Needle morphological evidence of the homoploid hybrid origin of Pinus densata based on analysis of artificial hybrids and the putative parents, Pinus tabuliformis and Pinus yunnanensis

Authors

  • Fangqian Xing,

    1. National Engineering Laboratory for Forest Tree Breeding, Key Laboratory for Genetics and Breeding of Forest Trees and Ornamental Plants of Ministry of Education, Beijing Forestry University, Beijing, China
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  • Jian-Feng Mao,

    1. National Engineering Laboratory for Forest Tree Breeding, Key Laboratory for Genetics and Breeding of Forest Trees and Ornamental Plants of Ministry of Education, Beijing Forestry University, Beijing, China
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  • Jingxiang Meng,

    1. National Engineering Laboratory for Forest Tree Breeding, Key Laboratory for Genetics and Breeding of Forest Trees and Ornamental Plants of Ministry of Education, Beijing Forestry University, Beijing, China
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  • Jianfeng Dai,

    1. National Engineering Laboratory for Forest Tree Breeding, Key Laboratory for Genetics and Breeding of Forest Trees and Ornamental Plants of Ministry of Education, Beijing Forestry University, Beijing, China
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  • Wei Zhao,

    1. State Key Laboratory of Systematic and Evolutionary Botany, Institute of Botany, Chinese Academy of Sciences, Beijing, China
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  • Hao Liu,

    1. College of Resources and Environment, College of agriculture and animal husbandry of Tibet University, Linzhi, China
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  • Zhen Xing,

    1. College of Resources and Environment, College of agriculture and animal husbandry of Tibet University, Linzhi, China
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  • Hua Zhang,

    1. College of Resources and Environment, College of agriculture and animal husbandry of Tibet University, Linzhi, China
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  • Xiao-Ru Wang,

    1. National Engineering Laboratory for Forest Tree Breeding, Key Laboratory for Genetics and Breeding of Forest Trees and Ornamental Plants of Ministry of Education, Beijing Forestry University, Beijing, China
    2. Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden
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  • Yue Li

    Corresponding author
    1. National Engineering Laboratory for Forest Tree Breeding, Key Laboratory for Genetics and Breeding of Forest Trees and Ornamental Plants of Ministry of Education, Beijing Forestry University, Beijing, China
    • Correspondence

      Yue Li, College of Biology Sciences and Technology, Beijing Forestry University, No. 35 East Qinghua Road, Haidian District, Beijing 100083, China. Tel: +86 10 62336064; Fax: +86 10 62336164; E-mail: liyue@bjfu.edu.cn

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Abstract

Genetic analyses indicate that Pinus densata is a natural homoploid hybrid originating from Pinus tabuliformis and Pinus yunnanensis. Needle morphological and anatomical features show relative species stability and can be used to identify coniferous species. Comparative analyses of these needle characteristics and phenotypic differences between the artificial hybrids, P. densata, and parental species can be used to determine the genetic and phenotypic evolutionary consequences of natural hybridization. Twelve artificial hybrid families, the two parental species, and P. densata were seeded in a high-altitude habitat in Linzhi, Tibet. The needles of artificial hybrids and the three pine species were collected, and 24 needle morphological and anatomical traits were analyzed. Based on these results, variations in 10 needle traits among artificial hybrid families and 22 traits among species and artificial hybrids were predicted and found to be under moderate genetic control. Nineteen needle traits in artificial hybrids were similar to those in P. densata and between the two parental species, P. tabuliformis and P. yunnanensis. The ratio of plants with three needle clusters in artificial hybrids was 22.92%, which was very similar to P. densata. The eight needle traits (needle length, the mean number of stomata in sections 2 mm in length of the convex and flat sides of the needle, mean stomatal density, mesophyll/vascular bundle area ratio, mesophyll/resin canal area ratio, mesophyll/(resin canals and vascular bundles) area ratio, vascular bundle/resin canal area ratio) relative to physiological adaptability were similar to the artificial hybrids and P. densata. The similar needle features between the artificial hybrids and P. densata could be used to verify the homoploid hybrid origin of P. densata and helps to better understand of the hybridization roles in adaptation and speciation in plants.

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