Study On The Biocontrol Of Maize Sheath Blight (Rhizoctonia Solani) With Bacillus Subtilis BS-8D Strain

Antagonistic agents of Bacillus spp.were isolated from the sheaths and rhizosphere of corn in different area. 800 isolates of Bacillus spp.were obtained and assayed for the antagonistic activity against Rhizoctonia solani by agar-plate technique. 36 isolates presented the antagonistic activity(10.50~35.23mm inhibition zone). One isolate BS-8D with strong antagonistic activity was selected for further investigation in detail.The results are as follows:1) By dual culture on PDA medium,the BS-8D strain showed strong ability against many common plant fungal pathogens in vitro, such as Exserohilum turcicum,Bipolaris maydis, Curvularia lunata,Fusarium graminearum, Verticillium dahliae,Sclerotinia sclerotiorum and Colleto gloeosporioides.2)The effect of BS-8D strain on controlling sheath blight and inducing plant growth of corn was tested in plot experiments. The results showed that the strain BS-8D could control effectively corn sheath blight caused by the Rhizoctonia solani, and very close to the control efficacy of Jinggangmycin fungicide and promoted plants growth significantly.3) The disease suppressing ability of BS-8D strain in field plot experiments by spraying suspension of BS-8D to soil and sheaths.The results showed that the strain BS-8D effectively controlled sheath blight caused by the pathogen.The control efficacy of the strain was about 45% at adult stage.4) To test the ability of BS-8D strain to colonize the roots of maize seedlings and sheaths at adult stage,BS-8D mutant of resistant Rif 300ug/mL was acquired by continuously screening on series concentration of Rif mediums.Compared with original strain,whose inhibition to R.solani wasn't changed. The experiment showed that BS-8D could colonize,propagate and temain high population for more than ten days. The highest colonizing...