Synergistic effect and safety evaluation of four kinds of spray adjuvants on Bacillus amyloliquefaciens Lx-11 strain

To improve the control efficacy of Bacillus amyloliquefaciens Lx-11 suspension concentrate on rice bacterial blight, four kinds of spray adjuvants (silicone, TM-10, lecithin, and SY-6535) were selected in this study and their effects on B. amyloliquefaciens Lx-11 bacterial content, the liquid's surface tension, contact angle changes, and the safety of rice growth were evaluated. In addition, the control effect of Lx-11 strain against bacterial blight in the pot experiment and the colonization dynamics on rice leaf surface were determined for an applicable spray adjuvant. The results showed that the bacterial content of B. amyloliquefaciens Lx-11 is significantly declining when treated with lecithin among four spray adjuvants. Silicone, TM-10, and SY-6535 effectively reduce the surface tension of the suspension solution and the contact angle on rice leaves. The safety evaluation of rice showed that silicone, TM-10, and SY-6535 does not affect the growth of rice seedlings. The pot experiment results showed that the control efficacy of biocontrol bacteria Lx-11 (4.0 × 10⁹ cfu/mL) against bacterial blight reaches 57.70% and 56.56% after adding TM-10 and SY-6535, which was significantly higher than that of the suspension agent without adjuvants. The colonization experiment showed that the colonization of Lx-11 strain on the rice leaf surface is significantly higher after adding adjuvants than that of the control treatment.