DefinePK

Research Objective

To manage citrus canker caused by Xanthomonas citri subsp. citri (Xcc) by evaluating the effectiveness of nine antibiotics and five copper-based chemicals under laboratory and field conditions, both individually and in combination.

Methodology

The study involved: 1) Isolation, purification, and identification of Xanthomonas citri subsp. citri (Xcc) from diseased citrus samples using standard microbiological techniques (NA medium, pathogenicity tests, and biochemical assays like pectinolytic activity, sugar utilization, H2S production, indole production, citrate utilization, and $\alpha$-methyle D glucoside test). 2) In vitro evaluation of nine antibiotics (Enrofloxacin, Enco-Mix, Pevivet-5, Kanamycin sulphate, Sinobiotic, Streptomycin sulphate, Gentam-20%, Benzyl Penicillin Sodium, Tylofurcin) using the disk plate method at concentrations of 300, 500, and 700ppm under a Complete Randomized Design (CRD). 3) In vivo evaluation of five copper-based chemicals (Copper nitrate, Copper hydroxide, Amistar top, Copper oxychloride, Copper acetate) at concentrations of 0.5%, 0.75%, and 1.00% via foliar spray on one-year-old citrus plants under field conditions. 4) Evaluation of the most effective antibiotic and copper chemical, both alone and in combination (specifically Cu(NO2)3 + Enrofloxacin), under field conditions, recording disease incidence over 15 days (D1, D2, D3).

Methodology Flowchart

                        graph TD; A[Collect Diseased Samples] --> B[Isolate, Purify, Identify Xcc]; B --> C[Biochemical Assays]; C --> D[In Vitro Antibiotic Testing CRD]; C --> E[Field Testing Copper Chemicals Foliar Spray]; D --> F[Identify Best AntibioticEnrofloxacin]; E --> G[Identify Best ChemicalCopper Nitrate]; F & G --> H[Test Best Agents Alone & Combined in Field]; H --> I[Record Disease Incidence Over 15 Days]; I --> J[Analyze Results & Conclude]; J --> K[Recommend $\textCu\textNO_2]_3$ + Enrofloxacin)                    

Discussion

Citrus canker poses a significant threat, causing 5-30% yield losses in Pakistan. Enrofloxacin was identified as the most effective antibiotic in the lab, potentially due to its mechanism of inhibiting bacterial DNA gyrase and topoisomerase IV. Copper Nitrate was the most effective copper chemical in the field. The combination of $\text{Cu}(\text{NO}_2)_3$ and Enrofloxacin proved superior in field management, suggesting a synergistic effect, although this specific combination had not been previously reported. Copper ions disrupt bacterial cell membrane integrity and can interact with bacterial DNA.

Key Findings

In vitro: Enrofloxacin showed the maximum inhibition zone (35.68mm), followed by Enco-Mix (33.50mm). Benzyl Penicillin Sodium and Tylofurcin showed no inhibition.
Field (Chemicals): Copper nitrate exhibited the minimum disease incidence (16.07%), compared to the control (65.00%).
Field (Combined): The mixture of Copper nitrate ($\text{Cu}(\text{NO}_2)_3$) + Enrofloxacin resulted in the minimum disease incidence (18.22%).

Conclusion

Enrofloxacin and Copper nitrate were the most effective agents individually against Xanthomonas citri subsp. citri under in vitro and field conditions, respectively. The combination of $\text{Cu}(\text{NO}_2)_3$ and Enrofloxacin is strongly suggested as a successful treatment for managing citrus canker in the field.

Fact Check

1. Citrus canker causes 5-30% yield losses in Pakistan. (Confirmed in Abstract and Introduction).
2. Enrofloxacin expressed the maximum inhibition zone in vitro at 35.68mm. (Confirmed in Abstract and Results).
3. Copper nitrate exhibited the minimum disease incidence in field experiments at 16.07%. (Confirmed in Abstract and Results).

Mind Map