Killiny Nabil, Hijaz Faraj, Gonzalez-Blanco Pedro, Jones Shelley E, Pierre Myrtho O, Vincent Christopher I
Department of Plant Pathology, Citrus Research and Education Center, IFAS, University of Florida, Lake Alfred, FL 33850, USA.
Department of Horticultural Sciences, Citrus Research and Education Center, IFAS, University of Florida, Lake Alfred, FL 33850, USA.
Antibiotics (Basel). 2020 Oct 6;9(10):677. doi: 10.3390/antibiotics9100677.
Recently in Florida, foliar treatments using products with the antibiotics oxytetracyclineand streptomycin have been approved for the treatment of citrus Huanglongbing (HLB), which iscaused by the putative bacterial pathogen ' Liberibacter asiaticus'. Herein, we assessedthe levels of oxytetracycline and '. L. asiaticus' titers in citrus trees upon foliar applications withand without a variety of commercial penetrant adjuvants and upon trunk injection. The level ofoxytetracycline in citrus leaves was measured using an oxytetracycline ELISA kit and '. L.asiaticus' titer was measured using quantitative PCR. Low levels of oxytetracycline were taken upby citrus leaves after foliar sprays of oxytetracycline in water. Addition of various adjuvants to theoxytetracycline solution showed minimal effects on its uptake by citrus leaves. The level ofoxytetracycline in leaves from trunk-injected trees was higher than those treated with all foliarapplications. The titer of '. L. asiaticus' in the midrib of leaves from trees receiving oxytetracyclineby foliar application was not affected after four days and thirty days of application, whereas thetiter was significantly reduced in oxytetracycline-injected trees thirty days after treatment.Investigation of citrus leaves using microscopy showed that they are covered by a thick lipidizedcuticle. Perforation of citrus leaf cuticle with a laser significantly increased the uptake ofoxytetracycline, decreasing the titer of '. L. asiaticus' in citrus leaves upon foliar application.Taken together, our findings indicate that trunk injection is more efficient than foliar spray evenafter the use of adjuvants. Our conclusion could help in setting useful recommendations for theapplication of oxytetracycline in citrus to improve tree health, minimize the amount of appliedantibiotic, reduce environmental exposure, and limit off-target effects.
最近在佛罗里达州，使用含有抗生素土霉素和链霉素的产品进行叶面处理已被批准用于治疗柑橘黄龙病（HLB），该病由假定的细菌病原体“亚洲韧皮杆菌”引起。在此，我们评估了在有或没有各种商业渗透助剂的情况下进行叶面喷施以及进行树干注射后，柑橘树中土霉素的含量和“亚洲韧皮杆菌”的滴度。使用土霉素酶联免疫吸附测定试剂盒测量柑橘叶片中土霉素的含量，并用定量PCR测量“亚洲韧皮杆菌”的滴度。在水中叶面喷施土霉素后，柑橘叶片吸收的土霉素含量较低。在土霉素溶液中添加各种助剂对其被柑橘叶片吸收的影响最小。树干注射树木的叶片中土霉素含量高于所有叶面处理的树木。通过叶面喷施接受土霉素处理的树木，在喷施四天和三十天后，叶片中脉的“亚洲韧皮杆菌”滴度没有受到影响，而在注射土霉素的树木中，处理三十天后滴度显著降低。使用显微镜对柑橘叶片进行研究表明，它们被一层厚厚的脂质化角质层覆盖。用激光在柑橘叶片角质层上打孔可显著增加土霉素的吸收，降低叶面喷施后土霉素在柑橘叶片中的“亚洲韧皮杆菌”滴度。综上所述，我们的研究结果表明，即使使用了助剂，树干注射也比叶面喷施更有效。我们的结论有助于为土霉素在柑橘中的应用制定有用的建议，以改善树木健康状况、减少抗生素施用量、降低环境暴露并限制非靶标效应。
