Journal of Fungi (Dec 2021)

Biocontrol Potential of Endophytic Actinobacteria against <i>Fusarium solani</i>, the Causal Agent of Sudden Decline Syndrome on Date Palm in the UAE

  • Aisha A. Alblooshi,
  • Gouthaman P. Purayil,
  • Esam Eldin Saeed,
  • Gaber A. Ramadan,
  • Saeed Tariq,
  • Amna S. Altaee,
  • Khaled A. El-Tarabily,
  • Synan F. AbuQamar

DOI
https://doi.org/10.3390/jof8010008
Journal volume & issue
Vol. 8, no. 1
p. 8

Abstract

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Thirty-one endophytic streptomycete and non-streptomycete actinobacteria were isolated from healthy date palm root tissues. In vitro screening revealed that the antifungal action of isolate #16 was associated with the production of cell-wall degrading enzymes, whereas with diffusible antifungal metabolites in isolate #28, albeit their production of volatile antifungal compounds. According to the 16S rRNA gene sequencing, isolates #16 and #28 were identified as Streptomyces polychromogenes UAE2 (Sp; GenBank Accession #: OK560620) and Streptomyces coeruleoprunus UAE1 (Sc; OK560621), respectively. The two antagonists were recovered from root tissues until 12 weeks after inoculation, efficiently colonized root cortex and xylem vessels, indicating that the date palm roots are a suitable habitat for these endophytic isolates. At the end of the greenhouse experiments, the development of sudden decline syndrome (SDS) was markedly suppressed by 53% with the application of Sp and 86% with Sc, confirming their potential in disease management. Results showed that the estimated disease severity indices in diseased seedlings were significantly (p Sp or Sc, respectively. In addition, conidial numbers of the pathogen significantly (p Sp and Sc, respectively, compared to infected seedlings with F. solani (control). Thus, the suppression of disease symptoms was superior in seedlings pre-inoculated with S. coeruleoprunus, indicating that the diffusible antifungal metabolites were responsible for F. solani retardation in these plants. This is the first report of actinobacteria naturally existing in date palm tissues acting as microbial antagonists against SDS on date palm.

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