Suppressiveness to Clubroot, Pea Root Rot and Fusarium Wilt in Swedish Soils

Natural soil samples, collected from farms in central and southern Sweden, were tested for soil disease-suppressiveness. The soils were mixed with inocula of either Plasmodiophora brassicae. Aphanomyces euteiches or Fusarium oxysporum. f.sp. spinaciae and disease symptoms were scored on Chinese cabbage, pea and spinach respectively, that were grown in the soil-inocula mixture under greenhouse conditions. Most field soils limited the development of disease to some degree compared with a commercial 5/)fta^num-sand-soil mixture, and about 10% were strongly suppressive to disease outbreaks caused by either P. brassicae, A. euiheiches. or F. oxysporum f.sp. spinaciae. Some tested soils gave higher disease indices of A. euteiches compared with the control growing medium and were regarded disease synergistic. The suppressiveness found was specific for each disease tested and in no case was a soil sample strongly suppressive to two of the diseases tested