人工栽培蛹虫草的病原真菌
Pathogenic fungi of artificially cultivated Cordyceps militaris
责任编辑: 王敏
收稿日期: 2021-04-10 接受日期: 2021-05-19
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Received: 2021-04-10 Accepted: 2021-05-19
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作者简介 About authors
ORCID:LIUQing(0000-0002-3453-9376) 。
董彩虹,中国科学院微生物研究所研究员,博士生导师现任中国菌物学会产业分会常务副秘书长;中国菌物学会蛹虫草分会秘书长,中国中药协会茯苓产业分会副秘书长从事珍稀食药用菌生物学研究,采用正、反向遗传学手段,结合多组学分析,揭示食用菌生殖方式、子实体发育和逆境胁迫机制;基因编辑进行食用菌菌种改良涉及类群包括冬虫夏草、蛹虫草、茯苓、羊肚菌和绣球菌等发表论文80余篇,授权专利8项,参编《中国冬虫夏草》和《食用菌栽培学》 , E-mail:dongch@im.ac.cn
蛹虫草规模化栽培过程中,真菌病害普遍发生且危害严重。本研究对人工栽培蛹虫草中真菌病害进行调研,对病原真菌进行分离、纯化、鉴定及致病性检验,并分析病害发生的特点。结果发现引起蛹虫草病害的病原真菌主要有虫草生齿梗孢、产扁虫菌素单端孢、镰刀菌、裂褶菌、哈茨木霉、淡紫拟青霉、稻绿核菌、粉红枝穗霉、卵孢单端孢、扩展青霉、黄曲霉和黑曲霉。其中虫草生齿梗孢为引起蛹虫草侵染性病害的主要病原真菌。虫草生齿梗孢、产扁虫菌素单端孢、镰刀菌、裂褶菌和哈茨木霉主要为害蛹虫草子实体;淡紫拟青霉、稻绿核菌、粉红枝穗霉、卵孢单端孢、扩展青霉、黄曲霉和黑曲霉主要为害栽培料与蛹虫草菌丝体。镰刀菌、裂褶菌、哈茨木霉、淡紫拟青霉、稻绿核菌和粉红枝穗霉为引起蛹虫草病害的首次报道。本研究为蛹虫草病害防控奠定基础,以促进产业健康发展。
关键词:
Fungal diseases occurred on cultivated Cordyceps militaris often caused severe damage. In this study, the pathogenic fungi of C. militaris were isolated, purified and identified and their pathogenicity was tested. The occurrence characteristics of the diseases were also analyzed. The results indicated that the pathogenic fungi of C. militaris were mainly Calcarisporium cordycipiticola, Trichothecium crotocinigenum, Fusarium sp., Schizophyllum commune, Trichoderma harzianum, Purpureocillium lilacinum, Ustilaginoidea virens, Clonostachys rosea, T. ovalisporum, Penicillium expansum, Aspergillus oryzae and A. niger. Calcarisporium cordycipiticola was the main pathogen causing infectious diseases of C. militaris. Calcarisporium cordycipiticola, T. crotocinigenum, Fusarium sp., S. commune and T. harzianum mainly infected fruiting bodies, while P. lilacinum, U. virens, C. rosea, T. ovalisporum, P. expansum, A. oryzae and A. niger mainly infected mycelia on culture media. Fusarium sp., S. commune, T. harzianum, P. lilacinum, U. virens and C. rosea were firstly reported as the pathogens of C. militaris. This study provides reference for prevention and control of C. militaris disease in industrialized large-scale cultivation of the fungus.
Keywords:
本文引用格式
刘晴, 王芬, 徐方旭, 徐岩岩, 董彩虹.
LIU Qing, WANG Fen, XU Fang-Xu, XU Yan-Yan, DONG Cai-Hong.
