火龙果茎腐病致病菌的鉴定

Identification on Pathogenic Fungi of Dragon Fruit Stem Rot Disease

为弄清火龙果茎腐病的病原和分类地位,并进一步为该病害的有效防治提供理论依据。本研究从琼海、临高、陵水等地广泛采集病样。经田间症状调查、组织纯化培养、病原形态观察、致病力测定、真菌ITS序列和系统进化分析,鉴定了该病害的病原。结果表明:病原分离物具有典型的镰刀菌形态特征,菌丝浓密,产生紫色素,小型分生孢子新月形,大型分生孢子镰刀形,有多个隔;而在ITS序列分析中,代表菌株47A4和47A5与NCBI数据库中尖孢镰刀菌的多条ITS序列(登录号分别为KJ653447.1, DQ535184.1和KM268692.1)相似性达100%;系统进化树上,47A4和47A5与尖孢镰刀菌聚在同一分支上,遗传距离最近,而与非纯培养镰刀菌克隆3.91E在不同分支上,遗传距离远。结合形态特征、序列分析和系统进化分析,将火龙果茎腐病的病原鉴定为尖孢镰刀菌(Fusarium oxysporum)。研究结果对火龙果茎腐病流行规律、致灾机理的研究具有重要的指导作用。

In order to understand the pathogen and classification status of dragon fruit stem rot disease,and further provide a theoretical basis for the effective control of the disease.This research was carried out.Several dragon fruit samples were collected from Qionghai,Lingao,Lingshui and so on.The pathogen of dragon fruit stem rot disease was studied by field symptom survey,routine tissue separation and purification,morphological identification,patho- genicity determination,analysis of fungic ITS and phylogene.The results showed that the pathogen separation had typical morphological characteristics of Fusarium oxysporum.There were dense myceliums.At the same time,it could produce purple pigment.The microconidia were crescent-shaped,and the macroconidium was sickle-shaped with multiple septums.The ITS sequences of 47A4 and 47A5 were similar to those ofFusarium oxysporum (Accession number of KJ653447.1,DQ535184.1 and K_M268692.1,respectively)with the similarity of 100%.By the phylogentic analysis,47A4 and 47A5 were clustered on the same branch of several sequences ofFusarium oxysporurn.They were clustered on the different branch of uncultured fusarium clone 3.91E (Accession NO.235759.1)with the farthest of genetic distance.Together with morphological characteristics,analysis of sequences and phylogentic, the pathogen of dragon fruit stem rot disease was identified Fusarium oxysporum.These research results had great significance to find out the epicemic law and pathogenesis of the stem rot disease of dragon fruit.