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Iron (Fe) is chronically low in saline sodic soils. The effect of nano iron (Fe) particles complexed with salicylic acid (nFe-SA) on the Fe supply and salinity tolerance of Pistacia vera ‘Akbari’ s...

Current commercial olive (Olea europaea) cultivars are susceptible to olive knot disease caused by Pseudomonas savastanoi pv. savastanoi. Here we report on the examination of the olive tree germplasm collection maintained at the USDA-ARS National Clonal Germplasm Repository (NCGR) in Winters, California for the incidence of olive knot disease. Over a two year period we evaluated olive knot disease incidence on 506 trees representing 144 unique accessions consisting of 104 named cultivars originating from the Mediterranean Basin, South America, and California, including several hybrids, and related subspecies e.g. Olea europaea ssp. cuspidata. All genotypes were replicated in four blocks with trees in these blocks ranging in age from 6 to 35 year old. The disease index was higher in 2014 (43.5%) than in 2013 (29.4%). The percentage of infection varied significantly (P

In this review, the main internal and environmental hypotheses regarding alternate bearing and abscission of inflorescence buds and also, the methods to mitigate this physiological phenomenon have been investigated. Alternate bearing is annually fluctuating heavy (‘on’) and light (‘off’) crops, which occurs in most fruit trees. There are multiple visible causes, decreased shoot growth and flower buds or imperfect flowers, but all occur in association with a heavy crop, suggesting a carbohydrate resource limitation to shoot growth, or flower initiation, induction or differentiation. Pistachios bear on 1-year-old shoots from axillary buds produced the previous year. The visible mechanism is bud abscission on current season’s growth during ‘on’ years and bud retention in low crop load (‘off’) years. Though bud abscission is visible, the underlying cause is unknown. This review classifies the multiple hypotheses as internal, genetic, carbohydrate resources and hormones or environmental, abiotic and biotic stresses. Our examination of potential hypotheses and recent research suggests alternate bearing in pistachio is a result of the carbohydrate resource limitation generated by the heavy ‘on’ year crop maturation. However, the specific signal producing bud abscission is unknown. Alternate bearing in pistachio can be mitigated by a vigorous rootstock, particularly if combined with proper pruning. We hypothesize the vigorous rootstock may produce a better carbohydrate resource status through a larger tree with more leaf surface area. The pruning does not address the bud abscission but alters the ratio of non-bearing to bearing shoots, resulting in a lower alternate bearing index. Furthermore, we conclude alternate bearing in pistachio, while a within shoot phenomenon, can be triggered by severe environmental events that damage a current crop.

Springtime flail mowing of row middles for weed control in California pistachio (Pistacia vera L.) orchards blows dust into the leafless canopy if it occurs during bloom. The effect of dust on pistachio pollination and fruit set is unknown. Rachises were bagged prebloom and hand pollinated with pollen and dust mixtures at 1:0, 1:1, 1:4, 1:16, and 0:1 volume/volume ratios on five successive days. The 2016 and 2017 trials demonstrated that the inflorescences treated with a high pollen:dust ratio (0:1, 1:4, and 1:16) had significantly lower split nut rates (commercially less profitable) compared with low dust ratio tests (1:0 and 1:1). Our results also showed that dust damaged both pollen viability and stigma quality, particularly if contaminated with herbicide residues (GlyStar® Plus and Treevix®). Decreased yield was a function of decreased fruit set; increased embryo abortion, parthenocarpy, or both; and a lower split nut percentage. The GA3 content in flowers of both the pollen and dust treatments was significantly higher than that in nonpollinated flowers, suggesting dust stimulated parthenocarpy, resulting in empty nutshells, “blanks” at harvest.

The production and consumption of nuts are increasing in the world due to strong economic returns and the nutritional value of their products. With the increasing role and importance given to nuts (i.e., walnuts, hazelnut, pistachio, pecan, almond) in a balanced and healthy diet and their benefits to human health, breeding of the nuts species has also been stepped up. Most recent fruit breeding programs have focused on scion genetic improvement. However, the use of locally adapted grafted rootstocks also enhanced the productivity and quality of tree fruit crops. Grafting is an ancient horticultural practice used in nut crops to manipulate scion phenotype and productivity and overcome biotic and abiotic stresses. There are complex rootstock breeding objectives and physiological and molecular aspects of rootstock–scion interactions in nut crops. In this review, we provide an overview of these, considering the mechanisms involved in nutrient and water uptake, regulation of phytohormones, and rootstock influences on the scion molecular processes, including long-distance gene silencing and trans-grafting. Understanding the mechanisms resulting from rootstock × scion × environmental interactions will contribute to developing new rootstocks with resilience in the face of climate change, but also of the multitude of diseases and pests. info:eu-repo/semantics/publishedVersion