蛹虫草Cordyceps militaris (L.) Fr.又名北虫草,隶属于子囊菌门Ascomycota、肉座菌目Hypocreales、虫草科Cordycipitaceae、虫草属Cordyceps,是虫草属的模式种,2009年原国家卫生部批准其为新资源食品(现名新食品原料)。目前蛹虫草已实现大规模人工栽培,全国大部分省市均有栽培,栽培模式主要有大棚、庭院式和工厂化,目前以大棚及庭院式栽培为主。据中国食用菌协会统计,2018年我国蛹虫草年产量90 559.7吨,早在2016年年产值已达100亿人民币,成为不可忽视的重要产业(董彩虹等 2016)。
蛹虫草规模化栽培过程中,除了菌种稳定性之外,另一个重要问题为病害的发生。常见的病害主要有真菌病害和细菌病害(边银丙 2016)。蛹虫草栽培过程中真菌病害占总病害的95%以上,全国各栽培产区及工厂化栽培车间均时有发生。
虽然蛹虫草的部分病害已有报道,但是缺乏对病原菌株的准确鉴定及致病性实验。本研究系统总结了蛹虫草人工栽培中的真菌病害,对病原菌进行分离纯化、鉴定及致病性检验,为蛹虫草真菌病害的控制及预防提供理论依据,以促进蛹虫草产业健康发展。
1 材料与方法
1.1 蛹虫草规模化栽培病害调研
对内蒙古赤峰、辽宁沈阳、北京通州、江苏徐州、江西遂州及本实验室蛹虫草栽培过程中出现的病害进行调查,记录发病症状和发病程度,并搜集病害样本。
1.2 蛹虫草病原菌的分离与纯化
首先对病害样品进行显微观察,记录染病部位形态。在超净工作台中用无菌刀片切取小块发病蛹虫草子实体(Pathogen A-F)或栽培料(Pathogen G-M),置于马铃薯葡萄糖培养基(PDA,同时加入青霉素和链霉素)中,发病部位紧贴培养基,20℃倒置培养。每天观察记录菌丝体生长,菌落形态与产孢情况,并对病原菌进行纯化,获得纯化菌株(方中达 1998)。
1.3 病原菌的形态学鉴定
将获得的纯培养病原菌接种于PDA平板,灭菌的盖玻片插入培养基中,20℃黑暗培养7d,插片取出后显微观察菌丝与孢子形态特征。观察病原菌平板正反面特征并拍照记录。参照Tamm & Põldmaa(2013)的方法对病原菌进行鉴定,以确定其分类地位。
1.4 病原菌分子鉴定
将分离纯化的病原菌接种于PDA平板,20℃黑暗培养7d,灭菌牙签刮取菌丝体至1.5mL离心管中,高通量组织破碎仪破碎,CTAB法提取DNA(Doyle & Doyle 1987)。使用ITS4、ITS5引物进行ITS片段扩增(White 1990)。PCR反应条件:95℃ 3min;95℃ 15s,55℃ 15s,72℃ 5s,扩增35个循环;72℃ 10min。以1%琼脂糖凝胶检测产物,纯化后送生工生物工程(上海)股份有限公司测序。
1.5 序列比对分析与系统发育树构建
从GenBank中选取与病原菌近缘物种序列及合适的外群,使用MEGA 7.0软件进行比对分析,最大似然法(maximum likelihood)构建系统发育树,Bootstrap重复检验1 000次。
1.6 病原菌致病性测定
以柯赫氏法则验证分离菌株对蛹虫草的致病性,蛹虫草633子实体栽培采用常规方法(Yang et al. 2016)。分别在蛹虫草菌丝长满栽培料(约7d)、子实体至2-3cm时(约25d),用无菌刀片切取0.5cm×0.5cm病原菌菌块(PDA平板,20℃黑暗培养7-10d),菌块长满菌丝孢子的一侧贴附蛹虫草菌丝体和子实体上,每个蛹虫草栽培瓶中接入6块,并对致病过程进行观察记录。不接种病原菌的蛹虫草菌丝体、子实体为对照组,每组3个生物学重复。同时按照1.2的方法再次分离病原菌株,对该病原菌株进行鉴定,并与接种的病原物进行比较。
2 结果与分析
通过对6个调查地点的蛹虫草病害调研,共发现13种真菌病害,并分别分离获得了病原真菌(图1)。通过形态观察与ITS序列分析,分别鉴定为:虫草生齿梗孢Calcarisporium cordycipiticola、产扁虫菌素单端孢Trichothecium crotocinigenum、镰刀菌Fusarium sp.、裂褶菌Schizophyllum commune、哈茨木霉Trichoderma harzianum、淡紫拟青霉Purpureocillium lilacinum、稻绿核菌Ustilaginoidea virens、粉红枝穗霉Clonostachys rosea、卵孢单端孢Trichothecium ovalisporum、扩展青霉Penicillium expansum、黄曲霉Aspergillus flavus和黑曲霉Aspergillus niger(图1,表1)。
图1
图1
蛹虫草病害症状与病原真菌菌落
A:虫草生齿梗孢;B:产扁虫菌单端孢;C:镰刀菌;D:镰刀菌;E:裂褶菌;F:哈茨木霉;G: 淡紫拟青霉;H:稻绿核菌; I:粉红枝穗霉;J: 卵孢单端孢;K:扩展青梅;L:黄曲霉;M:黑曲霉
Fig. 1
Symptoms on Cordyceps militaris and colonies of the pathogenic fungi.
A: Calcarisporium cordycipiticola; B: Trichothecium crotocinigenum; C: Fusarium sp.; D: Fusarium sp.; E: Schizophyllum commune;F: Trichoderma harzianum; G: Purpureocillium lilacinum; H: Ustilaginoidea virens;I: Clonostachys rosea; J: Trichothecium ovalisporum; K: Penicillium expansum; L: Aspergillus flavus; M: Aspergillus niger.
