Dai Y C
Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
Plant Dis. 2004 May;88(5):573. doi: 10.1094/PDIS.2004.88.5.573C.
Members of the Phellinus weirii complex cause laminated root rot of living conifers. The cedar type (P. weirii (Murrill) Gilb. sensu stricto) of the complex is usually found on species of the Cupressaceae family, especially Thuja plicata in western North America, and the Douglas-fir type (P. sulphurascens Pilát) is found on species of the Pinaceae family (1,2,3). Outside North America, P. weirii occurs on species of Juniperus in the Ural Mountains, and P. sulphurascens occurs on other conifers in eastern Asia, including China (1). During a field inventory of wood-decay fungi in western China in 2003, laminated root rot of Sabina przewalskii (synonym Juniperus przewalskii) was found in natural forests of the Qilian Mountains in Qinghai Province (37°36'N and 102°15'E). Trees were approximately 80 to 150 years old and occurred in pure stands. Distinct disease patches that were as much as one hectare consisted of dead-standing and symptomatic trees, suggesting that the fungus spread by root contact. Symptomatic trees showed slow growth, thin crowns, and chlorotic foliage. After cutting several of the symptomatic trees, cambial necrosis and wood decay were found, and the trees apparently died when the cambial necrosis girdled the base of the trees. The wood of infected trees was reddish brown at the early stages of decay and later had numerous small cavities and separated into sheets at the junction of annual rings. Perennial, poroid, resupinate, dark brown basidiocarps formed on the root surface of dead trees. The basidiocarps had a monomitic hyphal system, hyphae without clamp connections, trama tissue with hyphoid setae, and thin-walled, hyaline, smooth, ellipsoid basidiospores. The fungus was identified as P. weirii and distinguished from P. sulphurascens by its perennial basidiocarps, smaller pores (5 to 8 versus 4 to 5 per mm), and narrower hyphoid setae (4 to 6 versus 5 to 10 μm in diameter). P. weirii also resembles P. ferrugineofuscus (P. Karst.) Bourdot in macro-morphology, but the latter species is a saprophyte and has allantoid to almost lunate basidiospores. The studied specimens of P. weirii and P. sulphurascens are preserved at the herbaria of the Botanical Museum of the University of Helsinki, the Institute of Applied Ecology, and the Chinese Academy of Sciences as DAOM 8734, Lowe 6960, TAA 52744, 55644, and 103812, and Dai 988, 2053, 2061, 2527, and 5067. To my knowledge, this is the first report of P. weirii sensu stricto from China and the first report of laminated root rot on S. przewalskii. References: (1) Y. C. Dai and G. F. Qin. Fungal Sci. 13:101, 1998. (2) E. M. Hansen et al. Species limits for Phellinus weirii. Pages 119-127 in: Root and butt rots of forest tress. Int. Conf. Root and Butt Rots, INRA, France, 1998. (3) M. J. Larsen et al. Mycologia 86:121, 1994.
韦氏木层孔菌复合体的成员会引起活针叶树的层状根腐病。该复合体中的雪松型（狭义的韦氏木层孔菌（Phellinus weirii (Murrill) Gilb.））通常在柏科植物上发现，特别是在北美洲西部的美国扁柏（Thuja plicata）上，而花旗松型（硫黄木层孔菌（Phellinus sulphurascens Pilát））则在松科植物上发现（1,2,3）。在北美以外地区，韦氏木层孔菌出现在乌拉尔山脉的杜松属植物上，硫黄木层孔菌出现在东亚其他针叶树上，包括中国（1）。在2003年对中国西部木材腐朽真菌的野外调查中，在青海省祁连山的天然林中发现了祁连圆柏（Sabina przewalskii，同义词祁连圆柏（Juniperus przewalskii））的层状根腐病（北纬37°36′，东经102°15′）。树木年龄约为80至150年，生长在纯林中。明显的病害斑块面积达一公顷，由枯死立木和有症状的树木组成，表明该真菌通过根部接触传播。有症状的树木生长缓慢、树冠稀疏且叶片黄化。砍伐几株有症状的树木后，发现形成层坏死和木材腐朽，当形成层坏死环绕树基部时树木明显死亡。受感染树木的木材在腐朽初期呈红棕色，后期有许多小空洞，并在年轮交界处分离成薄片。多年生、具孔、平伏、深褐色的担子果在死树的根表面形成。担子果具有单系菌丝系统，菌丝无锁状联合，菌髓组织有类菌丝刚毛，以及薄壁、无色、光滑、椭圆形的担孢子。该真菌被鉴定为韦氏木层孔菌，通过其多年生担子果、较小的孔（每毫米5至8个，而硫黄木层孔菌为4至5个）和较窄的类菌丝刚毛（直径4至6微米，而硫黄木层孔菌为5至10微米）与硫黄木层孔菌区分开来。韦氏木层孔菌在宏观形态上也与铁锈色木层孔菌（Phellinus ferrugineofuscus (P. Karst.) Bourdot）相似，但后者是一种腐生菌，具有腊肠形至近新月形的担孢子。所研究的韦氏木层孔菌和硫黄木层孔菌标本保存在赫尔辛基大学植物博物馆、中国科学院应用生态研究所的标本馆中，编号分别为DAOM 8734、Lowe 6960、TAA 52744、55644和103812，以及戴氏988、2053、2061、2527和5067。据我所知，这是狭义的韦氏木层孔菌在中国的首次报道，也是祁连圆柏层状根腐病的首次报道。参考文献：（1）戴玉成、秦桂芳。真菌学报13:101，1998。（2）E.M.汉森等。韦氏木层孔菌的种的界定。载于：森林树木的根腐和干基腐病。国际根腐和干基腐病会议，法国国家农业研究院，1998，第119 - 127页。（3）M.J.拉森等。真菌学杂志86:121，1994。
