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山核桃Carya cathayensis隶属于胡桃科Juglandaceae中的山核桃属Carya,是一种著名的干果树种,因其干果富含营养和经济价值较高而得到了广泛栽培[1]。山核桃干腐病是山核桃生产上一种重要病害,不但影响山核桃的产量,而且会削弱树势,严重时则导致树木过早死亡,并造成重大经济损失[2]。2011年首次报道山核桃干腐病病原菌为Botryosphaeria dothidea(Moug. ex Fr.) Ces. & De Not,属于子囊菌门葡萄座腔菌科Botryosphaeriaceae的葡萄座腔菌属Botryosphaeria[3]。葡萄座腔菌科真菌是农业和林业上重要病原菌、内生真菌或潜在的致病菌,主要引起树木溃疡病。葡萄座腔菌属真菌广泛分布于世界各地,而且寄主范围广泛,是森林生态系统中的重要真菌类群[4]。该菌存在有性型和无性形阶段,其主要形态分类特征为子座、子囊、子囊孢子以及分生孢子的形状、纹饰、颜色、分隔、长宽比、大小及壁厚度等[5-6]。另外,培养菌落颜色、气生菌丝生长情况及子囊孢子表面超微结构(纹饰)也可用于葡萄座腔菌科真菌的分类和鉴定[7]。随着分子生物学的快速发展,越来越多的基因序列分析方法应用于葡萄座腔菌科真菌的分类鉴定及系统发育分析,如核糖体小亚基基因(SSU),核糖体大亚基基因(LSU),延长因子α基因(EF1-a),核糖体DNA内转录间隔区(rDNA-ITS),几丁质合酶基因,β微管蛋白(β-tubulin),A-肌动蛋白(A-actin)基因,钙调蛋白(calmodulin)基因等基因[8]。尤其rDNA-ITS序列是应用最普遍的基因序列,已广泛地应用于很多真菌目、科、属、种等的分类鉴定及系统发育分析。本研究采用形态学特征与与rDNA ITS相结合的方法对分离自中国山核桃的干腐病菌进行了鉴定研究。
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本研究分离得到129株菌株,选取7株作为实验菌株,室外接种健康山核桃枝条,保湿培养15 d后,所有实验菌株均具有致病性,枝条上出现黑色病斑,对病斑进行组织分离得到了相应的病原菌。根据不同菌株枝条发病数及其感病级数,计算得到各病原菌的感病指数。其中CXY1565,CXY1566,CXY1567致病性相近,其病情指数为77.8,其致病性最强(图 1F),其次为CXY1568和CXY1569,病情指数为15.6(图 2F),CXY1570和CXY1571菌株致病性最差,其病情指数为6.7(图 3F)。
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以上7株病原菌形态学鉴定后共分为3种,一种是Botryosphaeria dothidea (Moug. ex Fr.) Ces. & De Not,以CXY1567为代表菌株,分离频率为71.4%;另一种是B. fabicercianum sp. Nov.,以CXY1568为代表菌株,分离频率为14.3 %;第3种是B. obtusa De Not.,以CXY1570为代表菌株,分离频率为14.3%。
Botryosphaeria dothidea:在PDA上25 ℃菌落生长速率较快,3~4 d几乎布满平板(直径90.0 mm);初期菌落白色或无色,气生菌丝棉絮毛状,较稀疏;培养1~2 d后,有白色或黄色小点沿菌丝分布,菌落中间有墨绿色色素;随着色素的沉积,黄色色素逐渐被掩盖,最后整个菌落变为灰褐色;后期菌落边缘气生菌丝倒伏紧贴培养基,菌落背面黄绿色色素呈点状不均匀分布;随着色素沉积,整个培养皿背面逐渐变为墨绿色或黑色。分生孢子器沿菌落边缘生长,表生,球形或不规则形;多腔室,分生孢子梗着生于腔室内壁细胞上,无色,杆状。分生孢子无色,无隔,锤形,顶部钝圆,基部比顶部稍尖。大分生孢子18.0~22.2 μm × 4.6~6.9 μm,平均为21.5 μm × 5.6 μm。长/宽比为3.0~4.0,小分生孢子直径为4.0~6.0 μm(图 1)。
Botryosphaeria fabicercianum:在PDA上菌落生长迅速,5 d可长满培养皿(直径90.0 mm)。菌落初呈白色,菌丝绒毛状或棉絮状,4~6 d菌落中央呈烟灰色,边缘菌丝紧贴培养基;12~16 d气生菌丝由灰绿色变为橄榄绿色,最后变为墨绿色。分生孢子器表生,散生或聚生,深褐色,球状,表面有菌丝覆盖。分生孢子器壁分3层,外层厚,深褐色或浅棕色,角质状;中层细胞薄壁,浅棕色;内层细胞薄壁,无色。分生孢子梗缺。产孢细胞圆柱形或烧瓶形,无色,光滑,薄壁,顶端产生单个分生孢子。侧丝无。分生孢子薄壁,光滑,无色,单胞,纺锤形,中间至中上1/3处最宽,顶端尖锐,基部平截,边缘具一个细小褶皱。分生孢子萌发前形成1~2个隔膜。大分生孢子17.3~24.3 μm × 4.5~7.5 μm,平均为22.7 μm × 6.1 μm,长/宽比为3.5~4.5,小分生孢子直径为3.8~6.3 μm[9](图 2)。