表1 蛹虫草真菌病害调研及病原真菌汇总
Table 1
样品 编号 Sample number | 病害发生地点 Localites of the infection | 染病部位 Infected parts | 病害症状 Symptoms | 中文名/ 拉丁学名 Chinese/ scientific name | 病害类型 Types of infection |
---|---|---|---|---|---|
A | 北京通州、内蒙古赤峰、辽宁沈阳、江苏徐州、江西遂州、本实验室 Tongzhou district, Beijing; Chifeng, Inner Mongolia; Shenyang, Liaoning; Xuzhou, Jiangsu; Suizhou, Jiangxi; this laboratory | 栽培料表面至子实体任意部位 Surface of the cultures and any parts of the fruiting bodies | 多发生在蛹虫草生长发育后期;在子实体上形成白色菌落,覆盖于其表面,影响子实体发育,后期子实体倒伏,完全被白毛覆盖 The disease occurred at the late stage of the growth and development of C. militaris. White colonies covered the surface of fruiting bodies, affecting development of the fruiting bodies. The fruiting bodies collapsed and were completely covered by white mildew finally | 虫草生齿梗孢 Calcarisporium cordycipiticola | 侵染性/竞争性 Infectious/ competitive |
B | 北京通州、内蒙古赤峰、本实验室 Tongzhou district, Beijing; Chifeng, Inner Mongolia; this laboratory | 栽培料表面至子实体基部 Surface of the cultures and base of the fruiting bodies | 主要发病在原基形成之后,气生菌丝旺盛,菌丝体白色棉絮状,从基部向上蔓延,直至将整个蛹虫草子实体包围;被病原菌包围的子实体由深橘黄色变为浅橘黄色;侵染后期,子实体枯死 The disease mainly occurred after primordium formation. The mycelia were white, strong and cotton-like, and spread until covering the whole fruiting bodies. The infected fruiting bodies changed from dark orange into light orange, wilted and died eventually | 产扁虫菌素 单端孢 Trichothecium crotocinigenum | 侵染性/竞争性 Infectious/ competitive |
C | 内蒙古赤峰、本实验室 Chifeng, Inner Mongolia; this laboratory | 栽培料表面至子实体基部 Surface of the cultures and base of the fruiting bodies | 主要发病在原基形成之后,棉絮状菌丝迅速向上蔓延,造成子实体基部变软,子实体倒伏 The disease mainly occurred after primordium formation. Cotton-like mycelia spread upward rapidly, resulting in softening of the base and lodging of the fruiting bodies | 镰刀菌 Fusarium sp. | 侵染性/竞争性 Infectious/ competitive |
待续 | |||||
D | 北京通州 Tongzhou district, Beijing | 栽培料表面至子实体基部 Surface of the cultures and base of the fruiting bodies | 主要发病在原基形成之后,疏松的灰白色菌丝从子实体基部迅速向上蔓延,造成子实体基部变软,子实体倒伏 The disease mainly occurred after primordium formation, and loose grey white mycelia spread upward rapidly, resulting in softening of the base and lodging of fruiting bodies | 镰刀菌 Fusarium sp. | 侵染性/竞争性 Infectious/ competitive |
E | 内蒙古赤峰 Chifeng, Inner Mongolia | 栽培料表面至子实体基部 Surface of the cultures and base of the fruiting bodies | 气生菌丝旺盛,呈白色丝绵状,短时间内从基部向上覆盖蛹虫草子实体,侵染状态下未见孢子产生,仅依靠菌丝致病 Aerial mycelia were vigorous and white, covering the fruiting bodies from the base to the top in a short time. No spore was found | 裂褶菌 Schizophyllum commune | 侵染性/竞争性 Infectious/ competitive |
F | 北京通州、江苏徐州 Tongzhou district, Beijing; Xuzhou, Jiangsu | 栽培料表面至子实体基部 Surface of the cultures and base of the fruiting bodies | 发生于栽培料表面,病原菌丝迅速向四周蔓延,同时沿子实体向上蔓延,初始为白色,后产生分生孢子变成绿色,侵染后期整个子实体变成绿色 The disease occurred on the surfaces of media, spreading rapidly to the fruiting bodies. The mycelia were white at the beginning, then turned green because of conidiation, and the whole fruiting body turned green finally | 哈茨木霉 Trichoderma harzianum | 侵染性/竞争性 Infectious/ competitive |
G | 本实验室 This laboratory | 栽培料表面 Surface of the cultures | 可侵染蛹虫草菌丝,侵染部位不形成原基;其仅在侵染部位蔓延,不会造成病害的大范围爆发 The pathogen infected the mycelia of C. militaris, and no primordium was formed in the infected sites. The disease was limited partially and would not cause a large-scale outbreak | 淡紫拟青霉 Purpureocillium lilacinum | 竞争性/侵染性 Competitive/ infectious |
H | 内蒙古赤峰、本实验室 Chifeng, Inner Mongolia; this laboratory | 栽培料表面 Surface of the cultures | 依靠产生大量分生孢子致病,一般侵染蛹虫草栽培料和菌丝体,导致侵染部位不形成原基 The pathogen produced large amounts of conidia and infected mycelia on the media, leading to failed formation of primordium | 稻绿核菌 Ustilaginoidea virens | 竞争性/侵染性 Competitive/ infectious |
