongy and palisade mesophyll cells. No obvious difference in shape, size, undulation or the structure of the epicuticular wax was observed in SEM between high and moderate RH grown leaves. In conclusion, roses subjected to high RH showed differences in leaf anatomy, stomatal morphology and stomatal function, which may explain the loss of water control of these plants. Stomatal ontogenesis should occur at RH conditions below 85% to secure roses with a high postharvest quality potential. morphological changes as described for plants regenerated in vitro. In addition, the study was undertaken to evaluate if differences in leaf morphology between high and moderate RH could explain the distinct postharvest behavior of these roses. Materials and Methods PLANT MATERIAL AND GROWING CONDITIONS. Rooted stems of Rosa ×hybrida ‘Baroness ̓were grown in growth chambers from single-node segments with a mature leaf in water culture (Torre and Fjeld, 2001). During the rooting period, RH was kept above 90%. After rooting, RH was adjusted to either high: 90% ± 5% (–14.2 MPa) or moderate: 70% ± 5% (–48.2 MPa) RH. Temperature was kept at 20 ± 1 °C and the CO2 at 700 ± 50 μL–1·L–1 during the entire experimental period. All experiments were carried out during the darkest period of the year (January to April and September to December) with a minimal infl uence of natural sunlight. Artifi cial light provided by high-pressure-sodium-lamps (SON-T) was supplied 20 h every 24 h period with a 4 h dark period given in between. The average light intensity was 75 ± 10 μmol·m–2·s–1 (measured with a L1-185; LI-COR). Plants were harvested at commercial stage, A (Itzhaki et al., 1990). POROMETER MEASUREMENTS. Leaf conductance (mmol·m–2·s–1) was measured on the same plant for three days to study the stomatal response to water stress. Roses with intact roots were transferred from the chambers directly to a test room, placed in 0.5-L vases with double destilled water and acclimated for 8 h before the fi rst measurement with an AP4 porometer (Delta-T Devices LTD, Cambridge, U.K). The temperature in the test room was 20 °C, RH was 40% (–127.4 MPa) and an irradiation level of 14 μmol·m–2·s–1 was provided by fl uorescent tubes for 12 h per day. Measurements were taken on the abaxial side of the leaves, twice daily, once in the light period and once in the dark period (3 h after light off), corresponding to a time when plants had light or Received for publication 16 Oct. 2002. Accepted for publication 28 Jan. 2003. The authors thank Vigdis Revhaug for technical assistance. Thanks also to Elisabeth Eng and Trygve Krekling (Department of Chemistry and Biotechnology) and Nina Nagy (Norwegian Forest Research Institute) for assistance during the microscopy work. The work was fi nancially supported by the Norwegian Research Council, project number 107008/111.

Peach tree response to single and combined regulated deficit irrigation regimes under shallow soils

Abstract: Productive and vegetative tree responses were analyzed during 3 consecutive years in peach (Prunus persica (L.) Batsch cv. Sudanell) plots subjected to three regulated defi cit irrigation (RDI) strategies plus a control irrigation treatment. A postharvest RDI treatment (RDI-P) was irrigated at 0.35 of control after harvest. A Stage II RDI treatment (RDI-SII) was irrigated at 0.5 of control during the lag phase of the fruit growth curve. The third treatment (RDI-SII-P) applied RDI during Stage II at 0.5 of control and postharvest at 0.35 of control. The control treatment, like RDI-P and RDI-SII-P when not receiving RDI, was irrigated at 100% of a water budget irrigation scheduling in 1994 and 1996, full crop years, and 80% of the budget in 1995, an off year with a very small crop. A carry-over effect of defi cit irrigation was highly signifi cant in all parameters measured during the third year of the experiment. The general effect of water stress during Stage II did not affect return bloom and fruit set, whereas water stress during postharvest apparently reduced both parameters. As a consequence, fruit counts and fruit load manifested marked differences between treatments, which were also correlated to changes in fruit size. The RDI-II, which had the highest fruit yield, also had the smallest fruit size, whereas RDI-P manifested the lowest yield and largest fruit size. Vegetative growth (shoot elongation and trunk cross sectional area) was signifi cantly reduced during the fi rst 2 years of the experiment in accordance with the amount of the irrigation reduction. However, in 1996 growth was strongly governed by fruit load. The use of RDI-SII-P represented an intermediate cropping effect between the opposite bearing behavior of RDI-SII and RDI-P, while not expecting distinctive fruit yield or size reductions and offering remarkable water savings of 22% of the control applied water.

Particle Films Affect Carbon Assimilation and Yield in `Empire' Apple

Abstract: Processed-kaolin particle films (PKPFs) are used commercially in large quantities on horticultural crops to repel insects, and reduce heat stress and solar injury of fruit. Our studies determined the effect of two processed-mineral particle fi lm materials (kaolin and calcium carbonate), on whole plant carbon assimilation, water use effi ciency, yield, mean fruit weight and quality in 'Empireʼ apple ((Malus ×sylvestris (L.) Mill var. domestica (Borkh Mansf.))) over a four-year period. The application of a PKPF reduced canopy temperature, and probably reduced environmental stress, resulting in increased mean fruit weight and red color in two of the four years of the study. Whole canopy carbon assimi- lation studies indicated increased carbon assimilation only under conditions of high air temperature. The PKPF sprayed leaves also had reduced water use effi ciency; likely due to increased stomatal conductance associated with reduced leaf temperature. Calcium carbonate had none of the positive effects of PKPF and refl ected more photosynthetically active radiation (PAR) than the PKPF.

