Assessing management strategies for mitigating Rhizoctonia damping-off in

sugar beet cultivation

1.

 Dual Culture Test:

• B. subtilis Y1336 inhibited the mycelial growth of both Rhizoctonia solani strains in dual culture assays.
• The inhibition rates were 73.27% for the I8AF strain and 74.43% for the RhSA strain, indicating strong antifungal activity.
• Microscopic observations revealed that B. subtilis Y1336 caused structural changes in the mycelium of R. solani, including swelling, thinning, and the formation of hyphal clusters and vacuoles.

• When B. subtilis Y1336 was used as a seed coating, seeds inoculated with R. solani still showed a good germination rate.
• In treatments with both R. solani I8AF and RhSA strains, the germination rates were 73.27% and 75.43%, respectively, significantly reducing the incidence of damping-off disease compared to untreated seeds.
• Seeds treated with B. subtilis Y1336 and not inoculated with the pathogen showed no signs of damping-off, confirming that the BCA is non-pathogenic to sugar beet.

• Under greenhouse conditions, B. subtilis Y1336 significantly reduced the incidence of damping-off in sugar beet seedlings.
• The disease incidence was reduced by 58.75% when seeds treated with B. subtilis Y1336 were inoculated with R. solani, compared to untreated controls.
• In soil not inoculated with the pathogen, seeds treated with B. subtilis Y1336 showed no symptoms of damping-off, further confirming the effectiveness of the BCA.

• The study also assessed the compatibility of Bacillus subtilis Y1336 with chemical fungicides. Results showed that tebuconazole and difenoconazole had no inhibitory effect on the growth of B. subtilis, suggesting that these fungicides can be combined with the BCA for enhanced disease control.

• Bacillus subtilis Y1336 not only effectively inhibited the growth of R. solani, but also significantly reduced damping-off disease and promoted seed germination.
• When combined with certain chemical fungicides, B. subtilis Y1336 showed enhanced disease control without causing any harmful effects on the plants.
• This study was the first to demonstrate the effectiveness of Bacillus subtilis Y1336 in controlling sugar beet damping-off, and it holds great potential for application in other crops.