Method for controlling parasitic weeds (orobanche) in protoporphyrinogen oxidase (PPO)-inhibitor tolerant sunflower crop

Abstract

The present invention relates to a method for control of broomrape (Orobanche cumana) in Protoporphyrinogen Oxidase (PPO)-inhibitor tolerant sunflower crop, comprising applying to the sunflower pre- or post-emergence an effective amount of at least one PPO-inhibitor.

Description

[0001]Method for controlling parasitic weeds (orobanche) in Protoporphyrinogen Oxidase (PPO)-inhib- itor tolerant sunflower crop Field of the invention Background The present invention relates to a method for control of broomrape (Orobanche cumana) in Pro- toporphyrinogen Oxidase (PPO)-inhibitor tolerant sunflower crop, comprising applying to the sunflower pre- or post-emergence an effective amount of at least one PPO-inhibitor. In crop protection, it is desirable, in principle, to increase the specific activity of an active com- pound and the reliability of the effect. It is particularly desirable for the crop protection product to control the harmful plants effectively, but at the same time to be compatible with the useful plants in question. Also desirable is a broad spectrum of activity allowing the simultaneous con- trol of harmful plants. Further, cases of herbicide-resistant weeds are becoming increasingly common. These biotypes survive herbicide application at doses that usually give effective control of the species. Re- sistant weed biotypes are a consequence of basic evolutionary processes. Individuals within a species that are best adapted to a particular practice are selected for and will increase in the population. Once a weed population is exposed to a herbicide to which one or more plants are naturally resistant, the herbicide kills susceptible individuals, but allows resistant individuals to survive and reproduce. With repeated herbicide use, resistant weeds that initially appear as iso- lated plants or patches in a field can quickly spread to dominate the population and the soil seed bank. For example, herbicide resistance within weeds has become a major concern for farmers, re- sulting in dramatic weed control problems. Herbicides from the group of Acetolactate Synthase (ALS) and Acetyl CoA Carboxylase (ACCase) inhibitors are most affected by resistance evolu- tion but also various other types of herbicides. Sunflower (Helianthus annuus) is an important crop plant that is grown worldwide in temperate and subtropical climates. Sunflower is used primarily for the production of vegetable oil. Sun- flower seeds are also used for animal feed (such as bird feed) and food manufacture. Herbicides that inhibit Protoporphyrinogen Oxidase (hereinafter referred to as Protox or PPO; EC 1.3.3.4), a key enzyme in the biosynthesis of protoporphyrin IX, have been used for selec- tive weed control since the 1960s. PPO catalyzes the last common step in chlorophyll and heme biosynthesis which is the oxidation of protoporphyrinogen IX to protoporphyrin IX. PPO-inhibitors include many different structural classes of molecules (Duke et al.1991. Weed Sci.39: 465; Nandihalli et al.1992. Pesticide Biochem. Physiol.43: 193; Matringe et al.1989. FEBS Lett.245: 35; Yanase and Andoh.1989. Pesticide Biochem. Physiol.35: 70). These herbi- cidal compounds include (see HRAC Mode of Action Classification 2022 Map | Herbicide Re- sistance Action Committee (hracglobal.com)) Diphenyl ethers (e.g. Lactofen, Acifluorfen, Ox- yfluorfen, Fomesafen, Bifenox), N-Phenyl-oxidiazolones, (e.g. Oxadiazon), N-Phenyl-imides (e.g. Saflufenacil, Flumioxazin, Trifludimoxazin), N-Phenyl-triazolinones (e.g. Sulfentrazone) and Pyraflufen-ethyl. Herbicides targeting PPO (PPO-inhibitors) have a very rapid contact action, causing leaf burn- ing, desiccation and growth inhibition (Li and Nicholl, Development of PPO inhibitor-resistant cultures and crops. PestManag Sci 61:277–285 (2005)). Although PPO targeting herbicides were developed more than 50 years ago, natural occurrence of weed resistance to PPO inhibi- tors has only been reported for a few plants, for example for Amaranthus palmeri (Salas et al Manag Sci.2016 May;72(5):864-9. doi: 10.1002 / ps.4241. Epub 2016 Mar 4. PMID: 26817647; PMCID: PMC5069602). Li and Nicholl (supra) describe that PPO herbicide-resistance mutations tend to reduce enzymatic function. This could explain why only a few plants developed resistant enzymes so far. Further, Li et al. (Plant Physiol 133:736–747 (2003)) describe that it was impos- sible to develop a field-resistant transgenic maize event without an increase in promoter activity driving the mutant PPO gene. WO 2012 / 080975, WO 2013 / 189984, WO2015 / 022636 and WO 2016 / 203377 disclose plants in which the tolerance to PPO inhibitors had been increased by transforming said plants with nu- cleic acids encoding mutated PPO mutated enzymes. Amongst other crops, sunflower is men- tioned as a target crop. In WO 2012 / 080975, WO2015 / 022636 and WO 2016 / 203377, trans- genic plants have been produced expressing mutated PPO genes under control of the ubiquitin promoter which is a strong constitutive promoter. However, transgenic sunflowers were not pro- duced. The genome from sunflower has been sequenced. It is known that sunflower comprises two PPO genes, PPO1 and PPO2. For example, the sequence of the sunflower PPO2 gene is dis- closed under NCBI-Protein ID XP_021982414.1. However, the PPO genes have not been ana- lyzed so far, for example, in the context of PPO tolerance. Since the modification of the genome of sunflower is difficult, sunflower plants which are tolerant to a broad spectrum of PPO inhibitors have not been reported. Therefore, PPO herbicides are currently only used for sunflower in pre-plant burndown and pre-emergence applications for controlling weeds, i.e. before the emergence of the sunflower plant. The international patent application PCT / US2022 / 077037 (published as WO2023 / 049906A1) discloses a non-transgenic sunflower plant comprising a mutated protoporphyrinogen IX oxi- dase (PPO) gene encoding a mutated sunflower protoporphyrinogen IX oxidase, wherein the mutated sunflower protoporphyrinogen IX oxidase comprises a substitution of