Yamato Masahide, Takahashi Hiroshi, Shimono Ayako, Kusakabe Ryota, Yukawa Tomohisa
Department of Science Education, Faculty of Education, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan.
Department of Biology, Faculty of Education, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.
Mycorrhiza. 2016 Jul;26(5):417-27. doi: 10.1007/s00572-016-0680-9. Epub 2016 Feb 5.
Petrosavia sakuraii (Petrosaviaceae) is a rare, mycoheterotrophic plant species that has a specific symbiotic interaction with a narrow clade of arbuscular mycorrhizal (AM) fungi. In the present study, we tested the hypothesis that the distribution and abundance of mycobionts in two P. sakuraii habitats, Nagiso and Sengenyama (central Honshu, Japan), determine the distribution pattern of this rare plant. Nagiso is a thriving habitat with hundreds of P. sakuraii individuals per 100 m(2), whereas Sengenyama is a sparsely populated habitat with fewer than 10 individuals per 100 m(2). AM fungal communities associated with tree roots were compared at 20-cm distances from P. sakuraii shoots between the two habitats by molecular identification of AM fungal partial sequences of the small subunit ribosomal RNA gene. The percentage of AM fungal sequences showing over 99 % identity with those of the dominant P. sakuraii mycobionts was high (54.9 %) in Nagiso, but low (13.2 %) in Sengenyama. Accordingly, the abundance of P. sakuraii seems to reflect the proportion of potential mycobionts. It is likely that P. sakuraii mycobionts are not rare in Japanese warm temperate forests since 11.2 % of AM fungal sequences previously obtained from a deciduous broad-leaved forest devoid of P. sakuraii in Mizuho, central Honshu, Japan, were >99 % identical to those of the dominant P. sakuraii mycobionts. Thus, results suggest that the abundant mycobionts may be required for sufficient propagation of P. sakuraii, and this quantitative trait of AM fungal communities required for P. sakuraii may explain the rarity of this plant.
樱井石蒜（樱井石蒜科）是一种罕见的菌根异养植物物种，它与丛枝菌根（AM）真菌的一个狭窄分支存在特定的共生相互作用。在本研究中，我们检验了这样一个假设：在日本本州中部的名木和仙根山这两个樱井石蒜栖息地中，菌根共生体的分布和丰度决定了这种稀有植物的分布模式。名木是一个繁荣的栖息地，每100平方米有数百株樱井石蒜个体，而仙根山则是一个人口稀少的栖息地，每100平方米少于10株个体。通过对AM真菌小亚基核糖体RNA基因部分序列进行分子鉴定，比较了两个栖息地中距樱井石蒜嫩枝20厘米处与树根相关的AM真菌群落。在名木中，与优势樱井石蒜菌根共生体序列相似度超过99%的AM真菌序列百分比很高（54.9%），而在仙根山则很低（13.2%）。因此，樱井石蒜的丰度似乎反映了潜在菌根共生体的比例。樱井石蒜的菌根共生体在日本暖温带森林中可能并不罕见，因为之前从日本本州中部水穗的一片没有樱井石蒜的落叶阔叶林中获得的AM真菌序列中，有11.2%与优势樱井石蒜菌根共生体的序列相似度>99%。因此，结果表明，丰富的菌根共生体可能是樱井石蒜充分繁殖所必需的，而樱井石蒜所需的AM真菌群落的这种数量特征可能解释了这种植物的稀有性。
