Witches’ broom disease of lime contributes to phytoplasma epidemics and attracts insect vectors

A. M. Al-Subhi, A. M. Al-Sadi*, R. A. Al-Yahyai, Y. Chen, T. Mathers, Z. Orlovskis, G. Moro, S. Mugford, K. S. Al-Hashmi, S. A. Hogenhout

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


An insect-transmitted phytoplasma causing Witches’ Broom Disease of Lime (WBDL) is responsible for the drastic decline in lime production in several countries. However, it is unclear how WBDL phytoplasma (WBDLp) induces witches’ broom symptoms and if these symptoms contribute to the spread of phytoplasma. Here we show that the gene encoding SAP11 of WBDLp (SAP11WBDL) is present in all WBDLp isolates collected from diseased trees. SAP11WBDL interacts with acid lime (Citrus aurantifolia) TCP transcription factors, specifically members of the TB1/CYC class that have a role in suppressing axillary branching in plants. Sampling of WBDLp-infected lime trees revealed that WBDLp titers and SAP11WBDL expression levels were higher in symptomatic leaves compared with asymptomatic sections of the same trees. Moreover, the witches’ brooms were found to attract the vector leafhopper. Defense genes that have a role in plant defense responses to bacteria and insects are more downregulated in witches’ brooms compared with asymptomatic sections of trees. These findings suggest that witches’ broom-affected parts of the trees contribute to WBDL epidemics by supporting higher phytoplasma titers and attracting insect vectors.

Original languageEnglish
JournalPlant Disease
Issue number9
Publication statusPublished - Sept 2021


  • Effector
  • Hishimonus phycitis
  • SAP11
  • TCP
  • Transcription factors

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Plant Science


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