Kawai Masataka, Yamahara Mina, Ohta Akira
Nara Forest Research Institute, Takatori, Takaichi, Nara, 635-0133, Japan.
Shiga Forest Research Center, Kitasakura, Yasu, Shiga, 520-2321, Japan.
Mycorrhiza. 2008 Apr;18(4):205-210. doi: 10.1007/s00572-008-0167-4.
The mating systems of most ectomycorrhizal fungi have not been elucidated because of two reasons. One is the difficulty of obtaining homokaryotic isolates for mating tests caused by the low germination rate of basidiospores, and another is the difficulty of checking dikaryotization caused by the absence or inconsistent production of clamp connections on heterokaryotic mycelia under laboratory conditions. Basidiospore germination of a few ectomycorrhizal fungi has been induced by living roots of their host plants. Based on this information, we examined methods to obtain homokaryotic isolates of Rhizopogon rubescens using its host plant, Pinus thunbergii. The basidiospores of R. rubescens appeared to germinate well on an agar plate, on which axenic pine seedlings were grown in advance to induce germination, even when the seedlings were removed from the plate at the time of spore inoculation. To enhance the production rate of clamp connections on the heterokaryotic mycelia of R. rubescens, the culture medium composition was modified. The pH of the medium was critical for the production of clamp connections, and the optimal pH was higher for the production of clamp connections than for mycelial growth. These findings made it possible to conduct mating tests, and we found that the mating system of R. rubescens is bipolar with a multiallelic mating type factor.
由于两个原因，大多数外生菌根真菌的交配系统尚未阐明。一是担孢子萌发率低导致难以获得用于交配试验的同核分离物，另一个是在实验室条件下，异核菌丝体上缺乏或不一致产生锁状联合，导致难以检查双核化。一些外生菌根真菌的担孢子萌发已被其寄主植物的活根诱导。基于此信息，我们研究了利用其寄主植物黑松获得红绒盖牛肝菌同核分离物的方法。红绒盖牛肝菌的担孢子在琼脂平板上似乎萌发良好，在该平板上预先培养无菌松树苗以诱导萌发，即使在接种孢子时将树苗从平板上移除。为了提高红绒盖牛肝菌异核菌丝体上锁状联合的产生率，对培养基成分进行了改良。培养基的pH值对锁状联合的产生至关重要，产生锁状联合的最佳pH值高于菌丝体生长的最佳pH值。这些发现使得进行交配试验成为可能，并且我们发现红绒盖牛肝菌的交配系统是具有多等位基因交配型因子的双极性。
