The potential of antagonistic yeasts and bacteria from tomato phyllosphere and fructoplane in the control of Alternaria fruit rot of tomato

Abstract

The biocontrol potential of antagonistic bacteria and yeasts isolated from tomato phyllosphere and fructoplane was evaluated against fruit rot of tomato caused by Alternaria alternata. A total of 48 bacterial and 24 yeast isolates were obtained from field-grown tomato leaves/fruits collected from Barka, Oman. The antagonistic activities of these isolates were evaluated against A. alternata using in vitro dual culture assay. Among the 72 bacterial and yeast isolates tested, one yeast (Meyerozyma guilliermondii) and two bacteria (Enterobacter roggenkampii and Pseudomonas aeruginosa) showed inhibitory activity against A. alternata. Examination of hyphal morphology of A. alternata at the edge of inhibition zone using scanning electron microscopy revealed abnormalities such as twisting, shriveling, distortion and collapsing of hyphae. Postharvest treatment of tomato fruits with E. roggenkampii, P. aeruginosa and M. guilliermondii reduced the fruit rot lesion size by 60%, 57% and 50%, respectively, compared to untreated control. The antifungal metabolites produced by the antagonistic yeast M. guilliermondii were fractionated using thin-layer chromatography. Characterization of the bioactive fractions using gas chromatography-mass spectrometry revealed the presence of different types of alkanes, predominantly tricosane and pentacosane, suggesting that volatile compounds, especially alkanes, produced by M. guilliermondii might also be involved in the suppression of A. alternata.

KEYWORDS:

• Alternaria alternata
• biocontrol
• Enterobacter roggenkampii
• Meyerozyma guilliermondii
• Pseudomonas aeruginosa
• Solanum lycopersicum

Acknowledgements

We thank Ms Huda Khalfan Al-Ruqaishi for helping in GC-MS analysis. The authors thank Dr S. Muthukrishnan, Kansas State University, USA for critically reading the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Authors’ contributions

RV, AMA, SSA designed the study, SSA, SAKA, JNA conducted lab experiments, RV, AMA supervised the research project, SSA, RV, AMA, JNA wrote the manuscript.

Ethical approval

This article is original and has not been published elsewhere. All authors discussed the results, read and approved the final manuscript. The authors confirm that there are no ethical issues in the publication of the manuscript.

Data availability

All data generated or analyzed during this study are included in this article. The nucleotide sequences of antagonistic yeast and bacteria have been deposited in the NCBI database under GenBank accession numbers MK583585, MK583581, and MT176503. The nucleotide sequence of Alternaria alternata SQUCC-S4 can be found in the NCBI database (www.ncbi.nlm.nih.gov) under GenBank accession number MK583589.

Additional information

Funding

This work was supported by The Research Council, Oman [grant number RC/RG-AGR/CROP/19/02]; Sultan Qaboos University [grant number EG/AGR/CROP/12/03; IG/AGR/CROP/18/01].