待续 | |||||
I | 本实验室 This laboratory | 栽培料表面 Surface of the cultures | 依靠产生大量分生孢子致病,一般侵染蛹虫草栽培料或菌丝体,导致侵染部位不形成原基 The pathogen produced large amounts of conidia and infected the mycelia on the media, leading to failed formation of the primordium | 粉红枝穗霉 Clonostachys rosea | 竞争性/侵染性 Competitive/ infectious |
J | 北京通州、内蒙古赤峰 Tongzhou district, Beijing; Chifeng, Inner Mongolia | 栽培料表面 Surface of the cultures | 主要为害蛹虫草栽培料,菌落表面平坦;迅速产生大量浅粉色孢子堆,在栽培料表面呈现粉状 T. ovalisporum mainly colonized the media of C. militaris, forming a flat colony. A large number of light pink spores produced quickly, appearing powdery on the surface of media | 卵孢单端孢 Trichothecium ovalisporum | 竞争性 Competitive |
K | 北京通州、内蒙古赤峰、辽宁沈阳、江苏徐州、江西遂州、本实验室 Tongzhou district, Beijing; Chifeng, Inner Mongolia; Shenyang, Liaoning; Xuzhou, Jiangsu; Suizhou, Jiangxi; this laboratory | 栽培料表面 Surface of the cultures | 产生大量分生孢子,一般仅污染栽培料,形成竞争性病害,但在高温下(约35℃),可以形成侵染性病害 The fungus produced a large number of conidia. It only colonized the media and competed for nutrition generally, but it could infect the fruiting bodies of C. militaris at high temperature (about 35°C) | 扩展青霉 Penicillium expansum | 竞争性 Competitive |
L | 北京通州、内蒙古赤峰、辽宁沈阳、本实验室 Tongzhou district, Beijing; Chifeng, Inner Mongolia; Shenyang, Liaoning; this laboratory | 栽培料表面 Surface of the cultures | 产生大量分生孢子,一般仅污染蛹虫草栽培料,形成竞争性病害 The fungus contaminated the media by producing a large number of conidia, forming competition with C. militaris for nutrition | 黄曲霉 Aspergillus flavus | 竞争性 Competitive |
M | 北京通州、江西遂州、本实验室 Tongzhou district, Beijing; Suizhou, Jiangxi; this laboratory | 栽培料表面 Surface of the cultures | 产生大量分生孢子,一般仅污染蛹虫草栽培料,形成竞争性病害 The fungus contaminated the media by producing a large number of conidia, being in competition with C. militaris for nutrition | 黑曲霉 Aspergillus niger | 竞争性 Competitive |
2.1 虫草生齿梗孢
该病害于2016年被报道(Sun et al. 2016;张园园 2016),病原菌分离纯化后以新种虫草生齿梗孢Calcarisporium cordycipiticola Jing Z. Sun, Cai H. Dong, Xing Z. Liu and K.D. Hyde发表,隶属于真菌界Fungi、子囊菌门Ascomycota、子囊菌纲Sordariomycetes、肉座菌目Hypocreales、齿梗孢科Calcarisporiaceae、齿梗孢属(Sun et al. 2016)。本实验室前期经柯赫氏法则证实其为蛹虫草白毛病病原菌,并对其生物学、侵染特性及发病特点进行了研究(刘晴等 2018)。该病原菌主要引起侵染性病害,也可引起竞争性病害,且病害一般发生在蛹虫草生长发育后期,侵染子实体并产生大量分生孢子,生产上很难防控,为蛹虫草栽培过程中的头号杀手(图1A,图2A)。
图2
图2
病原真菌人工侵染蛹虫草菌丝体与子实体
A:虫农生齿梗孢;B:产扁虫菌素单端孢;C:镰刀菌;D:镰刀菌;E:裂褶菌;F:哈茨木霉; G:淡紫拟青霉; H:稻绿核菌; I:粉红枝穗霉; J:卵孢单端孢; K:扩展青霉;L:黄曲霉;M:黑曲霉
Fig.2
Mycelia and the fruiting bodies of Cordyceps militaris infected with the pathogenic fungi.
A: Carcorporo cortpticoi; B: Tihotheiem crotocinigenum; C: Fusarium sp.; D: Fusarium sp.; E: Schizophyllum commune; F: Trichoderma harzianum; G: Purpureocillium lilacinum; H: Ustilaginoidea virens; I: Clonostachys rosea; J: Trichothecium ovalisporum; K: Penicillium expansum; L: Aspergilus flavus; M: Aspergillus niger.
2.2 产扁虫菌素单端孢
来源于马铃薯的内生真菌产扁虫菌素单端孢,可产生重要化合物Trichothecrotocins A-L(Yang et al. 2018,2020);隶属于真菌界、子囊菌门、子囊菌纲、肉座菌目、单端孢属;该属真菌可产生多种次级代谢产物,如Diketopiperazine(Summerbell et al. 2011)。T. crotocinigenum被报道分布于世界各地(泰国、荷兰、美国、英国、加拿大及中国)(Summerbell et al. 2011)。本课题组首次报道了引起蛹虫草白霉病的病原真菌Trichothecium crotocinigenum(Liu & Dong 2020),并已保藏于中国普通微生物菌种保藏管理中心(China General Microbiological Culture Collection Center,CGMCC),保藏号为CGMCC5. 2214。蛹虫草不同发育阶段均可被侵染,且不同阶段侵染,病害症状不同。菌丝生长阶段侵染,蛹虫草菌丝全部被该病菌覆盖,不形成原基导致绝产(图3A);原基形成后被侵染,子实体不能正常发育,且病斑不断扩大,最终影响产量与质量(图3B)。人工侵染发现该病原菌可侵染蛹虫草菌丝体和子实体(图2B,图3C)。ITS序列扩增测序,系统发育分析鉴定其为产扁虫菌素单端孢(图4)。其同属种粉红单端孢Trichothecium roseum侵染鸡腿菇引起菌柄溃疡病(Dong & Bian 2013)。
图3
图3
产扁虫菌素单端孢在蛹虫草生长不同阶段侵染的症状
A:原基形成前发病;B:子实体阶段;C:人工侵染蛹虫草菌丝体
Fig. 3
Symptoms of Cordyceps militaris infected by Trichothecium crotocinigenum at different stages.
