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Screening of effective antagonists from potato rhizosphere against bacterial wilt pathogen

By: M. Ibrahim Tahir, M. Inam-ul-Haq, M. Ashfaq, Nadeem Akhtar Abbasi, Haris Butt, Hira Ghazal

Key Words: Potato, Bacterial wilt, Rhizobacteria, Antagonists, Biocontrol.

Int. J. Biosci. 8(2), 228-240, February 2016.



Potato is the most consumed vegetable while stands 4thamong food crops after wheat, rice, and maize in terms
of production. Bacterial wilt caused by Ralstonia solanacearum is one of the most devastating diseases
throughout the world causing substantial losses in potato and in other important crops. This study was
embarked to search for biocontrol of pathogen, keeping in view recent reports of disease incidence in major
potato growing areas of Pakistan. In this study, several potato growing areas of Punjab (Pakistan) were visited to
study the bacterial community residing in potato rhizosphere and also screen bacterial antagonists against the
virulent strains (Rs9, Rs17 and R43) of R. solanacearum. The results revealed that out of 221 rhizobacterial
isolates, Bacillus spp. (101) were dominantly isolated from potato rhizosphere, followed by Pseudomonas spp.
(76) and Serratia spp. (44). All these isolates were tested for antagonism using dual culture plate method which
showed 11 isolates to be highly antagonistic against either isolate of R. solanacearum. Against Rs9, Rs17, Rs43
and GMI1000 highest zone of inhibition was recorded with B28 (12.3 mm), P11 (10.2 mm), B9 (9.9 mm) and B85
(11.7 mm) respectively. Culture filtrate (CF) of antagonists was also checked against live R. solanacearum cells
which also showed inhibition in liquid medium. Antagonistic isolates were tested for plant growth promoting
(PGP) traits i.e. indole acetic acid (IAA), siderophore production, P-solubilization, root colonization, and
chitinase production. The isolates B28 and B85 were potential isolates possessing antagonistic activity along
with several PGP traits.


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