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Effective antibiotics against 'Candidatus Liberibacter asiaticus' in HLB-affected citrus plants identified via the graft-based evaluation.

Zhang M, Guo Y, Powell CA, Doud MS, Yang C, Duan Y - PLoS ONE (2014)

Bottom Line: Results of principal component (PCA) and hierarchical clustering analyses (HCA) demonstrated that 29 antibiotics were clustered into 3 groups: highly effective, partly effective, and not effective.The non-effective group, including 11 antibiotics alone with three controls, such as Amikacin, Cinoxacin, Gentamicin, Kasugamycin, Lincomycin, Neomycin, Polymixin B and Tobramycin, did not eliminate or suppress Las in the tested concentrations, resulting in plants with increased titers of Las.The effective and non-phytotoxic antibiotics could be potential candidates for control of citrus HLB, either for the rescue of infected citrus germplasm or for restricted field application.

View Article: PubMed Central - PubMed

Affiliation: Guangxi University, Nanning, 530004, China; Institute of Food and Agricultural Science-Indian River Research and Education Center, University of Florida, Fort Pierce, FL 34945, United States of America.

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. Actidione and Oxytetracycline were the most phytotoxic to citrus with less than 10% of scions surviving and growing; therefore, this data was not used in additional analyses. Results of principal component (PCA) and hierarchical clustering analyses (HCA) demonstrated that 29 antibiotics were clustered into 3 groups: highly effective, partly effective, and not effective. In spite of different modes of actions, a number of antibiotics such as, Ampicillin, Carbenicillin, Penicillin, Cefalexin, Rifampicin and Sulfadimethoxine were all highly effective in eliminating or suppressing Candidatus Liberibacter asiaticus indicated by both the lowest Las infection rate and titers of the treated scions and inoculated rootstock. The non-effective group, including 11 antibiotics alone with three controls, such as Amikacin, Cinoxacin, Gentamicin, Kasugamycin, Lincomycin, Neomycin, Polymixin B and Tobramycin, did not eliminate or suppress Las in the tested concentrations, resulting in plants with increased titers of Las. The other 12 antibiotics partly eliminated or suppressed Las in the treated and graft-inoculated plants. The effective and non-phytotoxic antibiotics could be potential candidates for control of citrus HLB, either for the rescue of infected citrus germplasm or for restricted field application.

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Related in: MedlinePlus

Dendrogram of the hierarchical cluster analysis for antibacterial activity against Las with 29 antibiotics.
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pone-0111032-g003: Dendrogram of the hierarchical cluster analysis for antibacterial activity against Las with 29 antibiotics.

Mentions: In hierarchical cluster analysis, antibiotics were classified on the basis of scion infected percentage, Las transmission percentage, and Ct values of scions and rootstocks in the inoculated plants, without considering the information about antibiotic class. The results obtained by HCA were shown as a dendrogram (Fig. 3) in which three well-defined clusters are visible in terms of their similarities. A group of antibiotics (group I), composed of six compounds, AMP, CAR, PEN, CEF, RIM and SDX, was clearly discernible. These antibiotics were associated with high antibacterial activities against Las, resulting in the lowest percentages of Las-infected scions and transmission of Las bacterium into the rootstocks, and the lowest bacterial titers in the scions and rootstocks of the graft-inoculated plants (Table 2). Group III consisting of 11 antibiotics (AMK, PMB, KSM, COL, STR, VAN, CIN, GAT, NEO, TOB and LIN) and the three solvent controls (water, DMSO and ethanol) had the lowest antibacterial effects. The highest percentage of infected scion and Las transmission and the bacterial titers (lowest Ct values) were observed in the plants grafted with scions soaked in these group III chemicals (Table 2). Thus, these compounds were not effective in eliminating or suppressing Las bacterium. Group II, which included CHL, VA, SMZ, CYS, KAN, SPT, ZS, HYG, RIX, CIP, STZ and RIF, partly eliminated or suppressed Las when compared to Group I and Group III data (Table 2 and Table 3).