Analysis of Sweet Cherry (Prunus avium L.) Cultivars Using SSR and AFLP Markers

Abstract: Simple sequence repeats (SSRs) and amplified fragment-length polymorphisms (AFLPs) were used to evalu- ate sweet cherry (Prunus avium L.) cultivars using quality DNA extracted from fruit flesh and leaves. SSR markers were developed from a phage library using genomic DNA of the sweet cherry cultivar Valerij Tschkalov. Microsatellite contain- ing clones were sequenced and 15 specific PCR primers were selected for identification of cultivars in sweet cherry and for cross-species amplification in Prunus. In total, 48 alleles were detected by 15 SSR primer pairs, with an average of 3.2 putative alleles per primer combination. The number of putative alleles ranged from one to five in the tested cherry cultivars. Forty polymorphic fragments were scored in the tested cherry cultivars by 15 SSRs. All sweet cherry cultivars were identified by SSRs from their unique fingerprints. We also demonstrated that the technique of using DNA from fruit flesh for analysis can be used to maintain product purity in the market place by comparing DNA fingerprints from 12 samples of 'Bing∑ fruit collected from different grocery stores in the United States to that of a standard 'Bing∑ cultivar. Results indicated that, with one exception, all 'Bing∑ samples were similar to the standard. Amplification of more than 80% of the sweet cherry primer pairs in plum (P. salicina), apricot (P. armeniaca) and peach (P. persica L.) showed a congeneric relationship within Prunus species. A total of 63 (21%) polymorphic fragments were recorded in 15 sweet cherry cultivars using four EcoRI-MseI AFLP primer combinations. AFLP markers generated unique fingerprints for all sweet cherry cultivars. SSRs and AFLP polymorphic fragments were used to calculate a similarity matrix and to perform UPGMA cluster analysis. Most of the cultivars were grouped according to their pedigree. The SSR and AFLP molecular markers can be used for the grouping and identification of sweet cherry cultivars as a complement to pomological studies. The new SSRs developed here could be used in cherry as well as in other Prunus species for linkage mapping, evolutionary and taxonomic study. The capability to distinguish among cherry (Prunus avium) culti- vars in breeding and cultivation is extremely important for scientific as well as for economic reasons. There is a demand for a rapid and reliable method of cultivar identification for Plant Breeder∑ s Rights (PBR) registration and protection. Classical methods of identifica- tion and characterization of cultivars in fruits have relied mostly upon a large set of phenotypic data that is often difficult to assess, may vary with environment and production practices, and can be time consuming to collect when surveying large populations that may be growing in different locations. Molecular markers based on DNA are stable, detectable in all tissues and independent of environmental or seasonal conditions. They can be used for cultivar identification, diversity analysis, assessment of parentage, patent issues and quality control of rootstock-seed lots. The ability to distinguish cherry cultivars would be greatly enhanced by the use of molecular markers. Molecular marker development and use within Prunus species has been most active in peach (P. persica) due to its relatively short juvenile period and commercial importance (Dirlewanger and Bodo, 1994; Sosinski et al., 1998). A variety of molecular techniques have been developed for measuring genetic variabil- ity. Of the possible alternatives, isozymes have been shown to be insufficiently variable in cherry due to low polymorphism of the species ( Tobutt and Boskovic, 1996). Randomly amplified poly- morphic DNA (RAPD) markers have also been assayed in fruit

Evaluation of Avocado Germplasm Using Microsatellite Markers

Abstract: Three horticultural races of avocado (Persea americana Mill.) are known: Guatemalan, Mexican, and West Indian. Each race has unique characteristics and current commercial varieties have been selected from within the races or from interracial hybrids. Using 14 microsatellite loci we investigated the genetic variation among 224 accessions (394 plants) maintained at the National Germplasm Repository (NGR) in Miami, Fla., and a set of 34 clones from the University of California South Coast Field Station (SCFS) located in Irvine, Calif. The 14 microsatellite loci had an average of 18.8 alleles per locus and average unbiased genetic diversity was 0.83. The total propagation error in the collection, i.e., plants that had been incorrectly labeled or grafted, was estimated to be 7.0%. Although many unique alleles did exist, no useful race-specific markers were found. A general concordance between the horticultural race and the clusters obtained from molecular data was observed. Principal Coordinate Analysis (PCA) grouped the Guatemalan and Mexican races into two distinct clusters. The West Indian also grouped into a unique major cluster but with an outlying group. Using the PCA a change in the racial designation or interracial hybrid status for 50 accessions (19.7%) is proposed. The unbiased gene diversity estimate was highest in the Mexican and Guatemalan races and lower in the West Indian group. This demonstrates the need to collect more of the West Indian germplasm to broaden the genetic diversity and to emphasize the identification of individuals conferring resistance to Phytophthora Root Rot (PRR). The avocado (Persea americana Mill.) is an evergreen sub- tropical tree that is native from Mexico to northern South America and produces a fruit that is unique and nutritious. This fruit was known by the Aztecs as ahuacacuauhitl, which was later shortened by the Spaniards to aguacate. In the United States avocado was introduced into Florida in 1833, California in 1848 and to Hawaii by 1855 (Nakasone and Paull, 1998). Major commercial produc- tion of avocado in the United States is limited to California and Florida. In 2000, global production exceeded 2.4 MMT and the major producers were Mexico, Indonesia, South Africa and the United States (Anonymous, 2001). P.americana has been subdivided into three horticultural groups: Mexican (P. americana var. drymifolia (Schect. & Cham.) Blake), Guatemalan (P. americana var. guatemalensis Wms.) and West Indian (P. americana var. americana Mill.) races. The West Indian race is known to be from the lowland areas of the Pacific coast of Central America and not the West Indies, while the Guatemalan and Mexican races are native to specific highland areas in each country (Scora and Bergh, 1992). The collection at the NGR-Miami contains 224 accessions with all three races represented, as well as hybrids between them. The earliest introductions were collected by Wilson Popenoe in Guatemala in the 1920s, and the newest introductions were collected by Avraham Ben-Ya∑ acov throughout Central and South America during the 1990s (Ben-Ya∑ acov, 1995; Popenoe,