The production and consumption of nuts are increasing in the world due to strong economic returns and the nutritional value of their products. With the increasing role and importance given to nuts (i.e., walnuts, hazelnut, pistachio, pecan, almond) in a balanced and healthy diet and in the prevention of various diseases, breeding of the nuts species has also been stepped up. Most recent fruit breeding programs have focused on scion genetic improvement. However, the use of locally adapted grafted rootstocks also enhanced the productivity and quality of tree fruit crops. Grafting is an ancient horticultural practice use in nut crops to manipulate scion phenotype and productivity and overcome biotic and abiotic stresses. There are complex rootstock breeding objectives and physiological and molecular aspects of rootstock–scion interactions in nut crops. In this review, we provide an overview of these, considering the mechanisms involved in nutrient and water uptake, regulation of phytohormones, and rootstock influences on the scion molecular processes, including long-distance gene silencing and trans-grafting. Understanding the mechanisms resulting from rootstock × scion × environmental interactions will contribute to developing new rootstocks with resilience in the face of climate change, but also of the multitude of diseases and pests and of the possible increase of their aggressiveness. They will also have to offer the premises of economic production, respectively yield and the quality, according to multiple destinations of nuts in the current consumption and food industry, but also the increasing exigencies of the consumer market and the profile industry.

Understanding the mechanisms of stress tolerance in diverse species is needed to enhance crop performance under conditions such as high salinity. Plant roots, in particular in grafted agricultural crops, can function as a boundary against external stresses in order to maintain plant fitness. However, limited information exists for salinity stress responses of woody species and their rootstocks. Pistachio (Pistacia spp.) is a tree nut crop with relatively high salinity tolerance as well as high genetic heterogeneity. In this study, we used a microscopy‐based approach to investigate the cellular and structural responses to salinity stress in the roots of two pistachio rootstocks, Pistacia integerrima (PGI) and a hybrid, P. atlantica x P. integerrima (UCB1). We analyzed root sections via fluorescence microscopy across a developmental gradient, defined by xylem development, for sodium localization and for cellular barrier differentiation via suberin deposition. Our cumulative data suggest that the salinity response in pistachio rootstock species is associated with both vacuolar sodium ion (Na+) sequestration in the root cortex and increased suberin deposition at apoplastic barriers. Furthermore, both vacuolar sequestration and suberin deposition correlate with the root developmental gradient. We observed a higher rate of Na+ vacuolar sequestration and reduced salt‐induced leaf damage in UCB1 when compared to P. integerrima. In addition, UCB1 displayed higher basal levels of suberization, in both the exodermis and endodermis, compared to P. integerrima. This difference was enhanced after salinity stress. These cellular characteristics are phenotypes that can be taken into account during screening for sodium‐mediated salinity tolerance in woody plant species.

Background The effects of passive modified-atmosphere packaging (passive-MAP) on the postharvest quality of de-hulled fresh pistachios (Pistacia vera L. cv. Kerman) stored at cold temperature (0 ± 0.5 °C) and 90 ± 1% relative humidity was investigated with fruits under ambient air condition as the control treatment. The fruit quality parameters measured included kernel firmness, color values (L* , a* , b* , h°, and C* ), weight loss, fungal decay and marketability, ethylene production, respiration rate, and sensory characteristics at 0, 30, 60, and 105 days of storage. The carbon dioxide (CO2 ) and oxygen (O2 ) concentrations in the package headspace were monitored during storage. Results A modified atmosphere of 0.95-3.35% O2 and 23.17-29.82% CO2 was achieved in the passive-MAP treatment. Fruit respiration rates increased significantly relative to controls throughout storage (P ≤ 0.01). However, storage had no significant effect on ethylene production rates. Additionally, passive-MAP-stored fruits maintained firmness, shell lightness, kernel color, and sensory quality with minimum weight loss and fungal decay, compared with the control. Conclusion These results demonstrate storage life of fresh pistachios in passive-MAP can be extended up to 105 days, compared with 30 days in ambient conditions. © 2019 Society of Chemical Industry.

The effect of irrigation and crop load on alternate bearing was studied in pistachio tree using a “branch carbon budget model” developed to calculate branch carbohydrate balance. Experiences were conducted in Sicily (37°26’N, 14°03’E, 360 m a.s.l.) on female trees of ‘Bianca’. Two treatments were applied: rainfed (T0) and 100 mm of irrigation (T100). At 29, 44, 65, 86, 103 and 121 DAFB, on one fully expanded leaf selected on three trees per treatment, were monitored leaf gas exchanges. At 15 days interval, three branches treatment-1 were excised and, in the lab, the following parameters were measured: total photosynthetically active leaf surface; number of leaves, fruits, shoot fresh weight (FW) and dry weight (DW). Photosynthetic response curves to PPFD were calculated on the base of data published in the literature. Irrigation positively affected branch carbon budget that resulted positive (6.87 g of C) at the end of the season, whereas in rainfed trees the carbon budget was negative (-13.98 g of C). In rainfed trees seasonal branch carbon assimilation was 44% lower as a consequence of reduced leaf area. 28 days after full bloom, when leaves reached full development, leaf area fruiting branch-1 in rainfed trees was 920 and 1300 cm2 in branches of irrigated tress. Branch of rainfed trees also showed intense leaf drop and yellowing that strongly reduced late season assimilation rate (Amax 4.5 µmol m-2 s-1 in branches of rainfed trees vs. 10 µmol m-2 s-1 in irrigated ones), affecting total seasonal carbon assimilation. Referring to the carbon budget of the branches, considering the interaction between crop load and irrigation, one cluster was the maximum sustainable crop load in rainfed trees while irrigation enabled the branches to sustain up to three clusters, maintaining a positive carbon budget until fruit ripening. The results reported confirm that the “branch carbon budget model”, after further validation, will be a valid tool to predict carbohydrate budget as function of crop load and irrigation, useful to help to manage orchard to reduce the severity of alternate bearing.

