进境哈萨克斯坦向日葵种子中向日葵黑茎病菌的鉴定

Identification of the quarantine fungus Plenodomus lindquistii from the sunflower seeds imported from Kazakhstan

自进境哈萨克斯坦向日葵种子中,采用常规平板分离法获得1株疑似向日葵黑茎病菌Plenodomus lindquistii菌株LL4,通过生物学性状、ITS序列测定和比对分析及致病性测定等方法对其进行了鉴定。结果表明,该病菌在PDA平板上培养初期菌丝无色,分隔分枝多,后期菌丝褐色或深褐色,常膨大;分生孢子器暗褐色,分散或聚集,球形、近球形或不规则形,大小为71.2-361.8μm;分生孢子形态变化较大,无色,单孢,肾形至椭圆形,大小为3.6-8.2μm×2.2-3.7μm,常含有2个油球;培养期间未见有性阶段。基于ITS序列分析比对发现,菌株LL4与Gen Bank中多个向日葵黑茎病菌分离物序列同源性达99%以上,系统进化树显示其与其它向日葵黑茎病菌分离物聚在同一个分支。菌株LL4可侵染向日葵根茎部,造成典型黑茎病症状。表明分离获得的菌株LL4为向日葵黑茎病菌P.lindquistii。

Strain LL4 was isolated from sunflower seeds imported from Kazakhstan by using conventional PDA plate method. To identify strain LL4,the biological traits,ITS sequencing and its pathogenicity were analyzed. The results showed that the strain LL4 grew well on PDA medium,and the mycelium was colorless at early culture stage with separate branches,and then turned brown or dark brown at late culture stage,often inflated. The pycnidia were dark brown,dispersed or aggregated,spherical,nearly spherical or irregular in shape,with a size of 71. 2- 361. 8 μm; the conidia form varied widely,colorless,single-spored,kidney-shaped or oval,with a size of 3. 6- 8. 2 μm × 2. 2- 3. 7 μm,which often contained two oil balls; there was no sexual stage in the culture period. The ITS sequence of strain LL4 was compared with those in Gen Bank database,showing that the sequence shared more than 99%identity with several sequences of Plenodomus lindquistii（ Frezzi） in Gen Bank. The phylogenetic tree showed that the strain LL4 gathered with other P. lindquistii isolates in a branch. The strain LL4 could infect sunflower stem,formed typical symptoms of black stem. Based on morphological characteristics,ITS sequence analysis and pathogenicity test results,the strain LL4 was identified as P. lindquistii.