Abstract

Plant Growth-Promoting Bacterial Endophytes (PGPBE) are organisms that live within plant tissues and are not harmful to the host plant. The organisms have the capacity to inhibit the growth of plant pathogens directly and indirectly. The purpose of this study was to find PGPBE isolates capable of controlling the fungus Curvularia lunata and Rhizoctonia solani Kühn in vitro. The experiment was carried out utilizing a Completely Randomized Design (CRD), with 24 treatments obtained from rice plant roots, leaves, and stems. Two species of pathogenic fungi, C. lunata and R. solani, were compared in dual culture on PDA media, with fungi lacking PGPBE serving as control agents. The experiment was replicated four times, with factors monitored such as the isolates' ability to reduce in vitro growth of the two harmful fungi. The findings revealed that seven PGPBE isolates, including LMA5 and LMA6 from rice roots, LMB35, LMB1, LMB4, and LMB21 from rice stems, and LMD13 from rice leaves, could suppress the growth of C. lunata and R. solani. These isolates could produce antifungal secondary metabolites such as hydrogen cyanide, siderophores, protease enzymes, and chitinase enzymes. The 16S rRNA gene identified LMA5, LMB21, LMB4, and LMD13 as Lysinibacillus fusiformis strains IRHB1-68, Bacillus cereus strain BS1, L. fusiformis strain S10510, and Bacillus thuringiensis strain Bt 35. All of these endophytic isolates demonstrated the potential to act as biocontrol agents for pathogenic fungus in rice.