A: Before primordium formation; B: Fruiting body; C: Artificial infection to the mycelia of C. militaris.
图4
图4
基于产扁虫菌素单端孢rDNA ITS序列采用最大似然法构建的系统发育树
Fig. 4
The phylogenetic tree based on ITS sequences of Trichothecium crotocinigenum and their close lineages by maximum likelihood.
2.3 镰刀菌
镰刀菌主要在蛹虫草子实体形成初期至成熟期为害严重。发病部位为栽培料表面或子实体基部,沿子实体向上蔓延,引起其根部软腐;气生菌丝浓密,为白色羊毛毡状(图5A)。人为侵染发现其可侵染蛹虫草子实体和菌丝体(图2C)。平板培养初始为白色,后期背面变为深红褐色(图5B,5C)。病原菌分生孢子近椭圆形,单生,无色,5.61-13.58×3.86-5.20μm(图5D-5F);厚垣孢子多数为球形,直径约为10μm(图5H)。ITS序列约550bp,序列提交GenBank数据库(登录号:MZ190456)并进行同源比对,与Fusarium proliferatum CBS131259(登录号:MH865926.1)ITS相似性为100%,结合形态特征确定该病原菌为镰刀菌Fusarium sp.,隶属于真菌界、子囊菌门、子囊菌纲、肉座菌目、丛赤壳菌科Nectriaceae、镰刀菌属(Wang et al. 2019),为引起人工栽培蛹虫草病害的首次报道。
图5
图5
镰刀菌的分离及其形态观察
A:被镰刀菌侵染的蛹虫草子实体;B,C:镰刀菌菌落;D-G:分生孢子和分生孢子梗;H:厚垣孢子. 标尺:A=4cm;B,C=2cm;D-H=10µm
Fig. 5
Morphology of Fusarium sp.
A: The fruiting bodies of Cordyceps militaris infected by Fusarium sp.; B, C: Colony of Fusarium sp.; D-G: Conidia and conidiophore; H: Chlamydospore. Scale bars: A=4cm; B, C=2cm; D-H=10μm.
同时,还分离到另外一种镰刀菌,发病部位为栽培料表面或子实体基部,沿子实体向上蔓延,在子实体形成初期至成熟时为害较严重,引起子实体基部软腐,但气生菌丝疏松,乳白色至灰白色,背部无色素沉积(图6A-6C)。人为侵染发现其可侵染蛹虫草子实体和菌丝体(图2D)。分生孢子近椭圆形,单生或双生,无色,5.25-11.58×2.26-3.60μm(图6D-6K)。ITS序列约550bp,序列提交GenBank数据库(登录号:MZ190457)并进行同源比对,与Fusarium proliferatum TH11-3(登录号:MT563411.1)ITS相似性为100%,结合形态特征确定该病原菌为镰刀菌Fusarium sp.,为引起人工栽培蛹虫草病害的首次报道。
图6
图6
镰刀菌的分离及其形态观察
A:被镰刀菌侵染的蛹虫草子实体;B,C:镰刀菌菌落;D-K:分生孢子和分生孢子梗. 标尺:A=4cm;B,C=2cm;D-K=10µm
Fig. 6
Morphology of Fusarium sp.
A: The fruiting bodies of Cordyceps militaris infected by Fusarium sp.; B, C: Colony of Fusarium sp.; D-K: Conidia and conidiophore. Scale bars: A=4cm; B, C=2cm; D-K=10μm.
串珠镰刀菌F. moniliform、半裸镰刀菌F. semitectum和禾谷镰刀菌F. graminearum引起平菇枯萎病(张克勤等 1992)。黑木耳白毛病病原菌为厚垣镰刀菌F. chlamydosporum、尖孢镰刀菌F. oxysporum(孔祥辉等 2011)。变红镰刀菌F. incarnatum和木贼镰刀菌F. equiseti复合侵染梯棱羊肚菌菌柄,导致菌柄腐烂(Guo et al. 2016)。
2.4 裂褶菌
气生菌丝旺盛,呈棉絮状,可短时间内从基部向上覆盖蛹虫草子实体(图7A-7C)。侵染状态及平板培养均未发现其孢子的产生,仅依靠菌丝致病(图7D-7G)。人为侵染发现其可侵染蛹虫草子实体和菌丝体(图2E)。ITS序列约600bp,序列提交GenBank数据库(登录号:MZ190458)并进行同源比对,与裂褶菌Schizophyllum commune S140099(登录号:KX097065.1)ITS相似性为100%;基于ITS序列的系统发育分析(图8),结合形态学鉴定其为裂褶菌;隶属于真菌界、担子菌门Basidiomycota、伞菌纲Agaricomycetes、伞菌目Agaricales、裂褶菌科Schizophyllaceae、裂褶菌属,为引起人工栽培蛹虫草病害的首次报道。
图7
图7
裂褶菌的分离及其形态观察
A:被裂褶菌侵染的蛹虫草子实体;B,C:裂褶菌菌落;D-G:菌丝. 标尺:A=4cm;B,C=2cm;D-G=10µm
Fig. 7
Morphology of Schizophyllum commune mycelia.
