Abstract:
Brown spot disease (BSD), caused by Bipolaris oryzae (Bo), is a major contributor to yield losses in Asia. Synthetic fungicides and fertilizers are used for higher yields. However, synthetic agrochemicals pose adverse environmental and health impacts. Therefore, developing alternatives for disease management and nutrient supply is important in sustainable agriculture. This study aims to assess a selected bacterial isolate (Bacillus sp.) against Bo under in vitro conditions, evaluate its effect on BSD suppression, and determine its impact on yield in rice variety Bg 300. Bo was isolated and identified based on mycelial and spore morphology. The poisoned food technique was used to evaluate Bacillus sp. (BF) on mycelial growth. Two greenhouse experiments were arranged in the complete randomized design to determine the effect of BF on vegetative growth and yield of Bg 300 under Bo-inoculated (BIC) and BSD-free conditions (BFC). Recommended inorganic fertilizers and BF non-inoculation served as positive (PC) and negative control (NC) respectively. BF significantly suppressed (p < 0.05) Bo with a mycelium diameter of 6.7 ± 0.65 cm in contrast to that of NC (9 ± 0.00 cm). Plants with BF inoculation under BFC showed a significantly better performance (p < 0.05) than those under BIC. Plant height (PH) was 83.0 ± 2.5 cm under BFC and 82.67 ± 2.08 cm under BIC in BF, whereas in NC, PH was 75.89 ± 1.3 cm and 75.24 ± 2.4 cm, respectively. In PC, PH was 81.78 ± 2.04 cm under BFC and 84.11 ± 1.8 cm under BIC. The SPAD meter reading of the flag leaf (SF) was 40.77 ± 0.4 under BFC and 39.76 ± 0.7 under BIC in the BF. In NC, SF was 31.71 ± 2.08 and 28.62 ± 0.88, while in PC, it was 43.84 ± 0.6 and 44.76 ± 0.7 under disease-free and inoculated conditions, respectively. The total yield per plant (TY) in BF was 151.89 ± 23.8 g under BFC and 92.67 ± 3.4 g under BIC. In NC, TY was 75.5 ± 5.7 g and 62.86 ± 7.2 g, while in PC, it was 161.13 ± 19.7 g and 159.11 ± 19.7 g under BFC and BIC, respectively. These findings suggest that BF holds promise as an alternative strategy for brown spot disease suppression and yield enhancement in rice cultivation.
