燕麦紫斑病的病原

Pathogen of oat purple spot disease

2013年8月在甘肃省通渭县的一块燕麦田中,叶片和小穗上出现大量紫色病斑,病株率达100%。采用组织分离法得到核腔菌属Pyrenophora(synonym:Drechslera)真菌。通过Koch’s法则明确了菌株ASA-13的致病性:在8-22℃下,接种植株产生紫色叶斑,在20-25℃下,接种植株产生中心黑色、周围黄褐色至淡黄色叶斑,一些病斑几乎成为条斑。在20℃下,菌株ASA-13人工接种可侵染皮燕麦、裸燕麦、高粱、小麦、玉米和青稞离体叶片。采用形态学和分子生物学方法对病原菌进行了鉴定,燕麦紫斑病病原为毛壳核腔菌Pyrenophora chaetomioides(syn.:D.avenae)。采用温度梯度法测定了试验菌株的适宜生长温度,在PDA培养基上菌株ASA-13的菌丝适宜生长温度为25-30℃。

In August 2013,purple spots seriously occurred on the leaves and spikelets of oat(Avena sativa)in a field located in Tongwei county,Gansu Province.The disease incidence was 100%.Pathogen isolation was carried out from diseased tissues,and fungal isolates of Pyrenophora(synonym:Drechslera)were obtained.Koch’s procedures were used to verify the pathogenicity of isolate ASA-13.At 8-22℃,isolate ASA-13 produced purple leaf spots on inoculated plants,while yellowish brown to pale yellow leaf spots with black center occurred at 20-25℃,and some leaf spots became striped.Inoculation test at 20℃ proved that isolate ASA-13 was able to infect the leaf explants of Avena sativa,A.nuda,Sorghum bicolor,Triticum aestivum,Zea mays and Hordeum vulgare var.nudum.Based on morphological and molecular biological methods the pathogen was identified as Pyrenophora chaetomioides(syn.:Drechslera avenae).BLASTn analysis showed that the rDNA-ITS sequences of isolate ASA-13(GenBank accession No.MN560117)had a 99.36% similarity with those of D.avenae isolate DA16(GenBank accession No.AF260328.1).Temperature gradient analysis showed that 25-30℃ was optimal for mycelial growth of the pathogen on PDA.