ALBERT

Description:    Effects of soil pH on damping-off of sugar beet by R. solani (AG2-2) and soil suppressiveness against the disease were studied by comparing disease incidences in pasteurized versus non-pasteurized, infested soils. Soil pH was correlated neither to disease incidence in five soils ranging from pH 4.5 to 7.2 nor to indigenous disease suppressiveness, the difference in disease incidences between non-treated soil and its pasteurized counterpart. When an alkaline soil was acidified with H 2 SO 4 , disease suppression markedly declined, increasing disease incidence in the non-pasteurized soil. Inversely, disease suppression was enhanced when an acidic soil was neutralized by adding Ca(OH) 2 . Soil amendment with dried peanut plant residue suppressed the disease in two pasteurized, near-neutral soils, lowering the incidence to the levels in the non-pasteurized soils, but was less effective in two pasteurized, acidic soils. In vitro mycelial growth of the pathogen and seedling growth was optimal at pH 4.5–5.5 and 6.0–6.5, respectively, and declined as the pH became higher or lower. (Conclusions) These results suggest that the seedlings were inhibited more than the pathogen at low pH, and that indigenous disease suppressiveness through the activity of antagonistic soil microorganisms operates effectively in near-alkaline soils, but is weakened or nullified in acidic soils. Content Type Journal Article Pages 1-14 DOI 10.1007/s11104-011-0843-6 Authors Kaori Watanabe, Department of Bio-productive Science, Faculty of Agriculture, Utsunomiya University, Utsunomiya, Tochigi, Japan Mariko Matsui, Department of Bio-productive Science, Faculty of Agriculture, Utsunomiya University, Utsunomiya, Tochigi, Japan Hitoshi Honjo, Department of Bio-productive Science, Faculty of Agriculture, Utsunomiya University, Utsunomiya, Tochigi, Japan J. Ole Becker, Department of Nematology, University of California at Riverside, Riverside, CA, USA Ryo Fukui, Department of Bio-productive Science, Faculty of Agriculture, Utsunomiya University, Utsunomiya, Tochigi, Japan Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X