Abstract
Huanglongbing (HLB), which is caused by the phloem-limited bacterium ‘Candidatus Liberibacter asiaticus,’ is an economically important disease of citrus in many regions of the world. Due to the significant damage caused by the HLB disease in recent years, the use of antibiotics was recommended for the therapy of this destructive disease. Products with active ingredients oxytetracycline and streptomycin have been approved for the control of the HLB via foliar application. However, previous work raised questions about the efficacy of foliar delivery of antibiotics in the field. In this study, we examined the effects of a variety of adjuvants on the uptake of oxytetracycline and streptomycin using the foliar application. We also compared the efficiency of foliar application of oxytetracycline and streptomycin with trunk injection. The ‘Ca. L. asiaticus’ titers in citrus plants were measured using quantitative PCR, and the levels of antibiotics were determined using the ELISA assay. Our results include extremely low levels of oxytetracycline and streptomycin in leaves that were covered during foliar application, indicating that neither streptomycin nor oxytetracycline was successfully systemically delivered by foliar application even after being mixed with adjuvants. Likewise, the ‘Ca. L. asiaticus’ titer0 was not affected by any of the foliar applications. High levels of streptomycin were detected in leaves that were exposed to direct foliar application, indicating that streptomycin was adsorbed or bound to citrus leaves. On the other hand, the trunk injection of oxytetracycline resulted in high levels of this antibiotic in leaves and significantly reduced the level of ‘Ca. L. asiaticus’ titer in citrus trees. Unfortunately, the trunk injection of streptomycin resulted in low levels of streptomycin in citrus leaves and did not affect the ‘Ca. L. asiaticus’ titer, indicating that streptomycin was either bound in the xylem of citrus trees or it was not applied in sufficient quantity required for the inhibition of ‘Ca. L. asiaticus.’ Taken together, our current results demonstrated that foliar application of oxytetracycline and streptomycin did not effectively deliver antibiotics in citrus despite using adjuvants. Our results also suggested that oxytetracycline could be more effective against the HLB pathogen than streptomycin, which is possibly due to differences between the two in systemic movement in citrus trees.
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Claims 10
Claim · model-written summary
Foliar oxytetracycline yielded extremely low concentrations in covered citrus leaves, even with adjuvants.
- Organ / stage
- leavese0
- Treatment
- foliar applicatione0
- Outcome
- levels of oxytetracyclinee0
- Direction
- extremely lowe0
CitrusNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“extremely low levels of oxytetracycline and streptomycin in leaves that were covered during foliar application”
t0“Citrus”
Claim · model-written summary
Foliar streptomycin yielded extremely low concentrations in covered citrus leaves, even with adjuvants.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“extremely low levels of oxytetracycline and streptomycin in leaves that were covered during foliar application”
t0“Citrus”
Claim · model-written summary
Foliar antibiotic treatments did not affect Ca. L. asiaticus titers.
- Treatment
- foliar applicationse0
- Interactor
- ‘Ca. L. asiaticus’e0pathogen
- Outcome
- ‘Ca. L. asiaticus’ titer0e0
- Direction
- not affectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the ‘Ca. L. asiaticus’ titer0 was not affected by any of the foliar applications”
t0“Citrus”
Claim · model-written summary
Direct foliar streptomycin application left high streptomycin levels in exposed citrus leaves.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“High levels of streptomycin were detected in leaves that were exposed to direct foliar application”
t0“Citrus”
Claim · model-written summary
The authors interpreted the high streptomycin in exposed leaves as adsorption or binding to citrus leaves.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“streptomycin was adsorbed or bound to citrus leaves”
Claim · model-written summary
Trunk injection of oxytetracycline produced high oxytetracycline levels in citrus leaves.
- Treatment
- trunk injection of oxytetracyclinee0
- Outcome
- levels of this antibiotic in leavese0
- Direction
- highe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the trunk injection of oxytetracycline resulted in high levels of this antibiotic in leaves”
t0“Citrus”
Claim · model-written summary
Trunk injection of oxytetracycline significantly reduced Ca. L. asiaticus titer in citrus.
- Treatment
- trunk injection of oxytetracyclinee1
- Interactor
- ‘Ca. L. asiaticus’e0pathogen
- Outcome
- ‘Ca. L. asiaticus’ titere0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“significantly reduced the level of ‘Ca. L. asiaticus’ titer in citrus trees”
e1“the trunk injection of oxytetracycline”
Claim · model-written summary
Trunk injection of streptomycin produced low streptomycin levels in citrus leaves.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the trunk injection of streptomycin resulted in low levels of streptomycin in citrus leaves”
Claim · model-written summary
Trunk injection of streptomycin did not affect Ca. L. asiaticus titer.
- Treatment
- trunk injection of streptomycine1
- Interactor
- ‘Ca. L. asiaticus’e0pathogen
- Outcome
- ‘Ca. L. asiaticus’ titere0
- Direction
- did not affecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“did not affect the ‘Ca. L. asiaticus’ titer”
e1“the trunk injection of streptomycin”
t0“Citrus”
Claim · model-written summary
The authors suggested oxytetracycline could be more effective against the HLB pathogen than streptomycin.
- Treatment
- oxytetracyclinee0
- Outcome
- effective against the HLB pathogene0
- Direction
- more effectivee0
- Comparator
- streptomycine0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“oxytetracycline could be more effective against the HLB pathogen than streptomycin”
t0“Citrus”
The same questions in other papers
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- no effect
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application · molecular: metabolites · CitrusPositive and negative results
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- no effect
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See all 14 papers →application · nutrient: content · CitrusPositive and negative results
14 papers in the same direction as this paper · 3 in the opposite direction
- no effect
- negative
- negative
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See all 18 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.