Alternate bearing in pistachio (Pistacia vera L.) is particularly severe. The developing nuts are a major sink, draining branch carbohydrates, producing inflorescence bud abscission and decreasing the following year's production. We investigated inflorescence bud drop as a function of branch crop load, embryo weight, and vegetative growth. The main objective of this study was to investigate the mechanism of alternate bearing. We also tested the efficacy of eight different foliar nutrient combinations for reducing inflorescence bud abscission: Acadian A LSC®, Acadian B, low-biuret urea, Acadian A LSC® + low-biuret urea, Acadian B + low-biuret urea, MaxCell®, MaxCell® + low-biuret urea, and untreated control (sprayed with water). The trial was conducted during the 2016 growing season on eight-year-old Kerman pistachio trees planted at 5.2 m in-row and 6.1 m between rows, on PG1 rootstock, 8 replications for each treatment. Average tree yields as dry in-shell marketable split nuts were not significantly different among treatments ranging from 27 to 31 kg tree(-1)). The treatment did not affect inflorescence bud abscission. The bud abscission percentage was significantly higher in bearing branches (~70%) versus non-bearing branches (~15%). In fruiting shoots, the percentage of inflorescence bud abscission was significantly and positively correlated with embryo growth. Length, width and weight of new wood and one-year-old wood correlated significantly and positively with nut production, and negatively with inflorescence bud abscission. The data collected support the hypothesis suggested in the literature that alternate bearing is function of crop load and carbohydrate depletion. Results reported here are the first step toward characterization of optimal shoot parameters, length, width and leaf area, for optimal and regular crop production.

Field observations suggest high air temperatures during bloom decrease fruit set of many sweet cherry (Prunus avium L.) cultivars. We investigated the role of temperature on stigma receptivity and ovule viability in four sweet cherry cultivars that exhibit variability in productivity and fertility: ‘Sweetheart’ (self-fertile, high productivity), ‘Benton’ (self-fertile, low productivity), ‘Rainier’ (self-sterile, high productivity), and ‘Tieton’ (self-sterile, low productivity). The development of the stigmatic surface, and pollen hydration, germination and tube growth in vivo, were evaluated by hand pollination and used as proxies for stigma receptivity. In addition, the senescence of primary and secondary ovules was analyzed with fluorescence microscopy. The stigmatic papillae began deteriorating by the second day after anthesis and had collapsed by the sixth day post-anthesis across cultivars. Pollen hydration exhibited 5 stages related to the length-width ratios of 2.5:1, 2:1, 1.75:1, 1.5:1 to 1:1. Maximum pollen hydration and pollen germination occurred on the stigmas within 2 days of bloom, depending on cultivar and air temperature. Pollen hydration and germination, and ovule senescence accelerated under warmer temperatures. At 7 days post-anthesis and under 24 °C approximately 80% of ‘Rainier’ ovules were viable compared to 30% in the three other cultivars. Under moderate temperature (18 °C) which mimicked the field average flowering temperature, ovule of the two high productivity cherry cultivars, ‘Rainier’ and ‘Sweetheart’, kept full viabilities for 3–4 days post-anthesis while only 1 day for the two low productivity cultivars ‘Benton’ and ‘Tieton’. These results reveal that low commercial productivity of sweet cherry cultivars in the Pacific Northwest (PNW) of U.S. is likely due to rapid ovule senescence, a condition exacerbated in warm conditions.

Pistachio (Pistacia spp.) is a tree nut crop with relatively high salinity tolerance. Currently, limited information exists on its rootstock’s cellular responses to salinity stress, especially in its roots. In this study, we investigated salinity tolerance at cellular level, in two pistachio rootstocks, Pistacia integerrima (PGI) and a hybrid, P. atlantica x P. integerrima (UCB1). Root tip sections were categorized across a developmental gradient according to their xylem development, and their sodium content and suberin deposition were analyzed with fluorescence microscopy. Our data demonstrated a correlation between vacuolar sequestration of sodium ions (Na+) and salinity tolerance in the UCB1 genotype. In addition, UCB1 displayed higher basal levels of suberization in both the exodermis and endodermis that increased further after salinity stress. Notably, the root region immediately distal to the region of secondary xylem initiation showed the highest amount of vacuolar Na+ sequestration, indicating a developmental regulation of this process. Our cumulative data demonstrate that salinity tolerance in pistachio rootstock species is associated with both vacuolar Na+ sequestration and suberin deposition at apoplastic barriers, and both are correlated with a root developmental gradient. These cellular characteristics are phenotypes that can be screened during the selection for salinity tolerant woody plant species.

