Available Herbicide Tolerance Technologies in Soybean
Soybean producers have myriad choices when choosing herbicide-tolerant varieties to plant. When selecting a variety or varieties, it is likely that producers now consider herbicide tolerance equally important as disease and insect tolerance/resistance traits. This is because weed resistance to herbicides has become a crucial consideration for profitability. The following narrative defines the herbicide tolerance technologies that are available in current soybean varieties.
Conventional (CONV). Seed of these varieties have tolerance to “conventional” herbicides, or those that were used for pre- and post-emergence weed control prior to the appearance of Roundup Ready soybean varieties. They have no genetic modification that imparts tolerance to herbicides. Weed management is accomplished with tillage and “conventional” herbicides that can be safely applied to soybeans with little or no resulting toxicity.
Roundup Ready (RR or GT). Seed of these varieties contain the original glyphosate-resistant Roundup Ready trait that is now off-patent. This trait is still available in seed of varieties originating from university breeding programs and some seed companies.
Roundup Ready 2 (RR2). This is the second generation of Roundup Ready technology available in soybean seed. This trait remains a stand-alone option for growers, and likely will be available in varieties for a few more years in ever-decreasing numbers.
Roundup Ready 2 Yield (RR2Y). This is the basic Roundup Ready technology that has been and is still being used for future advancements in soybean herbicide-tolerant traits. RR2Y soybean varieties are touted for having a higher yield potential compared to earlier iterations of the Roundup Ready technology.
Liberty Link (LL). Liberty Link soybean varieties have tolerance to glufosinate (Liberty) herbicide, which has a different mode of action than glyphosate.
Roundup Ready 2 Yield Xtend (RR2X). These varieties contain the industry’s first biotech-stacked trait with both dicamba and glyphosate herbicide tolerance. The RR2X system is built on the RR2Y soybean technology. Improved industry-developed dicamba formulations can be applied to soybean varieties that possess this technology so that herbicides with two modes of action can be applied to these tolerant varieties. This is a tool for deferring/delaying the development of weed resistance to herbicides.
XTENDFLEX (pending registration). Soybean varieties with this technology are the first with triple-stacked herbicide tolerance to over-the-top applications of dicamba, glyphosate, and glufosinate. The tolerance of these varieties to these herbicides with three different modes of action further decreases the potential for the development of weed resistance to herbicides by enabling more flexibility in the application of diverse herbicides.
Glyphosate/HPPD Group 27 (GT27). Varieties possessing this trait will be tolerant to both glyphosate and a new HPPD/Group 27 herbicide (Alite 27–pending EPA approval). Thus, GT27 soybean varieties will be tolerant of herbicides with two modes of action.
LibertyLinkGT27 (LLGT27). This is the first soybean trait that allows for the application of glufosinate (Liberty) and glyphosate herbicides, plus the aforementioned HPPD/Group 27 mode of action herbicide. Thus, these triple-stacked herbicide-tolerant varieties will allow the application of herbicides with three different modes of action. They do not contain the Roundup Ready gene, but rather a different glyphosate-tolerant trait.
Sulfonylurea-Tolerant Soybean (STS) or Sulfonylurea Ready (SR). Varieties with this non-GMO trait are more tolerant to sulfonylurea herbicides such as Classic, Pursuit, Synchrony XP, etc. A newer STS-tolerant platform (Bolt) contains two STS-tolerant genes that provide enhanced tolerance to sulfonylurea herbicides.
Enlist E3 (E3). All Enlist varieties have tolerance to over-the-top applications of 2,4-D choline and glyphosate herbicides. Enlist E3 soybean varieties have a triple-stacked trait that allows the application of 2,4-D choline, glyphosate, and glufosinate so that herbicides with three different modes of action can be applied safely to the soybean crop to thwart the development of herbicide-resistant weeds. Varieties with this technology will contain a non-Roundup Ready glyphosate-tolerant trait. There are two herbicide products registered for use on Enlist soybeans–Enlist One (2,4-D choline) and Enlist Duo (glyphosate and 2,4-D choline premix).
As stated above, there are now soybean varieties with stacked traits for herbicide tolerance. Some examples are LL/STS, RR2/STS, RR2Y/STS, RR2X/STS, E3/STS, and LL/GT27. This nomenclature is fairly standard among seed companies.
Private seed companies offer seed of varieties with varying levels of herbicide resistance; however, not all companies offer seed with all available herbicide tolerance technologies, and not all available herbicide tolerance traits are available in varieties of all maturity groups. Click here for access to the websites of soybean seed companies that show their variety portfolios with accompanying herbicide tolerance technologies.