Botryosphaeria obtusa:在PDA上25 ℃生长迅速,3 d布满平板(直径90.0 mm),菌落初为白色,气生菌丝稀疏不发达,较短,细绒毛状,边缘整齐;2 d后有墨绿色色素沉积。后期气生菌丝分布于菌落边缘,稀疏且长势较弱,中央无气生菌丝,或气生菌丝平铺。10 d后由于色素沉积,菌落变为墨黑色,有时具反光;菌落背面由灰黑色变为墨绿色或者黑色。分生孢子器散生,表生,多腔室,腔室圆形或近圆形,无褶皱,内壁上着生分生孢子梗。分生孢子初无色,单胞,后呈褐色,卵形;大分生孢子为17.3~22.5 μm × 8.8~11.3 μm,平均为21.9 μm ×10.2 μm,长/宽比为1.8~2.3,小分生孢子直径3.0~4.0 μm[10](图 3)。
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通过对供试7个菌株的rDNA-ITS序列测定和在GenBank中进行BLAST搜索和比对,结果表明:这些菌株均为葡萄座腔菌科真菌,分别为Botryosphaeria dothidea,B. fabicercianum和B. obtusa菌株(表 1)。
表 1 供试菌株rDNA-ITS序列与GenBank相关菌株的相似率
Table 1. Similarity of rDNA-ITS sequences of the tested fungal strains with related strains blasted in GenBank
菌株编号 菌株接收号 GenBank中相似的种类 相似率最高菌株 最高相似率/% 相似菌株接收号 CRY1567 TC527826 Botryosphaeria dothidea CBS 121484 99 EU650670 CRY1566 TC527822 B. dothidea CBS116743 99 AY786322 CRY1565 TC527825 B. dothidea CMW800 99 AY236949 CRY1568 TC527823 B. fabicercianum CMW24703 100 HQ332195 CRY1569 TC527824 B. fabicercianum CMW24703 99 HQ332195 CRY1570 TC527827 B. obtusa CBS119049 99 DQ458889 CRY1571 TC527828 B. obtusa CBS119049 99 DQ458889 -
根据同源性比对的结果,从GenBank中下载33个与供试菌株关系相近的ITS序列和1个Guignardia philoprina(球痤菌属)序列作为外群,将所有序列整理后进行比对分析。用PAUP 4.0b10对比对结果进行最大简约法分析,将所有的614个特征视为无序且权重相同,其中120个恒量特征,和63个无效的变量特征Bootstrap法重复1 000次评估得到各节点支持率(BS)。利用最大简约法构建合议树步长(tree length)为327,一致性指数(consistency index,CI)0.8,保留指数(retention index,RI)0.9,趋同性指数(homoplasy index,HI)0.2,可调一致性指数(rescaled consistency index,RC)0.7;利用MrModeltese 3.7分析后,在AIC(Akaike Information Criterion)标准下,获得最佳模型TIM+G。贝叶斯方法采用马氏链蒙特卡罗(MCMC)算法,共运行500万代,所得9 902个树的合议树中各支的拓扑学结构与简约法基本一致,后验概率(PP)为节点支持率为PP。最后节点支持率为BS/PP(图 4)。
基于rDNA-ITS序列构建的系统发育树,结果将供试7个菌株与相关葡萄座腔菌科真菌分为2个大的类群,其中第1个类群包括分支Ⅰ,分支Ⅱ,分支Ⅲ,第2个类群包括分支Ⅳ和分支Ⅴ。
分支Ⅰ包括无性型为Spencermartinsia viticola等2个菌株,系加利福尼亚柑橘枝干溃疡病病菌[11]。供试菌株CXY1570和CXY1571位于分支Ⅱ中,其无性型为Diplodia。这2个菌株与B. obtusa菌株聚集在同一分支,与 CBS119049的菌株的最大相似率为99%。分支Ⅴ为无性型Fusicuccom类群的菌株,包括Botryosphaeria dothidea,B. fabicercianum和B. cortici。最大简约法和贝叶斯法的分析结果均表明,中国山核桃干腐病菌包括 Botryosphaeria dothidea,B. fabicercianum和B. obtusa。分子鉴定结果与形态学鉴定结果一致。
Identification of the pathogens causing stem canker on Carya cathayensis