The California pistachio cultivars 'Kerman' and 'Peters' have an estimated requirement of 58 and 60 chill portions, respectively. In California's Central San Joaquin Valley, the recent combination of warmer winter temperatures and sharply decreased fogs have resulted in a reduction of winter chill accumulation. In 2015 and 2016, kaolin clay was applied to dormant pistachio trees attempting to increase chill accumulation by reflecting radiant heat. Four treatments including kaolin clay, kaolin clay plus 470 dormant oil, 470 dormant oil, and an untreated control were made to nine year old pistachio trees. Kaolin clay applications (33 kg ha-1) were applied twice with the first application occurring after leaf drop in mid-December and the second occurring in early-January. A 6% 470 dormant oil solution was applied at 150 L ha-1 on February 6th, 2016. Treatments were approximately 1.9 ha in size and were replicated four times utilizing a randomized complete block design. Temperature sensors measuring external wood temperature on the north and south side were installed on a single tree in multiple blocks. Yield was determined for each plot and evaluated for size and quality. Local weather station measurements indicate that adequate chill was received in 2015-2016. Never-the-less, wood surface temperatures in kaolin treated trees were lower than the untreated control, producing an increase in chill portion accumulation by ~15%. Yield, however, was higher in the 470 dormant oil than in the kaolin clay or untreated control (3,330 kg ha-1 vs. 2,796 and 2,774 kg ha-1, respectively). Results suggest that kaolin clay may be useful in increasing chill portion accumulation, but only if applied early in the dormant period. Our results also confirmed earlier reports that dormant oil increases pistachio yield in marginal to adequate chill years. Both techniques should be utilized as tools to help mitigate variable climate within pistachio orchards.

The effects of passive- and active-modified atmosphere packaging (passive- and active-MAP) were investigated on the physio-chemical and quality attributes of fresh in-hull pistachios stored at 4 ± 1 °C and 90 ± 5% R.H. Fresh pistachios were packaged under each of the following gas combinations: active-MAP1 (AMA1) (5% O2 + 5% CO2), AMA2 (5% O2 + 25% CO2), AMA3 (5% O2 + 45% CO2), AMA4 (2.5% O2 + 5% CO2), AMA5 (2.5% O2 + 25% CO2), and AMA6 (2.5% O2 + 45% CO2), all balanced with N2, as well as passive-MAP (PMA) with ambient air (21% O2 + 0.03% CO2 + 78% N2). Changes in quality parameters were evaluated after 0, 15, 30 and 45 days of storage. Results demonstrated that AMA6 and PMA had significantly lower (7.96 Log CFU g−1) and higher (9.81 Log CFU g−1) aerobic mesophilic bacteria counts than the other treatments. However, the AMA6 treatment decreased, kernel chlorophyll and carotenoid content, hull antioxidant capacity, and anthocyanin content. The PMA treatment produced a significant weight loss, 0.18%, relative to the other treatments. The active-MAP treatments were more effective than the passive-MAP in decreasing weight loss, microbial counts, kernel total chlorophyll (Kernel TCL), and kernel carotenoid content (Kernel CAC). The postharvest quality of fresh in-hull pistachios was maintained best by the AMA3 (5% O2 + 45% CO2 + 50% N2) treatment.

Root injuries, heat and desiccation after transplanting are abiotic stresses that may cause transplant failure. Stress signal transduction for preventing transplant failure due to root injuries and growing in hot dry conditions was evaluated using Pistacia vera , a species highly sensitive to transplanting, as the model plant. Pistachio seedlings were primed by exposure to salt stress using 100 mM CaCl 2 100 mM KNO 3 , 50 mM CaCl 2 + 50 mM KNO 3, and three foliar applications of 2.0 mM β-aminobutyric acid (BABA) for 7 days. After removing 30% of the root length, the plants were then grown under hot dry conditions for 60 days. Significant increases were observed in the plasma membrane thermostability and proline and malondialdehyde leaf concentrations after the priming treatments. The BABA and KNO 3 treatments increased leaf H 2 O 2 content by 26% while the KNO 3 + CaCl 2 treatment increased it by 63%. Detached leaves of non-primed plants lost water more quickly than leaves of primed plants. The BABA and KNO 3 + CaCl 2 treatments were most effective at limiting water loss from detached leaves. Transplanting killed all the non-primed plants. The CaCl 2 treatment increased transplant survival by 42.9% and the KNO 3 + CaCl 2 treatment by 100%. The survival rate of BABA and KNO 3 primed plants was 57.1%. These results suggest controlled salt stress could be a simple, rapid and efficient method of for controlling transplant shock.

