<p style="text-align: justify;">Rice lines LLRICE06 and LLRICE62 were developed using recombinant DNA techniques to allow the use of glufosinate ammonium, the active ingredient in phosphinothricin herbicides (Basta&reg;, Ignite&reg;, Rely&reg;, Liberty&reg;, Finale&reg;, RadicaleX&reg;), as a weed control option in rice crops. Currently, rice growers in the United States control weeds through a combination of herbicides, crop rotation, and cultural practices such as flooding and tillage. The <i>bar</i> gene, which encodes the enzyme phosphinothricin N-acetyltransferase (PAT), was isolated from the common aerobic soil actinomycete, <i>Streptomyces hygroscopicus</i> strain HP632, and introduced by direct DNA transfer into the rice genome.</p>

<p style="text-align: justify;">In addition to providing the trait of glufosinate herbicide tolerance, the PAT encoding gene was used as a selectable marker to identify transformed plants during regeneration in tissue culture. Glufosinate is a short name for the ammonium salt, glufosinate-ammonium. It is a broad-spectrum contact herbicide and is used to control a wide range of weeds after the crop emerges or for total vegetation control on land not used for cultivation. Glufosinate is a natural compound isolated from two species of Streptomyces fungi. It inhibits the activity of an enzyme, glutamine synthetase, which is necessary for the production of glutamine and for ammonia detoxification. The application of glufosinate leads to reduced glutamine and increased ammonia levels in the plant tissues. This causes photosynthesis to stop and the plant dies within a few days. Glufosinate also inhibits the same enzyme in animals. It is highly biodegradable, has no residual activity, and very low toxicity for humans and wild fauna. The PAT enzyme detoxifies phosphinothricin by acetylation into an inactive compound.</p>
