免费文献传递   相关文献

Infection Process of Metarhizium pingshaense on Melanotus cribricollis (Coleoptera: Elateridae) Observed by Scanning Electron Microscope

平沙绿僵菌侵染筛胸梳爪叩甲幼虫的扫描电镜观察


Larvae of Melanotus cribricollis (wireworm), one of the most important pests of bamboo at shoot stage in southern China, can be effectively controlled by Metarhizium pingshaense. Compared with many other pests, cuticle of the larva of M. cribricollis is harder and smoother, which makes the infection process of M. pingshaense on M. cribricollis still unclear. In this research, the infection process was studied by observation under scanning electron microscope. The results showed that the conidia of M. pingshaense were mostly found on segmacoria and tips of the foot, secondly on conjunctivum and corrugation on the abdomen, with fewer on the smooth and hard parts. The larvae of M. cribricolli were mostly invaded by germ tube and appressorium of M. pingshaense, and then the mycelia and conidia appeared on the larva body. A germ tube formed at one end of the conidia in 12 h after inoculation. A small part of conidia germinated on the larva body surface while most of conidia penetrated into the larvae by the formed germ tubes in 18 h after inoculation. The germ tubes failed to invade the larvae could form mycelia and grow on surface of the cuticle, and then formed germ tube and appressorium at weak parts. The cuticle penetrated by germtubes or appressoria could be observed at the corrugation parts. The white mycelia firstly appeared at the legsocket of the infected larvae, and the mycelia growing out of the infected larva cuticle began to form new conidiophores and conidia. This study can lay a foundation for research of infection mechanism of M. pingshaense on M. cribricollis.


全 文 :第 50 卷 第 11 期
2 0 1 4 年 11 月
林 业 科 学
SCIENTIA SILVAE SINICAE
Vol. 50,No. 11
Nov.,2 0 1 4
doi:10.11707 / j.1001-7488.20141126
收稿日期: 2014 - 01 - 08; 修回日期: 2014 - 08 - 01。
基金项目: 浙江省科技计划重大科技专项(2010C02005 - 3) ; “十二五”国家科技计划农村领域项目(2012BAD19B0803)。
* 舒金平为通讯作者。
平沙绿僵菌侵染筛胸梳爪叩甲幼虫的扫描电镜观察*
张亚波 吴小双 叶碧欢 吴盼盼 舒金平
(中国林业科学研究院亚热带林业研究所 富阳 311400)
关键词: 平沙绿僵菌; 筛胸梳爪叩甲; 金针虫; 侵染过程; 扫描电镜
中图分类号: S718. 7 文献标识码: A 文章编号: 1001 - 7488(2014)11 - 0197 - 05
Infection Process of Metarhizium pingshaense on Melanotus cribricollis
(Coleoptera: Elateridae) Observed by Scanning Electron Microscope
Zhang Yabo Wu Xiaoshuang Ye Bihuan Wu Panpan Shu Jinping
(Research Institute of Subtropical Forestry,CAF Fuyang 3114000)
Abstract: Larvae of Melanotus cribricollis ( wireworm),one of the most important pests of bamboo at shoot stage in
southern China,can be effectively controlled by Metarhizium pingshaense. Compared with many other pests,cuticle of the
larva of M. cribricollis is harder and smoother,which makes the infection process of M. pingshaense on M. cribricollis still
unclear. In this research,the infection process was studied by observation under scanning electron microscope. The
results showed that the conidia of M. pingshaense were mostly found on segmacoria and tips of the foot,secondly on
conjunctivum and corrugation on the abdomen,with fewer on the smooth and hard parts. The larvae of M. cribricolli were
mostly invaded by germ tube and appressorium of M. pingshaense,and then the mycelia and conidia appeared on the larva
body. A germ tube formed at one end of the conidia in 12 h after inoculation. A small part of conidia germinated on the
larva body surface while most of conidia penetrated into the larvae by the formed germ tubes in 18 h after inoculation. The
germ tubes failed to invade the larvae could form mycelia and grow on surface of the cuticle,and then formed germ tube
and appressorium at weak parts. The cuticle penetrated by germtubes or appressoria could be observed at the corrugation
parts. The white mycelia firstly appeared at the legsocket of the infected larvae,and the mycelia growing out of the
infected larva cuticle began to form new conidiophores and conidia. This study can lay a foundation for research of
infection mechanism of M. pingshaense on M. cribricollis.
