Biocontrol of peanut southern blight [sclerotium rolfsii] by bacillus subtilis

ABSTRACT

The effective strains of Bacillus subtilis for antagonism against Sclerotium rolfsii in dual cultures were selected. The effects of substrates and cultural conditions on the antagonism of B. subtilis were also studied. S. rolfsii Sacc. caused southern blight disease of a wide range of hosts including leguminosae. The tested peanut plants showed different pre-emergence and post-emergence infection responses towards the four tested S. rolfsii isolates. S. rolfsii isolate number 1 was the most virulent one. Sixteen out of 30 isolates of Bacillus species showed antagonistic activity against S. rolfsii isolate number 1. Richard's medium gave the maximum antagonistic activity. The optimum environmental conditions needed for B. subtilis to give maximum antagonistic activity were 72 hr incubation period, 35C incubation temperature and pH 6. Sucrose and potassium nitrate proved to be the best carbon and nitrogen sources, respectively. MnSO4 [0.01 g/l] was needed to give the maximum antagonistic activity