phenylalanine (F) to isoleucine (I) at a position corresponding to residue 383 in the protoporphyrinogen IX oxidase (F383I substitution). The plants were generated by mutagenesis. US 2015 / 026836 A1 discloses a method for producing a sunflower line containing a highly herit- able trait conferring tolerance to sulfonylurea herbicides, inhibiting the enzyme Acetolactate Synthase (ALS). The Protoporphyrinogen Oxidase (PPO) inhibitor sulfentrazone is mentioned in the background section. However, the document does not disclose sunflower plants with toler- ance to the PPO inhibitor sulfentrazone. WO 2020 / 126584 A1 discloses the use of herbicidally active combinations comprising the ALS inhibitor R-imazamox for the selective control of undesirable vegetation in cultures of crop plants such as ALS inhibitor tolerant sunflower. Several herbicides are disclosed as second ac- tive ingredient, for example PPO inhibitors. However, the document does not disclose Oroban- che cumana. Further, PPO inhibitor tolerant sunflower plants were not generated. Sunflower production is challenged by the presence of weeds, including the troublesome holo- parasitic broomrape (Orobanche cumana Wallr.), which is dependent on sunflower as host plant to survive and reproduce. The broomrape forms underground tubercles, which subsequently de- velop single flowering shoots that emerge above ground, forming thousands of tiny seeds. Broomrape is considered one of the major problems in sunflower cultivation in Europe. New races of broomrape have been reported in Europe in recent years, and there is no completely resistant sunflower hybrid to these new races due to the highly virulent behavior of broomrape against the existing resistant genes. The Clearfield system in sunflower has widely spread across Europe because the ALS-tolerant sunflowers could be sprayed over the top with imidazolinone herbicides such as imazamox, consistently controlling broomrape, while sunflower plants were tolerant to imazamox. Due to the potential risk of ALS-resistance evolution by broomrape, there is a need for hybrids that are tolerant to a herbicide with a mode of action other than ALS inhibition. Methods are needed for control of broomrape in sunflower crop, allowing for pre-emergence treatment or post-emergence treatment, i.e. the use of spray over techniques (OTT(over the top)) when applying PPO herbicides. Figure legends Figure 1 Number of broomrape tubercules per plant root between untreated and saflufenacil- treated PPO2_F420I mutants, grown in substrate infested with broomrape seeds – 30 DAT. Figure 2 Visual evaluation of roots from PPO2_F420I mutant plants from saflufenacil-treated and untreated control in substrate infested with broomrape seeds – 30 DAT. Figure 3 Count of broomrape tubercules taken from the roots of PPO2_F420I mutant plants at 30 DAT. On top, broomrape tubercule counts from untreated plant roots and on the bottom, broomrape counts from plant roots after treatment with saflufenacil. Brief summary of the present invention The present invention relates to a method for broomrape (Orobanche ssp) control in Protopor- phyrinogen Oxidase (PPO)-inhibitor tolerant sunflower crop, comprising applying to said sun- flower crop and / or the cultivation site of said sunflower crop an effective amount of at least one PPO-inhibitor. In an embodiment, the PPO-inhibitor is selected from the group consisting of Saflufenacil, Flumioxazin, Bifenox, Fomesafen, Pyraflufen-ethyl, Sulfentrazone, Trifludimoxazin and combi- nations thereof. In preferred embodiment, the PPO-inhibitor is Saflufenacil. In another preferred embodiment, the PPO-inhibitor is Flumioxazin. In yet another preferred embodiment, the PPO-inhibitor is a combination of Saflufenacil and Flumioxazin. In one embodiment, the PPO-inhibitor tolerant sunflower crop is a non-transgenic PPO-inhibitor tolerant sunflower crop. In another embodiment, the PPO-inhibitor tolerant sunflower crop is a transgenic PPO-inhibitor tolerant sunflower crop. In an embodiment, the sunflower crop comprises a mutated protoporphyrinogen IX oxidase (PPO) gene encoding a mutated sunflower protoporphyrinogen IX oxidase, wherein the mutated sunflower Protoporphyrinogen IX Oxidase comprises a substitution of phenylalanine (F) to iso- leucine (I) at a position corresponding to residue 383 relative to SEQ ID NO: 2 (F383I substitu- tion). Preferably, the mutated protoporphyrinogen IX oxidase comprises: an amino acid se- quence as shown in SEQ ID NO: 2, or a variant thereof being at least 98%, or at least 99% or at least 99.5% identical to SEQ ID NO: 2, with the proviso that the variant comprises a substitution of phenylalanine (F) to isoleucine (I) at a position corresponding to residue 383. In an embodiment, the broomrape is Orobanche cumana, in particular Orobanche cumana Wallr. In an embodiment, the sunflower crop and / or the cultivation site of said sunflower crop is in- fested with said parasitic weed, i.e. with broomrape. In one embodiment, the at least one PPO-inhibitor is applied post-emergence of the PPO inhibi- tor tolerant sunflower crop. In another embodiment, the at least one PPO-inhibitor is applied pre-emergence to the PPO inhibitor tolerant sunflower crop. In an embodiment, the sunflower crop additionally comprises a.a herbicide tolerance trait of (1) an AHASL (acetohydroxyacid synthase large sub- unit) having an A122(At)T substitution, or (2) an AHASL variant thereof that con- tains both the A122(At)T substitution and a second substitution that can be one or more of P197(At)Q, P197(At)S, P197(At)L T203(At)I, T203(At)X, A205(At)D, A205(At)V, W574(At)L, A653(At)N, A653(At)T, A653(At)F, or A653(At)V, wherein X may be selected as any natural amino acid; b.two herbicide tolerance traits, the trait with the AHASL A122(At)T substitution and a second trait having an AHASL with an A205(At)V substitution, an AHASL with a P197(At)S substitution, an AHASL with a P197(At)L substitution or an AHASL with a W574(At)L substitution; c.a herbicide tolerance trait having an AHASL with one A205(At)V substitution; d.a herbicide tolerance trait having an AHASL with one P197(At)L substitution; e.a herbicide tolerance trait having an AHASL