Boron Improves Growth, Yield, Quality, and Nutrient Content of Tomato

Abstract: ADDITIONAL INDEX WORDS. Lycopersicon esculetum, potassium, calcium, hydroponics, fruit crack, shelf life ABSTRACT. Boron deficiency in fresh-market tomatoes (Lycopersicon esculentum Mill.) is a widespread problem that reduces yield and fruit quality but is often not recognized by growers. Tomatoes were grown in fi eld and hydroponic culture to compare the effects of foliar and soil applied B on plant growth, fruit yield, fruit quality, and tissue nutrient levels. Regardless of application method, B was associated with increased tomato growth and the concentration of K, Ca, and B in plant tissue. Boron application was associated with increased N uptake by tomato in fi eld culture, but not under hydroponic culture. In fi eld culture, foliar and/or soil applied B similarly increased fresh-market tomato plant and root dry weight, uptake, and tissue concentrations of N, Ca, K, and B, and improved fruit set, total yields, marketable yields, fruit shelf life, and fruit fi rmness. The similar growth and yield responses of tomato to foliar and root B application suggests that B is translocated in the phloem in tomatoes. Fruit from plants receiving foliar or root applied B contained more B, and K than fruit from plants not receiving B, indicating that B was translocated from leaves to fruit and is an important factor in the management of K nutrition in tomato. foliar spray regime ensures a steady supply of B throughout the growing season without the management concerns of supplying B as a dry formulation. Application through the drip-irrigation system places B directly in the root zone and foliar B applica- tions allow uptake directly through the leaves. The objective of this study was to determine if B, applied in a liquid formulation to the foliage and/or roots, would improve yields, fruit quality, and nutrient content of tomatoes.

Changes in Photosynthesis and Carbohydrate Metabolism in Mature Apple Leaves in Response to Whole Plant Source-Sink Manipulation

Abstract: Photosynthesis and carbohydrate metabolism in apple (Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.) source leaves were monitored during a 7-day period after source-sink manipulations by girdling or partial defoliation treatments. In the girdling treatment, sorbitol, sucrose, glucose, and starch accumulated in leaves, and net photosynthetic rates (Pn) at 350 µL·L -1 CO2 decreased during a 7-day period. Pn measured at 1000 µL·L -1 (CO2) was also decreased but the changes were less. Stomatal conductance and intracellular CO2 concentration decreased markedly in leaves of girdled shoots. When shoots were partially defoliated, starch and glucose concentrations in remaining source leaves declined steadily during the 7-day study period. Sorbitol and sucrose concentrations decreased during the first 2 days after defoliation, then increased the following 5 days. Pn of the remaining leaves measured at ambient and elevated CO2 levels were enhanced markedly. Aldose-6-phosphate reductase activity in source leaves increased markedly from 27.5 to 39.2 µmol·h -1 ·g -1 fresh weight (FW) after partial defoliation but remained unchanged in leaves after girdling. Selective and maximum sucrose phosphate synthase (SPS) activities increased following partial defoliation and decreased following girdling. ADP-glucose pyrophosphorylase activity remained relatively unchanged in the partial defoliation treatments but increased markedly in the girdled-shoot leaves. These results suggested that girdling-induced photosyn- thetic inhibition is mainly due to stomatal limitation, however, the photosynthesis enhancement by partial defoliation may be due primarily to acceleration of photosynthetic capacity per se. These studies showed that the metabolism of sorbitol, sucrose and starch, three photosynthetic end products in mature apple leaves, was coordinately regulated in source leaves in response to source-sink manipulations.

