Host specificity of pathogenic Pythium species:: Implications for tree species diversity
Host specificity of pathogenic Pythium species:: Implications for tree species diversity
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DOI：
10.1111/j.1744-7429.2007.00326.x
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发表时间：
2007-11-01
期刊：
影响因子：
2.1
通讯作者：
Wilkinson, Henry T.
中科院分区：
文献类型：
--
作者：
Augspurger, Carol K.;Wilkinson, Henry T.
在Janzen-Connell假说中，寄主特异性天敌增强了物种多样性并影响了植物群落结构。本研究验证了引起萌发种子和幼苗阻尼病的土壤病原菌对寄主特异性的明确假设。我们从巴拿马热带森林的土壤中分离出了一种毕氏菌。然后，在接种实验中，我们确定了75株致病性未知的热带分离株和7株致病的温带分离株对8种热带树种的种子和/或幼苗的致病性。只有3个热带分离株具有致病性，其中1个鉴定为最后假单胞菌，2个鉴定为隐皮假单胞菌。热带致病性分离株对8种树种中的4 ~ 6株具有致病性。温带分离株对8种病原菌中0 ~ 4种致病，表明某些热带树种对新分离株有易感。没有一个树种对所有分离物都敏感，有2个树种对任何分离物都不敏感。综上所述，这些结果表明，这些分离株的致病性差异很大，导致潜在宿主物种的死亡率不同；同样地，不同树种对特定的毕氏菌的敏感性也不同。这些致病性和易感性的差异在一定程度上支持Janzen-Connell的宿主特异性假设。虽然它们并不局限于单一物种，但它们的中等水平特异性表明，Pythium sp .可能对森林群落结构和多样性产生一定影响。
In the Janzen-Connell hypothesis, host-specific natural enemies enhance species diversity and influence the structure of plant communities. This study tests the explicit assumption of host specificity for soil pathogens of the genus Pythium that cause damping-off disease of germinating seeds and seedlings. We isolated Pythium spp. from soil of a tropical forest in Panama. Then, in an inoculation experiment, we determined the pathogenicity of 75 tropical isolates of unknown pathogenicity and seven pathogenic temperate isolates of Pythium on seeds and/or seedlings of eight tropical tree species. Only three tropical isolates, one identified as P. ultimum and two as P. aphanidermatum, were pathogenic. Tropical pathogenic isolates were pathogenic on 4-6 of eight tree species. Temperate isolates were pathogenic on 0-4 of eight species, indicating that some tropical tree species are susceptible to novel isolates of Pythium. No tree species was susceptible to all isolates and two species were not susceptible to any isolate. Collectively, these results indicate that these Pythium isolates vary widely in their pathogenicity, causing differential mortality of potential host species; likewise, the tree species vary in their susceptibility to a given Pythium isolate. These differences in pathogenicity and susceptibility indicate some support for the Janzen-Connell assumption of host specificity. While they are not restricted to a single species, their intermediate level of specificity suggests that Pythium spp. have the potential to have some effect on forest community structure and diversity.