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Journal of Integrative Agriculture  2019, Vol. 18 Issue (10): 2284-2293    DOI: 10.1016/S2095-3119(19)62605-5
Special Issue: 植物病毒合辑Plant Virus
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Limited infection by ‘Candidatus Liberibacter asiaticus’ in ‘Valencia’ sweet orange trees in the presence of Citrus tristeza virus
FU Shi-min1, Cristina Gouin3, ZHOU Chang-yong1, John S. Hartung2
1 National Citrus Engineering Research Center, Citrus Research Institute, Chinese Academy of Agricultural Sciences/Southwest University, Chongqing 400712, P.R.China
2 Molecular Plant Pathology Laboratory, United States Department of Agriculture-Agricultural Research Service, Beltsville, Maryland 20705, USA
3 Biotechnology and Regulatory Services, United States Department of Agriculture-Animal and Plant Health Inspection Service, Riverdale, Maryland 20705, USA
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Abstract  Huanglongbing (HLB) is the most destructive disease of citrus and is associated with ‘Candidatus Liberibacter asiaticus’ (CLas), a member of the α-proteobacteria. Citrus tristeza virus (CTV) is another pathogen of citrus with very great historic as well as current importance. Both CLas and CTV are phloem-restricted pathogens. A severe CTV isolate, CTV-B6, and CLas-B232 induce a group of symptoms of phloem dysfunction that overlap, but the mild isolate CTV-B2 does not cause any loss to commercial trees. Prior inoculation and establishment of CLas-B232 did not affect subsequent establishment of either CTV-B2 or CTV-B6, while super infection by CLas-B232 was reduced by prior establishment of CTV-B2 and to a lesser extent by prior infection with CTV-B6. Trees co-infected with CTV-B6 and CLas-B232 developed more severe symptoms, typical of CTV-B6, than either of the two pathogens co-infected with CTV-B2. In this study, we confirmed that CLas established in the rootlets earlier and with higher concentration than in leaves. The distribution of CLas in the plant infected by CLas-B438 alone and with CTV-B2 fits a previously proposed model but CLas was more sporadically distributed in a plant co-infected by CLas and CTV-B2 than in a plant infected by CLas alone. These biological phenomena are aligned with previously analyzed transcriptome data and the study provides a novel idea that mild CTV strains may provide some protection against CLas by limiting its multiplication and spread. The protective effect may be due to opposite regulation of key host defense pathways in response to CTV-B2 and CLas-B438.
Keywords:  huanglongbing        plant defense        plant protection  
Received: 21 September 2018   Accepted:
Fund: This research was funded by the National Natural Science Foundation of China (31671992), the National Key R&D Program of China (2018YFD0201500), the Fundamental Research Funds for the Central Universities of China (XDJK2018C032), the China Postdoctoral Fund (2018M633307), and also supported by the Agricultural Research Serves, United States Department of Agriculture (USDA ARS).
Corresponding Authors:  Correspondence ZHOU Chang-yong, E-mail:; John S. Hartung, Tel: +1-301-504-6374, E-mail:   
About author:  FU Shi-min, E-mail:;

Cite this article: 

FU Shi-min, Cristina Gouin, ZHOU Chang-yong, John S. Hartung. 2019. Limited infection by ‘Candidatus Liberibacter asiaticus’ in ‘Valencia’ sweet orange trees in the presence of Citrus tristeza virus. Journal of Integrative Agriculture, 18(10): 2284-2293.

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