Key words: Metarhizium pingshaense; Melanotus cribricollis ; wireworm; infection process; SEM
金针虫是叩甲 (鞘翅目 Coleoptera 叩甲科
Elateridae)幼虫的通称,广布于世界各地,危害农作
物、林木及牧草等,是一类极为重要的地下害虫。筛
胸梳爪叩甲(Melanotus cribricollis)是浙江笋用林内
的优势种群,其幼虫(即金针虫)是笋期主要害虫之
一,在湖州地区德清和安吉、杭州地区余杭和临安等
重要竹区的早园竹 ( Phyllostachys praecox) 林中,鲜
笋带虫率可达 62%,种笋受害率更是高达 80% 以
上,严重制约了当地竹产业的健康发展 (徐天森,
2004),造成了巨大的经济损失。同时害虫防治中
大量使用化学农药又对竹笋的食用安全构成了严重
威胁。因此,安全、高效、环境友好的竹林金针虫防
治方法的研究尤为重要。平沙绿僵菌 (Metarhizium
pingshaense)菌株 wp08 是本实验室从筛胸梳爪叩甲
幼虫僵虫体上分离到的一株绿僵菌,室内毒力测定
结果表明,在 107 个·g - 1干土孢子浓度下,害虫校正
死亡率达到 100%,LT50为 13. 89 天(王鹏等,2010;
张亚波等,2012)。该菌株可能成为当前攻克竹林
内筛胸梳爪叩甲幼虫无公害防治难题的突破口。
国外应用绿僵菌防治农田金针虫已展开了较多
研究(Fox et al.,1958; Filipchuk et al.,1995; Kabaluk
et al.,2005; Kabaluk et al.,2007; Kabaluk et al.,
2007; Ansari et al.,2008),国内关于绿僵菌防治金针
虫的研究仅限本实验室对竹林金针虫的几篇相关报
林 业 科 学 50 卷
道(王鹏等,2010; 张亚波等,2012; 吴盼盼等,
2013)。以上研究仅围绕菌株筛选、毒力测定以及初
步的田间防效试验等方面,目前尚未见到绿僵菌分生
孢子对金针虫侵染过程的相关报道。
有研究认为虫生真菌对昆虫的致病力与孢子的大
小、萌发速度及其在昆虫体壁的附着能力有关(Altre
et al.,1999; Vega et al.,1999)。因此,不同学者研究
了绿僵菌分生孢子在不同昆虫体表附着、萌发和入
侵的过程以探求绿僵菌对昆虫的致病力 (王音等,
2005; 王达等,2010; 李茂业等,2011)。筛胸梳爪
叩甲幼虫体壁坚硬而光滑,其独特的体表结构不同
于已报道的其他寄主,致死速度较慢,但室内致死率
仍可达 100%。鉴于绿僵菌侵染筛胸梳爪叩甲幼虫
的方式和途径尚不清楚,本研究以平沙绿僵菌 wp08
菌株为研究材料,通过对筛胸梳爪叩甲幼虫侵染过
程的定期取样,利用扫描电镜观察分生孢子在筛胸
梳爪叩甲幼虫虫体的附着部位、孢子萌发、侵入时间
和侵入方式,为揭示平沙绿僵菌侵染筛胸梳爪叩甲
幼虫的途径、过程及机制提供直观的依据。
1 材料与方法
1. 1 供试菌株 平沙绿僵菌菌株 wp08,由本实验
室从筛胸梳爪叩甲幼虫(即金针虫)僵虫上分离,已
提交至中国科学院微生物菌种保藏中心专利保存
(保藏号 CGMCC No. 4226)。
1. 2 供试昆虫 筛胸梳爪叩甲于 2011 年 4 月在浙
江德清早园竹林采集,中国林业科学研究院亚热带
林业研究所养虫室内饲养,试验前 24 h 移至 25 ℃
培养箱 ( QHX-Ⅲ,上海新苗医疗器械制造有限公
司)中黑暗培养,筛选出大小一致、健康活跃的幼虫
作为供试虫体。
1. 3 侵染菌孢子悬浮液的制备及其对筛胸梳爪叩
甲幼虫的感染 将平沙绿僵菌菌株 wp08 在 PPDA
(Potato peptone dextrose agar) (张永军等,2001)培
养基中培养至完全产孢后,刮取分生孢子,用 0. 1%
吐温 80 的无菌水润湿,磁力搅拌器搅拌均匀,经血
