玉米麦根腐平脐蠕孢叶斑病的发生与病原鉴定

The occurrence and pathogen identification of leaf spot on maize

在河北省春播玉米WN2000和山东省夏播普通玉米上发现一种叶斑病,其病斑圆形或椭圆形,中心灰白色,边缘褐色,有黄褐色褪绿圈,糯玉米WN2000病斑较大,(3~10)mm×(3~5)mm;普通玉米病斑较小,(1~2)mm×(2~3)mm。通过病原菌分离培养、致病性测定、形态特征观察及r DNA-ITS和1,3,8-三羟基萘还原酶基因(3HNR)序列分析,证明两种大小病斑是由同一种病原菌—麦根腐平脐蠕孢(Bipolaris sorokiniana)引起。田间调查结果表明,在山东省夏播玉米各品种苗期叶片上均有不同程度的发病,发病率最高的为冠玉6号,病株率52%,最低的为五岳88,病株率2%;鲜食玉米仅在河北春播玉米WN2000上发生,发病率为32%。麦根腐平脐蠕孢侵染不同玉米品种产生两种大小不同的病斑在国内外尚属首次报道。

A leaf spot disease was found on fresh corn WN2000 in Hebei province and seeding corn in Shandong province.The disease was characterized with round or oval grey-whitish and brown-margined spots on affected tissues,which were surrounded by yellow-brown halos.The spots on WN2000 were larger than those on normal corn,where were（3-10） mm×（3-5） mm and（1-2） mm×（2-3） mm in size,respectively.This study proves the causal agent of this disease as Bipolaris sorokiniana by pathogen isolation,pathogenicity test,morphological observation,and rDNA-ITS and 3HNR gene sequence analyses.The field investigation showed that the disease incidence varied significantly.Guanyu6 was highly susceptible with disease incidence of 52%,wuyue88 showed strong resistances with disease incidence of 2%.Among the fresh maize,only cultivar WN 2000 was infected with disease incidence of 32%.This is the first report of B.sorokiniana causing leaf spot disease on maize with two sizes of lesions in the world.