新疆棉田一种新棉铃病害病原菌的鉴定

Identification of Pathogens of a New Cotton Boll Disease in Xinjiang Cotton Field

【目的】自2015年以来在新疆棉田出现一种与一般烂铃病害症状有明显区别的新棉铃病害,导致僵铃与裂铃,在潮湿的情况下铃面产生橄榄黑色的霉层。明确其病原种类对于该病害的防治具有重要意义。【方法】自南北疆20个植棉单位采集了38份病样,采用常规稀释分离法和单孢分离法对病原进行分离和纯化。然后,依据采样地点、棉花品种和菌落特征选取20个代表菌株,通过形态学观察,并运用核糖体DNA内转录间隔区(rDNA internal transcribed spacer,rDNA-ITS)、肌动蛋白(ACT)和翻译延长因子1-α(TEF1-α)的基因序列分析,对菌株进行鉴定。根据柯赫氏法则,选择其中3个代表性菌株C2、C13和C7的孢子悬浮液接种棉铃,观察并记录其发病情况,并且对病铃进行再分离,观察再分离菌株与接种菌株的异同。【结果】分离得到的菌株都属于枝孢属真菌(Cladosporium),根据其形态特征和分子生物学分析,20个供试菌株中有13个属于C.cladosporioides,4个属于C.velox,3个属于C.limoniforme。3个代表性菌株C2、C13和C7在有伤接种的情况下,发病症状与田间症状相似;无伤接种时发病较晚,病斑扩展也较慢。从病斑处再分离,可分离出接种菌株。【结论】新疆棉田导致僵铃与裂铃这种新棉铃病害的病原菌为3种枝孢菌:C.cladosporioides、C.velox和C.limoniforme,其中C.cladosporioides为优势种。

[Objective]Since 2015,there has been a new cotton boll disease in Xinjiang cotton fields which was obviously different from the common boll rot,leading to stiffness and cracking boll.Olive-black mildew layer was observed on the surface of diseased bolls under wet conditions.It is of great significance to clarify the types of pathogens for the prevention of the disease.[Method]From 20 cotton planting locations of Xinjiang,38 samples of stiffness and cracking boll disease were collected,and the pathogens were isolated and purified by conventional dilution separation and single-spore separation.And 20 representative strains were selected according to sampling location,cotton varieties and colony characteristics.The selected strains were identified by morphological observation and sequence analysis of rDNA internal transcribed spacer(rDNA-ITS),actin(ACT)and translation elongation factor 1-α(TEF1-α)gene.According to Koch’s law,the spore suspensions of three representative strains C2,C13 and C7 were inoculated to observe and record the incidence of the disease,and the diseased bolls were used for re-separation to observe the similarities and differences between the re-isolated strains and the inoculated strains.[Result]The result shows that these isolates belong to the Cladosporium,and according to its morphological characteristics and molecular biology analysis,13 of the 20 strains belong to C.cladosporioides,4 strains belong to C.velox,3 strains belong to C.limoniforme.The symptoms of three representative strains C2,C13 and C7 were similar to those in the field when inoculated with injuries,and the disease spread was slower when inoculated without injuries.The inoculated strains can be separated from the lesions.[Conclusion]The new cotton boll disease causing stiffness and cracking in Xinjiang cotton fields is caused by three species of Cladosporium,C.cladosporioides,C.velox and C.limoniforme,with C.cladosporioides as the dominant species.