图8
图8
基于裂褶菌rDNA ITS序列采用最大似然法构建的系统发育树
Fig. 8
The phylogenetic tree based on ITS sequences of Schizophyllum commune.
2.5 哈茨木霉
病害发生于栽培料表面,菌丝迅速向四周蔓延,同时沿子实体向上蔓延,后期覆盖蛹虫草子实体,被侵染的子实体逐渐软化并伴随大量细菌的滋生,最后腐烂发臭(图9A)。病原菌在PDA平板上生长迅速,20℃ 3-4d长满整个平板;初始菌落呈白色,菌丝稀疏,后逐渐产生小团的絮状分生孢子(图9B)。菌丝透明、有隔,分生孢子球形、淡绿色(图9C,9D)。该菌株ITS序列约650bp(登录号:MZ190459)与哈茨木霉Trichoderma harzianum CBS 130671(MH865859.1)相似性为100%,结合形态特征(张广志等 2011),确定该菌株为哈茨木霉,隶属于真菌界、子囊菌门、子囊菌纲、肉座菌目、肉座菌科Hypocreaceae、木霉属,为引起蛹虫草病害的首次报道。人工侵染发现,在蛹虫草正常栽培环境(约20℃)下,哈茨木霉不侵染菌丝和子实体。温度升高(>25℃),可侵染蛹虫草菌丝体和子实体(图2F)。除哈茨木霉外,贺宗毅等(2012)发现绿色木霉T. viride可在蛹虫草制种和菌丝体培养阶段为害菌丝体。李娟等(2016a,2016b)研究了蛹虫草栽培料中分离的深绿木霉T. atroviride和钩状木霉T. hamatum。刘国丽等(2020)报道在被污染的栽培料上,深绿木霉菌丝初期纤细呈白色絮状,菌丝生长速度快,形成圆形的菌落,后期产生大量绿色分生孢子,颜色逐渐变为绿色将料面覆盖,有强烈的霉味,蛹虫草菌丝和子座的生长完全被抑制。
图9
图9
哈茨木霉的分离及其形态观察
A:被哈茨木霉侵染的蛹虫草子实体;B:哈茨木霉菌落;C,D:哈茨木霉菌丝和分生孢子. 标尺:A=4cm;B=2cm;C,D=10µm
Fig. 9
Morphology of Trichoderma harzianum.
木霉Trichoderma在国内外食用菌栽培及菌种制备中普遍发生且为害严重,可发生侵染性和竞争性病害。为害香菇、平菇、灵芝、双孢蘑菇、金针菇、木耳、灰树花等众多食用菌,但不同食用菌感染木霉种类差别较大(边银丙 2016;Lu et al. 2016)。
2.6 淡紫拟青霉
蛹虫草栽培初期发生在栽培料表面,开始出现白色绒状菌丝,很快变为淡紫色,占据栽培料,与蛹虫草菌丝争夺养分,其菌丝不断扩张侵染蛹虫草菌丝体(图10A)。该菌在PDA平板上初始为白色,约10d左右,呈现疏松棉絮状,后颜色逐渐变成淡紫色(图10B,10C)。分生孢子梗帚状,分生孢子多数近球形,少数梭形或瓜子状(图10D-10H)。ITS序列约650bp,序列提交GenBank数据库(登录号:MZ190460)并进行同源比对,与淡紫拟青霉Purpureocillium lilacinum CBS 129474(登录号:MH865347.1)ITS相似性为100%;结合形态学观察,鉴定为淡紫拟青霉。淡紫拟青霉属子囊菌门、肉座菌目、线虫草科Ophiocordycipitaceae、Purpureocillium属(Jennifer et al. 2011),为引起人工栽培蛹虫草病害的首次报道。人为侵染发现其可侵染蛹虫草子实体和菌丝体(图2G)。淡紫拟青霉是具有腐生-内生-寄生复杂生活史的丝状真菌,能高效寄生线虫卵或抑制卵不育;同时淡紫拟青霉对动物寄生虫、人畜共患寄生虫、真菌病害均有防治效果(Diana et al. 2014),但是关于其重寄生大型食用菌的报道为首次。
图10
图10
淡紫拟青霉的分离及其形态观察
A:被淡紫拟青霉侵染的蛹虫草;B,C:淡紫拟青霉菌落;D-H:分生孢子及分生孢子梗形态. 标尺:A=0.5cm;B,C=2cm;D-H=10µm
Fig. 10
Morphology of Purpureocillium lilacinum.
A: Cordyceps militaris infected by P. lilacinum; B, C: Colony of P. lilacinum; D-H: Conidia and conidiophore. Scale bars: A=0.5cm; B, C=2cm; D-H=10μm.
