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United States Department of Agriculture

Agricultural Research Service

Research Project: Management and Characterization of Pecan (Carya) Genetic Resources and Related Wild Populations

Location: Crop Germplasm Research

Title: Phenotypic screening of pecan seedling rootstocks in search of nematode resistance

Authors
item Grauke, Larry
item Starr, James -

Submitted to: Trees: Structure and Function
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 6, 2014
Publication Date: June 28, 2014
Citation: Grauke, L.J., Starr, J.L. 2014. Phenotypic screening of pecan seedling rootstocks in search of nematode resistance. Trees: Structure and Function. Available: http://link.springer.com/article/10.1007/s00468-014-1038-6.

Interpretive Summary: Pecan seedling rootstocks are very susceptible to nematode damage caused by Meloidogyne partytila, the primary nematode pest of the genus Carya (pecan and hickory). This research used outdoor above ground box plots and showed that open-pollinated seedstocks for pecan vary in their susceptibility to nematode damage based on seedstock geographical origin. Although nematode damage varied, no reliable source of resistance was identified. The screening methods developed by this work help us understand regional patterns associated with useful traits in pecan and will lead to the selection, breeding, and deployment of better seedling rootstocks and particularly as related to nematode resistance.

Technical Abstract: Open-pollinated rootstocks of pecan, Carya aquatica, and their hybrid were screened for nematode resistance in outdoor above-ground box plots. Seedstocks were selected to represent the broad geographic range of species diversity. Seedlings were inoculated with eggs of Meloidogyne partytila, the primary nematode pest of Carya, and were harvested after one year. All seedlings except one manifested nematode damage at moderate to high levels. Evidence of galling was statistically greatest in seedlings from the southern provenance (Mexico), which rated comparably with 'Elliott'. No sources of resistance to Meloidogyne partytila were observed. Box structure allowed harvest of complete root systems and evaluation of plant composition in greater detail than previously observed. Seedlings from the southern provenance were generally distinguishable from other provenances in timing of seasonal growth, diameters and height which is consistent with previous observations. Root and stem dry weights were greatest in seedlings from the southern provenance, as expected based on size measurements. Percent root water varied significantly as a function of seedstock origin, and was negatively correlated with leaf weight. Leaf weights were positively correlated with dates of growth initiation. Uninfected control plants were not observed in this screening effort, and their absence limits the interpretation of patterns. Implications of these observations as evidence of regional adaptation should be explored in further research.

Last Modified: 11/26/2014
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