Possibility of biological management of potato bacterial wilt with microbial antagonists and latent potato viruses

Two strains of Pseudomonas fluorcscens (PF₁, PF₂), three each of Bacillus subtilis and Bacillus sp., four isolates of non-pathogenic aetinomycetes and potato viruses S and X singly and in combination were examined for their ameliorative effect on bacterial wilt of potato. The actinomycete isolate A₁ reduced wilt incidence to 10% as compared 72% in check. In addition, it also increased the incubation period for disease development to 62 days as compared to 27 days in check. The isolate A₂ also reduced wilt incidence to 43% and increased incubation period to 34 days. Among six isolates of B. subtilis and Bacillus sp., the S₁(Bacillus sp.) gave complete control of wilt throughout the growing period. Isolates S₂, S₄, S₅, and S₆ reduced wilt incidence to 54, 58, 36 and 33% respectively. Though both the isolates of P. fluoresceus inhibited the pathogen in vitro, one of them (PF₂) failed to reduce wilt incidence. Mixed infection of potato viruses S and X reduced wilt incidence to 30%. Individual inoculation by PVS and PVX resulted in 60% and 80% wilt incidence respectively. There was no correlation between antagonism in vitro and wilt control.