RANGEWIDE ANALYSIS OF FUNGAL ASSOCIATIONS IN THE FULLY MYCOHETEROTROPHIC CORALLORHIZA STRIATA COMPLEX (ORCHIDACEAE) REVEALS EXTREME SPECIFICITY ON ECTOMYCORRHIZAL TOMENTELLA (THELEPHORACEAE) ACROSS NORTH AMERICA
RANGEWIDE ANALYSIS OF FUNGAL ASSOCIATIONS IN THE FULLY MYCOHETEROTROPHIC CORALLORHIZA STRIATA COMPLEX (ORCHIDACEAE) REVEALS EXTREME SPECIFICITY ON ECTOMYCORRHIZAL TOMENTELLA (THELEPHORACEAE) ACROSS NORTH AMERICA
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DOI：
10.3732/ajb.0900230
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发表时间：
2010-04-01
影响因子：
3
通讯作者：
Koljalg, Urmas
中科院分区：
文献类型：
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作者：
Barrett, Craig F.;Freudenstein, John V.;Koljalg, Urmas
完全真菌异养植物提供了一个迷人的系统，研究系统发育协会和宿主和寄生虫之间的共生特异性的动态。这些植物经常寄生在真菌和树木之间的互惠共生的菌根共生体中。Corallorhiza striata是一种完全真菌异养的北美兰花，分布于墨西哥至加拿大，但其真菌协会和特异性的全部范围尚不清楚。对来自北美42个种群的107个个体的质体DNA（兰花）和ITS（真菌）进行了测序，以鉴定C。striata mycobions和测试真菌宿主特异性的假设。发现了四个分布广泛的兰花质体分支，所有真菌序列与外生菌根的毛苔菌（Tomentella）最相似，几乎都与毛苔菌（T.棕褐色兰花真菌基因树是不一致的，但非独立的，兰花分支与不同的真菌，一个分支的加州兰花subspecialized对一个狭窄的Tomentella fuscocineea分支。地理和兰花分支的真菌协会的重要决定因素，下面的地理镶嵌模型的特异性Tomentella真菌。这些发现证实了其他完全真菌异养兰花和单养植物中描述的模式，代表了对完全真菌异养植物最广泛的植物-真菌遗传研究之一，并对全球超过400种参与这种营养策略的植物物种具有保护意义。
Fully mycoheterotrophic plants offer a fascinating system for studying phylogenetic associations and dynamics of symbiotic specificity between hosts and parasites. These plants frequently parasitize mutualistic mycorrhizal symbioses between fungi and trees. Corallorhiza striata is a fully mycoheterotrophic, North American orchid distributed from Mexico to Canada, but the full extent of its fungal associations and specificity is unknown. Plastid DNA (orchids) and ITS (fungi) were sequenced for 107 individuals from 42 populations across North America to identify C. striata mycobionts and test hypotheses on fungal host specificity. Four largely allopatric orchid plastid clades were recovered, and all fungal sequences were most similar to ectomycorrhizal Tomentella (Thelephoraceae), nearly all to T. fuscocinerea. Orchid-fungal gene trees were incongruent but nonindependent; orchid clades associated with divergent sets of fungi, with a clade of Californian orchids subspecialized toward a narrow Tomentella fuscocinerea clade. Both geography and orchid clades were important determinants of fungal association, following a geographic mosaic model of specificity on Tomentella fungi. These findings corroborate patterns described in other fully mycoheterotrophic orchids and monotropes, represent one of the most extensive plant-fungal genetic investigations of fully mycoheterotrophic plants, and have conservation implications for the >400 plant species engaging in this trophic strategy worldwide.