The aim of this study was to evaluate the effects of treatment of common bean seeds with different fungicides on the survival of strains of Rhizobium tropici (SEMIA 4077) and Rhizobium freirei (SEMIA 4080), as well as on plant nodulation and on crop yield. Two experiments were carried out in sterilized substrate, under greenhouse conditions and in the experimental field of Embrapa Western Agriculture, in Dourados, Mato Grosso do Sul State, in a typical Oxisol. The fungicides (active ingredients) used in the experiments were: (1) carbendazim + thiram (Product A), (2) carbendazim + thiram (Product B), (3) carboxin + thiram, (4) fludioxonil + metalaxyl-M, (5) fludioxonil + metalaxyl-M + thiabendazole, (6) fluazinam + methyl thiophanate, (7) fipronil + methyl thiophanate + pyraclostrobin, (8) chlorothalonil + methyl thiophanate. The survival of R. tropici strains inoculated in bean seeds was affected by the application of fungicides, especially contact fungicides. In addition, fungicide application led to a reduction in the nodulation of bean plants, especially for nodular mass, either in assays carried out on sterilized substrate, in a greenhouse, or in the field experiment, where grain yield reduction was also noted with the use of most evaluated fungicides. The fungicides that mostly affected grain yield were carbendazim + thiram (Product B) and carboxin + thiram. The products fipronil + thiophanate methyl + pyraclostrobin, fludioxonil + metalaxyl-M + thiabendazole and fludioxonil + metalaxyl-M did not affect the crop yield, although the dry weight of nodules was reduced in all trials.
biological nitrogen fixation; nodulation
