Submitted to: Journal American Society Hortscience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 4, 2003
Publication Date: July 1, 2003
Citation: Thompson, T.E., Grauke, L.J. 2003. Pecan nut and kernel traits are related to shelling efficiency. HortScience. 38:586-590. Interpretive Summary: A century ago, almost all pecans were natives, which are generally small nuts with thick shells, and hard to shell. The proportion of the U.S. crop that is native has steadily decreased due to native pecan habitat annihilation and poor economics of native pecan production. Breeding efforts to improve pecan nut quality have been very successful, and continue to improve this native American nut species. This paper reports a study comparing actual shelling efficiency with laboratory measurements designed to accurately define ease of shelling in commercial shelling plants. Pecan samples were cracked, shelled, and rated for shell separation from kernels. We learned that nut shape, percent kernel, and nut size had little effect in determining ease of shelling. We also learned that many of the routine laboratory measurements that we spend a lot of time making are not worth the effort, as far as predictors of ease of shelling.
Technical Abstract: The USDA ARS conducts the largest and oldest pecan [Carya illinoinesnsis (Wangenh.) K. Koch] breeding program in the world, and evaluates thousands of nut and kernel samples each year using a standard nut and kernel evaluation system developed and refined for over 70 years. This report relates the effectiveness of these evaluations to commercial shelling efficiency by direct comparison of these data to commercially shelled samples from the same clone performance test. Visual ratings of shelled samples of kernel (1-5, with 1=best) were statistically correlated with time required to hand clean kernel samples (r2=0.55). As percent kernel increased, visual ratings of shelled kernels improved (decreased)(r2=-0.73). There were more intact halves recovered from shelled samples with the best (lowest) visual ratings (r2=-0.67). Conversely, there were fewer pieces of any size in samples with the best visual ratings. Visual ratings improved as nut density decreased (r2=0.33). Samples with the lightest kernel color also had the best visual ratings (r2=0.38) These data show that modifications to the standard USDA pecan nut and kernel evaluation system need to be refined by modifying selection pressure placed on various standard evaluation characteristics.