BIOLOGICAL CONTROL OF POTATO BACTERIAL WILT DISEASE UNDER EGYPTIAN CONDITIONS

[26]

Wafaa, M. Abd El-Sayed¹; R.A. Bayoumi² and N.Y. Abd El-Ghafar¹

ABSTRACT

The biological control of potato bacterial wilt disease is caused by Ralstonia solanacearum (Smith) Yabunchi et al. race 3, biovar II has been investigated under Egyptian conditions. The present work was planned to control the disease biologically using three isolates of Pseudomonas fluorescens (pf), three isolates of Streptomyces spp. and one isolate of Bacillus subtilis (Bs). All bioagents tested inhibited growth of R. solanacearum, in vitro. Isolates of P. fluorescens, Streptomyces spp. and B. subtilis were the most inhibitors on King’s B (KB), starch nitrate agar (SNA) and nutrient agar (NA) media, respectively. Bioagents populations increased in the rhizosphere potato plants with increasing the period after planting. Meanwhile, populations of P. fluorescens and B. subtilis were higher than Streptomyces spp. population at the end of 80 days from planting. Application of bioagents of a soil drench decreased the population of R. solanacearum in potato plants rhizosphere. However, severity of potato bacterial wilt disease was reduced with application of bioagents as tuber treatment or soil drench treatment, as compared with the control. Application of bioagents as soil drench treatment was better than tuber treatment. Pseudomonas fluorescens (Pf5) and Streptomyces griseoviridis (Sg) isolates were the most effective in the reduction of the disease severity and in increasing disease biocontrol. However, increasing a soil drench for three applications significantly reduced disease severity and thus increased the disease biocontrol comparable to only one application under the same specified Egyptian conditions.