European Journal of Plant Pathology

, Volume 138, Issue 1, pp 123–131 | Cite as

Virulence spectra and geographical distribution of Mal Secco disease of citrus caused by Phoma tracheiphila in the Mediterranean countries: Tunisia and Italy

  • Sana Ziadi
  • Samir Chebil
  • Imen Melki
  • Antonio Ippolito
  • Ahmed Mliki


This work aimed to find out patterns of virulence variability of a Phoma tracheiphila population of 51 isolates, to determine geographic distribution of Mal Secco disease in citrus orchards of six Mediterranean countries and also to establish correlation between geographic distribution and pathotypic distance of P. tr population structure over our sampling spatial scale. Based on unweighted pair-group method with arithmetic averaging clustering and mean disease rating scores, three distinct virulence groups were identified. The 51 isolates were classified into 20 pathotypes. Extensive virulence variability was detected in 51 isolates of P. tr causing MSD of citrus in the Mediterranean basin. Regression plot between pairwise virulence and geographical distance showed that virulence is independent of the geographical origin and that isolates collected from the same country have different degrees of virulence. The lack of significant correlation between virulence and geographic structure confirmed the absence of isolation-by-distance pattern, suggesting non-regular and non-gradual dispersal of the pathogen over this spatial scale.


Virulence Geographical distribution Mal Secco disease Citrus Mediterranean countries Tunisia and Italy 



We thank the Ministry of Higher Education and Scientific Research in Tunisia for his investigation by sponsoring this work which is a part of the improvement program of the citrus growing in Tunisia.


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Copyright information

© KNPV 2013

Authors and Affiliations

  • Sana Ziadi
    • 1
  • Samir Chebil
    • 1
  • Imen Melki
    • 1
  • Antonio Ippolito
    • 2
  • Ahmed Mliki
    • 1
  1. 1.Laboratory of Plants Molecular PhysiologyCentre of Biotechnology Borj-CedriaHammam-LifTunisia
  2. 2.Department of Agro Forestry and Environmental Biology and ChemistryUniversity of BariBariItaly

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