Effects of Abscisic Acid on Drought Responses of Kentucky Bluegrass

Abstract: Abscisic acid (ABA) is an important hormone regulating plant response to drought stress. The objective of this study was to investigate effects of exogenous ABA application on turf performance and physiological activities of kentucky bluegrass (Poa pratensis L.) in response to drought stress. Plants of two kentucky bluegrass cultivars, 'Brilliant' (drought susceptible) and 'Midnight' (drought tolerant), were treated with ABA (100 µM) or water by foliar application and then grown under drought stress (no irrigation) or well-watered (irrigation on alternate days) conditions in a growth chamber. The two cultivars responded similarly to ABA application under both watering regimes. Foliar application of ABA had no effects on turf quality or physiological parameters under well-watered conditions. ABA application, however, helped maintain higher turf quality and delayed the quality decline during drought stress, compared to the untreated control. ABA-treated plants exposed to drought stress had higher cell membrane stability, as indicated by less electrolyte leakage of leaves, and higher photochemical efficiency, expressed as Fv/Fm, compared to untreated plants. Leaf water potential was not significantly affected, whereas leaf turgor pressure increased with ABA application after 9 and 12 d of drought. Osmotic adjustment increased with ABA application, and was sustained for a longer period of drought in 'Midnight' than in 'Brilliant'. The results suggested that exogenous ABA application improved turf performance during drought in both drought-sensitive and tolerant cultivars of kentucky bluegrass. This positive effect of ABA could be related to increased osmotic adjustment, cell turgor maintenance, and reduced damage to cell membranes and the photosynthetic system.

Development and Characterization of Microsatellite Markers in Citrus

Abstract: We evaluated the potential of microsatellite markers for use in Citrus genome analysis. Microsatellite loci were identifi ed by screening enriched and nonenriched libraries developed from 'Washington Navelʼ Citrus. Micro- satellite-containing clones were sequenced and 26 specifi c PCR primers were selected for cross-species amplifi cation and identifi cation of cultivars/clones in Citrus. After an enrichment procedure, on average 69.9% of clones contained dinucleotide repeats (CA)n and (CT)n, in contrast to <25% of the clones that were identifi ed as positive in hybridiza- tion screening of a nonenriched library. A library enriched for trinucleotide (CTT)n contained <15% of the clones with (CTT)n repeats. Repeat length for most of the dinucleotide microsatellites was in the range of 10 to 30 units. We observed that enrichment procedure pulled out more of the (CA)n repeats than (CT)n repeats from the Citrus genome. All microsatellites were polymorphic except one. No correlation was observed between the number of alleles and the number of microsatellite repeats. In total, 118 putative alleles were detected using 26 primer pairs. The number of putative alleles per primer pair ranged from one to nine with an average of 4.5. Microsatellite markers discriminated sweet oranges (Citrus sinensis (L.) osb), mandarin (Citrus reticulata Blanco), grapefruit (Citrus paradisi Macf.), lemon (Citrus limon (L.) Burm.f.), and citrange (hybrids of trifoliate orange and sweet orange), at the species level, but indi- vidual cultivars/clones within sweet oranges, mandarins and grapefruit known to have evolved by somatic mutation remained undistinguishable. Since these microsatellite markers were conserved within different Citrus species, they could be used for linkage mapping, evolutionary and taxonomic study in Citrus. of purposes including fi nger-printing (Smith and Devey, 1994),

Temperature Effects on Dormancy Completion of Vegetative Buds in Apple

Abstract: ADDITIONAL INDEX WORDS. rest, chilling requirements, apical dominance, Malus sylvestris ABSTRACT. The relative contribution of various temperatures to dormancy completion of lateral vegetative apple (Malus sylvestris (L.) Mill. var. domestica (Borkh.) Mansf.) buds was studied quantitatively on whole container-grown trees. Trees were exposed continuously to 10 different temperatures and also to daily alternating temperatures in a 24-hour cycle. In addition, fully chilled vertically and horizontally positioned shoots were compared under forcing conditions. No budbreak occurred in shoots chilled above 12.5 OC. There was a steep increase in budbreak as the chilling temperature fell from 12.5 to 7.5 OC. There was little difference in the level of budbreak on shoots chilled between 7.5 and 0 OC. The relative contribution of temperature to chilling accumulation in apple found in our study differs from what has been proposed for stone fruit and for apple in previous studies, especially at temperatures <6 OC. The length of exposure to forcing conditions required to initiate budbreak diminished as the chilling temperature was reduced. No additional bud- break was apparent on shoots chilled longer than 2100 chilling hours. The chilling requirement found here for lateral vegetative buds is much higher than that needed for terminal vegetative and flower buds. Trees that were exposed to daily alternating temperatures had lower levels of budbreak when the high temperature in the diurnal cycle was greater than 14 OC. Practically no budbreak was apparent on trees that were exposed to diurnal cycles with a high temperature of 20 OC for 8 hours. Budbreak on horizontally positioned trees was more than twice that on the vertically positioned trees, emphasizing the magnitude of the apical dominance effect and its strong masking of the chilling effect on lateral buds in vertically grown apple trees. Based on the data collected here we propose a new response curve for vegetative budbreak in 'Golden Delicious∑ apple, within a temperature range between 0 to 15 OC. Buds of most temperate-zone deciduous trees have a dormancy period in the winter. Low temperatures are the most significant fac- tor affecting dormancy completion, although, there are indications that heat, light intensity, and mist, during the endodormancy phase affect dormancy completion to a certain extent (Chandler, 1960; Erez et al., 1966; Erez et al., 1968; Freeman and Martin, 1981). Knowing the exact response of apple (Malus sylvestris var. do- mestica) buds to temperature is important for a basic understanding of dormancy and for the practical application of dormancy release or bloom delay techniques. Spring frost may cause severe damage to flowers and young foliage in temperate zones; therefore, predic- tion of the date of budbreak is an important issue for growers in those regions. Budbreak is affected by two temperature-dependent processes: a) the accumulation of chilling to the level required for dormancy completion; and b) the accumulation of the heat units required for the buds to develop to bloom and foliation. These two processes were shown to be interdependent, i.e., fewer degree-days of heating are required as the previously accumulated chilling in- creases (Couvillon and Erez, 1985a). In warm regions, temperatures in the winter are not low enough, or the duration of exposure is not