Citrus mechanical harvesting has been investigated since the 1960's. Even though mechanical harvesting could significantly lower production costs, the implementation by the private sector has been slow. The current harvesting technologies detach the fruits with trunk, canopy or branch vibration. For late-season sweet orange varieties which simultaneously bear mature fruit, immature fruitlets and flowers, shaker harvesting decreases the subsequent year's yield. This study, investigated the frequency response of mature fruits and immature fruitlets to determine the optimum frequency range for an efficient and selective harvest. Laboratory vibration transmission tests were conducted with 14 branches bearing 76 mature fruits and 151 immature ‘Valencia’ fruitlets. The fruit and branch response to the forced vibration was measured by several sets of five triaxial accelerometers with a dynamic signal analyser. Three frequency ranges with the highest vibration transmission values were identified for mechanical harvesting lower than 10 Hz. The first frequency range (1.5–2.5 Hz) corresponded best with the most efficient vibration transmission, involving more than 90% of fruit. The second frequency range (4.5–5 Hz) successfully discriminated between mature fruit and immature fruitlets. In this frequency range, 53.4% of mature fruit amplified the acceleration a mean value of 2.2 times, while only 7.3% of immature fruitlets amplified the acceleration with a mean value of 4.4 times. The third frequency range (7–8 Hz) had the lowest vibration transmission value. The frequency response of mature citrus fruits, and their markedly higher fruit mass, were significant factors in efficient selective mechanical harvesting.

The super high density (SHD) model is a new olive growing system characterized by earlier and higher yields, fully mechanized harvesting and reduced orchard management costs. Until recently all commercial SHD orchards were planted primarily with three varieties: ‘Arbequina’, ‘Arbosana’ and ‘Koroneiki’. To increase variety diversity, broaden available olive oil chemical and organoleptic profiles, and olive oils for marketing, minor local varieties should be evaluated for adaptability to the SHD system. This study compares multiple Sicilian native genotypes to the three current cultivars ‘Arbequina’, ‘Arbosana’ and ‘Koroneiki’. The cumulative fruit and oil production, trunk-cross section area, canopy volume, alternate bearing behavior and oil quality were evaluated in a SHD system. Among the standard cultivars ‘Koroneiki’ had significantly higher and ‘Arbequina’ average productivity respectively compared to earlier reports and was chosen as the reference for evaluating the performance of the Sicilian genotypes. Many of the genotypes investigated had olive and oil yields equal to or higher than ‘Arbequina’; ‘Abunara’ and ‘ADE’ had very high productivity. ‘Abunara’ produced a medium-high quality oil. The ‘KALAT’ selection had high productivity and low vigor, and therefore high productive efficiency. However, the oil polyphenols were low. The ‘Cerasuola’ and ‘Piricuddara’ cultivars had good productivity and a very high quality oils. These results confirm the need to evaluate and preserve local genetic resources as a strategy for improving SHD olive management and increasing olive cultivar and oil diversity.

Pistachio is an economically important nut crop in California. Since temperature variations among geographical locations can influence biochemical processes during fruit development, it is of great relevance to understand the impact of growing area over the components that define the nutritional and sensory characteristics of pistachio nuts. Changes in moisture, fat content, fatty acid composition and volatile terpenes were studied during kernel development for "Kerman" and "Golden Hills" varieties in two different California Central Valley microclimates, Lost Hills and Parlier. Moisture content decreased from July to September for both cultivars at both locations. Kerman had a higher moisture content at both locations compared with Golden Hills. Harvest time affected fat content only for Kerman, where the values increased drastically from 21-July to 4-Aug, then remained constant. Golden Hills' fat content remained constant during the period of the study. The main fatty acid in pistachio oil is oleic acid (46% to 59%), followed by linoleic acid (26% to 36%) and palmitic acid (11% to 16%). C16:0, C16:1, C18:2, and C18:3 decreased with harvest time, while C18:1 increased. α-Pinene was the most concentrated volatile among the cultivars and locations. It decreased with harvest time for both cultivars at both locations, ranging from 105 to 2464 mg/kg. At harvest, Golden Hills and Kerman at Parlier both had higher concentrations of α-pinene than the two cultivars at Lost Hills. Our results demonstrate that microclimate affects biosynthesis of fatty acids and terpenes in pistachio kernels, the main compounds responsible for pistachio nutritional and sensory characteristics.

The genus Pistacia L. consists of 11 or more tree and shrub species belonging to the Anacardiaceae family. Pistacia vera L. is the only commercially-important species within this genus with nuts large enough to be consumed. The center of diversity of P. vera is northern Iran, southern Turkmenistan and parts of Afghanistan. Botanically, pistachio fruits are semidry drupes composed of a fleshy exocarp and mesocarp (pericarp or hull), and a hard endocarp (shell) containing the edible kernel. Pistachio is a wind pollinated dioecious tree with apetalous pistillate and staminate inflorescences on separate female and male trees. Currently pistachio cultivation is expanding in Iran, the USA, Turkey, Greece, Italy, Spain, China, Tunisia and many other countries. However, its commercial production has been affected by the undesired physiological characteristics of alternate bearing, shell indehiscence, blank nuts and susceptibility to abiotic stresses, including drought and salinity, and fungal foliar and root diseases. Genetic improvement of these characteristics should be a factor in future breeding attempts to produce superior pistachio cultivars. This chapter describes the advances in traditional and molecular breeding of pistachio cultivars. The traditional breeding and hybridization programs discussed are focused on new female and male cultivars, and rootstocks, introduced through pistachio genomics and breeding programs. The discussion of germplasm biodiversity and molecular breeding summarizes the current knowledge of intra- and inter-specific genetic diversity, cytogenetic evaluations, and marker-assisted selection in the genus Pistacia. The current knowledge of pistachio genetic engineering including micropropagation, regeneration systems, somaclonal variation and genetic stability, in vitro conservation and cryopreservation, and genetic transformation studies are also discussed.

