霸王花褐腐病的病原鉴定

Identification of the pathogen causing brown rot of Hylocereus undatus

【目的】明确导致广东省霸王花Hylocereusundatus褐腐病的病原种类．【方法】通过病组织分离、致病性测定、形态学观察及rDNA序列分析等方法对广东省霸王花褐腐病病原进行了种类鉴定．【结果和结论】在PDA培养基上，病原菌的菌落为深灰色，绒毛状．产生2种类型的节孢子：一种为浅色、薄壁的柱状孢子，大小为（5．00—10．69）μm×（2．61～4．52）μm；另一种为褐色、厚壁、圆形或椭圆形、基部平截、成链的孢子，大小为（5．15～12．39）μm×（3．87～6．07）um．应用真菌通用引物ITSI和ITS4进行PCR，获得该病原菌579bp的18S-28SrDNAITS序列．BLAST结果显示，该序列与Neoscytalidiumdimidiatum火龙果菌株的18S-28SrDNAITS序列相似性最高，为99％-100％．这些研究结果表明，引起广东省霸王花褐腐病的病原菌为N.dimidiatum．

[ Objective ] To confirm the pathogen species that caused brown rot disease on Hylocereus unda- tus. [ Method ] Diseased tissue isolation, indoor pathogenicity test, morphological observation and rDNA sequence analysis were used to confirm the pathogen species. [ Result and conclusion ] The colonies of the fungus were dark grey and fluffy on potato dextrose agar （PDA） medium. Two kinds of arthrospore were observed on PDA medium. One was columnar conidium with light-colored, thin-walled and （5.00 - 10. 69） μm x （2. 61 -4.52） μm in size, and the other was chained conidium with dark brown, thick- walled, circular or oval, base truncate and （ 5.15 - 12.39 ）μm （ 3.87 - 6.07 ） μm in size. Using PCR with primers ITS1 and ITS4 for internal transcribed spacer （ITS） sequences of fungal 18S-28S rD- NA, the sequence was cloned to be 579 bp in length. The BLAST results showed that the sequence had the highest sequence identity with that of Neoscytalidium dimidiatum strains isolated from pitahaya （99% -100% ）. These results indicated that night-blooming cereus brown rot in Guangdong was caused by N. dimidiatum.