Mapping and Evaluation of Malus ×domestica Microsatellites in Apple and Pear

Abstract: We mapped DNA polymorphisms generated by 41 sets of Simple Sequence Repeat (SSR) primers, developed independently in four laboratories. All primer sets gave polymorphisms that could be located on our 'White Angelʼ x 'Rome Beautyʼ map for apple (Malus sylvestris (L.) Mill. Var. domestica (Borkh.) Mansf.). The SSR primers were used to identify homologous linkage groups in 'Wijcik McIntoshʼ, NY 75441-58, 'Golden Deliciousʼ, and 'Libertyʼ cultivars for which relatively complete linkage maps have been constructed from isozyme and Random Amplifi ed Polymorphic DNA (RAPD) markers. In several instances, two or more SSRs were syntenic, and except for an apparent translocation involving linkage group (LG) 6, these linkages were conserved throughout the six maps. Twenty-four SSR primers were consistently polymorphic, and these are recommended as standard anchor markers for apple maps. Experiments on a pear (Pyrus communis L.) population indicated that many of the apple SSRs would be useful for mapping in pear. However some of the primers produced fragments in pear signifi cantly different in size than those in apple.

Vine Water Relations, Gas Exchange, and Vegetative Growth of Seventeen Vitis Species Grown under Irrigated and Nonirrigated Conditions in California

Abstract: ADDITIONAL INDEX WORDS. grapevines, water potential, photosynthesis, stomatal conductance, drought tolerance ABSTRACT. A comparison was made among 16 native North American Vitis species and Vitis vinifera L. ('Carignane') grown in the San Joaquin Valley of California with or without irrigation over 2 years. Predawn water potential (ΨPD), predawn leaf osmotic potential (Ψπ), midday leaf (Ψl), and stem water potential (Ψstem), stomatal conductance (gs), net CO2 assimilation rate (A), and intrinsic water use efficiency (WUE) were measured on five dates during the growing season the first year of the study and pruning weights were evaluated both years. Net gas exchange and water potential components taken on the last measurement date in 1992 and pruning weights of the nonirrigated species were less (or more negative for Ψ components) than those of the irrigated vines. The 17 Vitis species were ranked according to their relative drought tolerance based upon their performance without irrigation and when compared to their irrigated cohort. The Vitis species considered most drought tolerant were V. californica, V. champinii, V. doaniana, V. longii, V. girdiana, and V. arizonica. Those six species generally had high values of A, gs, and pruning weights and more favorable vine water status at the end of the study than the other species when grown without irrigation. The drought-induced reductions in the measured parameters also were less for those species when compared to their irrigated cohorts. The least drought tolerant species were, V. berlandieri, V. cinerea, V. lincecumii, V. riparia, and V. solonis. The drought-tolerant rankings were generally associated with the species' native habitat and probable soil water availability. sensitivity to changes in air humidity than did 'Shiraz' or 'Merlot' grapevines (Winkel and Rambal, 1990). There has been relatively little work done on the effects of soil water deficits on other Vitis species. The objective of this study was to rank the relative drought tolerance of 17 Vitis species under irrigated and nonirrigated conditions in the San Joaquin Valley of California. This was accomplished by measuring leaf water rela- tions, gas exchange and vine growth and then comparing each species within the nonirrigated portion of the vineyard with one another and with their irrigated cohort. In addition to several North American species, which are used either as commercial rootstocks or parents of other grape rootstocks, this study included several Vitis species indigenous to the arid southwestern United States. It was expected that the diverse, native habitats of the 17 species would have selected for a wide range drought tolerance characteristics that may be of use in future rootstock breeding programs.

Effects of 1-Methylcyclopropene and Heat Treatments on Ripening and Postharvest Decay in 'Golden Delicious' Apples

