Abstract

Bakanae is a critical disease in the cultivation of rice that leads to substantial output loss. An environment friendly control approach using rhizobacteria is considered promising because it can suppress the disease while supporting growth of plants. This study aimed to isolate and characterize rhizobacteria from the rice root zone that have the potential as biological control agents, biostimulants, and biofertilizers, and to identify several selected isolates through 16S rRNA gene analysis. A total of 16 treatments were tested, consisting of 14 rhizobacterial isolates (Kr 2.2, Kr 3.1, Kr 3.3, KG 2.2, KG 2.4, KG 3.4, LM 2.4, LM 3.1, PA 1.2, PA 2.1, PA 2.2, GS 2.2, GS 3.1 and Ps 1.1), one positive control, and one negative control, each with four replications. The result showed that four isolates namely Ps 1.1, PA 1.2, KG 2.2 and Kr 2.2 had a considerable capacity to inhibit the progression of bakanae disease, as evidenced by reduction in disease intensity (8-17% 8–17%) and severity (6-13%), the area under the disease progress curve (AUDPC) (94.69 –240.45), and infection rate (0.223–0.372). Furthermore, Ps 1.1 and PA 1.2 enhanced the growth of rice seedlings, showing growth percentage of 83 – 87%, a plant height of 37 –38 cm, and a root length of 18 – 21 cm. Five isolates showed plant growth-promoting capabilities, including siderophore formation, solubility of phosphate (index 1.60–2.30), indole acetic acid (IAA) synthesis (4.22–19.13 mg. kg-1), and nitrogen fixation. Molecular identification revealed that isolates Ps 1.1, PA 1.2, KG 2.2, Kr 2.2 and PA 2.1 had high sequence similarity (99 – 100%) with Ochrobactrum intermedium, Bacillus aryabhattai, Pseudomonas luteola, and Bacillus cereus, respectively. The results suggest that the isolates have high potential as biological control agents and growth promoters of rice plants.