Pecan is native to the United States. The US is the world’s largest pecan producer with an average yearly production of 250 to 300 million pounds; 80 percent of the world’s supply. Georgia, New Mexico, Texas, Arizona, Oklahoma, California, Louisiana, and Florida are the major US pecan producing states. Pecan trees frequently suffer from spring freeze at bud break and bloom as the buds are quite sensitive to freeze damage. This leads to poor flower and nut production. This review focuses on the impact of spring freeze during bud differentiation and flower development. Spring freeze kills the primary terminal buds, the pecan tree has a second chance for growth and flowering through secondary buds. Unfortunately, secondary buds have less bloom potential than primary buds and nut yield is reduced. Spring freeze damage depends on severity of the freeze, bud growth stage, cultivar type and tree age, tree height and tree vigor. This review discusses the impact of temperature on structure and function of male and female reproductive organs. It also summarizes carbohydrate relations as another factor that may play an important role in spring growth and transition of primary and secondary buds to flowers.

California's 300,000 acre pistachio industry consists of over 90% Pistacia vera. Cultivars with different harvest timing would relieve the pressure on processing facilities. A recently identified cultivar, 'Pete I' harvests earlier, but is producing unacceptably high percentages of early season aborted nuts, which abscise, as well as partially filled and blank nuts. Both overload the hullers and float tanks. Field observations suggested insect pressure and/or fungal infestation. In an insect exclusion study, flower buds were both covered by insect-impermeable mesh and left uncovered on the 'Pete I' trees for the season until harvest. The resulting clusters showed no significant difference in the final percentage of aborted nuts between the bagged and unbagged samples. Laboratory plating of early- and mid- season nuts for fungal pathogens detected none beyond background levels. Therefore, high percentages of blanking and partially filled nuts in the 'Pete I' pistachio cultivar were not due to either insect or fungal pressures. Other possibilities are pollen or ovule incompatibility, or self-thinning through embryo abortion.

With climate change and decreased water supplies, interest in irrigation scheduling based on plant water status is increasing. Stem water potential (ΨSWP) thresholds for irrigation scheduling in olive have been proposed, however, a physiologically-based evaluation of their reliability is needed. A large dataset collected at variable environmental conditions, growing systems, and genotypes was used to characterize the relation between ΨSWP and gas exchanges for olive. Based on the effect of drought stress on the ecophysiological parameters monitored, we described three levels of stress: no stress (ΨSWP above about −2 MPa), where the high variability of stomatal conductance (gs) suggests a tight stomatal control of water loss that limit ΨSWP drop, irrigation volumes applied to overcome this threshold had no effect on assimilation but reduced intrinsic water use efficiency (iWUE); moderate-stress (ΨSWP between about −2.0 and −3.5 MPa), where iWUE can be increased without damage to the photosynthetic apparatus of leaves; and high-stress (ΨSWP below about −3.5 MPa), where gs dropped below 150 mmol m−2 s−1 and the intercellular CO2 concentration increased proportionally, suggesting non-stomatal limitation to photosynthesis was operative. This study confirmed that olive ΨSWP should be maintained between −2 and −3.5 MPa for optimal irrigation efficiency and to avoid harmful water stress levels.

Developing mechanical harvesting for table olives will require decreasing fruit damage during harvest and postharvest handling, transport and storage. The susceptibility to bruising and its development over time were studied in three table olive varieties, cv. ‘Manzanilla’, ‘Gordal Sevillana’ and ‘Hojiblanca’. Bruising was produced with controlled energy impacts of 56, 26, 13 mJ. A strong correlation ( r 2 = 0.77–0.90) between bruise volume and impact energy was demonstrated. Bruise susceptibility was higher in the Manzanilla variety, followed by Hojiblanca and Gordal Sevillana cultivars. Bruise time evolution was evaluated using a spectrophotometer for visible and near infrared regions. A bruise index was developed using different wavelengths, 545, 670 and 800 nm. Most darkening due to the browning process happened within 1 h, was exponential and dependent on impact energy level. The discoloration was greatest in the Manzanilla, followed by Hojiblanca and Gordal Sevillana olives.