Effective antibiotics against 'Candidatus Liberibacter asiaticus' in HLB-affected citrus plants identified via the graft-based evaluation.

Zhang M, Guo Y, Powell CA, Doud MS, Yang C, Duan Y - PLoS ONE (2014)

Dendrogram of the hierarchical cluster analysis for antibacterial activity against Las with 29 antibiotics.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4220982&req=5

pone-0111032-g003: Dendrogram of the hierarchical cluster analysis for antibacterial activity against Las with 29 antibiotics.
Mentions: In hierarchical cluster analysis, antibiotics were classified on the basis of scion infected percentage, Las transmission percentage, and Ct values of scions and rootstocks in the inoculated plants, without considering the information about antibiotic class. The results obtained by HCA were shown as a dendrogram (Fig. 3) in which three well-defined clusters are visible in terms of their similarities. A group of antibiotics (group I), composed of six compounds, AMP, CAR, PEN, CEF, RIM and SDX, was clearly discernible. These antibiotics were associated with high antibacterial activities against Las, resulting in the lowest percentages of Las-infected scions and transmission of Las bacterium into the rootstocks, and the lowest bacterial titers in the scions and rootstocks of the graft-inoculated plants (Table 2). Group III consisting of 11 antibiotics (AMK, PMB, KSM, COL, STR, VAN, CIN, GAT, NEO, TOB and LIN) and the three solvent controls (water, DMSO and ethanol) had the lowest antibacterial effects. The highest percentage of infected scion and Las transmission and the bacterial titers (lowest Ct values) were observed in the plants grafted with scions soaked in these group III chemicals (Table 2). Thus, these compounds were not effective in eliminating or suppressing Las bacterium. Group II, which included CHL, VA, SMZ, CYS, KAN, SPT, ZS, HYG, RIX, CIP, STZ and RIF, partly eliminated or suppressed Las when compared to Group I and Group III data (Table 2 and Table 3).

Bottom Line: Results of principal component (PCA) and hierarchical clustering analyses (HCA) demonstrated that 29 antibiotics were clustered into 3 groups: highly effective, partly effective, and not effective.The non-effective group, including 11 antibiotics alone with three controls, such as Amikacin, Cinoxacin, Gentamicin, Kasugamycin, Lincomycin, Neomycin, Polymixin B and Tobramycin, did not eliminate or suppress Las in the tested concentrations, resulting in plants with increased titers of Las.The effective and non-phytotoxic antibiotics could be potential candidates for control of citrus HLB, either for the rescue of infected citrus germplasm or for restricted field application.

View Article: PubMed Central - PubMed

Affiliation: Guangxi University, Nanning, 530004, China; Institute of Food and Agricultural Science-Indian River Research and Education Center, University of Florida, Fort Pierce, FL 34945, United States of America.

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. Actidione and Oxytetracycline were the most phytotoxic to citrus with less than 10% of scions surviving and growing; therefore, this data was not used in additional analyses. Results of principal component (PCA) and hierarchical clustering analyses (HCA) demonstrated that 29 antibiotics were clustered into 3 groups: highly effective, partly effective, and not effective. In spite of different modes of actions, a number of antibiotics such as, Ampicillin, Carbenicillin, Penicillin, Cefalexin, Rifampicin and Sulfadimethoxine were all highly effective in eliminating or suppressing Candidatus Liberibacter asiaticus indicated by both the lowest Las infection rate and titers of the treated scions and inoculated rootstock. The non-effective group, including 11 antibiotics alone with three controls, such as Amikacin, Cinoxacin, Gentamicin, Kasugamycin, Lincomycin, Neomycin, Polymixin B and Tobramycin, did not eliminate or suppress Las in the tested concentrations, resulting in plants with increased titers of Las. The other 12 antibiotics partly eliminated or suppressed Las in the treated and graft-inoculated plants. The effective and non-phytotoxic antibiotics could be potential candidates for control of citrus HLB, either for the rescue of infected citrus germplasm or for restricted field application.

Show MeSH
Related in: MedlinePlus