Glyphosate Effect on Nitrogen Fixation and Metabolization in RR Soybean

Nayane Cristina Pires Bomfim,Gilberto Costa Justino,Lucas Anjos Souza,Leandro Ferreira Aguiar,Liliane Santos Camargos,Beatriz Gonçalves Pereira Costa

doi:10.5539/jas.v9n10p114

Nayane Cristina Pires Bomfim, Gilberto Costa Justino + Show 4 more

Open Access

https://doi.org/10.5539/jas.v9n10p114

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Abstract

To evaluate under controlled temperature conditions, nutrition and water supply, the influence of glyphosate on nitrogen fixation capacity in Roundup Ready (RR) soybean, BRS Valiosa Roundup Ready. Commercially available seeds were sown in pots containing vermiculite and washed sand (1:1) and after germination, the seeds were inoculated with Bradyrhizobium sp. and kept in nutrient solution without nitrogen, in greenhouse, with temperature control to 27 ºC without photoperiod control, at UNESP, Ilha Solteira, SP. At the vegetative stage, glyphosate was applied at a concentration of 1.8 mg glyphosate/plant once a week. There were two harvests: after 15-21 days after herbicide application, and at reproductive stage. The chlorophyll content in leaves was analyzed and the organs were separated (leaves, roots and nodules) for extraction and quantitation of nitrogenous compounds, in addition to the enzyme allantoinase activity analysis (in vitro) and nitrogenase activity (in vivo). Nodules were counted and weighted. Means were compared by 5% Tukey’s test. It was observed that the application of glyphosate in RR soybeans moderately affected N fixation and assimilation. There were no drastic metabolic changes for the aminoacids, proteins, chlorophylls and ureides in RR soybean treated with glyphosate.

Highlights

Soybean (Glycine max (L.) Merril) is one of the most important crop, and its cultivation is increasing over the years
The resistance was achieved by the insertion of the AroA gene from Agrobacterium sp., strain CP4, that codify a variant of the enzyme EPSPs (CP4EPSPs), that is specially tolerant to the inhibition by glyphosate (Padgette et al, 1995)
Chlorosis have not been observed, as well as yellowing signs on Roundup Ready (RR) soybean leaves treated with glyphosate, Tuffi-Santos et al (2008) reported chlorosis in plants of Eucalyptus urograndis, sprayed with glyphosate (172.8 and 345.6 g ha-1), and necrosis and yellowing on Ricinus communis leaves by Sizenando-Filho et al (2013)

Summary

Introduction

Soybean (Glycine max (L.) Merril) is one of the most important crop, and its cultivation is increasing over the years. The resistance was achieved by the insertion of the AroA gene from Agrobacterium sp., strain CP4, that codify a variant of the enzyme EPSPs (CP4EPSPs), that is specially tolerant to the inhibition by glyphosate (Padgette et al, 1995). Under glyphosate treatment, these transgenic plants are not affected due to the non-inhibition of CP4EPSPs (Santos et al, 2007), the weeds are controlled without affecting soybean production. It is estimate that more than 20% of total carbon fixed by photosynthesis, pass through this pathway to the synthesis of aromatic amino acids, as reported by Sizenando-Filho et al (2013)

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