The effect of two fruit maturity stages on the quality attributes of four fresh fig cultivars was examined, including consumer acceptance and antioxidant capacity. Fig quality attributes such as weight, soluble solids concentration (SSC), titratable acidity (TA), SSC:TA, firmness, antioxidant capacity, and consumer acceptance varied by cultivar. Fig cultivars harvested at the advanced maturity stage (“tree ripe”) had lower TA and firmness but higher weight, SSC, and SSC:TA than figs harvested at “commercial maturity.” Fig maturity did not affect antioxidant capacity, but tree ripe figs had higher consumer acceptance than commercial maturity figs. SSC was more highly correlated with consumer acceptance than TA or SSC:TA, but other factors may also be important in controlling this relationship. Cultivars with high SSC and firmness, at a maturity stage high enough to tolerate harvesting and postharvest handling, should be selected to develop the fresh fig industry. Because fig firmness is a concern, changes to packaging should be evaluated to protect the flavor of advanced maturity figs during postharvest handling.

Most fig (Ficus carica) cultivars have potentially two crops; fruit from the first crop are called brebas. This crop is commercially important in some Mediterranean area cultivars. The second or main crop, called figs, is the commercially important crop for most fig cultivars. Due to labor cost increases, harvest of the breba crop, with its low production and lower quality fruit, has become economically unviable in some cultivars. Unharvested brebas are potential sites for fungal pathogens and they attract insects. Spring ethephon applications of 250 to 500 ppm applied before full leaf expansion, when the largest fruit are about 1.5 to 2 cm in diameter reduced the breba crop load (≈92%) without adverse side effects. The use of early fall ethephon applications of 500 ppm also resulted in breba crop load reductions (≈30%), but with significantly lower efficacy than spring treatments. These fall and/or spring ethephon treatments did not affect the percentage of vegetative budbreak, breba weight, breba soluble solids concentration, fig crop load, fig weight, or ethephon residues. Thus, early spring ethephon application at 300 ppm (0.22–0.36 kg·ha−1), when breba fruit and leaves are just starting to develop and figs are not present, was a safe, effective and inexpensive way (about $16 per hectare) to reduce the breba crop. Currently, ethephon is included in the federal IR-4 program, and residue studies are ongoing as a protocol for future registration.

The California table olive (Olea europaea L.) industry relies exclusively on hand harvesting of its primary Manzanillo cultivar. Increased harvesting costs have intensified industry interest in identifying an abscission agent that can be used with developing mechanical harvesting technologies to increase removal rates. Table olives are harvested immature green at horticultural maturity but before physiological maturity. The goal of this research was to reevaluate the potential of ethylene-releasing compounds (ERCs) as olive-loosening agents and to screen additional candidates previously shown to accelerate citrus fruit abscission. Eleven compounds were screened at two separate table olive-growing sites (Fresno and Tehama counties) in California in September until Nov. 2006. Compounds were applied at various concentrations alone or in combination. Fruit detachment force (FDF) and percent fruit drop were measured and leaf loss assessed. Of the compounds evaluated, the ERC ethephon (2-chloroethyl phosphonic acid) and 1-aminocyclopropane-1-carboxylic acid were the most efficacious. In whole tree applications, concentrations of ethephon or 1-aminocyclopropane-1-carboxylic acid above 1000 mg·L−1 reduced FDF to less than 50% of the untreated control within 17 days, but leaf drop increased with increasing concentrations. Addition of 1-methylcyclopropene reduced efficacy of ethephon and delayed leaf drop. Monopotassium phosphate + ethephon (4% and 1000 mg·L−1, respectively) reduced FDF and leaf loss was equivalent to the ethephon alone treatment. Compounds such as methyl jasmonate, coronatine, dikegulac, MAXCEL, traumatic acid, and 5-chloro-3-methyl-4-nitro-1H-pyrazole were not efficacious.

Additional index words. Ficus carica, pollination biology, postharvestThe genus Ficus includes species rangingin number from 600 to more than 1900, withmost found in the tropics or subtropics andonly a handful with fruits considered edible(reviewed in Condit, 1969). The cultivatedfig, Ficus carica L., (Moraceae), is clearly ofgreatest importance as a source of humanfood. The fig fruit has long been associatedwithhorticulture in the Mediterranean region(Zohary and Spiegel-Roy, 1975) and is con­sidered to have been"first brought into cul­tivation in southern Arabia" (Storey, 1975).Wild or "nearly wild" figs are reportedthroughout much of the Middle East andMediterranean region (De Candolle, 1886).Cultivated figs are reported to have becomeestablished across the

SummarySimple Sequence Repeat (SSR) and Sequence-Related Amplified Polymorphism (SRAP) molecular marker systems were used to analyse four commercially important pistachio rootstocks: two species of Pistacia atlantica (cv. ‘Standard Atlantica’), P. integerrima (cv. ‘Pioneer Gold’) and two interspecific hybrids of the same, ‘Pioneer Gold II’ (‘PGII’) and ‘University of California at Berkeley 1’ (‘UCB-1’). A total of 35 putative alleles were detected by 12 SSR primer pairs with an average of 2.9 alleles per locus. The number of putative alleles ranged from 2 to 5 in the pistachio rootstocks tested. The number of bands produced by the SRAP protocol was highly variable, ranging from 11 to 38, with an average of 25.2 per primer combination. Eight primer combinations resulted in 104 (51%) polymorphic markers in these samples. SSR and SRAP markers successfully identified all pistachio rootstocks tested from their unique fingerprints. Both SSR and SRAP molecular markers confirmed that the observed variation in ‘UC...

