Study On Biocontrol Of Maize Sheath Blight (Rhizoctonia Solani) With Bacillus Subtilis 12-041 And 12-059

The objective of this research was aimed at screening the antagonistic effect of endophytic bacillus on the Maize Sheath Blight. The antagonistic strains were identified.The fermentation medium and the growth condition were optimized. The inhibitory substance produced by the antagonistic strains was studied preliminarily..(1) Two antagonistic strains 12-041 and 12-059 were selected from one hundred and thirty-two endophytic bacillus strains isolated from peanuts and medicinal plants by primary screening of dual culture, the inhibitory ability of the filtrated fermentation cultures and pot inoculation experiment.(2) The fermented medium and conditions for strains 12-041 and 12-059 was investigated.The medium was modified SDAY medium, which contained peptone 10g, yeast extract paste 10g, glucose 40g, MnSO₄·4H₂O 1.62g(5mmol/L), distilled water 1000ml. The optimal growth conditions were temperature 30℃, 200prm, intial pH7.5, culture time 72h with 30ml medium in 250ml triangular flask. The bacterial sporulation quantity and the inhibitory activity of the fermented filtrate could reach to the best.(3) The antifungal compound produced by strains 12-041 and 12-059 was not the crude protein extracted by ammonium sulfate precipitation at different concentrations. The low weight molecules extracted by acid precipitation and 75% alcohol abstraction had strong inhibitory activity to R. solani.(4) In pot experiment, 12-041 and 12-059 biocontrol efficacies against Maize Sheath Blight were 69.37% and 68.42%, respectively, which were significantly higher than that of Jinggangmycin.(5) The strains 12-041 and 12-059 were both identified as Bacillus subtilis according to their morphological, physiological, biochemical characteristics and sequences of 16S rDNA.