玉米穗腐病样品中木贼镰孢菌的分离鉴定及生物学特性

为明确甘肃玉米（Zea mays L.）穗腐病的病原菌种类，在甘肃4大生态区采集玉米穗腐病样品，以组织分离法进行病原物的分离培养，对分离得到的镰孢菌（Fusarium）菌落进行纯化和单孢分离后，以形态学为基础，参照 Leisle 分类系统进行鉴定。结果表明：分离到271株镰孢菌菌株中有14株经形态学鉴定为木贼镰孢菌（F. equiseti），占分离镰孢菌的5.17%。按照柯赫氏法则用混合菌株接种法进行致病性测定，证实木贼镰孢菌对玉米果穗的致病性。选取3株木贼镰孢菌菌株进行rDNA-ITS基因序列分析，将PCR产物回收测序后在GenBank上比对，菌株GSJC5-2-1和GSZY16-1-1的序列与GenBank上登记的木贼镰孢菌GQ505694和GQ505743；菌株GSZN7-2-2与FJ459981，HQ248199，HQ380774，AB425996和FJ459975的亲缘关系最近，同源性达99%。利用DNAStar软件绘制其系统发育树状图，菌株GSJC5-2-1，GSZY16-1-1和GSZN7-2-2分别与以上亲缘关系最近的木贼镰孢菌位于系统发育树的同一分支，聚为一类，与形态学的鉴定结果相一致。木贼镰孢菌GSJC5-2-1的生长温度范围为15～35℃，最适温度为25℃；菌落在pH值为4～10的培养基上能够迅速扩展，最适pH为6～7；碳源和氮源对木贼镰孢菌菌丝生长影响相对稳定；完全黑暗条件下，菌丝扩展最快；病原菌菌丝致死温度为60℃下10 min。

Isolation,Identification and Biological Characteristics of Fusarium equiseti from Maize Ear Rot Samples

In order to know the pathogens of maize ear rot in Gansu province, samples were collected from 4 ecological zones in September, 2009. The pathogens were isolated by tissue isolation method from cankered maize ear on standard medium. Fusarium colonies obtained were identified according to the taxonomic system of Leisle after being subcultured and single-spored. Results showed the 14 isolates in total 271 were identified as F. equiseti, contributing about 5.17% of the Fusarium isolates. According to Koch's Postulate, the pathogenicity of F. equiseti was tested with mixed isolates on maize. It was verified that F. equiseti was pathogenic to maize ear. Three F. equiseti isolates were selected for rDNA-ITS gene sequence analysis. The PCR products of the three isolates were collected, purified, and sequenced. The sequences were aligned in GenBank. It was showed that isolated GSJC5-2-1 and GSZY16-1-1 had a very close relationship with GQ505694 and GQ505743; isolated GSZN7-2-2 with FJ459981, HQ248199, HQ380774, AB425996 and FJ459975 downloaded from GenBank, and their max similarity were 99%. Microsoft DNAStar was used to draw the phylogenetic tree. Isolated GSJC5-2-1, GSZN7-2-2 and GSZY16-1-1 were clustered in the same group with GQ505694 and GQ505743 which was consistent with the results of morphological identification. These results also indicated that The Fusarium could grow under15～35℃, pH 4～10, with optimal condition at 25℃, pH 6～7. Vegetative growth of F. equiseti was found to be relative steadily influenced by both nitrogen source and carbon source. The best cultural condition for mycelial was 24 h under dark. The lethal temperature of F. equiseti hypha was 60℃ for 10 min.