with one P197(At)S substitution; or f. a herbicide tolerance trait having an AHASL with one W574(At)L substitution. In an embodiment, the method of the present invention further comprises applying to said sun- flower crop and / or the cultivation site of said sunflower crop an effective amount of at least one ALS inhibitor. In some embodiment,s the ALS inhibitor is selected from the group consisting of imidazoli- nones, sulfonylureas and combinations thereof. For example, the ALS-inhibitor is selected from the group consisting of Imazamox, Imazapyr, Imazethapyr, and Tribenuron methyl. In some embodiments, the broomrape to be controlled is Acetolactate Synthase (ALS) inhibitor resistant. In an embodiment, the method of the present invention further comprises applying to said sun- flower crop and / or the cultivation site of said sunflower crop an effective amount of at least one further herbicide selected from Acetyl CoA Carboxylase (ACCase), Very Long-Chain Fatty Acid (VLCFA) Synthesis, Microtubule Assembly and Photosynthesis at PSII, and combinations thereof. In some embodiments, one or more of the following weeds are controlled as well: Convolvulus arvensis, Cirsium arvense, Xanthium spp., Abuthilon theophrasti, Polygonum spp., Sorghum halepense, Portulaca oleracea, Ambroisa artimisifolia, Sonchus oleraceus, Datura stramonium, Chenopodium album, Amaranthus spp., Echinochloa crus-galli. Setaria spp., Sinapis spp. and / or Matricaria chamomilla. In an embodiment of the present invention, the PPO herbicide and optionally the at least one ALS inhibitor and / or the at least one further herbicide is (are) applied by spraying, e.g. by spray- ing to the sunflower crop or the cultivation site. In an embodiment, the herbicide(s) is (are) ap- plied by foliar spraying (post-emergence). In an embodiment, the herbicide(s) is (are) applied in the form of microgranules. The application in the form of microgranules can be done, if the herbicide(s) is (are) applied pre-emergence. However, the herbicide(s) can be also applied by spraying, if the herbicide(s) is (are) applied pre-emergence. In an embodiment, the at least one PPO-inhibitor is applied post-emergence to the PPO inhibi- tor tolerant sunflower crop, wherein the at least one PPO-inhibitor is applied during BBCH stages 10 to 32 of the sunflower crop, for example at BBCH stage 11, 12, 13, 14, 15, 16, 17 or 18 of the sunflower crop. Herein, the application rates [g / ha] refer to the respective active ingredient. In an embodiment, the application rate of at least one PPO-inhibitor is in the range of from 0.1 to 100 g / ha and in particular from 0.5 to 85 g / ha, such as 1, 6.25, 12.5, 18.75, 25, 40, 50, 60, 70, 71, 72 or 80 g / ha. As described above, at least one PPO-inhibitor is preferably applied pre- emergence or post-emergence to the sunflower crop and / or to the cultivation site of said sun- flower crop. The cultivation site may be any site at which the sunflower is grown or will be grown, such as a greenhouse or a field. In case the cultivation site is a greenhouse, the applica- tion rate of the at least one PPO-inhibitor is preferably in the range of from 0.1 to 100 g / ha, more preferably 0.1 to 10 g / ha, such as in the range of from 0.1 to 6.25 g / ha, such as 0.5, 1, 2 or 5 g / ha. Preferably, the cultivation site is a field. In this case, the application rate of the at least one PPO-inhibitor is preferably in the range of from 0.1 to 100 g / ha, in particular from 1 to 90 g / ha, such as 1, 2, 5, 6.25, 12.5, 18.75, 25, 40, 50, 60, 70, 71, 72 or 80 g / ha. In an embodiment, the at least one PPO-inhibitor is Flumioxazin or an agriculturally acceptable salt or derivative thereof and the application rate of the PPO-inhibitor is in the range of from 0.1 to 100 g / ha, preferably from 0.5 to 90 g / ha, and in particular from 40 to 80 g / ha, such as 40, 50, 60, 70, 71,72 or 80 g / ha, in particular from 71 to 72 g / ha. In case the cultivation site is a green- house and the PPO-inhibitor is Flumioxazin, the application rate of the PPO-inhibitor is prefera- bly in the range of from 0.1 to 100 g / ha, more preferably 0.1 to 10 g / ha, such as in the range of from 0.1 to 6.25 g / ha, such as 0.1 to 5 g / ha, such as 0.5, 1, 2 or 5 g / ha. Preferably, the cultiva- tion site is a field. In case the cultivation site is a field and the PPO-inhibitor is Flumioxazin, the application rate of the PPO-inhibitor is preferably in the range of from 0.1 to 100 g / ha, in particu- lar from 40 to 80 g / ha, such as 40, 50, 60, 70, 71, 72 or 80 g / ha, in particular from 71 to 72 g / ha. In an embodiment, the at least one PPO-inhibitor is Saflufenacil or an agriculturally acceptable salt or derivative thereof and the application rate of the PPO-inhibitor is in the range of from 0.1 to 60 g / ha, preferably from 0.5 to 50 g / ha, such as 1, 2, 5, 6.25, 12.5, 18.75, 25 or 50 g / ha. In case the cultivation site is a greenhouse and the PPO-inhibitor is Saflufenacil, the application rate of the PPO-inhibitor is preferably in the range of from 0.1 to 60 g / ha, more preferably 0.1 to 10 g / ha, such as in the range of from 0.1 to 6.25 g / ha, such as 0.1 to 5 g / ha, such as 0.5, 1, 2 or 5 g / ha. Preferably, the cultivation site is a field. In case the cultivation site is a field and the PPO-inhibitor is Saflufenacil, the application rate of the PPO-inhibitor is preferably in the range of from 0.1 to 60 g / ha, more preferably 1 to 50 g / ha, such as 1, 2, 5, 6.25, 12.5, 18.75, 25 or 50 g / ha. In an embodiment, pre-emergence or post-emergence of the sunflower crop, the sunflower crop and / or the cultivation site of the sunflower crop is treated with a combination of two herbicides Saflufenacil or an agriculturally acceptable salt or derivative thereof and Flumioxazin or an agri- culturally acceptable salt or derivative thereof, and the application rate of Saflufenacil is in the range of from 0.1 to 60 g / ha, preferably from 0.5 to 50 g / ha, such as 1, 2, 5, 6.25, 12.5, 18.75, 25 or 50 g / ha, and the application rate of the Flumioxazin is in the range of from 0.1 to 100 g / ha, preferably from 0.5 to 90 g / ha, and in particular from 40 to 80 g / ha, such as 40, 50, 60, 70, 71, 