我国北方玉米上平脐蠕孢属和弯孢属真菌及其所致叶斑病

Bipolaris and Curvularia species associated with corn leaf spot in northern China

平脐蠕孢属(Bipolaris)和弯孢属(Curvularia)真菌可引起多种玉米叶斑病。为了解当前玉米生产上此类病害的发生情况,2014年8-9月对我国玉米主产区北京、河北、河南、黑龙江和吉林5省市玉米上疑似由该两属真菌引起的叶部病斑样品进行了采集,随后进行了真菌的分离和鉴定。共采集样品42份,根据其形状特点归为4类:长条形、椭圆形、小点状和梭形病斑。经组织分离获得平脐蠕孢属和弯孢属真菌28株,基于形态学和rDNA-ITS序列的系统发育分析共鉴定出5个种:玉蜀黍平脐蠕孢(B.maydis)、玉米平脐蠕孢(B.zeae)、玉米生平脐蠕孢(B.zeicola)、新月弯孢(C.lunata)和穂状弯孢(C.spicifera)。从长条形病斑和椭圆形病斑上分离到的主要是B.maydis和B.zeicola,从小点状病斑分离到的主要是C.lunata,其次是B.zeae。分离出C.lunata的样品病斑较为稀疏、颜色略浅、呈苍白色,分离出B.zeae的样品病斑更为密集、颜色较深。从梭型病斑分离到的是C.spicifera。有少数样品可分离到上述两种菌。采用孢子悬浮液喷雾法对温室玉米苗接种,上述5种真菌均可致病。以接种B.maydis发病最快,发病最重;接种B.zeicola、C.lunata或C.spicifera发病较慢,症状明显;接种B.zeae发病最慢,仅引起小点状病斑。研究结果可为玉米叶斑病的正确诊断提供资料和依据。

Several species of Bipolaris and Curvularia can cause common corn leaf spot.To investigate current corn diseases caused by these fungal species,we collected the suspected samples of corn leaf spot caused by species of the two genera from five provincial regions,including Beijing,Hebei,Henan,Heilongjiang,and Jilin,the main corn-growing areas in China in August to September in2014.Then the fungi were isolated and identified.A total of 42 collected samples were divided into four types based on the form of the lesions：elongate,elliptic,speckle,and spindle.Twenty-eight strains of Bipolarisand Curvularia were obtained by the tissue isolation method,and identified as B.maydis,B.zeae,B.zeicola,C.lunata and C.spicifera based on their morphological characteristics and the phylogenetic analysis of rDNA-ITS sequences.The strains isolated from the elongate and elliptic lesions were mainly B.maydis and B.zeicola.The strains isolated from the speckle lesions were mostly C.lunata,followed by B.zeae.The lesions were sparse and pale on the samples with C.lunataisolated,and serried and dark on the samples with B.zeae isolated.The strains isolated from the spindle lesions were C.spicifera.There were a few samples with two fungal species being isolated from the same sample.All the five fungal species were pathogenic to corn seedlings in inoculation experiments by using the spore suspension spray method.The plants inoculated with B.maydis showed symptoms quickly and severely,and those inoculated with B.zeicola,C.lunata or C.spicifera showed symptoms slowly and markedly,while those inoculated with B.zeae showed only small speckle spots on corn leaves.The results may be helpful for the diagnosis of corn leaf spot.