橘-芝麻套种模式下芝麻青枯病初侵染源分析

 净作11年的橘园首次套种芝麻,发现园内芝麻青枯病发生严重。为探明芝麻青枯病初侵染源,本研究从芝麻青枯病株上分离到菌株JXRs02,通过形态学、分子生物学以及聚类分析,鉴定其为青枯雷尔氏菌演化型I。利用针刺接种法,将JXRs02菌株接种至柑橘园中的4种杂草凹头苋、青葙、空心莲子草以及加拿大蓬,发现JXRs02能够侵染凹头苋杂草,造成枯萎症状;LAMP检测的结果显示,在凹头苋病株组织内能够检测到青枯雷尔氏菌。依据柯赫氏法则,利用分子生物学方法证明了对凹头苋杂草具有致病性的菌株和造成芝麻青枯症状的病原菌同为青枯雷尔氏菌演化型I。同时发现,在凹头苋、青葙、空心莲子草和加拿大蓬4种杂草的根际土壤中芝麻青枯病菌均能够定殖繁衍。推测凹头苋杂草可能为芝麻青枯病菌的中间寄主,凹头苋、青葙、空心莲子草和加拿大蓬等杂草根际土壤积累的菌源可能为橘园套种芝麻后青枯病的初侵染来源。本研究对制定作物青枯病的防治策略具有一定科学意义。

Analysis oninitial infection sources of sesame bacterial wilt under the interplanting mode of citrus-sesame

An outbreak of sesame bacterial wilt caused by Ralatonia solanacearum was observed after first interplanting of citrus-sesame in an 11-years old orange orchard. To investigate the original infection pathogen, a strain JXRs02 was screened from the tissues of sesame infected with Ralstonia solanacearum. By morphology, molecular biology, and cluster analysis, JXRs02 was identified as R. solanacearum phylotypeⅠ. Four kinds of weeds including Amaranthus blitum, Alligator alternanthera, Feather cockscomb and Erigeron canadensis appeared in the orange orchard were inoculated with strain JXRs02 by pin prick. The results showed that JXRs02 could infect and cause wilt symptoms in Am. blitum. And the pathogen in the infected tissues of Am. blitum was identified as R. solanacearum by Loop-mediated isothermal amplification (LAMP). According to Koch’s postulates, the molecular biological methods were applied to verify that the pathogenic strains which are pathogenic to the Am. blitum or the pathogen causing the symptoms of sesame wilt are the R. solanacearum strains of phylotype I. Meanwhile, the results also showed that R. solanacearum isolated from the infected tissues of sesame could multiply in the rhizospheric soil of Am. blitum, Al. alternanthera, F. cockscomb and E. canadensis. These results indicated that Am. blitum, Al. alternanthera, F. cockscomb and E. canadensis may be the intermediate host of R. solanacearum, and the pathogen accumulated in its rhizospheric soil may be the primary source of R. solanacearum after citrus trees were interplanted with sesame cultivars. These data could provide scientific guidance on disease control strategies of bacterial wilt disease on crops.