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摘要: 葡萄座腔菌科Botryosphaeriaceae真菌是很多木本植物溃疡病和枯梢病的重要病原菌。已有报道认为:山核桃干腐病病原菌为茶藨子葡萄座腔菌Botryosphaeria dothidea,但对于葡萄座腔菌科其他真菌与山核桃干腐病的关系还没有深入研究。分离得到了山核桃干腐病相关病原菌,通过比较其形态学特征和核糖体DNA内转录间隔区(rDNA ITS)序列特征,将分离得到的供试菌株分为3组。根据形态学特征和基于ITS序列的系统发育分析,3组菌株分别鉴定为Botryosphaeria dothidea,B.fabicercianum和B.obtusa。其中B.dothidea为优势菌株,分离频率为71.42%,B.fabicercianum和B.obtusa分离频率分别为14.28%。经致病性测定,上述分离菌株均能引起健康山核桃Carya cathayensis枝条发病,但致病性存在差异。在山核桃上发现的B.obtusa和B.fabicercianum为首次报道。Abstract: Species of the Botryosphaeriaceae family are important pathogens causing cankers and die-back on many woody plants. In previous studies Botryosphaeria dothidea has commonly been reported as a pathogen of Chinese hickory(Carya cathayensis) canker; however, it was unclear whether other species of Botryosphaeriaceae were also related to hickory canker. In one study, several species of Botryosphaeriaceae were isolated from Chinese hickory, and then they were identified based on anamorphic morphology and rDNA Internal Transcribed Spacer(ITS) sequences. A phylogentic analysis indicated that these isolates formed three clades and were identified as B. dothidea, B. fabicercianum, and B. obtusa with isolation rates of B. dothidea (71.42%) predominant and B. fabicercianum and B. obtusa being much lower(14.28%). In pathogenicity testing, all three pathogens caused stem cankers on Chinese hickory but had different degrees of pathogenicity. B. obtusa and B. fabicercianum were first reported as a pathogen of Carya cathayensis canker.
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Key words:
- forest protection /
- cash forestry /
- canker /
- Botryosphaeriaceae /
- Botryosphaeria dothidea /
- phylogeny /
- Carya cathayensis
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表 1 供试菌株rDNA-ITS序列与GenBank相关菌株的相似率
Table 1. Similarity of rDNA-ITS sequences of the tested fungal strains with related strains blasted in GenBank
菌株编号 菌株接收号 GenBank中相似的种类 相似率最高菌株 最高相似率/% 相似菌株接收号 CRY1567 TC527826 Botryosphaeria dothidea CBS 121484 99 EU650670 CRY1566 TC527822 B. dothidea CBS116743 99 AY786322 CRY1565 TC527825 B. dothidea CMW800 99 AY236949 CRY1568 TC527823 B. fabicercianum CMW24703 100 HQ332195 CRY1569 TC527824 B. fabicercianum CMW24703 99 HQ332195 CRY1570 TC527827 B. obtusa CBS119049 99 DQ458889 CRY1571 TC527828 B. obtusa CBS119049 99 DQ458889 -
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链接本文:
https://zlxb.zafu.edu.cn/article/doi/10.11833/j.issn.2095-0756.2014.02.012