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Michele Renee Warmund

, kernel size, kernel percent, tendency to yield large pieces of kernels when cracked, and flavor, kernel color is a component of black walnut fruit quality ( Funk, 1979 ). However, kernel color can be highly variable and is apparently affected by cultural

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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.

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L.J. Grauke, T.E. Thompson, E.F. Young Jr., and H.D. Petersen

The Munsell color system was used to study kernel color differences between four pecan [Carya illinoinensis (Wangenh.) K. Koch] cultivars (`Cheyenne', `Choctaw', `Western', and `Wichita') grown at four locations (Tulare, Calif., and Brownwood, Crystal City, and El Paso, Texas) during two seasons (1987 and 1988) and stored under different temperatures (20 to 24 °C and -5 °C). Kernel color changed over time from yellow to red hues and from lighter to darker values, but changed very little in chroma. Initial ratings of each color attribute by cultivar were positively correlated with patterns of change in that attribute over time. Kernels collected in 1987 were more yellow and had greater color saturation than kernels collected in 1988. `Cheyenne' kernels were the most yellow of the cultivars tested and `Wichita' kernels were the most red. `Cheyenne' kernels were lighter than those of any other cultivar. Kernels frozen 6 or 12 months were more red in hue than unfrozen kernels, but could not be distinguished on the basis of value (lightness). Kernels frozen 12 months had reduced chroma compared to those frozen 6 months or unfrozen. Shelled kernels of `Wichita' changed hue more in storage than kernels of other cultivars. Shelled kernels held at 20 to 24 °C became darker and developed red coloration quicker than unshelled pecans. Variation in hue and value accounted for the majority of color difference between cultivars. Changes in hue accounted for the majority of color change over time. Differences among cultivars in value (lightness) were consistent over time.

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

The Munsell system of color notation was used to study differences in kernel color arising between four pecan cultivars (`Cheyenne', `Choctaw', `Western', and `Wichita') grown at four locations (Tulare, Calif., and Brownwood, Crystal City and El Paso, Texas) during two seasons (1987 and 1988) and were stored under different temperatures (ambient and frozen). The hue, value, and chroma of pecan kernels varied significantly in the 2 years of the test. Kernels collected in 1987 were more yellow and lighter and had greater color saturation than kernels collected in 1988. Cultivars differed in hue, value, and chroma at the initial color determination. `Cheyenne' kernels were the most yellow (hue of 18.8) and were the lightest (value of 6.4) of any cultivars tested. `Wichita' kernels were more intensely colored (chroma of 4.7) than `Cheyenne' or `Choctaw' kernels. Kernels from pecan trees in El Paso were more yellow than those from other locations and were lighter than kernels from either Brownwood or Tulare, Calif. Kernels evaluated after being frozen 6 or 12 months could be distinguished from fresh kernels on the basis of hue. Frozen samples were more red than fresh kernels. Kernels frozen 12 months were less intensely colored than fresh kernels or those frozen only 6 months. There was a significant linear relationship between time in the freezer and each color attribute. Hue and chroma were negatively correlated with storage time, while value was positively correlated.

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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.

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Scott A. Brawner and Michele R. Warmund

: 1) identify a quantifiable method to determine optimal times of harvest for ‘Emma K’, ‘Kwik Krop’, and ‘Sparrow’ black walnuts; 2) assess kernel color at successive harvest dates; and 3) develop a quantifiable color classification system for these

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Saadat Sarikhani Khorami, Kazem Arzani, Ghasem Karimzadeh, Abdolali Shojaeiyan, and Wilco Ligterink

selected based on phenotypic data and were superior in terms of some important breeding traits such as nut and kernel weight and kernel percentage, respectively, more than 13 g, 6.5 g, and 50%, thin shell, L– EL kernel color, and easy removal in halves

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Scott A. Brawner, Michele R. Warmund, and Mark V. Coggeshall

