掌叶大黄根腐病病原菌的分离与鉴定

Isolation and identification of the pathogens causing Rheum palmatum root rot

通过对甘肃礼县种植的二年生掌叶大黄根腐病发病部位分离纯化,然后利用根部离体接种法致病性测定,旨在明确导致掌叶大黄根腐病的病原物,为其防治提供理论依据。结果表明,从掌叶大黄根腐病株中共获得8种分离物,主要致病菌分别为粉红单端孢霉、尖孢镰刀菌和立枯丝核菌,其分离频率随病原菌种类和植株发育进程而异,粉红单端孢霉和立枯丝核菌在不同生长期发病部位均可分离获得,分离频率分别为41.18%～55.56%和3.03%～44.44%,尖孢镰刀菌仅在生长后期获得,分离频率为9.09%。刺伤大黄幼根接种致病菌后,根腐病发病率均较无刺伤接种显著提高。尖孢镰刀菌潜育期最短,病斑面积最大,致病力最强,而粉红单端孢霉和立枯丝核菌潜育期长,病斑面积小,致病力相对较弱。以上说明伤口有助于掌叶大黄根腐病病原菌的侵染,建议掌叶大黄定植和栽培管理过程中要尽量保证植株的完整性,严防伤口产生。另外,利用根部离体接种法进行根腐病致病性测定操作简单,回接时间短,再分离率高,结果可靠,可在植物根部病害研究中应用。

To provide a scientific basis for control of Rheum palmatum root rot,potential pathogens were isolated from rotted roots and identified before use in root segment inoculation pathogenicity tests.Eight species of fungi were isolated from rotted roots of biennial R.palmatum cultivated in Lixian county of Gansu.The chief pathogens were Trichothecium roseum,Fusarium oxysporum,and Rhizotonia solani.Their isolation frequencies varied with the pathogens and plant growth stage.T.roseum and R.solani could be isolated from different growth stages with frequencies of 41.18%-55.56% and 3.03%-44.44%,respectively.However,F.oxysporum could only be isolated from plants in the late growth stages,with an isolation frequency of 9.09%.The incidence of root rot after inoculation of pathogens into wounded radicles was significantly higher than that into non-wounded radicles.The incubation period of F.oxysporum was short with large disease spots indicating a strong pathogenic ability,while the incubation period of T.roseum and R.solani were long with small spots indicating a weak pathogenic ability.All the above shows that wounds are helpful for root rot pathogens to infect the plants.It suggests that transplanting and cultivation should be done carefully to maintain the plant integrity and prevent wounding.In addition,root segment inoculation is easy to do and may be extensively used in plant root disease research for its short inoculation time,high re-isolation frequency,and reliable result.