Effects of Interactions Between Chemical Seed Dressings And Bradyrhizobium Japonicum on Soybean Seeds

Abstract

Soybean seeds, both untreated and dusted with selected pesticides, were inoculated with Bradyrhizobium japonicum and stored in the laboratory at room temperature. Approximately 1 hour, 24 hours and 48 hours following inoculation samples of the seeds were taken to count the surviving rhizobia and to grow soybean plants in the greenhouse experiment. Numbers of B. japonicum cells surviving on soybean seeds (two cultivars) treated with the tested pesticidal dressings and on the untreated seeds did not differ significantly when analysed within the first hour following seed inoculation with the rhizobia. However, analyses performed 24 hours and 48 hours later showed no B. japonicum cells surviving on the seeds dressed with mancozeb (fungicide), while the numbers of these bacteria on the untreated seeds and on the seeds treated with a mixture of carbendazim + thiram (fungicides) or with carbosulfan (insecticide) were similar and remained on relatively high levels. Only soybean plants that developed from mancozeb treated seeds had significantly less nodules, both in terms of numbers and mass, as well as lower fresh and dry weight of shoots as compared to the plants grown from the control seeds and the seeds treated with the other pesticides tested. The toxicity of mancozeb to the symbiosis was particularly severe when soybean seeds inoculated with B. japonicum were stored for 24-48 hours before planting

Keywords:

• Bradyrhizobium Japonicum
• Pesticides
• Seed Dressing
• Soybean Toxicity