Fungi and Gram‐negative bacteria as soilborne minor pathogens of goat's rue (Galega orientalis Lam.)

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SummaryFungi and Gram‐negative bacteria were isolated from inside the roots of field‐grown goat's rue (Galega orientalis). Fungi were isolated from three plants out of a total of 45 tested. Two multinuclear Rhizoctonia solani isolates were identified to the anastomosis group 5 (R. solani AG‐5‐Gal) using pairings with known AG test cultures. One fungal isolate was identified to Phoma chrysanthemicola. Gram‐negative bacteria were isolated from three plants out of 25 tested. They were identified using classical methods, the BIOLOG identification system based on the utilisation of 95 different carbon sources, and the MIDI system for the analysis of whole cell fatty acids. The two latter systems were computer‐associated and utilised an extensive reference library of isolates. One bacterial isolate was identified as Enterobacter agglomerans and two isolates as Pseudomonas marginalis. R. solani AG‐5‐Gal reduced the emergence of Lupinus luteus, L. polyphyllus and french bean (Phaseolus vulgaris) and the growth of broad bean (Viciafaba), L. luteus and french bean, but did not cause obvious damage in goat's rue and pea (Pisum sativum). However, R. solani AG‐5‐Gal was re‐isolated from the roots of all the test plant species following inoculation. P. chrysanthemicola reduced the emergence of L. polyphyllus and the growth of goat's rue, french bean and broad bean, and it was re‐isolated from all of the test plant species (except for french bean) following inoculation.All the bacteria reduced the emergence of french bean, but not that of goat's rue and pea, when applied to the soil. When the roots were dipped into bacterial suspension, all the bacteria damaged french bean and L. polyphyllus. Additionally, P. marginalis JV3 damaged goat's rue and red clover. The pathogenicity of the fungi and bacteria were not changed when they were double‐inoculated in pairs, except for R. solani AG‐5‐Gal and P. marginalis JV2 which reduced the emergence of goat's rue when inoculated together but not when inoculated separately.