Epstein, L., Beede, R., Kaur, S., and Ferguson, L. 2004. Rootstock effects on pistachio trees grown in Verticillium dahliae-infested soil. Phytopathology 94:388-395. In a field trial in soil infested with Verticillium dahliae, we compared the yield, growth, incidence of symptoms of Verticillium wilt, and mortality of two interspecific hybrid pistachio tree rootstocks (UCBI and PGII) with the standard rootstocks: the V. dahliae-resistant and susceptible Pistacia integerrima and P. atlantica, respectively. After 10 years, the trees were destructively sampled for V. dahliae in the xylem at the graft union. The results indicate that trees on the (P. atlantica ‘KAC’ × P. integerrima) hybrid UCBI rootstock grew and yielded as well as those on P. integerrima. Trees on the hybrid PGII yielded the least. Analysis of variance and log-linear models indicate that in soil infested with V. dahliae, three associations significantly affect pistachio nut yield. Rootstock affects scion vigor and extent of infection. Third, the extent of infection and scion vigor are inversely associated. Although trees on the P. integerrima rootstock had the highest ratings in a visual assessment of vigor, 65% were infected with V. dahliae in the trunk in the graft region compared with 73% in P. atlantica and 25% in UCBI. Thus, P. integerrima and UCBI have at least one different mechanism for resistance to V. dahliae. Additional keyword: nut trees.

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

Heritability of flowering and leafing date of pistachio (Pistacia vera L.) were estimated based on half-sib family and parent-offspring regression analyses. Narrow sense heritabilities of flowering date ranged from 0.68 to 0.88 based on half-sib analyses and from 0.89 to 0.95 based on parent-offspring regression analyses. The narrow sense heritability of leafing date was 0.75 based on half-sib analyses and 0.60 from parent-offspring regression analysis. First leafing date was highly correlated with flowering date (r =0.59–0.78), suggesting that first leafing date could be used to select for flowering date in seedlings long before the onset off lowering.

Performance of `Kerman' pistachio (Pistacia vera L.) trees on three rootstocks (P. atlantica Desf., P. integerrima Stewart and `UCB-1', a P. atlantica × P. integerrima hybrid) was evaluated with 2-year-old trees grown in sand-tank lysimeters under combined SO42- and Cl- salinity and boron (B) stress for 6 months. Four salinity treatments were imposed by irrigating the plants with water at electrical conductivity (ECiw) of 3.5, 8.7,12, or 16 dS·m-1 each containing B at 10 mg·L-1. Growth of `Kerman' was evaluated based on increase in total leaf area, increase in trunk diameter, and total above-ground biomass production. All growth parameters decreased as salinity increased, but were not significant until ECiw exceeded 12 dS·m-1. However, growth of `Kerman' on P. atlantica and `UCB-1' was considerably better than on P. integerrima at 16 dS·m-1. The onset and severity of foliar injury differed among scions and treatments and was attributed primarily to B toxicity, rather than the effects of salinity. Concentrations of B in injured leaf tissue ranged from 1000 to 2500 mg·kg-1. Leaf injury decreased with increasing salinity, although leaf B was not significantly reduced suggesting an internal synergistic interaction between B and other mineral nutrients. However for P. vera on P. integerrima, the highest level of salinity produced the greatest injury, possibly as a combination of B plus Cl- and/or Na+ toxicity. Leaf transpiration, stomatal conductance, and chlorophyll concentration of P. vera, determined by steady-state porometry, were also reduced to a greater degree by combined salinity and B when budded on P. integerrima than on the other two rootstocks.

Pistachio nut (cv `Kerman') development was examined on light-bearing and heavy-bearing trees during the 1993 and 1994 growing seasons to characterize fruit development. The highest incidence of damage by other means (DBOM) occurred during May when fruit thinning was occurring and shells were developing. Disease, insects, and mechanical damage were eliminated as causing DBOM. Dormant spraying of calcium, manganese, and boron resulted in no significant mitigation of DBOM. However, the incidence of DBOM appeared to increase with increasing crop load. From an anatomical study it appeared that the process leading to tissue degeneration in pistachio fruit pericarp may start as early as the second week after bloom, although in some cases its onset is later. The most affected tissue is the endocarp parenchyma, whose cells become necrotic and collapse, thus causing shrinkage and fracture in the shell. In the worst cases only the mesocarp (hull) remains functional, providing thin protection for the embryo, as no shell is present in the affected areas. The degeneration may also involve the mesocarp, at times with hypertrophy. The localized curly aspect of the nuts occurs when the degeneration is not simultaneous, or equal, on the entire wall. The macroscopic degeneration ranges from dramatic to barely noticeable.