Herbicide Resistant Rice

Abstract

Rice plants are disclosed with multiple sources of resistance to herbicides that normally inhibit a plant's acetohydroxyacid synthase (AHAS) enzyme. Besides controlling red rice, many AHAS-inhibiting herbicides also effectively control other weeds that are common in rice fields. Several of these herbicides have residual activity, so that one treatment can control both existing weeds and weeds that sprout later. With effective residual activity against red rice and other weeds, rice producers now have a weed control system superior to those that are currently available commercially.

What is claimed: 
     
         1 . A method for confirming the presence of a herbicide-tolerance phenotype in rice plants, wherein at least some of the rice plants express a herbicide-tolerant acetohydroxyacid synthase;
 wherein said method comprises:
 (a) placing rice seed in conditions that are favorable for growth, except that an acetohydroxyacid synthase-inhibiting herbicide is present in a concentration that would normally inhibit the growth of rice plants; and 
 (b) observing that the growth of at least some of the rice seed is not inhibited by the presence of the herbicide; thereby confirming the presence of a herbicide-tolerance phenotype in at least some of the rice plants. 
   
     
     
         2 . The method of  claim 1 , wherein the herbicide comprises a herbicidally-effective imidazolinone. 
     
     
         3 . The method of  claim 2 , wherein the herbicide comprises imazethapyr. 
     
     
         4 . The method of  claim 2 , wherein the herbicide comprises imazapic. 
     
     
         5 . The method of  claim 2 , wherein the herbicide comprises imazapyr. 
     
     
         6 . The method of  claim 2 , wherein the herbicide comprises imazaquin. 
     
     
         7 . The method of  claim 2 , wherein the herbicide comprises imazamox. 
     
     
         8 . The method of  claim 1 , wherein the herbicide comprises a herbicidally-effective sulfonylurea. 
     
     
         9 . The method of  claim 8 , wherein the herbicide comprises nicosulfuron. 
     
     
         10 . The method of  claim 8 , wherein the herbicide comprises metsulfuron methyl. 
     
     
         11 . The method of  claim 8 , wherein the herbicide comprises thifensulfuron methyl. 
     
     
         12 . The method of  claim 8 , wherein the herbicide comprises tribenuron methyl. 
     
     
         13 . The method of  claim 8 , wherein the herbicide comprises pyrithiobac sodium. 
     
     
         14 . A method for confirming the presence of a herbicide-tolerance trait in one or more rice plants, said method comprising:
 (a) providing tissue from the one or more rice plants;   (b) extracting acetohydroxyacid synthase (AHAS) from the tissue;   (c) incubating the extracted AHAS with pyruvate and with a herbicide that normally inhibits acetohydroxyacid synthase; and   (d) confirming that the concentration of acetoin in the reaction mixture following said incubating step is consistent with the presence of a herbicide-tolerant AHAS; and wherein, by contrast, a lower level of acetoin would instead have indicated the presence of a herbicide-susceptible AHAS.   
     
     
         15 . The method of  claim 14 , wherein the herbicide comprises a herbicidally-effective imidazolinone. 
     
     
         16 . The method of  claim 15 , wherein the herbicide comprises imazethapyr. 
     
     
         17 . The method of  claim 15 , wherein the herbicide comprises imazapic. 
     
     
         18 . The method of  claim 15 , wherein the herbicide comprises imazapyr. 
     
     
         19 . The method of  claim 15 , wherein the herbicide comprises imazaquin. 
     
     
         20 . The method of  claim 15 , wherein the herbicide comprises imazamox. 
     
     
         22 . The method of  claim 14 , wherein the herbicide comprises a herbicidally-effective sulfonylurea. 
     
     
         23 . The method of  claim 22 , wherein the herbicide comprises nicosulfuron. 
     
     
         24 . The method of  claim 22 , wherein the herbicide comprises metsulfuron methyl. 
     
     
         25 . The method of  claim 22 , wherein the herbicide comprises thifensulfuron methyl. 
     
     
         26 . The method of  claim 22 , wherein the herbicide comprises tribenuron methyl. 
     
     
         27 . The method of  claim 22 , wherein the herbicide comprises pyrithiobac sodium.