Melanin-producing Streptomyces spp. respond to potato plant growth and differentially to potato cultivars

Abstract

Population dynamics of Streptomyces spp. producing melanoid pigments were monitored in field plots planted to the potato cultivars 'Chippewa' (susceptible to common scab) or 'Superior' (resistant), and in fallow control plots. Relative frequencies of streptomycetes most commonly isolated from soil, the rhizosphere, and potato tuber surfaces were determined during two growing seasons. Shannon indices of diversity indicated populations in soils planted to potatoes were more diverse than populations in fallow soil. In 1986, S. diastatochromogenes and S. longisporus accounted for ≥38% of all streptomycetes observed in all three environments. In 1987, S. diastatochromogenes was observed frequently in soil, while S. longisporus was observed rarely in all environments. Relative numbers of three Streptomyces spp. differed in the rhizospheres of 'Chippewa' and 'Superior' (P ≤ 0.05). This is the first report of a differential response of Streptomyces spp. to potato cultivars. Key words: rhizosphere, Solanum tuberosum, Streptomyces spp., melanin.