A METHOD OF ISOLATING ACTINOMYCETES FROM SCABBY POTATO TISSUE AND SOIL WITH MINIMAL CONTAMINATION

Abstract

The isolation of actinomycetes from soil or from scabby potato tubers was facilitated by a 10-min. treatment of the material from which the isolations were to be made with phenol in dilution of 1: 140. This eliminated most bacterial contaminants and reduced fungal contaminants especially those of the spreading type. Treatment of the material with higher concentrations of phenol progressively decreased the number of actinomycetes until there was no growth after treatment with 1: 70 dilution of phenol. Optimum development and maximum numbers of actinomycetes occurred when phenol-treated material was cultured on media adjusted to pH 6.5. More actinomycetes developed on glucose-asparagine agar than on Czapek's agar inoculated with phenol-treated material from scab-infected potatoes. However, when phenol-treated soil suspensions were tested, Czapek's agar was more favorable to the development of actinomycete colonies. A comparison of the phenol method with another in which sodium propionate is incorporated into the culture medium showed that the phenol method was more efficient in reducing contaminants and in permitting a larger number of actinomycete colonies to develop.