2.7 稻绿核菌
蛹虫草栽培初期零星发生,开始出现白色绒状菌丝,占据栽培料,与蛹虫草菌丝争夺养分(图11A)。菌丝白色浓密且菌落不规则,边缘向中间隆起(图11B,11C)。PDA 20℃培养10d,仅观察到小型分生孢子的产生,分生孢子椭圆形(图11D-11G)。ITS序列约650bp,序列提交GenBank数据库(登录号:MZ190461)并进行同源比对,与稻绿核菌Ustilaginoidea virens isolate GS171(登录号:MN511331.1)ITS相似性为100%;结合形态学观察,鉴定为稻绿核菌。稻绿核菌属子囊菌门、肉座菌目、麦角菌科Clavicipitaceae、绿核菌属(方中达 1998),为引起人工栽培蛹虫草病害的首次报道。人为侵染发现其可侵染蛹虫草子实体和菌丝体(图2H)。
图11
图11
稻绿核菌的分离及其形态观察
A:被稻绿核菌污染的蛹虫草;B,C:稻绿核菌菌落;D-G:分生孢子及产孢结构. 标尺:A=0.5cm;B,C=2cm;D-G=5µm
Fig. 11
Morphology of Ustilaginoidea virens.
A: Cordyceps militaris contaminated by U. virens; B, C: Colony of U. virens; D-G: Formation of conidiophore and conidia. Scale bars: A=0.5cm; B, C=2cm; D-G=5μm.
2.8 粉红枝穗霉
蛹虫草栽培初期发生在栽培料表面,初始为白色绒状菌丝,菌丝转色后至原基形成过程中也可观察到该种病害的发生(此时病原菌菌丝为白色、蛹虫草菌丝为橙黄色),占据栽培料与蛹虫草菌丝争夺养分,其菌丝不断扩张侵染蛹虫草菌丝体(图12A)。在PDA平板上为白色,背面无色素沉积(图12B,12C)。分生孢子梗轮枝状,分生孢子长椭圆形3-5×1-2.5µm(图12E-12H)。ITS序列约550bp,序列提交GenBank数据库(登录号:MZ190462)并进行同源比对,与粉红枝穗霉Clonostachys rosea CBS 127294(登录号:MH864507.1)ITS相似性为100%;结合形态学观察,鉴定为粉红枝穗霉。粉红枝穗霉隶属于子囊菌门、肉座菌目、生赤壳科Bionectriaceae、Clonostachys属,为引起人工栽培蛹虫草病害的首次报道。人为侵染发现其可侵染蛹虫草子实体和菌丝体(图2I)。
图12
图12
粉红枝穗霉的分离及其形态观察
A:被粉红枝穗霉污染的蛹虫草;B,C:粉红枝穗霉菌落;D-H:分生孢子及产孢结构. 标尺:A=0.5cm;B,C=2cm;D-H=5µm
Fig. 12
Morphology of Clonostachys rosea.
A: Cordyceps militaris infected by C. rosea; B, C: Colony of C. rosea; D-H: Formation of conidiophore and conidia. Scale bars: A=1cm; B, C=2cm; D-H=5μm.
2.9 卵孢单端孢
卵孢单端孢为2014年本课题组从蛹虫草子实体栽培料中分离得到的1个中国新记录种。该菌生长于蛹虫草栽培料表面,菌落表面平坦,因产生大量浅粉色孢子而呈现粉状,主要侵染栽培料(图13A-13C)(何曼妮等 2013)。菇农常常称为镰孢霉或粉色石膏霉。经过分离、培养和序列测定,该菌株ITS序列约600bp与卵孢单端孢Trichothecium ovalisporum CGMCC 3.17049序列(KF470758.1)相似性为100%,其形态特征及DNA序列与食用菌生产中常见的病原菌白色石膏霉Scopulariopsis fimicola存在明显差别,鉴定为卵孢单端孢(图13D-13K)。人为侵染发现其不侵染蛹虫草子实体和菌丝体(图2J)。
图13
图13
卵孢单端孢的分离及其形态观察
A:被卵孢单端孢污染的蛹虫草;B,C:卵孢单端孢菌落;D-H:分生孢子及分生孢子梗;I-K:分生孢子. 标尺:A=4cm;B,C=2cm;D-K=10µm
Fig. 13
Morphology of Trichothecium ovalisporum.
2.10 扩展青霉
图14
图14
扩展青霉的分离及其形态观察
A;被扩展青霉污染的蛹虫草;B,C:被扩展青霉侵染的蛹虫草子实体;D,E:扩展青霉菌落;F-I:分生孢子及分生孢子梗. 标尺:A-C=4cm;D,E=2cm;F-I=10µm
Fig. 14
Morphology of Penicillium expansum.
