The relationship between virulence and cytokinin production by Rhodococcus fascians (Tilford 1936) Goodfellow 1984

Qualitative and quantitative analyses were made of cytokinins secreted into liquid culture by virulent and avirulent strains of Rhodococcus fascians, and of the endogenous cytokinins in pea plants inoculated with the same strains. Both virulent and avirulent strains secreted a range of cytokinins into liquid culture. The non-hydroxylated cytokinins were present in the liquid cultures at levels up to 1000-fold higher than hydroxylated cytokinins, but the virulent strains secreted only slightly higher levels of isopentenyladenine (iP), isopentenyladenosine (iPA) and the tentatively identified methylthioisopentenyladenosine (ms-iPA), than the avirulent strains. Pisum sativum cv. Novella plants that were inoculated with virulent strains contained only slightly higher levels of iP and ms-iPA but had lower levels of the cytokinin nucleotides than those plants that had been inoculated with the avirulent strains. The origin of the cytokinins secreted by avirulent and virulent strains is discussed, as is the significance of the cytokinin content of fasciated plants.