72 or 80 g / ha g / ha. In an embodiment, pre-emergence or post-emergence of the sunflower crop, the sunflower crop and / or the cultivation site of the sunflower crop is alternatively or additionally treated with at least one PPO-inhibitor selected from the group consisting of Bifenox, Fomesafen, Pyraflufen- ethyl, Sulfentrazone, Trifludimoxazin and combinations thereof. In an embodiment, the at least one PPO-inhibitor is Bifenox, and the application rate of the herbicide is in the range of from 120 to 800 g / ha and in particular from 150 to 720 g / ha, such as 150, 360, 480, 600 or 720 g / ha. In an embodiment, the at least one PPO-inhibitor is Fomesafen, and the application rate of the herbicide is in the range of from 100 to 500 g / ha and in particular from 120 to 450 g / ha, such as 120, 187.5, 275, 350 or 450 g / ha. In an embodiment, the at least one PPO-inhibitor is Pyraflufen-ethyl, and the application rate of the herbicide is in the range of from 1 to 30 g / ha and in particular from 1.5 to 20 g / ha, such as 1.5, 5, 10, 15 or 20 g / ha. In an embodiment, the at least one PPO-inhibitor is Sulfentrazone, and the application rate of the herbicide is in the range of from 20 to 150 g / ha and in particular from 30 to 140 g / ha, such as 40, 75, 80, 100, 120 or 140 g / ha. In an embodiment, the at least one PPO-inhibitor is is Trifludimoxazin, and the application rate of the herbicide is in the range of from 5 to 40 g / ha, and in particular from 12.5 to 37.5 g / ha, such as 15, 20, 25 or 30 g / ha. In an embodiment, pre-emergence or post-emergence of the sunflower crop, the sunflower crop and / or the cultivation site of the sunflower crop is additionally treated with at least one ALS in- hibitor selected from the group consisting of Imazamox, Imazapyr, Imazethapyr, Tribenuron-me- thyl and combinations thereof. In an embodiment, the at least one ALS inhibitor is Imazamox, and the application rate of the herbicide is in the range of from 5 to 60 g / ha and in particular from 10 to 50 g / ha, such as 10, 25, 32, 40 or 50 g / ha. In an embodiment, at least one ALS inhibitor is Imazapyr, and the application rate of the herbi- cide is in the range of from 5 to 20 g / ha and in particular from 7.5 to 15 g / ha, such as 7.5, 10, 12.5 or 15 g / ha. In an embodiment, the at least one ALS inhibitor is Imazethapyr, and the application rate of the herbicide is in the range of from 20 to 70 g / ha and in particular from 30 to 60 g / ha, such as 30, 40, 50 or 60 g / ha. In an embodiment, the at least one ALS inhibitor is Tribenuron-methyl, and the application rate of the herbicide is in the range of from 2 to 40 g / ha and in particular from 5 to 30 g / ha, such as 5, 15, 18, 22.5 or 30 g / ha. In case of a pre-emergence treatment, the herbicide(s) is (are) applied before sowing of the sunflower crop, at the time of sowing, or after sowing up to the emergence of the sunflower crop. In an embodiment, the herbicide(s) is (are) applied up to 14 days, such as up to 10 days, preferably up to 3 days after sowing of the PPO inhibitor tolerant sunflower crop. In case of a post-emergence treatment, the herbicide(s) is (are) applied after the emergence of the sunflower crop. In an embodiment, the herbicide(s) is (are) applied at BBCH stages 11 to 18 of the PPO inhibitor tolerant sunflower crop. Detailed description of the present invention – Definitions In the studies described in the examples section, the inventors tested the effect of one PPO-in- hibitor on the growth of broomrape in broomrape infested PPO)-inhibitor tolerant sunflower plants. Specifically, the herbicidal effect of Saflufenacil was tested on broomrape. Advanta- geously, the PPO herbicide had an herbicidal effect on the growth of broomrape. Thus, PPO herbicide can be advantageously used in weed control in PPO-inhibitor tolerant sunflower crop. As used herein "herbicide" refers to one or more agents, compounds and / or compositions hav- ing herbistatic and / or herbicidal activity. The terms “treating” and “applying” are used inter- changeably herein. The preferred amount or concentration of the herbicide is an “effective amount” or “effective concentration.” By “effective amount” and “effective concentration” is in- tended an amount and concentration, respectively, that is sufficient to kill or inhibit the growth broomrape (such as of broomrape attached to a sunflower root), but an amount or concentration does not kill or inhibit as severely the growth of the PPO tolerant sunflower plant. The herbicide can be applied in accordance with conventional methods, for example, by spray- ing, irrigation, dusting, or the like. According to an alternative embodiment, the herbicides are applied to the plants by spraying (in particular foliar spraying) or in the form of microgranules. Further, it is envisaged to apply the herbicide (or a composition comprising said herbicide) post- emergence of the sunflower at any growth stage before row closure. Moreover, it is envisaged that the PPO-inhibitor is applied more than once. In some embodiments, the herbicides as referred to herein are applied to the sunflower crop or the cultivation site in form of a composition which comprises besides the herbicide(s) other addi- tives customary in crop protection. Additives include other herbicides, detergents, adjuvants, spreading agents, sticking agents, stabilizing agents, or the like. Preferably, the composition comprising the at least one PPO inhibitor (and optionally one or more further herbicides as referred to herein) further comprises an adjuvant. Typically, an adju- vant is added to provide improved performance of the composition application. Commonly used adjuvants may include, for example, surfactants, spreaders, petroleum and plant derived oils and solvents and wetting agents. Examples of commonly used adjuvants include, but are not limited to, paraffin oil, horticultural spray oils (e.g., summer oil), methylated rape seed oil, meth- ylated soybean oil, highly refined vegetable oil and the like, polyol fatty acid esters, polyethox- ylated esters, ethoxylated alcohols, and alkyl polysaccharides and blends. In an embodiment, the composition is a liquid composition comprising