球计数板测定孢子悬浮液浓度,调整至 108 个
·mL - 1。
采用虫体直接浸蘸法,将大小一致的竹林筛胸
梳爪叩甲幼虫放于盛有平沙绿僵菌孢子悬浮液中浸
蘸 5 s,待虫体晾干后,放入灭菌的蛭石中,喂养新鲜
的玉米幼嫩根茎,在人工气候箱中 25 ℃、RH85%条
件下培养。每隔 6 h 取样 1 次,直至菌丝穿出筛胸
梳爪叩甲幼虫体壁。
1. 4 扫描电镜样品的制备和观察 样品用 2. 5%
的戊二醛和 1% 锇酸固定,0. 1 mol·L - 1、pH7. 0 的
磷酸缓冲液漂洗 3 次,每次 15 min。50%,70%,
80%,95%,100%酒精逐级脱水,每级 30 min。乙
醇与乙酸异戊酯混合液( V /V = 1 /1)处理 30 min,
乙酸异戊酯处理 1 ~ 2 h,临界点干燥 ( Hitachi
HCP-2 critical point dryer),真空喷镀仪 ( Eiko IB5
ion coater)喷金镀膜。日立 TM-1000 型扫描电镜
观察、拍照。
2 结果与分析
2. 1 平沙绿僵菌对筛胸梳爪叩甲幼虫不同部位的
附着情况 筛胸梳爪叩甲幼虫不同部位的体壁外形
结构差别较大,因此平沙绿僵菌在体壁的附着情况
也不同。分生孢子分布密度最大的部位是胸足的节
间膜、足末端等处(图 1A,B,C); 其次为腹部的节
间膜、褶皱处,该处组织相对柔软,利于孢子的附着
和侵染(图 1D); 毛孔、沟、缝等角质层相对薄弱的
部位较少(图 1E,F,G); 虫体的光滑坚硬部位孢子
的分布量最少(图 1H,I)。
2. 2 绿僵菌在筛胸梳爪叩甲幼虫体表的萌发及侵
入过程 从扫描电镜观察,平沙绿僵菌侵染筛胸梳
爪叩甲幼虫,可由分生孢子萌发的芽管直接侵入体
壁,也可以产生附着胞后再侵入。接种后 12 h,平沙
绿僵菌的孢子大量附着于虫体表面,极个别孢子已
经萌发,在孢子一端出现芽状突起(图 2A); 接种后
18 h,小部分孢子已经萌发,多数以芽管形式直接穿
透体壁,部分产生附着胞结构,紧贴着体壁上,末端
侵入体表(图 2B,C); 24 h 后,芽管继续伸长,寻找
适宜侵入点,末端膨大形成附着胞 (图 2D)。30 ~
36 h 时,在未找到侵入点时芽管可以形成菌丝在体
表横向生长,在褶皱处可见附着胞穿透筛胸梳爪叩
甲幼虫体壁(图 2E,F),观察中发现在附着胞或芽
管周围有粘液状物质产生,使得菌体表面凹凸不平;
36 ~ 96 h,侵入筛胸梳爪叩甲幼虫体腔的菌丝,吸收
虫体内的营养物质,大量繁殖菌丝,直至体腔内完全
被菌丝充满,最后突破体壁,最先在足窝处长出白色
菌丝(图 2G); 120 h 时,菌丝上已经开始萌生分生
孢子梗和新的分生孢子,虫体表面逐渐布满墨绿色
分生孢子(图 2H,I)。平沙绿僵菌分生孢子侵染筛
胸梳爪叩甲幼虫过程包括分生孢子附着、孢子萌发、
穿透体壁、寄主体内短菌丝(虫菌体)增殖、入侵组
织器官、菌丝穿出体壁、产生分生孢子,侵染循环完
成。平沙绿僵菌在筛胸梳爪叩甲幼虫体表产生的分
生孢子成熟后扩散并继续侵染其他寄主,形成再侵
染;而对照处理的虫体完整,未见菌丝。
891
第 11 期 张亚波等: 平沙绿僵菌侵染筛胸梳爪叩甲幼虫的扫描电镜观察
图 1 寄主体表不同结构区绿僵菌孢子的附着情况
Fig. 1 Adherence of the spores of M. pingshaense on different parts of the host surface
A,B,C: 胸足的节间膜、足末端 The sections between the conjunctiva of thoracic leg and the end of leg; D: 腹部区域 The abdomen area;
E,F,G: 毛孔、沟缝处 The alveoluses and groove joints; H,I: 虫体光滑区域 The smooth parts of the surface.