Abstract: Prestorage heat, CA storage, and pre- and poststorage treatments with the ethylene action inhibitor, 1- methylcyclopropene (MCP), were tested for their efficacy at inhibiting fungal decay and maintaining quality in 'Golden Delicious' apples (Malus sylvestris (L.) Mill. Yellow Delicious Group) stored 0 to 5 months at 0 °C and 7 days at 20 °C. Before storage in air at 0 °C, preclimacteric fruit were treated with either MCP at a concentration of 1 µL·L -1 for 17 hours at 20 °C, 38 °C air for 4 days, MCP plus heat, or left untreated. Some sets of untreated fruit were stored in a controlled atmosphere of 1.5 kPa O2 and 2.5 kPa CO2 at 0 °C while other sets were removed from cold storage in air after 2.5 or 5 months, warmed to 20 °C, and treated with 1 µL·L -1 MCP for 17 hours. Prestorage MCP, heat, MCP plus heat treatments and CA storage decreased decay severity caused by wound-inoculated Penicillium expansum Link, Botrytis cinerea Pers.:Fr., and Colletotrichum acutatum Simmonds (teleomorph Glomerella acutata J.C. Guerber & J.C. Correll sp.nov.). Poststorage MCP treatment had no effect on decay severity. Both prestorage MCP treatment and CA storage delayed ripening as indicated by better retention of green peel color, titratable acidity, and Magness-Taylor flesh firmness, and the reduced respiration, ethylene production rates, and volatile levels that were observed upon transferring the fruit to 20 °C. The prestorage MCP treatment delayed ripening more than CA storage. Following 5 months cold storage, the prestorage MCP treatment maintained the shape of the compression force/deformation curve compared with that of fruit at harvest, as did CA storage, but at a lower force profile. The heat treatment had mixed effects on ripening: it hastened loss of green peel color and titratable acidity, but maintained firmness and delayed increases in respiration, ethylene production and volatile levels following cold storage. The MCP plus heat treatment inhibited ripening more than heat treatment alone but less than MCP treatment alone. In one of 2 years, the MCP plus heat treatment resulted in superficial injury to some of the fruit. Results indicated that MCP may provide an effective alternative to CA for reducing decay severity and maintaining quality during postharvest storage of 'Golden Delicious' apples. Prestorage heat to control decay and maintain quality of apples needs further study, especially if used in combination with MCP.

Identification of QTL Conditioning Resistance to White Mold in Snap Bean

Abstract: Host resistance is an important component of integrated disease management strategies for control of Sclerotinia white mold disease in snap bean (Phaseolus vulgaris L.). Few resistant snap bean cultivars have been bred, however, because genetic resistance to white mold is not well understood. This study was conducted to examine in- heritance and identify quantitative trait loci (QTL) for white mold resistance in an F5:7 recombinant inbred line (RIL) population ('Bentonʼ/NY6020-4). 'Bentonʼ snap bean is susceptible to white mold. Snap bean germplasm line NY6020-4 has partial resistance. The parents and 77 F5:7 RILs were tested for resistance to white mold across four greenhouse and two fi eld environments. Moderately high heritability estimates were observed for straw test (0.73) and fi eld (0.62) reaction. Selective mapping of 27 random amplifi ed polymorphic DNA (RAPD) markers detected two QTL condition- ing resistance to white mold on linkage groups B6 and B8 of the core map. The B6 QTL explained 12% and B8 QTL 38% of the variation for disease reaction in the straw test. The two QTL explained 13% and 26% disease reaction in the fi eld, respectively. Favorable alleles for all the QTL were derived from NY6020-4, except for the B6 QTL condi- tioning resistance to white mold in the fi eld, which was derived from 'Bentonʼ. The B6 QTL was located near the Ur-4 rust resistance gene, and was associated with canopy height and lodging traits that condition disease avoidance. The B8 QTL was associated with increased internode length, an undesirable trait in snap bean, which may hamper use of white mold resistance derived from NY6020-4.

Relationship between Flesh Firmness and Ground Color in Peach as Influenced by Light and Canopy Position

Abstract: The influence of photosynthetic photon flux (PPF) on peach (Prunus persica (L.) Batsch) fruit quality and the relationship between ground color and flesh firmness was studied by performing three experiments. Fruit with varying ground colors were sampled from different canopy positions with varying PPF. Fruit skin color was measured with a tristimulus colorimeter and values for L* (lightness), chroma (brightness), and hue angle (numerical values for color) were calculated for each fruit. Fruit from the canopy exterior generally were larger, had more surface area colored red, had higher soluble solids concentrations, and were darker, duller, and redder than fruit harvested from interior positions. In all three experiments, the relationship between hue angle and fruit firmness was affected by PPF, but the nature of the relationship (linear vs. curvilinear) and the influence of position was not consistent. When fruit were covered with aluminum foil or a section of the fruit surface was covered with duct tape to prevent light-induced red coloration of the skin, the relationship between hue angle and fruit firmness was similar for different canopy positions. Therefore, the relationship between ground color and fruit firmness is influenced by the light environment in which a fruit develops, and not by canopy position. Ground color does not seem to be a good indicator of fruit firmness because fruit with the same hue angle had greatly differing firmnesses. was not significantly correlated with canopy height. Dann and Jerie (1988) reported that maturation and fruit quality of peach fruit were influenced more by proximity to the roots than to light interception. Fruit developing farthest from the roots matured earliest, and had the greatest dry weight and soluble solids concentration. Results from a limb-shading experiment indicated that peach soluble solids concentra- tion, surface red color, and flesh firmness, but not fruit weight, were reduced by shading (Marini et al., 1991). Fruit from shaded branches had greener ground color and softer flesh than fruit from nonshaded branches. This indicates that light or canopy position may alter the relationship between ground color and flesh firmness. If the rela- tionship between ground color and flesh firmness is affected by canopy position or light exposure, then fruit from different canopy positions should be harvested with different ground colors. The objectives of this study were to determine the influence of canopy position and PPF on peach fruit quality characteristics, and to determine if canopy position and PPF influence the relationship between ground color and fruit firmness.

