Plants having increased tolerance to herbicides

A method for controlling undesired vegetation at a plant cultivation site, the method comprising the steps of:

• a) providing, at said site, a plant that comprises at least one nucleic acid comprising a nucleotide sequence encoding a protoporphyrinogen oxidase (PPO) polypeptide which is resistant or tolerant to a “PPO inhibiting herbicide”;
• b) applying to said site an effective amount of said herbicide,
• wherein the PPO inhibiting herbicide is a phenylpyridine of formula (I)
• wherein the variables have the following meanings:
• R1 halogen, C1-C4-haloalkyl or SO2CH3;
• R2 H, CH3 or NH2;
• R3 halogen;
• R4 H or halogen;
• R5 halogen or CN;
• R6 H or CH3;
• R7 C1-C6-alkoxy, C1-C6-haloalkoxy, C3-C6-alkenyloxy, C3-C6-alkynyloxy;
• R8 OR9, SR9, NR10R11, NR9S(O)R10, NR9S(O)2R10, NR9S(O)NR10R11, or NR9S(O)2NR10R11,
• wherein
• R9 is hydrogen, C1-C6-alkyl, C3-C6-alkenyl, C3-C6-alkynyl, C1-C6-halo-alkyl, C3-C6-haloalkenyl, C3-C6-haloalkynyl, C1-C6-cyanoalkyl, C1-C6-alkoxy-C1-C6-alkyl, C1-C6-alkoxy-C1-C6-alkoxy-C1-C6-alkyl, di(C1-C6-alkoxy)C1-C6-alkyl, C1-C6-haloalkoxy-C1-C6-alkyl, C3-C6-alkenyloxy-C1-C6-alkyl, C3-C6-haloalkenyloxy-C1-C6-alkyl, C3-C6-alkenyloxy-C1-C6-alkoxy-C1-C6-alkyl, C1-C6-alkylthio-C1-C6-alkyl, C1-C6-alkylsulfinyl-C1-C6-alkyl, C1-C6-alkylsulfonyl-C1-C6-alkyl, C1-C6-alkylcarbonyl-C1-C6-alkyl, C1-C6-alkoxycarbonyl-C1-C6-alkyl, C1-C6-haloalkoxycarbonyl-C1-C6-alkyl, C3-C6-alkenyloxycarbonyl-C1-C6-alkyl, amino, (C1-C6-alkyl)¬amino, di(C1-C6-alkyl)amino, (C1-C6-alkylcarbonyl)amino, amino-C1-C6-alkyl, (C1-C6-alkyl)amino-C1-C6-alkyl, di(C1-C6-alkyl)amino-C1-C6-alkyl, aminocarbonyl-C1-C6-alkyl, (C1-C6-alkyl)aminocarbonyl-C1-C6-alkyl, di(C1-C6-alkyl)aminocarbonyl-C1-C6-alkyl,
• —N═CR12R13, wherein R12 and R13 independently of one another are H, C1-C4-alkyl or phenyl;
• C3-C6-cycloalkyl, C3-C6-cycloalkyl-C1-C6-alkyl, C3-C6-heterocyclyl, C3-C6-heterocyclyl-C1-C6-alkyl, phenyl, phenyl-C1-C4-alkyl or a 5- or 6 membered heteroaryl,
• wherein each phenyl or heteroaryl ring can be substituted by one to four substituents selected from R14 or a 3- to 7-membered carbocyclus,
• which carbocyclus optionally has in addition to carbon atoms one or two ring members selected from the group consisting of —N(R12)—, —N═N—, —C(═O)—, —O— and —S—, and
• which carbocyclus is optionally substituted with one to four substituents selected from R14;
• wherein R14 is halogen, NO2, ON, C1-C4-alkyl, C1-C4-haloalkyl, C1-C4-alkoxy or C1-C4-alkoxycarbonyl;
• R10, R11 independently of one another are R9, or together form a 3- to 7-membered carbocyclus,
• which carbocyclus optionally has in addition to carbon atoms one or two ring members selected from the group consisting of —N(R12)—, —N═N—, —C(═O)—, —O— and —S—, and
• which carbocyclus is optionally substituted with one to four substituents selected from R14;
• X O or S;
• and
• Y O or S;
• including their agriculturally acceptable salts, and wherein the effective amount of said herbicide does not kill or inhibit the growth of the herbicide-tolerant plant of a).