Isolation and screening rhizobacteria to control <i>Gilbertella persicaria</i> causing dragon fruit rot

Abstract

&lt;i&gt;Gilbertella persicaria&lt;/i&gt; is a fungus causing dragon fruit rot discovered recently and there is still no effective measure to control this fungus. Several studies demonstrated that microorganisms were applied for controlling &lt;i&gt;G. persicaria&lt;/i&gt; on other crops. The purpose of this study was to evaluate the potential application of rhizobacteria in the &lt;i&gt;in vitro&lt;/i&gt; control of &lt;i&gt;G. persicaria&lt;/i&gt;. Eighty-nine bacterial isolates were collected from eleven rhizosphere soil samples. Four isolates, including LA2.9, LA3.2, LA4.5, and LA6.1, were screened based on inhibitory zone diameters and the ratio between the diameter of the inhibitory zone and the diameter of the bacterial growth zone. All of these four isolates were identified as belonging to the &lt;i&gt;Bacillus&lt;/i&gt; genus and were compatible with each other. Random combinations of the selected strains could increase the&lt;i&gt; in vitro&lt;/i&gt; growth inhibition of &lt;i&gt;Gilbertella persicaria&lt;/i&gt; GTC2.3.1 in some cases. These results once again showed that the individual or multiple applications of the antagonistic bacterial strains was a promising approach to control &lt;i&gt;G. persicaria&lt;/i&gt;. Therefore, it is necessary to isolate and collect more bacterial antagonists to develop targeted fungicidal formulations.