Efficacy of Biological Product of Bacillus subtillis NS–03 to Control Narrow Brown Spot of Rice Caused by Cercospora oryzae

Abstract

The antagonistic bacterium of Bacillus subtillis NS–03 was produced as a biological product of 3 formulas by using biochar powder mixed with talcum powder to be carriers. The different radios of biochar and talcum powers in the 100 g of biological product, formula 1 containing 60 g of biochar powder and 10 g of talcum powder, formula 2 containing 40 g of biochar powder and 30 g of talcum powder, formula 3 containing 20 g of biochar powder and 50 g of talcum powder. After storage at room temperature for 12 months found that biological products contained with the increased proportion of biochar had the increased survival of B. subtillis NS–03, which was significantly different (P < 0.01). Consequently, formula 1, 2, and 3 had the population of B. subtillis NS–02 at 1.2 × 10¹⁰ , 1.0 × 10⁹, and 2.5 × 10⁸  cfu/g, respectively. The results of biological products to inhibit the mycelial growth of Cercospora oryzae, the cause of Narrow brown spot of rice cv. Patumthanee 1 on potato dextrose agar, found that formula 1 provided the highest inhibition of C. oryzae. The lower treatments were formula 2 and 3 that could inhibit C. oryzae by 51.20, 47.78, and 44.63%, respectively. The greenhouse experiment for controlling Narrow brown spot of Patumthanee 1 rice, the use of 3 biological products of antagonistic bacterium sprayed on Patumthanee 1 rice found that had a significant difference (P < 0.05) when compared with control treatment. Carbendazim chemicals, the biological products of formula 1, 2 and 3 were able to control the Narrow brown spot by 75.64, 69.33, 56.29, and 41.87% respectively. In addition, the antagonistic bacteria of Bacillus spp. colonized rice leave by 62.30–89.26% after 2^nd  spray of biological products for 14 days.