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Somatic embryogenic cultures of pecan (Carya illinoinensis) were induced on medium with either naphthaleneacetic acid (NAA) or 2,4-dichlorophenoxyacetic acid (2,4-D). Percent embryogenesis, embryo development, and subsequent performance were assessed. Cultures induced on medium with NAA were more zygotic-like, with a higher frequency of embryos that had well-defined shoot apices. In contrast, cultures induced with 2,4-D exhibited more extensive callusing and more fused and/or abnormal embryos. Adjustment of the auxin used during induction may be a means of obtaining higher quality embryos, that have higher rates of conversion into plants.

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`Oconee' pecan [Carya illinoinensis (Wangenh.) K. Koch] scions were grafted on seedling rootstock from nine open-pollinated seedstocks. Rootstock included three seedstocks each of pecan, water hickory [C. aquatica (F. Michx.) Nutt.], and their interspecific hybrid, Carya × lecontei (Little). Pecan seedlings had the largest basal diameters and water hickory seedlings the smallest. Seedlings of `Elliott' and `Curtis' seedstocks were larger than seedlings from `Moore' seedstock. Pecan and C. × lecontei seedlings were grafted more successfully than water hickory. Graft success varied among seedstocks of pecan and C. × lecontei Foliage color of seedlings, possibly indicative of iron nutritional status, was influenced by species; pecan seedling leaves were darker green than those of water hickory seedlings, but similar to C. × lecontei leaves. `Oconee' scion leaves were darker green on pecan rootstock than when grafted on C. × lecontei rootstock.

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Pollen from five cultivars of pecans [Carya illinoinensis (Wangenh.) K. Koch] was analyzed for cytoplasmic lipid classes and constituent fatty acids. Lipid classes in all cultivars included free fatty acids, triglycerides, and the phosphatide of inositol, serine, choline, glycerol, and ethanolamine. Triglycerides were the predominant class of lipids in all cultivars analyzed. Gas chromatography and mass spectral analysis were used to identify and quantify the fatty acids, which included palmitic, stearic, oleic, linoleic, and linolenic. Quantities of individual and total fatty acids varied greatly and were influenced significantly by cultivar, year, and location, as well as by interactions of main effects The percent composition of individual fatty acids was remarkably stable, despite wide variation in quantities of fatty acids. Therefore, pollen fatty acid ratios may be a valuable measure of taxonomic relationship across Carya sp. Total fatty acids varied from 2.53% to 0.25% of dry weight. Variability in stored energy in the form of lipids may affect orchard production.

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`Oconee' pecan (Carya illinoinensis (Wangenh.) K. Koch) was grafted on seedling rootstocks from nine open-pollinated seedstocks. Rootstocks included three seedstocks each of pecan, water hickory (C. aquatica (F. Michaux.) Nutt.) and their hybrid, Carya X lecontei (Little). Pecan seedlings had the largest basal diameter, water hickory seedlings the smallest, and hybrid seedlings were intermediate. Seedlings of `Elliott' and 'Curtis' seedstocks were larger than seedlings from `Moore' seedstock. Pecan and hybrid seedlings were more successfully grafted than water hickory. Graft success varied between seedstocks of the hybrid, with some as high as pecan. Foliage color of seedlings, indicative of iron nutrient status, was influenced by the species of rootstock: pecan seedlings were darker green than water hickory seedlings, but were inseparable from hybrid seedlings. `Oconee' scions on pecan seedlings were darker green than when grown on hybrid seedlings.

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ohridella ) on reproduction in Aesculus hippocastanum Trees (Berl.) 17 383 388 10.1007/s00468-003-0249-z Thompson, T.E. Grauke, L.J. 1991 Pecans and other hickories ( Carya ) Acta Hort. 290 839 904 U.S. Department of Agriculture 2008 Official soil series

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Putative resistance to the blackmargined aphid (Monellia caryella Fitch) in `Pawnee' pecan [Carya illinoinensis (Wangenh.) K. Koch] was first noted in greenhouse tests by rating cultivars for relative amounts of honeydew on adaxial leaf surfaces. This resistance was confirmed in two field tests monitored from mid-June to mid-October. `Pawnee' supported significantly lower aphid populations during every rating period when relatively large numbers of these insects were present. `Navaho' also showed resistance, with `Desirable' having intermediate resistance and `Stuart' being very susceptible. Insect populations were also monitored on the four quadrants of each tree, with quadrant effect being significant in only one test. This test had the highest populations on the western quadrant and lowest populations on the eastern quadrant. In determining individual clone resistance, it is recommended that the general orchard aphid infestation level be determined so that only two or three well-timed clonal ratings are needed. We also recommend that all sides of the tree be monitored.

