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A. Talaie and A. Khezrian

To select proper varieties, several seedlings of Carya illinoensis (pecan) were imported from the United States about 28 years ago and were planted at the Safiabad Research Center, Iran. Because of the existence of docogamy in pecan, protandrous and protoginous cultivars were first determined. Then, qualitative and some quantitative characteristics were studied in a completely random plant test and, with regard to treatments and repetitions, the total yield of trees, weight of kernel, kernel: bark ratio, oil percentage (fat), protein percentage, and the size of fruit were examined. With regard to all circumstances and statistical results, out of 14 examined varieties, varieties 12 (`Wichita') and 1 (`Gratex') were selected on the basis of their high yields, respectively.

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Martinez T. Miguel and Duarte U. Miguel

Ethephon and NAA in 2 combinations were applied to 17 year old “Western” pecan trees near the coast of Hermosillo, in Sonora, Mexico. The treatments were: a) 300 ppm NAA plus 800 ppm Ethephon; b) 300 ppm NAA plus 500 ppm Ethephon. These treatments were applied at three different times: first, when nut physiological maturity was reached, second, 10 days after nut physiological maturity and third, 21 days after physiological maturity was reached. The best treatment was the combination of 300 ppm NAA plus 800 ppm Ethephon applied 10 days after physiological maturity. This treatment resulted in 100% shuck dehiscence, 10% leaf abscission, 2 weeks advance in harvest and the best kernel color when compared to control.

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Darrell Sparks

The inter-relationship of precocity, prolificacy, and kernel percentage was studied in pecan [Carya illinoensis (Wangenh.) C. Koch]. Prolificacy was highly correlated with precocity, but the relationship was not one to one. Increased precocity resulted in proportionately smaller increase in prolificacy. Variability in kernel percentage increased with prolificacy.

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Darrell Sparks and I.E. Yates

Sooty mold washed from leaves of four cultivars of pecan [Carya illinoensis (Wangenh.) C. Koch] was quantified. The amounts of sooty mold accumulation differed significantly (P ≤ 0.05) among the cultivars. Leaf surface morphology of each cultivar was examined. A higher incidence of sooty mold was associated with cultivars having a rough, granulated leaf topography than those with smoother leaf surfaces. Characteristics of leaf surface morphology may be useful in selecting germplasms with reduced susceptibility to sooty mold accumulation.

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William D. Goff, Monte L. Nesbitt, and Cathy L. Browne

Fourteen pecan (Carya illinoensis) clones with desirable traits selected from preliminary screenings were evaluated for scab resistance, foliage condition and foliage retention. No fungicide or insecticide sprays were applied in order to increase pest and disease pressure and to better assess suitability of the selections for low input plantings. Most clones were equal to or better than `Elliott', the resistant standard cultivar and were superior to `Desirable', the susceptible standard cultivar, in scab incidence and foliage condition.

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Ray E. Worley

Pecan [Carya illinoensis (Wangenh.) C. Koch] tree height was gradually reduced by removing one, two, or three limbs per year at a height <9 m. Pruning improved tree vigor and color, increased trunk circumference, terminal shoot growth, nut size, and leaf N, P, and Mg, but reduced leaf K and percentage of fancy grade kernels relative to unpruned trees. Yield was not influenced by selective limb pruning.

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Robert D. Marquard

Six phosphoglucomutase phenotypes were observed in pecan [Carya illinoensis (Wangenh.) K. Koch] progeny after controlled pollinations. At least one locus (Pgm-1) is present that controls polymorphism of phosphoglucomutase (PGM) isozymes in pecan. The inheritance appears simple with three observed alleles. However, progeny produced from two crosses resulted in significant deviation from the expected segregation ratios. Out of 65 named cultivars, 61 were of a single phenotype, and two of six possible phenotypes were not observed. Only one region of PGM activity was consistently expressed by gel electrophoresis from pecan tissue.

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Chung Soo Chung, Marvin K. Harris, and J. Benton Storey

Annual variation in fruiting by pecan [Carya illinoensis (Wangenh.) K. Koch] obtained from anecdotal records and state, district, county, and orchard data from Texas indicate exceptionally high synchronous fluctuations typically occurred every 34 years with a range of 2-7 years over the 66-year data base examined. Synchrony in fruit production was inversely related to the spatial distribution of pecans reflected in coefficients of variation ranging from about 60 at the state level to about 120 for two 10-ha orchards. These characteristics show that pecan exhibits roasting and that the species warrants further examination vis a vis interactions with nut feeders.

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Hazel Y. Wetzstein and Choong-Suk Kim

Although somatic embryogenesis in vitro has been carried out successfully in a number of plants, a limiting factor in many somatic embryogenic systems is that plantlet regeneration is not obtainable or restricted to low frequencies. We have developed a repetitive, high frequency somatic embryogenic system in pecan (Carya illinoensis) and have identified effective treatments for improved somatic embryo conversion. A 6 to 10 week cold treatment followed by a 5 day desiccation, promoted enhanced root germination and extension, and epicotyl elongation. Light and transmission electron microscopic evaluations of somatic embryo cotyledon development will be presented and related to conversion enhancing treatments and their possible roles in embryo maturation.

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Hazel Y. Wetzstein and Choong-Suk Kim

Although somatic embryogenesis in vitro has been carried out successfully in a number of plants, a limiting factor in many somatic embryogenic systems is that plantlet regeneration is not obtainable or restricted to low frequencies. We have developed a repetitive, high frequency somatic embryogenic system in pecan (Carya illinoensis) and have identified effective treatments for improved somatic embryo conversion. A 6 to 10 week cold treatment followed by a 5 day desiccation, promoted enhanced root germination and extension, and epicotyl elongation. Light and transmission electron microscopic evaluations of somatic embryo cotyledon development will be presented and related to conversion enhancing treatments and their possible roles in embryo maturation.