الملخص الإنجليزي
The antibiotics: erythromycin, oxytetracycline-HCl and streptomycin were used in vitro and in vivo experiments to study their effect on suppressing the phytoplasma causing Witches; Broom Disease of Lime (WBDL). Sterilized infected shoots of lime were cultured in autoclaved Murashige & Skoog (MS) medium including Benzyl Adenine (BA) with or without 2,4-D and the antibiotics at 200mgl-? were filter sterilized. Polymerase Chain Reaction (PCR) was carried out for the cultures to detect the pathogen and determine its concentration. In vivo assessments were conducted in two-phase trials. In the first phase, 60 WBDL-infected lime trees were chosen with severity levels ranging from 0-5 as per a given scale at 3 experimental sites. They were injected after severe
pruning. The antibiotics were injected at 2 replications/farm of 0.3g!", 0.6gl' and 0.9g1-with sterile distilled water as a control. In the second phase 45 infected lime trees with a severity level ranging between 0-4 per a severity scale were injected with oxytetracycline-HCI. The concentrations were 0.25g, 0.5g, 1.0g, 2.og active ingredients per tree and sterile distilled water as a control, al with 3 replications. Application was done once, twice or three times at given weekly intervals for 6 weeks. Samples were collected from the injected tree for detection of oxytetracycline-HCl residue level from leaf, fruit and root at different time interval, Results from in vitro cultured shoots, showed a higher survival rate in cultures containing oxytetracycline-HCI. Similarly in vivo injections showed better survival and symptom suppression in both injection experiments with oxytetracycline-HCL than the other antibiotics. Streptomycin and erythromycin gave phytotoxic effect to the injected WBDL infected lime trees. Detected oxytetracycline-HCI residue levels were much lower than the accepted tolerant levels for leaf, fruit and root of injected. WBDL infected lime trees.
