Abstract The antagonistic potential of Bacillus subtilis 5/B and Pseudomonas diminuta A6 isolates had been evaluated against bacterial leaf blight of rice caused by Xanthomonas oryzae pv. oryzae (Xoo). Bioformulation improved the shelf life of antagonist bacteria and the stability of the product in different environmental conditions. The objectives of this research were to develop bioformulation, to evaluate the effectiveness of seed treatment using bioformulation after 6 months of storage on seed quality and Xoo population, and to evaluate the effectiveness of the bioformulation in improving plant growth and yield in the field. This research consisted of three experiments: (1) development of bioformulation ( B. subtilis 5/B + P. diminuta A6 + 125 mL bacteria suspension 10 8 cfu), the formulation was developed using three carrier materials, namely talc, zeolite, and gypsum with the dosages were 1, 2.5 and 5 g respectively for 2000 seeds; (2) evaluation on the effectiveness of the bioformulation through seed treatment on rice cv. IR64 after 6 months of storage; (3) evaluation of the bioformulation effect on plant growth and yield in the field. The biocontrol agents survived well in talc and zeolite 3 months after storage with an average of 16.55 x 10 7 cfu B. subtilis 5/B and 2.83 x 10 7 cfu P. diminuta A6 , respectively. Seed treatments with bioformulation suppressed the Xoo population in the rice seeds. The Xoo population in the treated seeds decreased periodically (the initial Xoo population was 4.9 x 10 8 cfu). The population of Xoo in the sixth month of storage showed that the 2.5 g gypsum, 2.5 g zeolite, and 5 g zeolite were the lowest (0.05 x 10 7 cfu). The 2.5 g zeolite-based bioformulation was the best formula for improving seed germination (90.7%) and vigor index (88.7%) after 6 months of storage. However, talc was the best carrier material for the bioformulation to improve the viability of the biological agents. Therefore, talc-based bioformulation was selected and used for the seed treatment in the field. In addition, talc is cheaper and more applicable than other carrier materials. The biocontrol formulation using 1g of talc increased the yield by 25.6%.
Mulyani et al. (Tue,) studied this question.