The intensity of non-target site mechanisms influences the level of resistance of sourgrass to glyphosate

Communications in Plant Sciences, vol 4, issues 1-2, p.11-17, 2014

DOI: http://dx.doi.org/10.26814/cps201411

Full title: The intensity of non-target site mechanisms influences the level of resistance of sourgrass to glyphosate

Authors: Flávia Regina da Costa, Leonardo Bianco de Carvalho, Hugo Enrique Cruz-Hipolito, Pedro Luis da Costa Aguiar Alves and Rafael De Prado

Abstract: Non-target site mechanisms are involved in the resistance of sourgrass (Digitaria insularis) to glyphosate. Studies on the 14C-glyphosate absorption and translocation as well as the detection of glyphosate and its metabolites in sourgrass plants were carried out under controlled conditions to investigate if the differential response of resistant sourgrass biotypes (R1 and R2) is derived from the intensity of non-target site mechanisms involved in the resistance to glyphosate. Different pattern of absorption was observed between S (susceptible) and R2 from 12 up to 48 hours after treatment with glyphosate (HAT), and between S and R1 just at 12 HAT. The initial difference in glyphosate absorption among the biotypes did not maintained at 96 HAT and afterwards. Smaller amount of herbicide left the treated leaf into the rest of shoot and roots in R2 (25%) than in S (58%) and R1 (52%). In addition, slight difference in glyphosate translocation was observed between S and R1. We found high percentage (81%) of glyphosate in the S biotype up to 168 HAT, while just 44% and 2% of glyphosate was recovered from R1 and R2 plant tissues. In addition, high percentage of glyphosate metabolites was found in R2 (98%) and R1 (56%) biotypes, while a very low percentage (11%) was found in the S biotype. As previous studies indicated resistant factors of 3.5 and 5.6 for R1 and R2, respectively, we conclude that the differential response of sourgrass biotypes is derived from the intensity of the non-target site mechanisms involved in the resistance to glyphosate.

Keywords: Digitaria insularis, N-phosphonomethylglycine, weed resistance, non-target site resistance.

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