1 针叶树干基腐朽病是世界上最严重的森林病害之一
针叶树干基腐朽病是世界范围内最具毁灭性的森林病害之一（戴玉成 2005）,引起针叶树干基腐朽病的病原菌能够侵染150多种林木（Sinclair et al. 1987）,对27种针叶树造成树木干基白色腐朽病害,直接造成森林的大面积死亡（Woodward et al. 1998）,特别是对松属Pinus、云杉属Picea、冷杉属Abies、铁杉属Tsuga和黄杉属Pseudotsuga等针叶树危害严重（Capretti & Moriondo 1983;Woodward et al. 1998）。该病害广泛分布于北半球,其南北跨度从最北分布达芬兰北部至最南分布到非洲北部和中美洲,由于该病害分布广泛且危害严重,被国际林学界称为世界第一大森林病害（Woodward et al. 1998）。
2 针叶树干基腐朽病原菌的多样性
异担子菌属Heterobasidion Bref.种类是引起针叶树干基腐朽病的主要病原菌,过去基于形态学研究认为该属包括2个种,即多年异担子菌H. annosum (Fr.) Bref.和岛生异担子菌H. insulare (Murrill) Ryvarden,其中多年异担子菌H. annosum广泛分布于欧洲、北美和亚洲,而岛生异担子菌H. insulare主要分布在亚洲（Gilbertson & Ryvarden 1986;Ryvarden & Gilbertson 1993;Núñez & Ryvarden 2001;Yuan et al. 2021）。随后的交配实验研究表明上述2个物种为存在性不亲和的生物种（Korhonen 1978;Capretti et al. 1990;Dai & Korhonen 1999;Dai et al. 2002,2003）;从而证明了多年异担子菌H. annosum和岛生异担子菌H. insulare实际为复合种（the species complex）。基于单孢交配、致病性、寄主范围和生物地理学的研究,欧洲发现有3种异担子菌,即狭义多年异担子菌H. annosum s. str.、小孔异担子菌H. parviporum Niemelä & Korhonen和冷杉异担子菌H. abietinum Niemelä & Korhonen,其中狭义多年异担子菌H. annosum s. str.主要侵染松属树木、小孔异担子菌H. parviporum主要侵染云杉属树木、冷杉异担子菌H. abietinum主要侵染冷杉属树木（Woodward et al. 1998）。北美洲发现2种异担子菌,即变孔异担子菌H. irregulare Garbel. & Otrosina和西方异担子菌H. occidentale Otrosina & Garbel.,前者主要侵染松属和柏属Juniperus树木,而且广泛分布于北美洲,后者主要侵染冷杉属、铁杉属、黄杉属Pseudotsuga和巨杉属Sequoiadendron树木且分布于北美洲西部（Otrosina & Garbelotto 2010）。基于多基因标记的系统发育分析并结合单孢交配、致病性、寄主范围和生物地理学研究证明亚洲发现9种异担子菌,分别为淀粉孢异担子菌H. amyloideum Y.C. Dai et al.（Chen et al. 2014）、阿曼德异担子菌H. armandii Y.C. Dai et al.（Yuan et al. 2021）、南方异担子菌H. australe Y.C. Dai & Korhonen（Dai & Korhonen 2009）、岛生异担子菌H. insulare（Yuan et al. 2021）、林芝异担子菌H. linzhiense Y.C. Dai & Korhonen（Dai et al. 2007）、东方异担子菌H. orientale Tokuda et al.（Tokuda et al. 2009）、拟岛生异担子菌H. subinsulare Y.C. Dai et al.（Yuan et al. 2021）、拟小孔异担子菌H. subparviporum Y.C. Dai et al.（Yuan et al. 2021）和西藏异担子菌H. tibeticum Y.C. Dai et al.（Chen et al. 2014）。在上述9种亚洲分布的异担子菌中只有拟小孔异担子菌H. subparviporum可能具有弱侵染力,偶尔造成云杉属、冷杉属、落叶松属Larix和松属树木干基腐朽（Dai & Korhonen 1999;Yuan et al. 2021）,其侵染能力明显弱于欧洲和北美洲分布的异担子菌;其他8种亚洲分布的异担子菌都是腐生菌,不造成针叶树活立木病害。此外,在澳大利亚分布的南洋杉异担子菌H. araucariae P.K. Buchanan为腐生真菌,不侵染活立木（Buchanan 1988）。
因此,基于形态学、遗传学、生态学和分子生物学的研究,异担子菌属Heterobasidion从20世纪80年代的2个种发展到目前的15个种,其中欧洲3种、北美洲2种、亚洲9种和大洋洲1种,这15种的分布在洲际范围内几乎不重叠。致病力强的病原菌有5种,即冷杉异担子菌H. abietinum、狭义多年异担子菌H. annosum s. str.、变孔异担子菌H. irregulare、西方异担子菌H. occidentale和小孔异担子菌H. parviporum,这些种类都分布于欧洲和北美洲;致病力弱的有1种,即拟小孔异担子菌H. subparviporum,分布在亚洲,其余种类是腐生菌（Yuan et al. 2021）。