图 2 绿僵菌侵染筛胸梳爪叩甲幼虫体表过程
Fig. 2 Infection process of M. pingshaense on the wireworm
A: 12 h 孢子出现芽状突起 Bud protrusions of the spores showed 12 h after inoculation; B,C: 18 h 牙状突起增大 Bud protrusions increased further
12 h after inoculation; D: 24 h 附着胞形成 Appressoriums formed 24 h after inoculation; E,F: 30 ~ 36 h 菌丝侵入虫体 The mycelium began to
invade the wireworms 30 ~ 36 h after inoculation; G: 96 h 菌丝突破虫体体壁 The cuticle was breakthroughed 96 h after inoculation; H,I: 120 h 虫
体表面布满菌丝和孢子 The surface of the worms was covered with white mycelia and conidia 120 h after inoculation
991
林 业 科 学 50 卷
3 讨论
真菌的分生孢子与寄主昆虫建立寄生关系的前
提是能成功附着于寄主昆虫的体壁,分生孢子附着
于寄主昆虫表皮后不一定能建立寄生关系,还必须
识别体壁营养是否适合其寄生及寄主体表细菌等物
质的抑制作用(Smith et al.,1981; Lord et al.,2004;
Maketon et al.,2007 ),这是病原真菌能否成功地侵
染寄主和完成生活史的关键。平沙绿僵菌分生孢子
接种筛胸梳爪叩甲幼虫后 12 h 即有极个别孢子已
经萌发出现芽状突起,直至 120 h 虫体表面逐渐布
满墨绿色分生孢子,其在筛胸梳爪叩甲幼虫体壁上
完成了一个生活史,但电镜观察显示绿僵菌分生孢
子侵染筛胸梳爪叩甲幼虫各个过程并不十分统一,
有的孢子萌发快,大部分几天后仍未萌发,通常在孢
子聚集较多的地方,只有贴近体壁的分生孢子萌发,
聚集成堆的萌发较少,这可能与孢子所处的位置
有关。
绿僵菌对不同寄主或寄主昆虫的不同部位侵染
能力有很大差别,Butt 等(1995)通过研究比较绿僵
菌对蚜虫和跳甲的入侵行为发现,寄主体壁对绿僵
菌的萌发行为和为寄主的致病力有重要影响。王音
等(2005)用绿僵菌侵染小菜蛾 7 h 时孢子可见萌发
迹象,10 h 大量孢子萌发伸出芽管,向体壁穿透。
本研究中平沙绿僵菌孢子接种后 12 h 个别孢子才
出现萌发迹象,18 h 小部分孢子萌发侵入虫体,萌
发侵入时间相对较长,且在观察中发现附着在体表
的孢子只有少部分萌发,大多数孢子一直没有萌发。
这与该菌株对筛胸梳爪叩甲幼虫的致死中时较长也
相符(王鹏等,2010),说明筛胸梳爪叩甲幼虫体表
结构坚硬光滑不利于孢子的萌发侵入,在绿僵菌与
筛胸梳爪叩甲幼虫相互作用过程中,只有少数孢子
在节间膜等相对较软的部位成功侵入。
昆虫病原真菌在入侵昆虫体壁的过程中,会分
泌蛋白酶 ( proteinases)、几丁质酶 ( chitinase)、脂酶
( lipase) 等多种胞外水解酶类 ( Charnley et al.,
1991)。通过诱导分泌的孢外蛋白酶类作用,分生
孢子牢固地附着在昆虫体壁上。Wang 等(2007)研
究发 现 金 龟 子 绿 僵 菌 孢 子 表 面 的 粘 着 蛋 白
( adhesin)MAD1 基因,伴随孢子萌发,该基因表达
水平逐渐增强。笔者在观察中发现孢子表面分泌一
层粘状物质,可能是孢子在侵入过程中分泌的活性
物质。
另外笔者发现,气门虽然作为筛胸梳爪叩甲幼
虫体内与体外气体交换的重要通道,但是绿僵菌的
分生孢子却不能附着于筛胸梳爪叩甲幼虫的气门
上,也不能以此为侵入途径。王晓红等(2009)在研
究白僵菌感染桑天牛时也观察到该现象,这可能与
气门的结构及质地有关,气门密布刚毛且骨化而不
利于孢子的侵入,也可能与筛胸梳爪叩甲幼虫在遇
到外界侵染时的自我保护机制有关。
参 考 文 献
李茂业,林华锋,金 立,等 . 2011. 黄绿绿僵菌对褐飞虱侵染过程的
扫描电镜观察 .应用昆虫学报,48(5) :1412 - 1416.
王 达,袁芳芳,黄大庄,等 . 2010. 绿僵菌侵染光肩星天牛幼虫过程
的透射电镜观察 .林业科学,46(5) :113 - 115.
王 鹏,张亚波,舒金平,等 . 2010.金龟子绿僵菌小孢变种对筛胸梳
爪叩甲幼虫致病力的生物测定 . 中国生物防治,26 ( 3 ) :
274 - 279.
