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.
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.
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.
Michael W. Smith and James C. Gallott
Fruit of `Mohawk' in 1986 and 1988 and `Shoshoni' pecan [Carya illinoensis (Wangenh.) C. Koch] in 1986 were thinned during early August using a pecan shaker with modified shaker pads. Fruit removed ranged from 44% to 57% of the crop load. Fruit thinning increased nut size of `Mohawk' in both years, but did not affect nut size of `Shoshoni'. Kernel percentage of thinned `Mohawk' and `Shoshoni' trees increased, and kernel grade of `Mohawk' improved relative to unthinned trees. Return bloom of `Mohawk' was not affected either year by thinning, but return bloom on `Shoshoni' was increased by thinning. Mechanical fruit thinning appears to be a useful commercial tool until better thinning methods are available.
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.
Ray E. Worley
Nitrogen at 112 and 224 kg·ha-1 and K at 0, 56, 112, 168, and 224 kg·ha-1 were applied to young `Desirable' pecan [Carya illinoensis (Wangenh.) C. Koch] trees to evaluate their influence on leaf scorch. Scorch severity in the orchard decreased with time even though large imbalances of N and K existed. Scorch was increased only slightly by the high N and the zero K treatments. Little scorch was observed in trees receiving K applications. Increasing K rates >56 kg·ha-1 did not reduce scorch. Correlation was not significant or very weak for leaf N, leaf K, or the leaf N: K ratio with leaf scorch in the Ray City, Ga. study, depending on the year of observation. Another study at Tifton, Ga., revealed no correlation between scorch and leaf K or the leaf N: K ratio. A very weak correlation occurred for scorch and leaf N in 1 of 2 years.
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.
Hening Hu and Darrell Sparks
The effect of Zn deficiency on reproductive growth of `Stuart' pecan [Carya illinoensis (Wangenh.) C. Koch] was studied. At the most severe Zn-deficiency level, shoots were rosetted and produced neither. staminate nor pistillate inflorescences. At less severe Zn-deficiency levels, catkin length and weight decreased as Zn concentration in the leaf decreased. The number of fruits produced per shoot was reduced by Zn deficiency. Even though fruit abortion was not affected by Zn status of the shoot, fruit death and drying in situ increased with increasing Zn deficiency. Zinc deficiency dramatically suppressed fruit development and resulted in delayed and staggered shuck dehiscence.
Bruce W. Wood, Jerry A. Payne, and Owen Jones
Overcrowding in young high-density pecan [Carya illinoensis (Wangenh.) C. Koch] orchards has prompted a study of tree transplanting and evaluation of survival and tree performance. Shoot growth and nut production characteristics of 13-year-old `Stuart' and `Farley' pecan trees subjected to different stubbing and pruning treatments and then transplanted with a large tree spade indicated that transplants can survive with little or no pruning if moved when dormant. Shoot regrowth was proportional to the degree of pruning, and nut production was inversely proportional to the degree of pruning.
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.