我国部分地区玉米丝核菌组成及其致病类型分析

Profile and disease symptoms of Rhizoctonia isolates associated with maize in China

采用改进的组织分离法从山东、安徽、江苏、湖北和陕西5省10地市的270份类似玉米纹枯病的标样中,分离到204株丝核菌分离物。根据培养性状将这些丝核菌分为6种类型,DAPI染色显示,它们分别属于多核丝核菌、双核丝核菌和单核丝核菌,其中多核丝核菌占97.55%,双核丝核菌占1.47%,单核丝核菌占0.98%。经5.8SrDNA-ITS序列分析,多核丝核菌为AG1-IA、WAG-Z、AG-4-HG-I及AG-54个融合群,各融合群分别占菌株总数的84.80%、5.88%、3.43%和3.43%,其中AG1-IA为主要融合群;双核丝核菌为AG-A融合群;单核丝核菌种类尚不确定。对各融合群的致病类型进行初步比较发现,属于AG1-IA融合群的菌株,可在玉米叶鞘形成典型的云纹状病斑,其它菌株虽可引起玉米发病,但与AG1-IA的症状存在明显差异。

Two hundreds and four isolates of Rhizoctonia spp. were collected from the 270 samples of sheath and leaves of maize in Shandong, Anhui, Jiangsu, Hubei and Shaanxi provinces showing symptoms like sheath blight disease. The isolates were divided into six types of colonies and they belonged to multinucleate, binucleate and uninucleate Rhizoctonia according to the mycelium nucleates after staining with DAPI. The ratio of multinucleate, binucleate and uninucleate Rhizoctonia was 97.55%, 1.47% and 0.98% respectively. Characterization of anastomosis groups （AGs） was performed using sequencing of the 5.8S rDNA-internal transcribed spacer （ITS） region. Within the multinucleate isolates, the most prevalent AG was AG1-IA about 84.80% of all isolates, followed by WAG-Z （5.88%）, AG-4-HG-I （3.43%） and AG-5 （3.43%）. The binucleate Rhizoctonia isolates belonged to AG-A. The uninucleate isolates had not been identified yet. The pathogenicity potential of the Rhizoctonia isolates collected was tested. Isolates of WAG-Z, AG-4-HG-I, AG-5, AG-A and uninucleate Rhizoctonia were pathogenic, but only AGI-IA can cause typical symptoms of sheath blight on maize plants.