methylated seed oil (MSO), such as 0.5 to 1.0% (v / v) methylated seed oil. The composition can be a wet or dry preparation and can include, but is not limited to, wettable powder, wettable granuales, emulsifiable concentrates, suspension concentrates and liquid con- centrates. Generally, if the herbicides which can be employed in the context of the present invention, are capable of forming geometrical isomers, for example E / Z isomers, it is possible to use both, the pure isomers and mixtures thereof, in the compositions useful for the present invention. If the herbicides as described herein have one or more centers of chirality and, as a consequence, are present as enantiomers or diastereomers, it is possible to use both, the pure enantiomers and diastereomers and their mixtures, in the compositions according to the invention. If the herbicides as described herein have ionizable functional groups, they can also be em- ployed in the form of their agriculturally acceptable salts. Suitable are, in general, the salts of those cations and the acid addition salts of those acids whose cations and anions, respectively, have no adverse effect on the activity of the active compounds. Preferred cations are the ions of the alkali metals, preferably of lithium, sodium and potassium, of the alkaline earth metals, preferably of calcium and magnesium, and of the transition metals, preferably of manganese, copper, zinc and iron, further ammonium and substituted ammonium in which one to four hydrogen atoms are replaced by C1-C4-alkyl, hydroxy-C1-C4-alkyl, C1-C4- alkoxy-C1-C4-alkyl, hydroxy-C1-C4-alkoxy-C1-C4-alkyl, phenyl or benzyl, preferably ammo- nium, methylammonium, isopropylammonium, dimethylammonium, diisopropylammonium, tri- methylammonium, heptylammonium, dodecylammonium, tetradecylammonium, tetrame- thylammonium, tetraethylammonium, tetrabutylammonium, 2-hydroxyethylammonium (olamine salt), 2-(2-hydroxyeth-1-oxy)eth-1-ylammonium (diglycolamine salt), di(2-hydroxyeth-1-yl)ammo- nium (diolamine salt), tris(2-hydroxyethyl)ammonium (trolamine salt), tris(2-hydroxypropyl)am- monium, benzyltrimethylammonium, benzyltriethylammonium, N,N,N-trimethylethanolammo- nium (choline salt), furthermore phosphonium ions, sulfonium ions, preferably tri(C1-C4-al- kyl)sulfonium, such as trimethylsulfonium, and sulfoxonium ions, preferably tri(C1-C4-alkyl)sul- foxonium, and finally the salts of polybasic amines such as N,N-bis-(3-aminopropyl)methylamine and diethylenetriamine. Anions of useful acid addition salts are primarily chloride, bromide, fluo- ride, iodide, hydrogensulfate, methylsulfate, sulfate, dihydrogenphosphate, hydrogenphosphate, nitrate, bicarbonate, carbonate, hexafluorosilicate, hexafluorophosphate, benzoate and also the anions of C1-C4-alkanoic acids, preferably formate, acetate, propionate and butyrate. The herbicides as described herein having a carboxyl group can be employed in the form of the acid, in the form of an agriculturally suitable salt as mentioned above or else in the form of an agriculturally acceptable derivative, for example as amides, such as mono- and di-C1-C6-alkyla- mides or arylamides, as esters, for example as allyl esters, propargyl esters, C1-C10-alkyl es- ters, alkoxyalkyl esters, tefuryl ((tetrahydrofuran-2-yl)methyl) esters and also as thioesters, for example as C1-C10-alkylthio esters. Preferred mono- and di-C1-C6-alkylamides are the methyl and the dimethylamides. Preferred arylamides are, for example, the anilides and the 2-chloroan- ilides. Preferred alkyl esters are, for example, the methyl, ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, mexyl (1-methylhexyl), meptyl (1-methylheptyl), heptyl, octyl or isooctyl (2-ethylhexyl) es- ters. Preferred C1-C4-alkoxy-C1-C4-alkyl esters are the straight-chain or branched C1-C4- alkoxy ethyl esters, for example the 2-methoxyethyl, 2-ethoxyethyl, 2-butoxyethyl (butotyl), 2- butoxypropyl or 3-butoxypropyl ester. An example of a straight-chain or branched C1-C10-al- kylthio ester is the ethylthioester. According to a preferred embodiment, the PPO-inhibitor or an agriculturally acceptable salt or derivative thereof to be applied is saflufenacil. Saflufenacil is the common name of 2-chloro-5-[3,6-dihydro-3-methyl-2,6-dioxo-4-(trifluorome- thyl)-1-(2H)pyrimidinyl]-4-fluoro-N-[[methyl(1-methylethyl)amino]-sulfonyl]benzamide. Saflufenacil is a herbicidal active substance which has been disclosed in WO 01 / 083459. Fur- ther processes for its preparation are described in WO 03 / 097589, WO 05 / 054208, and WO 06 / 125746. A crystalline and essentially solvent-free form of Saflufenacil, also referred to as the crystalline anhydrate form, is disclosed in WO 08 / 043835. Saflufenacil is the active ingredient in the commercially available herbicide Kixor®. The application rate of Saflufenacil is preferably in the range of from 0.1 to 60 g / ha and in partic- ular from 0.5 to 50 g / ha, such as 0.5, 1, 2, 5, 6.25, 12.5, 18.75, 25 or 50 g / ha. It is to be understood that the amount g / ha as used in the context of the present invention refers to the amount of the active ingredient (ai) applied, thus in this case to the total amount of saflufenacil applied. According to a further preferred embodiment, the PPO-inhibitor is Flumioxazin. The herbicide Flumioxazin, chemical name 2-[7-fluoro-3,4-dihydro-3-oxo-4-(2-propyn-1-yl)-2H-1,4-benzoxazin- 6-yl]-4,5,6,7-tetrahydro-1H-isoindole-1,3(2H)-dione, is the active ingredient in the commercially available herbicide Valor® (available from Valent USA Corporation). The application rate of Flumioxazin is preferably in the range of from 0.1 to 100 g / ha and in particular from 0.5 to 90 g / ha, such as 0.5, 1, 40, 50, 60, 70, 71, 72 or 80 g / ha g / ha According to a further preferred embodiment, a combination of Saflufenacil and Flumioxazin is used as herbicide. In this case, the application rate of Flumioxazin is preferably in the range of from 0.1 to 100 g / ha and in particular from 0.5 to 90 g / ha, such as 0.5, 1, 0, 50, 60, 70, 71, 72 or 80, and the application rate of Saflufenacil is preferably in the range of from 0.1 to 60 g / ha and in particular from 0.5 to 50 g / ha, such as 0.5, 1, 2, 5, 6.25, 12.5, 18.75, 