Identification of Pistachio (Pistacia vera L.) Nuts with Microsatellite Markers

Abstract: A genomic DNA library enriched for dinucleotide (CT)n and (CA)n and trinucleotide (CTT)n microsatellite motifs has been developed from 'Kerman∑ pistachio (Pistacia vera L.). The enrichment method based on magnetic or biotin capture of repetitive sequences from restricted genomic DNA revealed an abundance of simple sequence repeats (SSRs) in the pistachio genome which were used for marker development. After an enrichment protocol, about 64% of the clones contained (CT)n repeats while 59% contained (CA)n for CT and CA enriched libraries, respectively. In the (CT)n enriched library, compound sequences were 45% while for (CA)n it was 13.5%. In both dinucleotide enriched libraries, about 80% of the clones having microsatellites have a repeat length in the range of 10 to 30 units. A library enriched for trinucleotide (CTT)n contained <19% of the clones with (CTT)n repeats. Of the clones that contained microsatellites, 62% had sufficient flanking sequence for primer design. An initial set of 25 pairs of primers was de- signed, out of which 14 pairs amplified cleanly and produced an easily interpretable PCR product in the commercially important American, Iranian, Turkish, and Syrian pistachio cultivars. The efficient DNA extraction method developed for pistachio kernels and shells (roasted and nonroasted) yielded DNA of sufficient quality to use PCR to create DNA fingerprints. In total, 46 alleles were identified by 14 primer pairs and a dendrogram was constructed on the basis of that information. The SSR markers distinguished most of the tested cultivars from their unique DNA fingerprint. An UPGMA cluster analysis placed most of the Iranian samples in one group while the Syrian samples were the most diverse and did not constitute a single distinct group. The maximum number of cultivar specific markers were found in 'Kerman∑ (4), the current industry standard in the United States, and the Syrian cultivar Jalab (5). The technique of using extracted DNA from pistachio kernal or shell coupled with the appropriate marker system developed here, can be used for analyses and measurement of trueness to type.

Genetic diversity of basil (Ocimum spp.) based on RAPD markers

Abstract: Molecular markers were used to assess genetic diversity in basil (Ocimum L. spp., Lamiaceae). Using randomly amplified polymorphic DNA (RAPD) analysis, 11 primers generated 98 polymorphic bands, ranging from 300 to 2,000 base pairs, that discriminated among 37 accessions across nine Ocimum spp. Means of genetic similarities within Ocimum spp. showed that the domesticated species, O. minimum L. (0.887), O. basilicum L. (0.769), and O. ×citriodorum Vis. (0.711) had highest similarity indices within species, while the nondomesticated, O. americanum L. (0.580), O. gratissimum L. (0.408), and O. kilimandscharicum Guerke (0.559) showed the lowest similarity. RAPD results indicated that O. minimum should not be considered a distinct species but rather a variety of O. basilicum. Consistent clusters among all but one of the O. ×citriodorum spp., all containing citral as the major constituent, were identified using bootstrap analysis. RAPD analysis was useful in discriminating among Ocimum spp., although within species resolution will require a higher number of polymorphic bands.

Effect of Artificial Shading and Temperature on Radical Scavenging Activity and Polyphenolic Composition in Sweetpotato (Ipomoea batatas L.) Leaves

Abstract: The phenolic content and the radical scavenging activity were compared in leaves of sweetpotato (Ipomoea batatas L.) cultivars Shimon-1, Kyushu-119 and Elegant Summer grown under different temperature and shading conditions. Compared to cultivar differences, there was less effect of temperature and shading on the total phenolic content in sweetpotato leaves, however certain polyphenolic components differed widely among the treatments. The positive correlation between the radical scavenging activity and the level of total phenolics (r = 0.62) suggests that phenolic compounds are important antioxidant components of sweetpotato leaves. All the reverse-phase high-performance liquid chromatography (RP-HPLC) profiles of the cultivars tested showed peaks at the same retention times but peak areas of individual phenolic compounds differed with respective temperature and shading treatments. The phenolic compounds identified in the sweetpotato leaf were caffeic acid, chlorogenic acid, 4,5-di-O-caffeoylquinic acid, 3,5-di-O-caffeoylquinic acid, 3,4-di-O- caffeoylquinic acid, and 3,4,5-tri-O-caffeoylquinic acid. Most of the phenolic compounds were highest in leaves from plants grown at 20 °C without shading except 4,5-di-O-caffeoylquinic acid. The results indicate that growing leaves under moderately high temperatures and in full sun enhances the accumulation of phenolic components. These phenolic components have possible value in enhancing human health.

