Tolerance of DAS-444ø6-6 and DAS-444ø6-6 x DAS-81419-2 Soybeans to 2,4-D and Glyphosate in the Cerrado Region of Brazil

ABSTRACT: The DAS-444Ø6-6 soybean expresses AAD-12, 2mEPSPS and PAT enzymes to provide, respectively, tolerance to 2,4-D, glyphosate and ammonium glufosinate. This event is also associated with DAS-81419-2 expressing Cry1Ac and Cry1F proteins to provide protection against a broad spectrum of soybean lepidopteran insect species. Successful adoption by growers of these technologies relies on the traits performing in the diverse environments of Brazil, especially under adverse weather conditions. The objective of this study was to characterize the tolerance of DAS 444Ø6-6 and DAS-444Ø6-6 x DAS-81419-2 soybeans to 2,4-D and glyphosate in the Cerrado region of Brazil. Eight trials across four sites were conducted in the 2015/2016 summer rainy season using a randomized complete block design, with a factorial arrangement of treatments. Factor A was 2,4-D choline salt (456 g a.e. L-1) + glyphosate DMA salt (480 g a.e. L-1) at 975 + 1,025 and 1,950 + 2,050 g a.e. ha-1, respectively and ready-mix of (2,4-D choline salt 195 g a.e. L-1 + glyphosate DMA salt 205 g a.e. L-1) at 2,000 (975 + 1,025) and 4,000 (1,950 + 2,050) g a.e. ha-1. Factor B was application timing at V3, V6 and R2 soybean growth stages. No visible symptoms of leaf chlorosis, epinasty, or growth inhibition were observed. Slight leaf droop was observed at 1 day after treatment (DAT), but it was null at 7 DAT. Less than 6% and 13% of leaf necrosis or injury were observed at 7 DAT, respectively, at 975 + 1,025 and 1,950 + 2,050 g a.e. ha-1 of 2,4-D choline salt + glyphosate DMA salt, regardless of applied as a ready-mix or not, but it was always 2% or less at 28 DAT. Crop grain yield was not influenced by herbicide treatments, application timing and their interaction, regardless of the soybean event and experimental site. DAS-444Ø6-6 and DAS-444Ø6-6 x DAS-81419-2 soybeans showed high tolerance to 2,4-D choline salt and glyphosate DMA in the Cerrado region of Brazil