25 or 50 g / ha. In a preferred embodiment, wherein the PPO inhibitor is a combination of Saflufenacil and Flumioxazin. the weight ratio of Saflufenacil to Flumioxazin is the range of from 1:10 to 1:0.5, preferably from 1:7 to 1: 0.7. In some embodiments, the PPO-inhibitor is selected from the group consisting of Bifenox, Fomesafen, Carfentrazone, Pyraflufen-ethyl, Sulfentrazone, Trifludimoxazin and combinations thereof. Preferred amounts to be applied are described elsewhere herein. According to a further preferred embodiment, at least one ALS inhibitor is applied – in addition to the at least one PPO inhibitor - to the PPO inhibitor tolerant sunflower plant or the cultivation site of the PPO inhibitor tolerant sunflower plant. Acetolactate synthase (ALS) inhibitors are also known as acetohydroxyacid synthase (AHAS) inhibitors. ALS inhibitors are compounds which have a Mode of Action which includes the inhibi- tion of branched chain amino acid biosynthesis steps in plants and which belong to group B of the HRAC Classification (see HRAC, Classification of hormones according to Mode of Action, http: / / www.plantprotection.org / HRAC / MOA. html). The term "ALS inhibitor" is also meant herein to include the respective salts, isomers and esters of the above compounds, as already discussed above. Suitable salts are, in particular, alkali metal or alkaline earth metal salts or ammonium salts or organic ammonium salts, such as so- dium, potassium, ammonium, isopropylammonium salts and the like. Suitable isomers are, for example, stereoisomers such as enantiomers. Suitable esters are, for example, C1-C8(branched or unbranched) alkyl esters, such as methyl, ethyl and isopropyl esters. The ALS inhibitor is preferably selected from the group consisting of imidazolinones, sulfonylu- reas and combinations thereof, more preferably, the ALS inhibitor is selected from the group consisting of Imazamox, Imazapyr, Imazethapyr, Tribenuron methyl, Thifensulfuron-methyl, Thiencarbazone-methyl, Sulfosulfuron, Tritosulfuron, Nicosulforon, Foramsulforon, Iododulfu- ron-methyl, Mesosulforon-methyl, Metsulfuron-methyl and combinations thereof, more prefera- bly, the ALS inhibitor is selected from the group consisting of Imazamox, Imazapyr, Ima- zethapyr, Tribenuron-methyl, Thifensulfuron-methyl, Thiencarbazone-methyl, Sulfosulfuron and combinations thereof, more preferably, the ALS inhibitor is selected from the group consisting of Imazamox, Imazapyr, Imazethapyr, Tribenuron-methyl, and combinations thereof. Preferably, in said case, the application rate of the herbicide the at least one ALS inhibitor is preferably in the range of from 2 to 100 g / ha , more preferably in the range of from 5 to 70 g / ha. In case, the at least one ALS inhibitor is Imazamox (5-(methoxymethyl)-2-(4-methyl-5-oxo-4- propan-2-yl-1H-imidazol-2-yl)pyridine-3-carboxylic acid), the application rate of the herbicide is preferably in the range of from 5 to 60 g / ha, more preferably in the range of from 10 to 60 g / ha and in particular from 10 to 50 g / ha, such as 10, 15, 25, 32, 40 or 50 g / ha. In a preferred embodiment, wherein the at least one PPO inhibitor is Saflufenacil and the at least one ALS inhibitor is Imazamox, the weight ratio of Saflufenacil to Imazamox is the range of from 1:10 to 1:0.2, preferably from 1:5 to 1:1. In another preferred embodiment, wherein the at least one PPO inhibitor is Flumioxazin and the at least one ALS inhibitor is Imazamox, the weight ratio of Flumioxazin to Imazamox is the range of from 1:2 to 1:0.1, preferably from 1:1.25 to 1:0.3. In case, the at least one ALS inhibitor is Imazapyr ((RS)-2-(4-Methyl-5-oxo-4-propan-2-yl-1H- imidazol-2-yl)pyridine-3-carboxylic acid), the application rate of the herbicide is preferably in the range of from 2 to 30 g / ha, more preferably in the range of from 5 to 20 g / ha and in particular from 7.5 to 15 g / ha, such as 7.5, 10, 12.5 or 15 g / ha. In a preferred embodiment, wherein the at least one PPO inhibitor is Saflufenacil and the at least one ALS inhibitor is Imazapyr, the weight ratio of Saflufenacil to Imazapyr is the range of from 1:3 to 1:0.1, preferably from 1:1.5 to 1:0.2. In another preferred embodiment, wherein the at least one PPO inhibitor is Flumioxazin and the at least one ALS inhibitor is Imazapyr, the weight ratio of Flumioxazin to Imazapyr is the range of from 10:5 to 10:0.5, preferably from 10:4 to 10:0.8. In case, the at least one ALS inhibitor is Imazethapyr (5-ethyl-2-(4-methyl-5-oxo-4-propan-2-yl- 1H-imidazol-2-yl)pyridine-3-carboxylic acid), the application rate of the herbicide is preferably in the range of from 10 to 100 g / ha, more preferably in the range of from 20 to 70 g / ha and in par- ticular from 30 to 60 g / ha, such as 30, 40, 50 or 60 g / ha. In a preferred embodiment, wherein the at least one PPO inhibitor is Saflufenacil and the at least one ALS inhibitor is Imazethapyr, the weight ratio of Saflufenacil to Imazethapyr is the range of from 1:10 to 1:0.5, preferably from 1:5 to 1:1. In another preferred embodiment, wherein the at least one PPO inhibitor is Flumioxazin and the at least one ALS inhibitor is Imazethapyr, the weight ratio of Flumioxazin to Imazethapyr is the range of from 1:3 to 1:0.1, preferably from 1:2 to 1:0.2. In case, the at least one ALS inhibitor is Tribenuron-methyl (Methyl 2-[[(4-methoxy-6-methyl- 1,3,5-triazin-2-yl)-methylcarbamoyl]sulfamoyl]benzoate), the application rate of the herbicide is preferably in the range of from 2 to 40 g / ha and in particular from 5 to 30 g / ha, such as 5, 15, 18, 22.5 or 30 g / ha. In a preferred embodiment, wherein the at least one PPO inhibitor is Saflufenacil and is Tribe- nuron-methyl, the weight ratio of Saflufenacil to Tribenuron-methyl is the range of from 1:5 to 1:0.3, preferably from 1:3 to 1:0.5. In another preferred embodiment, wherein the at least one PPO inhibitor is Flumioxazin and is Tribenuron-methyl, the weight ratio of Flumioxazin to Tribenuron-methyl is the range of from 1:1 to 1:0.05, preferably from 1:0.75 to 1:0.1. In addition, the compositions described herein may further comprise at least one safener. Safeners are chemical compounds which prevent or reduce damage on