北京市生菜链格孢根腐病病原菌鉴定

Identification of the pathogens causing lettuce Alternaria root rot in Beijing

为明确北京市生菜链格孢根腐病的病原菌种类,采用常规组织分离法分离获得病原菌,依据柯赫氏法则对病原菌进行致病力检测,并利用分子生物学技术结合形态学鉴定确定病原菌分类地位。结果显示,从生菜病样组织中分离到2种病原菌共18株,形态学鉴定结果为芸薹链格孢Alternaria brassicae和万寿菊链格孢A.tagetica,分离比例分别为55.6%和44.4%,且二者均能单独侵染生菜根部,前者致病力较后者强,亦能复合侵染。对致病菌株进行GAPDH基因的PCR扩增和测序,并建立了基于GAPDH基因序列的系统发育树,聚类分析结果与形态学鉴定结果一致,因此证实北京市生菜链格孢根腐病是由芸薹链格孢和万寿菊链格孢复合侵染所致。

In order to clarify the cause of dead lettuce in Beijing and the types of pathogens causing root rot of lettuce, the isolated pathogens were tested for pathogenicity and the classification status of the pathogens was determined by using molecular techniques combined with morphological identification. The results showed that 18 strains of pathogens were isolated. The morphological identification results were Alternaria brassicae and A. tagetica. The segregation ratios were 55.6% and 44.4%, respectively. All of them could infect the roots of lettuce alone. The former had stronger pathogenicity than the latter but could also coinfect. The pathogenic strains were amplified and sequenced based on the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene. All the sequences were submitted to the GenBank database and the accession numbers were obtained. A phylogenetic tree based on the GAPDH gene sequences was established. The results of phylogenetic analysis were consistent with the morphological identification results, suggesting that the root rot of lettuce in Beijing was caused by A. alternata and A. tagetica.