Surface barriers of mandarin 'okitsu' leaves make a major contribution to canker disease resistance

Phytopathology. 2014 Sep;104(9):970-6. doi: 10.1094/PHYTO-10-13-0277-R.


Field evaluations have shown that Satsuma mandarin (Citrus unshiu) 'Okitsu' is one of the mandarin cultivars that shows substantial resistance to Xanthomonas citri subsp. citri (X. citri), the causal agent of citrus bacterial canker disease. However, the mechanisms underlying this resistance are not well understood. In this study, we have shown that 'Okitsu' leaves are nevertheless susceptible to X. citri infection during a period of their development; however, this period is shorter than that seen in the susceptible mandarin 'Clemenules' (C. clementina). Under controlled growth conditions, the resistance of 'Okitsu' to X. citri was associated with the age of the leaf and was evident in spray-inoculated plants but not in those inoculated by infiltration. Furthermore, X. citri showed reduced attachment and biofilm formation in 'Okitsu' leaves compared with 'Clemenules'. Taken together, our data suggest that structural features of the 'Okitsu' leaf surface, such as the physical properties of the cuticle, are involved in the resistance to X. citri.

Keywords: canker resistance; leaf surface properties; phenological stages.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biofilms
  • Citrus / anatomy & histology
  • Citrus / growth & development
  • Citrus / immunology*
  • Citrus / microbiology
  • Disease Resistance*
  • Plant Diseases / immunology*
  • Plant Diseases / microbiology
  • Plant Leaves / anatomy & histology
  • Plant Leaves / growth & development
  • Plant Leaves / immunology*
  • Plant Leaves / microbiology
  • Species Specificity
  • Time Factors
  • Virulence
  • Xanthomonas / growth & development
  • Xanthomonas / pathogenicity
  • Xanthomonas / physiology*