useful plants without having a major impact on the herbicidal action of the herbicidal active components towards un- wanted plants. Safeners can be applied before sowings (e.g. seed treatments), on shoots or seedlings as well as in the pre-emergence or post-emergence treatment of useful plants and their habitat. Exemplary safeners include benoxacor, cloquintocet, cyometrinil, cyprosulfamide, dichlormid, dicyclonon, dietholate, fenchlorazole, fenclorim, flurazole, fluxofenim, furilazole, isoxadifen, mefenpyr, mephenate, naphthaleneacetic acid, naphthalic anhydride, oxabetrinil, 4- (dichloroacetyl)-1-oxa-4-azaspiro[4.5]decane (MON4660, CAS 71526-07-3), 2,2,5-trimethyl-3-( dichloroacetyl)-1,3-oxazolidine (R-29148, CAS 52836-31-4), N-(2-Methoxybenzoyl)-4-[(methyla- minocarbonyl)amino]benzenesulfonamide (CAS 129531-12-0), and agriculturally acceptable salts, esters or amides thereof. In particular, the safener is selected from the group consisting of benoxacor, cloquintocet, cy- prosulfamide, isoxadifen, mefenpyr, and agriculturally acceptable salts, esters or amides thereof. Most preferably, the safener is selected from the group consisting of benoxacor, cloquintocet- mexyl, cyprosulfamide, isoxadifen-ethyl, and mefenpyr-diethyl. The herbicides described hereinunder and above and the safeners are known herbicides and safeners, see, for example, The Pesticide Manual, British Crop Protection Council, 16th edition, 2012; The Compendium of Pesticide Common Names http: / / www.alanwood.net / pesticides / ); Farm Chemicals Handbook 2000 volume 86, Meister Publishing Company, 2000; B. Hock, C. Fedtke, R. R. Schmidt, Herbizide [Herbicides], Georg Thieme Verlag, Stuttgart 1995; W. H. Ahrens, Herbicide Handbook, 7th edition, Weed Science Society of America, 1994; and K. K. Hatzios, Herbicide Handbook, Supplement for the 7th edition, Weed Science Society of Amer- ica, 1998. lf the safeners as described herein are capable of forming geometrical isomers, for example E / Z isomers, it is possible to use both, the pure isomers and mixtures thereof, in the compositions, uses and methods according to the invention. lf the safeners as described herein have one or more centers of chirality and, as a consequence, are present as enantiomers or diastereomers, it is possible to use both, the pure enantiomers and diastereomers and their mixtures, in the compositions, uses and methods according to the invention. PPO-inhibitor tolerant sunflower plants The herbicides as referred to herein (such as the PPO herbicides) or the compositions thereof, as referred to herein shall be used in weed control in PPO-inhibitor tolerant sunflower plants. The plants may also have tolerance to other herbicides with a different mode of action, in partic- ular to ALS inhibitors. In an embodiment, the PPO-inhibitor tolerant sunflower crop is transgenic PPO-inhibitor tolerant sunflower crop. In some embodiments, the transgenic sunflower plant comprises at least one recombinant mutated PPO gene. The term “mutated PPO gene” is described herein below. Typ- ically, a recombinant gene has been introduced into the plant by transformation. In another embodiment, the PPO-inhibitor tolerant sunflower crop is non-transgenic PPO-inhibi- tor tolerant sunflower crop. Preferably, the non-transgenic crop plant is the PPO tolerant sun- flower plants as defined in PCT / US2022 / 077037 (published as WO2023 / 049906A1) which here- with is incorporated by reference with respect to the entire disclosure content (including the se- quence listing), in particular with respect to the plant. Seeds of the non-transgenic sunflower plant comprising a mutated protoporphyrinogen IX oxidase that are described in the Example section of the above PCT application (Helianthus annuus L., HA452 inbred line, designated “ 21LHHA000892”) have been deposited on April 22, 2022 at the National Collections of Indus- trial, Food and Marine Bacteria (NCIMB, full address: Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen, AB219YA Scotland (United Kingdom)).under the provisions of the Buda- pest treaty on the International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedure. The deposited seeds were assigned the accession number NCIMB 43974. The deposition of seeds was made only for convenience of the person skilled in the art and does not constitute or imply any confession, admission, declaration or assertion that deposited seed are required to fully describe the invention, to fully enable the invention or for carrying out the invention or any part or aspect thereof. Also, the deposition of seeds does not constitute or imply any recommendation to limit the application of any method of the present invention to the application of the plants derived from said seeds. The deposited plants are herein also referred to “PPO2_F420I mutant” (see Examples and Fig- ures). However, they comprise the F383I substitution. Typically, the sunflower crop comprises a mutated protoporphyrinogen IX oxidase (PPO) gene encoding a mutated sunflower protoporphyrinogen IX oxidase, wherein the mutated sunflower protoporphyrinogen IX oxidase comprises a substitution of phenylalanine (F) to isoleucine (I) at a position corresponding to residue 383 relative to SEQ ID NO: 2 (F383I substitution). Protoporphyrinogen IX oxidase (herein also referred to as “PPO” or “Protoporphyrinogen IX oxi- dase” catalyzes the seventh step in biosynthesis of protoporphyrin IX. In plants, protoporphyrin IX is the precursor to chlorophyll. Specifically, protoporphyrinogen IX oxidase (EC 1.3.3.4) cata- lyzes the dehydrogenation of protoporphyrinogen IX to form protoporphyrin IX. Preferably, the PPO polypeptide is a PPO2 polypeptide. For purposes herein, it is noted that PPO type II is used interchangeably with PPO2. The term “mutated PPO gene” refers to a PPO nucleic acid molecule having a sequence that is mutated from a wild-type PPO gene, i.e. the wild-type PPO2 gene. The nucleic acid sequence of the sunflower wild-type PPO2 coding sequence is shown in SEQ ID NO: 3. The amino acid sequence of the wild-type PPO2 polypeptide is shown in SEQ ID NO: 4. As compared to the wild-type polypeptide, the mutated sunflower polypeptide shall comprise at least