青枯雷尔氏菌在芝麻植株内的分布及消长动态

芝麻青枯病是我国南方芝麻生产上的重要土传病害。通过测定健康植株、不同发病时期的自然病株及人工接种病株内不同部位青枯雷尔氏菌数量,旨在明确病菌在芝麻植株内的分布及消长动态。结果表明:发病初期,病株内青枯雷尔氏菌总数量随着病情的发展而增加,之后随着病情严重度的加重而下降。病菌的致病力则随着病情发展呈现持续上升的趋势。检测的所有芝麻健株各部位均无青枯雷尔氏菌分布,说明芝麻植株不存在无症状侵染现象。青枯雷尔氏菌在芝麻病株内的分布呈现丰富的多态性,自然病圃和灌根接种的Ⅱ类、Ⅲ类病株各部位菌量分布随着植株高度的升高而递减,但其Ⅰ类病株中下部菌量却高于基部。针刺接种的Ⅰ类、Ⅱ类和Ⅲ类病株,接种点以下的根部和基部均有青枯雷尔氏菌分布,说明青枯雷尔氏菌不仅可随植物蒸腾向上扩散,也可向下蔓延。

Distribution and Dynamic Change of Ralstonia solanacearum in Sesame Plant

Bacterial wilt of sesame is one of the most destructive soil?borne diseases in major sesame pro?duction areas of south China. To illustrate the distribution and the population dynamics of Ralstonia so?lanacearum in its infected sites of sesame seedlings,the population of R. solanacearum in the infected sesame seedlings treated by different methods were investigated in this study,including irrigating root inoculation,pin?prick inoculation and spontaneous infected in infected field,compared with the healthy control group.At the ini?tial stage,the total population of R. solanacearum increased rapidly in the infected sesame seedlings associated with symptoms on the sesame seedlings.However,the total population of R. solanacearum began to decline at the later period with severity of infection in sesame seedlings. The results indicated that the pathogenicity of R. so?lanacearum showed an increasing tendency on the infected sesame seedlings.No the pathogens of R. solanacearum were detected in all the healthy sesame seedlings by contrast with the sesame seedlings response to R. so?lanacearum,which indicated that asymptomatic infection of the seseame seedlings response to R. solanacearum did not existed.The population of R. solanacearum in its infected sites of the type Ⅱ and Ⅲ infected sesame seedlings treated respectively by irrigating root inoculation and spontaneous infected in infected field began to decrease progressively in contrast to the height of infected sites of sesame seedlings.But the population of R. so?lanacearum in its infected sites of the type Ⅰ infected sesame seedlings in the middle was higher than in its roots and stems.It was observed that a highly abundant polymorphism distribution of R. solanacearum presented in the infected sesame seedlings.The pathogens of R. solanacearum were detected under its infected sites of the type Ⅰ,Ⅱand Ⅲinfected sesame seedlings treated by pin?prick inoculation.This result showed that the mobil?ity of R. solanacearum in its infected sites of the infected sesame seedlings could move upwards and down?wards.