该菌株ITS序列约600bp与扩展青霉Penicillium expansum模式菌株ATCC 7861序列(NR_077154)相似性为100%,结合形态学鉴定为扩展青霉,刘国丽等(2020)已报道该病害对蛹虫草的危害。除扩展青霉外,贺宗毅等(2012)报道引起蛹虫草病害的青霉菌还有白色青霉P. albicans和软毛青霉P. puberulum。栽培料被青霉污染后,长出的菌落初呈白色粉末状,随着分生孢子大量繁殖颜色逐渐变为蓝绿色,主要为害蛹虫草栽培料和菌丝体。
2.11 黄曲霉
蛹虫草栽培初期零星发生,开始出现白色绒状菌丝,很快即变为有色的粉状霉层,形成黄绿色粉末状分生孢子,占据栽培料与蛹虫草菌丝争夺养分(图15A-15C)。主要污染栽培料,不侵染子实体(图2L)。分生孢子梗由特化的厚壁、膨大的足细胞生出,并略垂直于足细胞的长轴,不分枝,顶端膨大成球形顶囊,其表面产生辐射状单层或双层的小梗,在小梗顶端串生分生孢子,最后成为不分枝的链;分生孢子球形或卵圆形,淡绿色(图15D-15I)。ITS序列约600bp,与黄曲霉Aspergillus flavus CBS 139338菌株序列(KU296246.1)相似性为100%,结合形态学鉴定为黄曲霉。贺宗毅等(2012)报道黄曲霉能抑制蛹虫草菌丝生长,发病时栽培料内长出黄色霉状物,同时散发霉味。
图15
图15
黄曲霉的分离及其形态观察
A:被黄曲霉污染的蛹虫草;B,C:黄曲霉菌落;D-I:分生孢子形成过程. 标尺:A=4cm;B,C=2cm;D-I=10µm
Fig. 15
Morphology of Aspergillus flavus.
A: Cordyceps militaris contaminated by A. flavus; B, C: Colony of A. flavus; D-I: Formation of conidiophore and conidia. Scale bars: A=4cm; B, C=2cm; D-I=10μm.
2.12 黑曲霉
蛹虫草栽培初期发生在栽培料表面,开始出现白色绒状菌丝,很快变为有色的粉状霉层,形成黑色粉末状分生孢子,占据栽培料与蛹虫草菌丝争夺养分(图16A)。不侵染菌丝体和子实体,仅污染栽培料(图2M,图16A)。该菌株在PDA培养基上蔓延迅速,初始为白色絮状,茂密整齐,逐渐变为深黑色,背面为白色,呈辐射状的钩纹(图16B,16C)。菌丝透明,具隔膜,呈蔓延式生长,营养菌丝会生长出分支,分支上可继续分支。分生孢子球形或近球形,且部分为深褐色(图16D-16F)。ITS序列约600bp,与黑曲霉Aspergillus niger strain 7M1菌株序列(MT620753.1)相似性为100%,结合形态学鉴定为黑曲霉。
图16
图16
黑曲霉的分离及其形态观察
A:被黑曲霉污染的蛹虫草;B,C:黑曲霉菌落;D-F:分生孢子. 标尺:A=2cm;B,C=4cm;D-F=10µm
Fig. 16
Morphology of Aspergillus niger.
3 讨论
病原真菌依靠大量产孢或(和)气生菌丝旺盛生长侵染栽培料、蛹虫草菌丝或(和)子实体,导致蛹虫草菌丝体生长受阻、不形成原基或中后期子实体被病原菌覆盖死亡。仅虫草生齿梗孢可发病于子实体任意部位;其他病害均发生于栽培料表面或子实体基部。
调研发现虫草生齿梗孢、产扁虫菌素单端孢、镰刀菌、裂褶菌和哈茨木霉主要为害蛹虫草子实体发生侵染性病害,但人工侵染哈茨木霉,仅在温度升高时侵染蛹虫草菌丝和子实体。卵孢单端孢、扩展青霉、黄曲霉、黑曲霉等主要引起竞争性病害,与蛹虫草菌丝争夺水分和养料,影响其生长。但当温度升高、湿度增加、通风不好的情况下,也可发展为侵染性病害,为害蛹虫草菌丝体或子实体。因此侵染性病害与竞争性病害的界限并不是固定的,有些竞争性病害在一定条件下(高温等)可侵染蛹虫草菌丝体或子实体,而成为侵染性病害。蛹虫草人工栽培过程中正常控温为15-20℃,30℃基本停滞生长;而部分病原菌,其最适生长温度大于25℃,如木霉可在35℃的环境下较好生长。因此高温导致病原菌生长发育受阻、抗病力减弱;而此时的高温环境有利于病原菌生长繁殖,增加病原菌致病力。
除本研究中分离纯化得到的13种病原真菌外,贺宗毅等(2012)报道了毛霉Mucormycosis、黑根霉Rhizopus nigicans等,主要为害蛹虫草菌丝体。张园园(2016)报道了藤仓赤霉菌Gibberella intermedia侵染蛹虫草菌丝和子实体;发病后期,白色菌丝吞噬蛹虫草子实体,导致倒伏,并最终无法正常生长。
根据各病害的发生特点,提出蛹虫草病害防治的几点措施:(1)接种区和冷却区消毒,保持良好的卫生条件;(2)栽培室控制适当的温度、湿度并适当通风;(3)明确病原菌的侵染特点;(4)及时清理发病子实体,切勿在培养室打开染病栽培瓶或盒;(5)带有病原菌的培养基质灭菌后再丢弃;(6)选育抗病菌株。
目前,蛹虫草病害研究体系尚不成熟,有很多问题亟待解决。无论是真菌侵染还是细菌侵染,大部分致病机制尚不明确。未来的研究应加强侵染致病机理和蛹虫草抗病机制研究,为病害防控提供参考,为蛹虫草抗病品种选育提供指导。
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