|ZHANG, MU-QING - University Of Florida|
|GUO, YING - University Of Florida|
|POWELL, CHARLES - University Of Florida|
|YANG, CHUANYU - University Of Florida|
Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/25/2014
Publication Date: 11/5/2014
Citation: Zhang, M., Guo, Y., Powell, C., Doud, M.S., Yang, C., Duan, Y. 2014. Effective antibiotics against 'Candidatus Liberibacter asiaticus' in HLB-affected citrus plants identified via the graft-based evaluation. PLoS One. 9(11):e111032. doi: 10.1371/journal.pone.0111032.
Interpretive Summary: Citrus huanglongbing (HLB) is a devastating bacterial disease of citrus. In the United States, HLB is caused by the bacterium ‘Candidatus Liberibacter asiaticus’ (Las). Currently, there is no adequate control for this disease. Although HLB resistant citrus varieties are being developed to combat the disease, it will likely take over 10 years to produce and evaluate these resistant varieties in Florida. Since Florida citrus trees are already infected, it is essential to develop an efficient treatment to combat HLB in the interim. Development of a bactericide or other therapeutic compound would provide an additional tool for the control of HLB. In this article, 31 antibiotics were screened for their ability to kill Las in infected citrus and also screened to determine if the compound is toxic to citrus. Results show that the 31 antibiotics were either highly effective, effective, or not effective at killing or suppressing Las in infected citrus. In addition, these compounds had varying levels of phytotoxicity towards the citrus. Actidione, Oxytetracycline, Ampicillin, Carbenicillin, Penicillin, Rifampicin, and Sulfadimethoxine were the most effective at eliminating or greatly suppressing the amount of Las bacteria in the infected citrus. However, Actidione and Oxytetracycline were the most toxic to the citrus plants. As a result of this study, effective compounds were identified that could be used to treat Las-infected citrus trees thus rescuing HLB trees from an early death.
Technical Abstract: Citrus huanglongbing (HLB), caused by three species of fastidious, phloem-limited ‘Candidatus Liberibacter’, is one of the most destructive diseases of citrus worldwide. To date, there is no established cure for this century-old and yet, newly emerging disease. As a potential control strategy for citrus HLB, 31 antibiotics were screened for effectiveness and phytotoxicity using the optimized graft-based screening system with ‘Candidatus Liberibacter asiaticus’ (Las)-infected citrus scions. Results off principal component (PCA) and hierarchical clustering analysis (HCA) demonstrated that 31 antibiotics were clustered into 3 groups, highly effective, effective, and not effective. Actidione, Oxytetracycline, Ampicillin, Carbenicillin, Penicillin, Rifampicin and Sulfadimethoxine were highly effective in eliminating or suppressing Las bacteria within both the lower scion and rootstock. The non-effective group, included Amikacin, Polymixin B, Colistinmethane, Streptomycin, Vancomycin, Cinoxacin, Gentamicin, Tobramycin, Kasugamycin, Neomycin and Lincomycin, did not eliminate or suppress Las bacteria, resulting in plants with increased titer of Las. The other 13 antibiotics could partly eliminate or suppress the Las. Actidione and Oxytetracycline were highly phytotoxic to citrus. These effective non-phytotoxic antibiotics have potential as a therapy for control of citrus HLB and other Liberibacter-associated diseases.