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United States Department of Agriculture

Agricultural Research Service

Research Project: MANAGEMENT OF GENETIC RESOURCES FOR VITIS, PRUNUS, JUGLANS, FICUS, OLEA, PISTACIA, PUNICA, DIOSPYROS, ACTINIDIA, AND MORUS

Location: National Clonal Germplasm Rep - Tree Fruit & Nut Crops & Grapes

Title: Genetic variation in walnuts (Juglans regia, j. sigillata and Juglandaceae) species distinctions, human impacts, and the conservation of agrobiodiversity in yunnan, china

Authors
item Gunn, Bee -
item Aradhya, Mallikarjuna
item Salick, Jan -
item Miller, Allison -
item Yongping, Yang -
item Lin, Liu -

Submitted to: American Journal of Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 26, 2009
Publication Date: February 5, 2010
Repository URL: http://www.ars.usda.gov/main/site_main.htm?modecode=53-06-20-00
Citation: Gunn, B.F., Aradhya, M.K., Salick, J.M., Miller, A.J., Yongping, Y., Lin, L. 2010. Genetic variation in walnuts (Juglans regia and J. sigillata; Juglandaceae): Species distinctions, human impacts, and the conservation of agrobiodiversity in Yunnan, China1 . American Journal of Botany 97:660-671.

Interpretive Summary: Walnuts are a major crop of many countries and mostly cultivated in large-scale plantations with few cultivars. Landraces provide important genetic reservoirs; thus, understanding factors influencing the geographic distribution of genetic variation in crop resources is a fundamental goal of agrobiodiversity conservation. Here, we investigated the role of human settlements and kinship on genetic variation and population structure of two walnut species: Juglans regia, an introduced species widely cultivated for its nuts, and J. sigillata, a native species cultivated locally in Yunnan. The objectives of this study were to characterize sympatric populations of J. regia and J. sigillata using 14 molecular markers and evaluate the role of Tibetan villages and kin groups (related households) on genotypic variation and population structure of J. regia and J. sigillata. Our results based on 220 walnut trees from six Tibetan villages show that although J. regia and J. sigillata are morphologically distinct, the two species are indistinguishable based on microsatellite data. Despite the lack of interspecific differences, AMOVAs partitioned among villages (5.41%, P = 0.0068) and kin groups within villages (3.34%, P = 0.0068) showed significant genetic variation. These findings suggest that village environments and familial relationships are factors contributing to the geographic structure of genetic variation in Tibetan walnuts.

Technical Abstract: Walnuts are a major crop of many countries and mostly cultivated in large-scale plantations with few cultivars. Landraces provide important genetic reservoirs; thus, understanding factors influencing the geographic distribution of genetic variation in crop resources is a fundamental goal of agrobiodiversity conservation. Here, we investigated the role of human settlements and kinship on genetic variation and population structure of two walnut species: Juglans regia, an introduced species widely cultivated for its nuts, and J. sigillata, a native species cultivated locally in Yunnan. The objectives of this study were to characterize sympatric populations of J. regia and J. sigillata using 14 molecular markers and evaluate the role of Tibetan villages and kin groups (related households) on genotypic variation and population structure of J. regia and J. sigillata. Our results based on 220 walnut trees from six Tibetan villages show that although J. regia and J. sigillata are morphologically distinct, the two species are indistinguishable based on microsatellite data. Despite the lack of interspecific differences, AMOVAs partitioned among villages (5.41%, P = 0.0068) and kin groups within villages (3.34%, P = 0.0068) showed significant genetic variation. These findings suggest that village environments and familial relationships are factors contributing to the geographic structure of genetic variation in Tibetan walnuts.

Last Modified: 4/23/2014
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