Genetic diversity, aggressiveness and metalaxyl sensitivity of Pythium aphanidermatum populations infecting cucumber in Oman

A. M. Al-Sa'di*, A. Drenth, M. L. Deadman, E. A.B. Aitken

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

32 Citations (Scopus)


Seventy three isolates of Pythium aphanidermatum obtained from cucumber from four different regions of Oman and 16 isolates of muskmelon from the Batinah region in Oman were characterized for aggressiveness, sensitivity to metalaxyl and genetic diversity using AFLP fingerprinting. Twenty isolates of P. aphanidermatum from diverse hosts from different countries were also included in the study. Most isolates from Oman were found to be aggressive on cucumber seedlings and all were highly sensitive to metalaxyl (EC50 < 0.80 μg mL-1). Isolates from cucumber and muskmelon were as aggressive as each other on both hosts (P > 0.05), which implies a lack of host specialization in P. aphanidermatum on these two hosts in Oman. AFLP analysis of all isolates using four primer-pair combinations resolved 152 bands, of which 61 (∼40%) were polymorphic. Isolates of P. aphanidermatum from Oman and other countries exhibited high genetic similarity (mean = 94.1%) and produced 59 different AFLP profiles. Analysis of molecular variance indicated that most AFLP variation among populations of P. aphanidermatum in Oman was associated with geographical regions (FST = 0.118; P < 0.0001), not hosts (FST = -0.004; P = 0.4323). These data were supported by the high rate of recovery (24%) of identical phenotypes between cucumber and muskmelon fields in the same region as compared to the low recovery (10%) across regions in Oman, which suggests more frequent movement of Pythium inoculum among muskmelon and cucumber fields in the same region compared to movement across geographically separated regions. However, recovering clones among regions and different countries may imply circulation of Pythium inoculum via common sources in Oman and also intercontinental spread of isolates.

Original languageEnglish
Pages (from-to)45-56
Number of pages12
JournalPlant Pathology
Issue number1
Publication statusPublished - Feb 2008


  • AFLP
  • Damping-off
  • Genetic differentiation
  • Genetic similarity
  • Phenotypes

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Genetics
  • Plant Science
  • Horticulture


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