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Yields and economic returns above treatment variable costs were determined for young `Desirable' pecan [Carya illinoinensis (Wangenh.) C. Koch] trees grown for nine seasons under ten combinations of orchard floor management practice and irrigation. Orchard floor management practices were 1) no weed control, 2) mowed, 3) total weed control with herbicides, 4) grass control only with herbicides, or 5) disking, and trees were either irrigated or nonirrigated. Total weed control with herbicides increased cumulative yield through the ninth growing season by 358% compared to no weed control. In the humid environment where this experiment was conducted, irrigation did not increase crop value obtained from the young trees, except for 1 year. At the end of the ninth season, total weed control with herbicides was the only treatment to have a positive net present value. These data indicate that establishment costs for young `Desirable' pecan trees can be recovered as early as the eighth growing season if competition from weeds is totally eliminated.

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Zinc deficiency is a widespread nutritional disorder in plants and occurs in both temperate and tropical climates. In spite of its physiological importance, cytological and ultrastructural changes associated with zinc deficiency are lacking, in part because zinc deficiency is difficult to induce. A method was developed to induce zinc deficiency in pecan (Carya illinoinensis (Wangenh.) C. Koch) using hydroponic culture. Zinc deficiency was evaluated in leaves using light and electron microscopy. Zinc deficiency symptoms varied with severity ranging from interveinal mottling, overall chlorosis, necrosis, and marginal curving. Zinc deficient leaves were thinner, and palisade cells were shorter, wider, and had more intercellular spaces than zinc sufficient leaves. Cells in zinc deficient leaves had limited cytoplasmic content and accumulated phenolic compounds in vacuoles. Extensive starch accumulation was observed in chloroplasts. This work represents the first detailed microscopic evaluations of zinc deficiency in leaves, and provides insight on how zinc deficiency affects leaf structure and function.

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Pecans (Carya illinoinensis) are produced under a wide array of environmental conditions—from the warm humid southeastern states, to the continental climate of the central plains, to the arid climates of the American west. In addition, pecan cultural systems vary from the low-input management of native stands of seedling trees to the intensive management of single-cultivar pecan orchards. This wide diversity of pecan agroecosystems has fostered the development of innovative, site-specific approaches toward pecan pest management. Current pecan pest management programs require an intimate knowledge of orchard ecology. Growers use monitoring methods and prediction models to track pest populations. Biological control agents are conserved by habitat manipulation and/or augmented through inoculative releases. Selective pesticides are used to control target pests while conserving natural enemies. Four pecan cultural systems are described in detail to illustrate how ecological principles are applied to widely diverse pecan agroecosystems.

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This study was established to assess the effect of aldicarb on newly transplanted pecan (Carya illinoinensis) nursery trees. Although labeled for use on pecans for more than 25 years, the aldicarb label for pecans was voluntarily dropped by the manufacturer in 2010. Bare-root seedling, ‘Cape Fear’, ‘Sumner’, and ‘Elliott’ trees were planted in Feb. 2007. Ten trees each were treated with one of the following treatments: aldicarb (0.25 lb at budbreak), aldicarb (0.25 lb applied at budbreak and again in June for a total of 0.5 lb/tree), and a nontreated control. Aldicarb increased shoot length, trunk diameter, leaf chlorophyll index, total dry weight, stem dry weight, and root dry weight of pecan seedlings after 1 year's growth. Aldicarb increased trunk diameter of ‘Cape Fear’, ‘Sumner’, and ‘Elliott’ during the course of the study. Nut production of ‘Cape Fear’ was enhanced in the third year of production. These observations indicate that aldicarb is of value in pecan orchard establishment.

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