Pathological phenotypes of Xanthomonas citri pv. citri causal agent of citrus bacterial canker and in vitro efficiency assessment of copper compounds in its inhibition

Document Type : Research Article

Authors

1 A Part of a PhD dissertation presented to the College of Agriculture, Shiraz University, Shiraz, Iran

2 Professor of Plant Pathology, Department of Plant Protection, College of Agriculture, Shiraz University, Shiraz, Iran

10.22034/ijpp.2024.710590

Abstract

As a consequence of the abundant use of copper bactericides, some species of plant pathogenic bacteria, 
including Xanthomonas citri pv. citri (Xcc), have developed resistance to copper. This study evaluates 
pathological phenotypes and in vitro efficiency of prevalent copper compounds in inhibiting Xcc. Sampling 
was conducted across citrus orchards during 2021-2022. One hundred and seventeen citrus orchards were 
surveyed and 132 strains identified as Xanthomonas citri pv. citri based on phenotypic and genotypic 
characteristics. Different pathogenic phenotypes were observed by inoculating the representative strains on 
different cultivars of lime, orange, citrumelo and grapefruit, but tangerine cultivars did not show disease 
symptoms. All the strains showed an intermediate level of sensitivity and grew in the medium containing 100 
and 150 mg/l of copper sulfate. In addition higher concentrations (250, 300, 350 and 400 mg/liter) showed 
inhibition rate more than 90%. Copper carboxylate at the concentration of 0.75 g/liter prevented the growth 
of more than 85% of the strains. Also, Copper oxychloride showed the best inhibition rate in concentrations 
higher than 3 g/liter. 1.5 ml/liter of Bordeaux mixture controlled more than 80% of the strains. None of 
copper resistance gene clusters copLAB and copABCD were detected in tested Xanthomonas citri strains. The 
proper characterization of pathological phenotypes and sensitivity to copper leads more confident decisions 
in citrus canker disease management.

Keywords

Iranian Journal of Plant Pathology
Volume 59, Issue 2
July 2024
Pages 103-85

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