Abstract
ABSTRACT Soybean has traditionally been produced in systems that include the use of herbicides, often in higher than recommended doses. The process of symbiotic nitrogen fixation in legumes can be hampered by these herbicides, both by direct effects on rhizobia and indirect effects on the host plant. An outdoor experiment was performed to evaluate the effects of different doses of a glyphosate herbicide on Bradyrhizobium strains and biological nitrogen fixation in soybean BMX Potência RR plants. Soybean seeds were inoculated with Bradyrhizobium elkanii (SEMIA 5019) and Bradyrhizobium japonicum (SEMIA 5079) strains in a commercial liquid inoculant. The treatments consisted of the absence and presence of Bradyrhizobium genotypes inoculated via seed and four doses of the herbicide glyphosate applied on the leaves (0, 1.0, 2.0, and 4.0 L ha-1 of the commercial product) at the V3 stage. The leaf chlorophyll index of inoculated RR soybean plants did not change on the application of glyphosate and, regardless of inoculation, plants had the capacity to recover from the effects of glyphosate application, without impaired development.
Highlights
Modified soybean (Glycine max (L.) Merril) Roundup Ready (RR), glyphosate-resistant, is one of the most economically important biotech products developed in the last 20 years (Bervald et al, 2010)
The objective of this study was to evaluate the effects of different doses of glyphosate herbicide on the development of RR soybean, with or without inoculation with Bradyrhizobium strains
Several authors have shown that the leaf chlorophyll index measured with a portable chlorophyllometer has many advantages, mainly owing to the ease and speed of the results
Summary
Modified soybean (Glycine max (L.) Merril) Roundup Ready (RR), glyphosate-resistant, is one of the most economically important biotech products developed in the last 20 years (Bervald et al, 2010). Soybeans have traditionally been produced in systems that include the use of herbicides, often at doses above the recommended levels, owing to the ability of some weeds to acquire herbicide tolerance (Bervald et al, 2010). With the increase in herbicide use, greater tolerance has developed in weedy species, leading to the greater and more frequent use of herbicides than recommended by the manufacturers (Vilvert et al, 2014). Biological nitrogen fixation (BNF) may be impaired by glyphosate, by effects both directly on the rhizobia and indirectly on the host plant, which may reduce its efficacy (Chagas Junior et al, 2013)
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