Development of Sweet Melon (Cucumis melo) Genotypes Combining High Sucrose and Organic Acid Content

Abstract: The sweet cultivars of Cucumis melo are characterized by high sucrose levels, together with low acid levels in the mature fruit fl esh. The trait of high sugar accumulation in C. melo fruit is determined by a single recessive gene, suc. High acid content, conferred by a single dominant gene, So, is found only in C. melo varieties that do not accumulate high levels of sugar and are used for nondessert purposes. We combined the genetic traits of high acid content (low pH) and high sugar levels by crossing the nonsweet, high acid C. melo var. fl exuosus, 'Faqqousʼ (So/So, Suc/Suc), with high sugar, low acid C. melo genotypes (so/so, suc/suc) and generating the recombinant genotype So/__, suc/suc. Segregating F2 populations derived from the cross between 'Faqqousʼ and a standard high sugar, low acid line showed that the traits of high sugar and low pH were inherited independently of each other. The accumulation of acid and sugar in the developing fruit of a recombinant high acid, high sugar breeding line, A6, were also temporally independent, with acid accumulation preceding the rise in sucrose levels. The low pH of A6 was correlated with the developmental increase in titratable acid- ity and particularly of citric acid levels. The combination of increased acidity and high sugar provides the melons with a unique taste due to a sugar to acid ratio not present in sweet C. melo cultivars. These results are discussed in terms of the evolution under domestication of C. melo.

Carbon Assimilation and Carbohydrate Metabolism of `Concord' Grape (Vitis labrusca L.) Leaves in Response to Nitrogen Supply

Abstract: One-year-old grapevines (Vitis labrusca L. 'Concordʼ) were supplied twice weekly for 5 weeks with 0, 5, 10, 15, or 20 mM nitrogen (N) in a modifi ed Hoaglandʼs solution to generate a wide range of leaf N status. Both light-saturated CO2 assimilation at ambient CO2 and at saturating CO2 increased curvilinearly as leaf N increased. Although stoma- tal conductance showed a similar response to leaf N as CO2 assimilation, calculated intercellular CO2 concentrations decreased. On a leaf area basis, activities of key enzymes in the Calvin cycle, ribulose-1,5-bisphosphate carboxylase/ oxygenase (Rubisco), NADP-glyceraldehyde-3-phosphate dehydrogenase (GAPDH), phosphoribulokinase (PRK), and key enzymes in sucrose and starch synthesis, fructose-1,6-bisphosphatase (FBPase), sucrose phosphate synthase (SPS), and ADP-glucose pyrophosphorylase (AGPase), increased linearly with increasing leaf N content. When expressed on a leaf N basis, activities of the Calvin cycle enzymes increased with increasing leaf N, whereas activities of FBPase, SPS, and AGPase did not show signifi cant change. As leaf N increased, concentrations of glucose-6-phosphate (G6P), fructose-6-phosphate (F6P), and 3-phosphoglycerate (PGA) increased curvilinearly. The ratio of G6P/F6P remained unchanged over the leaf N range except for a signifi cant drop at the lowest leaf N. Concentrations of glucose, fructose, and sucrose at dusk increased linearly with increasing leaf N, and there was no difference between predawn and dusk measurements. As leaf N increased, starch concentration increased linearly at dusk, but decreased linearly at predawn. The calculated carbon export from starch degradation during the night increased with increasing leaf N. These results showed that 1) grapes leaves accumulated less soluble carbohydrates under N-limitation; 2) the elevated starch level in low N leaves at predawn was the result of the reduced carbon export from starch degradation during the night; and 3) the reduced capacity of CO2 assimilation in low N leaves was caused by the coordinated decreases in the activities of key enzymes involved in CO2 assimilation as a result of direct N limitation, not by the indirect feedback repression of CO2 assimilation via sugar accumulation. Photosynthesis depends on the function and coordination of

Orchard Floor and Nitrogen Management Influences Soil and Water Quality and Tart Cherry Yields

Abstract: Designing and implementing more productive, nutrient-efficient, and environmentally sound orchard management systems requires a better understanding of plant and soil responses to more biologically driven management practices. This study explored the effect of orchard floor and N management on soil organic C and N, populations of nematodes, NO3 leaching, and yields in tart cherry (Prunus cerasus L. 'Montmorency') production. A baseline conventional orchard system consisting of an herbicide-treated tree row and a full rate of N fertilizer was compared to two modified-conventional and ten alternative orchard floor and N management systems. Living ground cover and the use of mulch with or without composted manure increased total C and the active C and N pools in the soil. For instance, supplemental mulch or mulch applied using a side-delivery mower increased soil C by >20% above the conventional baseline. The size of the active C pool increased 45% and 60% with the use of the species mix 2 ground cover and compost, respectively. Increases in the active N pool ranged from a low of 25% in the soils using mulch or a ground cover mix to a high of 60% when compost was used. As a result, the ability of these soils to provide N to growing plants was enhanced. Total soil N increased in the treatment using natural weeds as ground cover and the full rate of N fertilizer. It is likely that weeds were able to convert significant amounts of fertilizer N into organic forms. Increasing the active C and N pools stimulates microbial activity, and may favor populations of nonplant parasitic nematodes over plant parasitic species. Using a trunk-to-trunk cover crop mix under the cherry trees reduced NO3 leaching by >90% compared to a conventional, herbicide treated soil, even when N fertilizer was used at full rate. Nitrate leaching also dramatically diminished when N fertilizer was fertigated at a reduced rate or when compost was used as N source. Alternative orchard floor and N management did not reduce yields when compared to the baseline conventional treatment.