从亲缘关系上分析,15种异担子菌可以分为3个类群,第一个类群为松树寄生类群包括狭义多年异担子菌H. annosum s. str.和变孔异担子菌H. irregulare;第二个类群为杉树寄生类群包括冷杉异担子菌H. abietinum、西方异担子菌H. occidentale、小孔异担子菌H. parviporum和拟小孔异担子菌H. subparviporum;第3个类群为针叶树腐生类群包括淀粉孢异担子菌H. amyloideum、南洋杉异担子菌H. araucariae、阿曼德异担子菌H. armandii、南方异担子菌H. australe、岛生异担子菌H. insulare、林芝异担子菌H. linzhiense、东方异担子菌H. orientale、拟岛生异担子菌H. subinsulare和西藏异担子菌H. tibeticum（Yuan et al. 2021）。
基于分子钟起源演化研究表明：异担子菌属物种可能起源于中新世早期的欧亚大陆,随后在中新世中期和上新世早期扩散至其他大陆并形成物种。变孔异担子菌H. irregulare和西方异担子菌H. occidentale分别越过白令海峡和北大西洋路桥在北美成种,南半球南洋杉异担子菌H. araucariae可能是由人类迁徙引入。板块构造和长距离扩散是影响异担子菌成种和生物地理分布的最可能因素（Chen et al. 2015;戴玉成等 2021）。
3 针叶树干基腐朽病菌的检疫措施和预防对策
3.1 建议将狭义多年异担子菌H. annosum s. str.等5个病原菌列为进境植物检疫性有害生物
传统的多年异担子菌H. annosum sensu lato是复合种,过去认为该菌分布于包括中国在内的北半球（袁嗣令 1997）。目前研究表明,我国只分布弱致病性的拟小孔异担子菌H. subparviporum,而侵染力最强的狭义多年异担子菌H. annosum s. str.、冷杉异担子菌H. abietinum、小孔异担子菌H. parviporum、西方异担子菌H. occidentale和变孔异担子菌H. irregulare分布于欧洲和北美洲,能够引起重大森林病害,并造成巨大的经济损失。由于我国目前没有上述5种病原菌的分布,而且目前我国未将这5种病原菌列为对外检疫对象（国家林业局 2013）,因此在建立有害生物全面风险评估和深度风险分析基础上,建议将狭义多年异担子菌H. annosum s. str.、冷杉异担子菌H. abietinum、小孔异担子菌H. parviporum、西方异担子菌H. occidentale和变孔异担子菌H. irregulare列为我国进境植物检疫性有害生物。
3.2 异担子菌属种类的分子检测
我国是木材进口大国,2019年全国进口原木5 980万m3,其中超过50%为针叶树原木,加拿大、美国、俄罗斯和欧洲等为主要进口国家和地区,树木种类几乎包括这些国家和地区所有常见针叶树,而上述5种侵染力最强的针叶树干基腐朽病原菌就分布于上述国家和地区。进口的原木和木材上几乎找不到病原异担子菌的子实体,但其菌丝可以在原木和木材中存活多年,因此携带病原菌菌丝的原木和木材极有可能造成外来生物入侵。以史为鉴,第二次世界大战期间分布于北美洲的变孔异担子菌H. irregulare由美国军队运输木质物资而传播到意大利,目前已导致该病原菌在欧洲中部爆发式扩散并引起当地森林的严重病害,造成林业经济和生态不可逆的重大损失（Ryvarden & Melo 2017）。
目前已知RNA聚合酶II大亚基序列（RPB1）分子标记在异担子菌种类中敏感性最高,是通过基因手段鉴别不同异担子菌种类的可信片段（Yuan et al. 2021）。因此如果能从进境原木和木材中分离到病原异担子菌的菌丝,然后进行纯化培养后提取DNA,分别以GAR TGY CCD GGD CAY TTY GG（Af）和CCN GCD ATN TCR TTR TCC ATR TA（Cf）为引物进行PCR扩增和测序,获得RPB1序列,在NCBI（www. ncbi.nlm.nih.gov）网站上通过BLASTN分析比对,就能准确鉴定原木或木材中是否携带了病原异担子菌。因此,分子检测是一种操作简单、特异性强、灵敏度高、结果易判断的针叶树干基腐朽病原菌的有效基因鉴定技术。
3.3 加强对针叶树干基腐朽病病原菌的检疫措施
随着我国经济建设的快速发展,国内木材供给落后于国内需求,中国对于进口原木、木材和苗木的需求也不断增加,需通过由其他国家进口来填补这个缺口,在进口原木、木材和苗木的过程中,极有可能使这些针叶树干基腐朽病病原菌入侵到我国境内。因此,不同国家和地区在与我国开展贸易往来时,对针叶树干基腐朽病原菌有分布的国家,应进行有针对性的重点检疫,建立进口原木、木材和苗木的快速检测技术体系和标准,开展重点木材进口地区的检疫人员专业培训,为海关检疫部门提供可靠的技术保证。通过加强林木有害生物检疫措施,做到从源头上阻止针叶树干基腐朽病原菌传入我国。
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