Search Results

You are looking at 11 - 20 of 24 items for

  • Author or Editor: Tommy E. Thompson x
Clear All Modify Search
Free access

Tommy E. Thompson and L.J. Grauke

Free access

Tommy E. Thompson, L.J. Grauke and E.F. Young Jr.

The Munsell Color System was used to study pecan [Carya illinoinensis (Wangenh.) K. Koch] kernel colors and color changes for 21 clones, 11 locations, and five storage methods for nuts collected over 4 years. Hue readings ranged from 10.0 (10 red) to 22.5 (2.5 yellow). Value readings ranged from 2.0 to 8.0, and chroma readings ranged from 1.0 to 8.0. A total of 91 classes (individual combinations of hue, value, and chroma) were needed to describe all kernel colors. Overall, one class 115.0/5/4 (hue/value/chroma)] accounted for 3979 of the 32,078 readings taken, and the 15 most common classes accounted for 80.7% of all the readings. This system of color determination was well-suited for pecan color determinations and continues to be used routinely as a part of our breeding and genetics program to define this important quality trait in pecan.

Free access

Tommy E. Thompson, L.J. Grauke and E.F. Young Jr.

The Munsell Color System was used to define pecan [Carya illinoinensis (Wangenh.) K. Koch] kernel colors and color changes for 21 clones, 11 locations, and 4 storage methods for nuts collected over a 4-year period. Hue readings ranged from 10.0 (10 red) to 22.5 (2.5 yellow). Value readings ranged from 2.5 to 8.0, and chroma readings ranged from 1.0 to 8.0. A total of 91 color chips (individual combinations of hue, value, and chroma) were needed to describe kernel color variability. In 1987 and 1988, one color [15.0/5/4 (hue/value/chroma)] accounted for 3,979 of the 32,078 readings taken, and the 15 most common colors accounted for 80.7% of all the readings. The Munsell system of color determination was well suited for pecan color determinations. A simplified color rating system with only six color classes was developed for general use by the pecan industry. This system is also routinely used in our breeding and genetics program to define this very important quality trait in pecan.

Free access

Tommy E. Thompson, L.J. Grauke and William Reid

Free access

Tommy E. Thompson, Samuel D. Senter and L.J. Grauke

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.

Free access

Tommy E. Thompson, Samuel D. Senter and L.J. Grauke

Pollen from five cultivars (cvs.) of pecans [Carya illinoinensis (Wangenh.) K. Koch] was sampled at Brownwood and College Station, Texas, in 1991 and 1992. Samples were analyzed for cytoplasmic lipid classes and constituent fatty acids. Lipid classes in all cvs. included phosphatidyl inasitol, phosphatidyl swine, phosphatidyl choline, phosphatidyl glycerol, phosphatidyl ethanolamine, free fatty acids, and triglycerides. Triglycerides were the predominant class of lipids in all cvs. analyzed. Fatty acids, qualitated and quantitated by gas chromatographic-mass spectral analysis, included palmitie (16:0), stearic (18:0), oleic (18:1), linoleic (18:2), and linolenic (18:3) adds. Quantities of individual and total fatty acids were significantly influenced (P> 0.05) by tree age. Within a uniform age class, quantities of individual and total fatty acids varied greatly and were significantly influenced by cultivar, year, and location as well as by interactions of main effects. The percent composition of individual fatty acids was stable in relation to total fatty acids in the sample, despite wide variation in quantities of fatty acids in different samples. Total fatty acids varied from 2.53% to 0.25% of dry weight. How this large variability in stored energy levels among pollen sources may affect orchard production is discussed.

Free access

Shyi-kuan Ou, J. Benton Storey and Tommy E. Thompson

Preharvest germination (viviparity) can be a problem with nuts of pecan [Carya illinoinensis (Wangenh.) K. Koch]. Two southern-adapted cultivars (`Cherokee' and `Wichita') and one northern-adapted cultivar (`Johnson') were paternal parents in controlled crosses with the maternal parent `Wichita'. `Wichita' × `Johnson' seed took much longer to germinate than seed from either the `Wichita' × `Cherokee' cross or the `Wichita' self, therefore indicating that pollen source may influence germination characteristics.

Free access

Tommy E. Thompson, L. J. Grauke and Leonardo Lombardini

Free access

LJ Grauke, Maria Azucena Mendoza-Herrera, Carol Loopstra and Tommy E. Thompson

Microsatellite or Simple Sequence Repeat (SSR) markers are being developed in ongoing research in the USDA ARS Pecan Breeding Program. These co-dominant markers provide a powerful tool for the verification of parentage. To confirm their utility, SSR profiles were used to confirm the parentage of 19 of the 25 controlled crosses released by the breeding program. Questions were raised concerning the parentage of some crosses thought to be known. When the genotype of the maternal parent is known, the paternal genotype necessary to have produced the progeny can be determined. A SAS program was written to query a database that includes 288 pecan accessions to find appropriate paternal genotypes given a maternal pattern. If neither parent is known, all possible parental combinations can be derived based on the progeny. Putative parents can be qualified on the basis of genotype as well as other evidence, such as nut morphology, dates of origin, locations of origin, and dichogamy. Using these techniques, putative parents are suggested for the historic cultivars `Riverside' and `Western'. Although the probabilities for a particular genotypic pattern can be determined based on allele frequencies within the population, assigning numeric probabilities to other evidence is more challenging. Meticulous records are necessary to establish the linkage between an inventory of an accession and its historic origin, thereby placing putative parents in combination at the proper place and appropriate time. Records of USDA–ARS National Plant Germplasm System, as exemplified by logbooks and vouchers of the McKay Collection of the National Arboretum, provide evidence for confident molecular genetic verification of cultivar identity and parentage, increasing the value of the living accessions in the NPGS.