A study was conducted to: 1) evaluate the use of a durometer for determining husk softening and the date of black walnut harvest and 2) elucidate the relationship between husk hardness, kernel color and weight, and date of harvest. Thirty nuts were randomly collected weekly from mature `Sparrow', `Emma K', `Kwik Krop', and `Football' trees from 1 Sept. to 13 Oct. 2004. Husk denting, hardness, and color measurements were recorded immediately after harvest. Husk denting is the method commonly used by growers to determine the optimum time of harvest. Nuts were then hulled within 48 hours and the in-shell fresh weights were recorded. After drying under natural conditions for 5 weeks, kernel color and weights were assessed. On 15 Sept., 99% of `Sparrow' husks dented with a mean durometer value of 54. On 29 Sept., ≥99% of `Emma K' and `Kwik Krop' husks dented with mean durometer values of 63 and 68, respectively. By 13 Oct., 80% of `Football' husks dented with a mean durometer value of 74. From the first harvest date to the time of maximum denting, kernel weight and color (L*, hue values) of `Sparrow' and `Emma K' generally increased. The L* and hue values of `Kwik Krop' were inversely related to increased kernel weight over time. Kernel color of `Football' remained relatively constant as kernel weight increased over time.

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J.B. Storey, L.J. Grauke, Laurence Sistrunk, and Tommy E. Thompson

Four cultivars of pecan [Carya illinoinensis (Wangenh.) K. Koch] were studied for 3 years to determine if variations in yield influence fatty acid composition of kernels. Trees used in the study are part of the U.S. Dept. of Agriculture, Agricultural Research Service Historical Block, a test orchard planted in randomized block design with four blocks, having one single-tree replication per block and containing 36 cultivars. Four trees of each of four cultivars (`Cheyenne', `Mohawk', `Pawnee', and `Osage') were used in this test. Trees were in their 5th to 7th leaf from grafting and showed patterns of increasing yield over time for each cultivar. `Osage' was earliest to mature nuts each year and produced nuts with the lowest linoleic acid content. `Cheyenne' was latest to mature nuts and had nuts with the highest linoleic acid content. Oleic acid composition varied with yield in `Osage' and `Pawnee': as yield (kilogram/square decimeter trunk area) increased, oleic acid content decreased. Kernel color, as determined by a Hunter LabScan 5100 Spectrocolorimeter, varied in relation to fatty acid composition for `Osage' and `Pawnee': as oleic acid content increased, kernel lightness decreased. High oleic acid content and light kernel color are associated with high-quality pecans. The pattern of decreasing oleic acid content associated with increasing kernel lightness raises questions concerning the role kernel color evaluation should play in selecting high-quality pecan cultivars.

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Laurence Sistrunk, Dan Chapman, and J. Benton Storey

The influence of temperatures during nut filling on nut size, kernel percentage, kernel color, percent oil, and fatty acid composition were evaluated over 3 years in `Cheyenne', `Mohawk', and `Pawnee' pecans [Carya illinoenensis (Wangenh.) C. Koch]. Nuts were harvested at shuck split at 14 sites located in Texas, Oklahoma, Kansas, Nebraska, Arizona, and California and Coahuila, Mexico. Weather data for 12 weeks before shuck split at each site were used to determine degree days by the formula: degree days = summation n(m–t) where n = number of days, m = (max + min temperature) ÷2, and t = 10°C. The degree days ranged from 996 to 1675. The oleic: linoleic ratios in all three cultivars were positively correlated with degree days in 2 of 3 years. `Mohawk' nut size was positively correlated with degree days all 3 years and `Cheyenne' and `Pawnee' were larger 2 of 3 years in the warmer climates. `Pawnee' kernel percentage and oil content was higher in the warmer climates. Warmer developmental temperatures had no influence on `Cheyenne' kernel color. `Mohawk' kernels were not affected 2 of 3 years, but `Pawnee' developed darker colors 2 of 3 years.