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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...

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.

Working in tandem with root exclusion, stems may provide salt-tolerant woody perennials with some additional capacity to restrict sodium (Na) and chloride (Cl) accumulation in leaves. The Pistacia genus, falling at the nexus of salt tolerance and human intervention, provided an ideal set of organisms for studying the influences of both variable root exclusion and potentially variable discontinuities at the bud union on stem processes. In three experiments covering a wide range of salt concentrations (0 to 150 mM NaCl) and tree ages (1, 2 and 10 years) as well as nine rootstock-scion combinations we show that proportional exclusion of both Na and Cl reached up to ~85% efficacy, but efficacy varied by both rootstock and budding treatment. Effective Na exclusion was augmented by significant retrieval of Na from the xylem sap, as evidenced by declines in the Na concentrations of both sap and wood tissue along the transpiration stream. However, while we observed little to no differences between the concentrations of the two ions in leaves, analogous declines in sap concentrations of Cl were not observed. We conclude that some parallel but separate mechanism must be acting on Cl to provide leaf protection from toxicity specific to this ion and suggest that this mechanism is recirculation of Cl in the phloem. The presented findings underline the importance of holistic assessments of salt tolerance in woody perennials. In particular, greater emphasis might be placed on the dynamics of salt sequestration in the significant storage volumes offered by the stems of woody perennials and on the potential for phloem discontinuity introduced with a bud/graft union.

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.

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.

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.

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.

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.

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.

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.

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.

The effects of four mechanical pruning treatments [hedging, topping, hedging/topping, and hand-pruning (control)] on nut yield, nut quality, alternate bearing, and growth of 14-year-old female `Kerman' pistachio trees on Pistacia atlantica L. rootstocks were assessed. A single pruning was done before an “off,” or low-crop, year followed by retopping of those treatments incorporating topping the first year. Over 7 years, yields of hedged/topped and topped trees were equal to those of control trees, while hedged trees produced significantly less. The incidence of nonsplit shells and blank nuts were not affected by pruning. Nuts weighed more all years for hedged/topped and topped trees than for the others. Alternate-bearing indices within 7 years were lower for pruning treatments incorporating topping. Topping mitigated the fluctuating annual vegetative growth pattern and resulted in 27% of the shoots retaining buds through three successive alternate-bearing cycles after the year of treatment. Hedged/topped and topped trees had significantly less alternation in annual girth growth than control or hedged trees. These results demonstrated that two successive seasons of mechanical topping, started before the off year, produced changes in shoot growth, trunk growth, and bud retention that mitigated alternate bearing through three biennial cycles, without decreasing yield. Thus, severe annual hand-pruning could be used to prevent or minimize alternate bearing of pistachios.

The influence of rootstock selection on leaf nutrient concentrations in commercial pistachio (Pistacia vera cv. ‘Kerman') was studied. Five commercially important pistachio rootstocks were used. The pistachio rootstock Pistacia atlantica was clearly superior in enhancing leaf concentrations of the elements, boron (B), copper (Cu), zinc (Zn), and phosphorus (P) from a range of soil types. The influence of rootstock on leaf nutrient concentration was apparent both in grafted and non‐grafted trees and was most pronounced when leaf nutrient levels were low. Leaf B, Cu, and Zn concentrations were from 1.2 to 2.4 times higher in pistachio grafted to P. atlantica than in those grafted on other rootstocks. For Cu and Zn, elements that are often deficient in Californian pistachio orchards, the choice of rootstock was sufficient to overcome visual deficiencies of these elements. In soils low in a particular element selection of rootstock may significantly influence management decisions and the need for fer...

Trunk cross-sectional area from a population of 6192 pistachio trees was used to estimate tree growth from 1995 to 1997. The narrow-sense heritabilities of trunk cross-sectional area were near zero across multiple locations based on analyses of progenies from 20 half-sib families. However, within individual location, there were values from 0.20 to 0.56 for 1995, 1996, and 1997, respectively. Broad-sense heritability estimates were considerably higher, from 0.36 to 0.64 at multiple locations and 0.51 to 1.35 for individual locations. These results suggest that dominance and significant interaction effects, epistatic and genotype by environment, were important. Breeding strategies should emphasize selection of superior parents based on individual performance, and parents should be selected in the environment in which the progeny are intended to be used.

A deformity designated as `damage by other means' (DBOM) by California pistachio processors appeared in California's San Joaquin Valley orchards in 1990. Incidence, higher during the heavy crop year of this alternate bearing cultivar, was as high as 5% of harvested yield. This represents a significant loss as DBOM nuts cannot be used for shelling stock. In 1993 ten weekly individual cluster samples from five heavily and five lightly cropped trees demonstrated a higher incidence of DBOM on heavily cropped trees. Further the damage occurred within one month of nut set, was exclusively on subterminal, adaxial positions of the rachis, and, often did not involve the nutmeat unless the deformity was extensive enough to expose the developing nutlet causing desiccation and abscission. Microanatomical studies demonstrated a deterioration of the parenchyma cells that form the inner cell layers of the endocarp (nut shell).

Pistacia integerrima (rootstock cultivar Pioneer Gold) is resistant to Verticillium dahliae, and P. atlantica (rootstock cultivar Standard Atlantica) is susceptible in the field. We developed greenhouse and laboratory assays that differentiate between the resistant and the susceptible cultivars. After injection of the stems of seedlings with conidia, the cultivars showed differential symptoms. After infusion of conidia into stems, V. dahliae colonized significantly fewer xylem vessels in the resistant than in the susceptible cultivar (...)

10 B, carbohydrate reserves, fruit tree nutrition, 15 N, Pistacia vera, uptake efficiancy Abstract. The effects of alternate bearing on recovery and loss of isotonically labeled fertilizer N and B and on the accumulation of carbohydrate and N reserves were assessed in mature 'Kerman' pistachio (Pistacia vera L.) trees. Total recovery of labeled fertilizer N applied once (in late January) was ≈ 60% greater if applied to trees entering an "off' than an "on" year, with respect to fruiting. Eleven percent more labeled B was recovered in off- than on-year trees. Five times more N (1 vs. 0.2 kg N) was lost from the tree in fruit and senescent leaflets from on- than off-year trees. In dormant trees, 144% and 22% more starch and N reserves, respectively, were present after off than on years. Thus, on-year trees were characterized by a greater reproductive demand for N and carbohydrates, reduced accumulation of C and N (i.e., storage) reserves in perennial tree parts, and reduced recovery of January-applied labeled fertilizer N than off-year trees. As B is absorbed passively, the higher transpiration that may accompany the 43% larger leaf area per tree and the probability of increased root growth probably contributes to its increased uptake during off years. The enhanced labeled N recovery in early spring by trees entering their off year preceded fruit and seed development in on-year trees. The differential tree capacity for nutrient uptake in spring may have been conditioned the previous rather than the current year. The increased uptake of labeled N by trees entering an off year (i.e., emerging from an on year) was associated with lower levels of carbohydrate and N reserves than for on-year trees that had just completed an off year. Future experimentation should assess the comparative capacity for nutrient uptake by on-and off-year trees at other stages of phenology, e.g., during seed development and postharvest. Alternate bearing-the alternation of high and low crop years—