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On an edible portion basis, pecan moisture, protein, lipid, total soluble sugars, and ash contents ranged from 2.1% to 6.4%, 6.0% to 11.3%, 65.9% to 78.0%, 3.3% to 5.3%, and 1.2% to 1.8%, respectively. With the exception of a high tannin (2.7%) Texas seedling, pecan tannin content was in a narrow range (0.6-1.85%). Unsaturated fatty acids (>90%) dominated pecan lipid composition with oleic (52.52-74.09%) and linoleic (17.69-37.52%) acids as the predominant unsaturated fatty acids. Location significantly influenced pecan biochemical composition. Pecan lipid content was negatively correlated with protein (r = -0.663) and total sugar (r = -0.625). Among the samples tested using SDS-PAGE a common pattern, with minor differences, in subunit polypeptide profiles was revealed. Rabbit polyclonal antibody-based immunoblotting experiments (Western blot) also illustrated the similarity in polypeptide profiles with respect to immunoreactivity. All tested cultivars registered similar immunoreactivity when their protein extracts (each at 1 mg/mL) were assessed using inhibition ELISAs (mean +/- standard deviation = 0.89 +/- 0.20; n = 27) with the USDA "Desirable" cultivar as the reference standard (immunoreactivity designated as 1.0).

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A microsatellite-enriched library was developed from `Halbert', a native pecan [Carya illinoinensis (Wangenh.) K. Koch] selection from Coleman County, Texas. A genomic library enriched for simple sequence repeats (SSR) containing 6144 clones was archived in 384 well plates for screening. In total, 439 clones were identified after Southern hybridization using di- and tri-nucleotide repeats as probes. In total, 125 positive clones were sequenced and primers were designed for 24 repeats. The SSR markers chosen for analysis include di-(CT and GA) and tri-nucleotide repeats (CTT, GAA and GAT). Of the 24 primer pairs tested, 19 successfully amplified microsatellites from `Halbert'. DNA was isolated from 48 pecan and hickory accessions selected to strategically represent the genetic diversity of the National Clonal Germplasm Repository (NCGR) Carya collections. The 19 SSR primers that produced good amplification products in `Halbert' were used to evaluate the collection, with 11 revealing polymorphism. The number of fragments amplified with different primer combinations ranged from 4 to 32 in the 48 genotypes tested. Evaluation of the data confirms the utility of the microsatellites in delimiting known relationships.

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Heritability estimates for pecan [Carya illinoinensis (Wangenh.) K. Koch] nut weight, nut buoyancy, nut volume, nut density, kernel weight, and percentage kernel were determined from 8748 nut samples representing 152 families collected during 25 years in the U.S. Dept. of Agriculture (USDA) pecan breeding program at Brownwood, Texas. Measurements were corrected for year-to-year environmental variability using least-squares constants of individual year effects. Adjusted values were then regressed on midparent means. Generally, heritability (h2) estimates were low to moderate: nut weight 0.35, nut buoyancy 0.18, nut volume 0.35, nut density 0.03, kernel weight 0.38, and percentage kernel 0.32. The low values are probably due to the extreme alternate bearing tendency of this species, since crop load affects pecan nut characteristics so directly. Phenotypic correlations among these traits showed that larger or heavier nuts had significantly higher kernel weight, buoyancy, and percentage kernel. Nut density increased with higher nut and kernel weight, but decreased with nut volume.