王晓红,黄大庄,杨忠岐,等 . 2009.白僵菌感染桑天牛幼虫致病过程
的显微观察 .蚕业科学,35(2) :374 - 378.
王 音,雷仲仁,张青文,等 . 2005.绿僵菌侵染小菜蛾体表过程的显
微观察 .昆虫学报,48(2) :188 - 193.
吴盼盼,吴小双,舒金平,等 . 2013. 平沙绿僵菌 wp08 菌株固态发酵
条件的优化 .林业科技开发,27(1) :94 - 97.
徐天森,王浩杰 . 2004.中国竹子主要害虫 . 北京: 中国林业出版社 .
张永军,王中康,殷幼平,等 . 2001. 球孢白僵菌的生物学特性及对小
麦蚜虫的毒力 .西南农业大学学报,23(2) :144 - 146.
张亚波,吴盼盼,舒金平,等 . 2012.一株绿僵菌的鉴定及其生物学特
性研究 .林业科学,48(12) :134 - 140.
Altre J A,Vandenberg J D,Cantone F A. 1999. Pathogenicity of
Paecilomyces fumosoroseus Isolates to Diamondback Moth,Plutella
xylostella: Correlation with spore size,germination speed,and
attachment to cuticle. Journal of Invertebrate Pathology,73(3) :332
- 338.
Ansari M A,Evans M,Butt T M. 2008. Identification of pathogenic
strains of entomopathogenic nematodes and fungi for wireworm
control. Crop Protection,15: 1 - 4.
Butt T M,Ibrathim L,Clark S J,et al. 1995. The germination behaviour of
Metarhizium anisopliae on the surface of aphid and flea beetle
cufcles. Mycological Research,99(8) :945 - 950
Charnley A K,St Leger R J. 1991. The role of cuticle-degrading enzymes
in fungal pathogenesis in insects∥ Cole E T,Hoch H C. Fungal
Spore Disease Initiation in Plants and Animals. New York: Plenum
Press,267 - 287.
Filipchuk O D, Yaroshenko V A, Ismailov V Y, et al. 1995.
Effectiveness of biological and chemical preparations against tobacco
pests. Agrokhimiya,8: 81 - 86.
Fox C J S,Jaques R P. 1958. Note on the green-muscardine fungus,
Metarrhuzium anisopliae(Metch. ) Sor.,as a control for wireworms.
The Canadian Entomologist,90(5) : 314 - 315.
Kabaluk J T, Goettel M, Erlandson M, et al. 2005. Metarhizium
anisopliae as a biological control for wireworms and a report of some
other naturally-occurring parasites. IOBC /wprs Bulletin,28 ( 2 ) :
109 - 115.
Kabaluk J T,Jerry D E. 2007. Metarhizium anisopliae seed treatment
002
第 11 期 张亚波等: 平沙绿僵菌侵染筛胸梳爪叩甲幼虫的扫描电镜观察
increases yield of field corn when applied for wireworm control.
Agronomy Journal,99(5) : 1377 - 1381.
Kabaluk J T,Robert S V,Goettel M S. 2007. Mortality and infection of
wireworm, Agriotes obscurus [Coleoptera: Elateridae ], with
inundative field applications of Metarhizium anisopliae.
Phytoprotection,88(2) :51 - 56.
Lord J C,Howard R W. 2004. A proposed role for the cuticular fatty
amides of Liposcelis bostrychophila ( Psocoptera: Liposcelidae) in
preventing adhesion of entomopathogenic fungi with dry-conidia.
Mycopathologia,158(2) : 211 - 217.
Maketon M,Sawangwan P,Sawatwarakul W. 2007. Laboratory study on
the efficacy of Metarhizium anisopliae ( Deuteromycota:
Hyphomycetes ) in controlling Coptotermes gestroi ( Isoptera:
Rhinotermitidae) . Entomologia Generalis,30(3) : 203 - 218.
Smith R J,Pekrul S,Grula E A. 1981. Requirement for sequential
enzymatic activities for penetration of the integument of the corn
earworm (Heliotis zea ) . Journal of Invertebrate Pathology,38(3) :
335 - 344.
Vega F E,Jackson M A,McGuire M R. 1999. Germination of conidia and
blastospores of Paecilomyces fumosoroseus on the cuticle of the
silverleaf whitefly,Bemisia argentifolii. Mycopathologia,147 ( 1 ) :
33 - 35.
Wang C,St Leger R J. 2007. The MAD1 adhesin of Metarhizium
anisopliae links adhesion with blastospore production and virulence
to insects,and the MAD2 adhesin enables attachment to plants.
Eukaryot Cell,6(5) :808 - 816.
(责任编辑 朱乾坤)
102