Difficulties in identifying Xanthomonas citri subsp. citri A pathotypes
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A total of 350 citrus canker bacterial isolates, representing different citrus growing regions in Saudi Arabia, were identified as Xanthomonas citri subsp. citri (Xcc). DNA alignment of the 16S-rDNA of the three citrus canker organisms (Xcc, pathotypes A, X. fuscans pv. aurantifolii, pathotype B, and C) showed that they can be distinguished by using two SNPs. All the 350 Saudi Xcc strains belonged to the 16-rDNA haplotype of Xcc-A pathotypes. Pathogenicity in leaf assays using differential citrus cultivars, grapefruit (Citrus paradisi) and Mexican lime (C. aurantifolia), divided the Saudi Arabian bacterial isolates into two groups. The first group produced typical symptoms of Xcc, including erumpent canker lesions with water-soaked margins on all hosts. However, the second group caused atypical symptoms on grapefruit leaves. REP-PCR analysis grouped Xcc strains into three clusters that were not correlated with host, pathogenicity or geographic origin. However, the Baha Xcc population had the highest genetic variability, suggesting that this region may be responsible for disseminating Xcc strains to Saudi southern citrus-growing regions through movement of contaminated planting materials. Although we were able to definitely identify the Saudi citrus canker bacteria as Xcc-A pathotypes, its pathotypes still needs more investigation to be recognized. To our knowledge, this also is the first report of occurrence of citrus canker of sweet orange in the Abha region of Saudi Arabia.
KeywordsPathogenicity test 16S-rDNA Rep-PCR Citrus canker Pathotypes
The authors would like to extend their sincere appreciation to the Deanship of Scientific Research, King Saud University, Saudi Arabia, for its funding of this research group No. RG-1438-065.
Compliance with ethical standards
Human and animal participants
This article does not contain any studies with human participants or animals performed by any of the authors.
Conflict of interest
The authors declare that they have no conflict of interest.
Informed consent was obtained from all individual participants included in the study.
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