Abstract

The interaction between Streptomyces griseoviridis and the pathogens Alternaria brassicicola, Botrytis cinerea, Fusarium oxysporum, Mycocentrospora acerina, Rhizoctonia solani and Sclerotinia sclerotiorum was studied by SEM both on autoclaved seeds and living seedlings of turnip rape and carrot and the fungi Phomopsis sclerotioides and Pythium ultimum on cucumber seedlings. The samples were prepared by the standard method for examination by scanning electron microscope. The hyperparasitism of S. griseoviridis was clearly shown. S. griseoviridis tightly wound around Alternaria conidia and Sclerotinia hyphae, eventually disintegrating them. It grew along the hyphae of B. cinerea, P. sclerotioides and M. acerina, dissolving them. The hypha of F. oxysporum seemed to be slightly affected, and its conidia not at all. The hyperparasite grew only loosely on the hypha of R. solani and on the mycelium and oogonia of Pythium which seemed not to sustain much injury.

Highlights

  • Streptomyces griseoviridis Anderson et al, isolated from Finnish light coloured Sphagnum peat, has been reported to be antagonistic to the plant pathogens Alternaria brassicicola (Schw.) Wiltshire, Botrytis cinerea Pers.: Fr., Fusarium avenaceum (Fr.: Fr.) Sacc., F. culmorum

  • The seeds were placed on water agar in Petri dishes and inoculated with pathogens, Alternaria brassicicola, isolated from cauliflower seeds, Botrytis cinerea and Sclerotinia sclerotiorum, isolated from carrots or Fusarium oxysporum and Rhizoctonia solani, isolated from turnip rape

  • The hyperparasitism of one of these antagonists was clearly shown in the present study

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Summary

Introduction

Streptomyces griseoviridis Anderson et al, isolated from Finnish light coloured Sphagnum peat, has been reported to be antagonistic to the plant pathogens Alternaria brassicicola (Schw.) Wiltshire, Botrytis cinerea Pers.: Fr., Fusarium avenaceum (Fr.: Fr.) Sacc., F. culmorum Griseoviridis (Tahvonen 1982 a) It controlled damping-off caused by A. brassicicola and R. solani on cauliflower and P. debaryanum on sugar beet in in vivo tests. It reduced the mortality of barley sprouts and foot rot caused by F. culmorum (Tahvonen 1982 b, Tahvonen and Avikainen 1987). The present study was done to elucidate the nature of the host-mycoparasite interactions between Streptomyces griseoviridis and some plant pathogenic fungi. The interaction between Mycocentrospora acerina Deighton, isolated from carrot and S. griseoviridis was examined directly on mycelia grown on potato dextrose agar (PDA) in Petri dishes. Agar blocks with mycelia were frozen in liquid nitrogen at —lBO°C (Hexland CT 100), dehydrated at —BO°C in vacuum in a cryonit, coated with gold and examined under a scanning electron microscope (Cambridge Instrument S 360) at the Kemira Research Center

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