甘肃省马铃薯炭疽病的鉴定及室内药剂筛选

在甘肃省马铃薯主要种植区的田间和贮藏库中分别采集不同时期发病植株和块茎,进行症状描述,并进行病原菌分离鉴定和致病性测定,以及室内药剂筛选。结果表明,该病害在茎秆上形成褐色长条斑;叶片上症状多不明显;薯块上病斑近圆形或不规则形,略下陷,逐渐褐色腐烂;在发病部位形成分生孢子盘;马铃薯炭疽病菌菌丝无色至浅褐色,有隔膜;分生孢子盘黑褐色,其上着生有分隔和顶部渐尖的刚毛;分生孢子棒状,无色;分生孢子梗无色,具分隔,紧密排列在分生孢子盘上;通过ITS序列同源性分析,与已报道的Colletotrichum coccodes相似性达100%。基于病原形态特征和ITS序列分析结果,鉴定该病原菌为球炭疽菌(Colletotrichum coccodes),其引起的病害为马铃薯炭疽病。经室内毒力测定,甲基硫菌灵、苯醚甲环唑、丙环唑.苯醚甲环唑、苯醚甲环唑.嘧菌酯、肟菌.戊唑醇、咪鲜胺锰盐和噻霉酮对马铃薯炭疽病菌的EC50小于10,理论上对该病害有较好的控制作用。

Identification of potato black dot disease caused by Colletotrichum coccodes and screening for fungicides in the laboratory in Gansu Province

The plants and tubers at different stages were collected from major potato planting areas in Gansu Province in the field and storage. Symptoms were described. Isolation, identification and pathogenicity test were conducted for screening for the pathogen causing potato black dot disease. The results showed that the symptoms of stem were long brown spots, but not obvious on the leaves. The nearly round or irregular spots occurred on the infected potato tuber. Furthermore, the spots were slightly sinking and gradually decay with brown. More acervuli with black setae were often produced on the infected stems and potato tuber, and the setae were septate and pointed at the tip. The hyphae with septa were colorless to light brown in color and superficial. The conidia were rod like and colorless. The conidiophores with septa were closely packed on the acervulus and colorless. The ITS sequence analysis exhibited 100% identity with that of Colletotrichum coccodes. The morphologic characteristics and ITS sequence analysis both indicated that the pathogenic fungus was C. coccodes and the disease was black dot disease. Through toxicity determination, the EC50 of thiophanate methyl, difenoconazole, propiconazole·difenoconazole, difenoconazole·azoxystrobin, trifloxystrobin·tebuconazole, prochloraz manganese chloride complex and benziothiazolinone were less than 10, which theoretically suggested that these fungicides could control potato black dot. The study was the first report for potato black dot in China, which helped control this disease.