one mutation. Preferably, the mutated sunflower protoporphyrinogen IX oxidase comprises a substitution of phenylalanine (F) to isoleucine (I) at a position corresponding to residue 383 of SEQ ID NO: 4 or SEQ ID NO: 2 (F383I substitution). Thus, the mutated PPO oxidase shall comprise such a substitution at residue 383 relatively to SEQ ID NO: 4 (when aligned using blast). Position 383 in the sunflower PPO2 polypeptide corresponds to position 420 in the Amaranthus tuberculatus type II PPO. In an embodiment of the present invention, the mutated protoporphyrinogen IX oxidase com- prises an amino acid sequence as shown in SEQ ID NO: 2. However, the present invention is not limited to SEQ ID NO: 2. Rather, the present invention pertains also to variants of the mu- tated protoporphyrinogen IX oxidase comprising an amino acid sequence as shown in SEQ ID NO: 2, provided that the variant comprises the substitution of phenylalanine (F) to isoleucine (I) at a position corresponding to residue 383 of SEQ ID NO: 2 or 4. In an embodiment, the mutated protoporphyrinogen IX oxidase (PPO) gene is the mutated pro- toporphyrinogen IX oxidase (PPO) gene of the sunflower plant obtained from growing a seed of mutant line 21LHHA000892, a sample of said seed having been deposited under NCIMB acces- sion number 43974. The expression “mutated amino acid” will be used below to designate the amino acid which is replaced by another amino acid, thereby designating the site of the mutation in the primary se- quence of the protein. The term “variant” with respect to a sequence (e.g., a polypeptide or nucleic acid sequence of the invention) is intended to mean substantially similar sequences. The variant polypeptide shall have protoporphyrinogen IX oxidase activity. Enzyme variants may be defined by their sequence identity when compared to a parent en- zyme. Sequence identity usually is provided as “% sequence identity” or “% identity”. To deter- mine the percent-identity between two amino acid sequences in a first step a pairwise sequence alignment is generated between those two sequences, wherein the two sequences are aligned over their complete length (i.e., a pairwise global alignment). The alignment is generated with a program implementing the Needleman and Wunsch algorithm (J. Mol. Biol. (1979) 48, p.443- 453), preferably by using the program “NEEDLE” (The European Molecular Biology Open Soft- ware Suite (EMBOSS)) with the programs default parameters (gapopen=10.0, gapextend=0.5 and matrix=EBLOSUM62). The preferred alignment for the purpose of this invention is that alignment, from which the highest sequence identity can be determined. The following example is meant to illustrate two nucleotide sequences, but the same calcula- tions apply to protein sequences: Seq A: AAGATACTG length: 9 bases Seq B: GATCTGA length: 7 bases Hence, the shorter sequence is sequence B. Producing a pairwise global alignment which is showing both sequences over their complete lengths results in Seq A: AAGATACTG- ||| ||| Seq B: --GAT-CTGA The “I” symbol in the alignment indicates identical residues (which means bases for DNA or amino acids for proteins). The number of identical residues is 6. The ” symbol in the alignment indicates gaps. The number of gaps introduced by alignment within the Seq B is 1. The number of gaps introduced by alignment at borders of Seq B is 2, and at borders of Seq A is 1. The alignment length showing the aligned sequences over their complete length is 10. Producing a pairwise alignment which is showing the shorter sequence over its complete length according to the invention consequently results in: Seq A: Seq B: Producing a pairwise alignment which is showing sequence A over its complete length accord- ing to the invention consequently results in: Seq A: Seq B: Producing a pairwise alignment which is showing sequence B over its complete length accord- ing to the invention consequently results in: Seq A: Seq B: The alignment length showing the shorter sequence over its complete length is 8 (one gap is present which is factored in the alignment length of the shorter sequence). Accordingly, the alignment length showing Seq A over its complete length would be 9 (meaning Seq A is the sequence of the invention). Accordingly, the alignment length showing Seq B over its complete length would be 8 (meaning Seq B is the sequence of the invention). After aligning two sequences, in a second step, an identity value is determined from the align- ment produced. For purposes of this description, percent identity is calculated by %-identity = (identical residues / length of the alignment region which is showing the two aligned sequences over their complete length) *100. Thus, sequence identity in relation to comparison of two amino acid sequences according to this embodiment is calculated by dividing the number of identical residues by the length of the alignment region which is showing the two aligned sequences over their complete length. This value is multiplied with 100 to give “%-identity”. According to the ex- ample provided above, %-identity is: (6 / 10) * 100 = 60 %. Generally, amino acid sequence variants will have at least 70%, e.g., preferably at least 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, to 79%, generally at least 80%, e.g., 81%-84%, at least 85%, e.g., 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, at least 98%, at least 99% or at least 99.5% polypeptide “sequence identity” to the polypeptide of SEQ ID NO: 2, provided that the encoded polypeptide comprises the substitution of phenylalanine (F) to isoleu- cine (I) at a position corresponding to residue 383 of SEQ ID NO: 2. Thus, the variant polypep- tide shall comprise an isoleucine residue at the position corresponding to position 383 of SEQ ID NO: 2 (or SEQ ID NO: 4). Similarly, nucleotide sequence variants will have at least 30, 40, 50, 60, to 70%, e.g., preferably 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, to 79%, generally at least 80%, e.g., 81%-84%, at least 85%, e.g., 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, at least 98%, at least 99% or at least 99.5% nucleotide “sequence identity” to the nucleotide sequence encoding a polypeptide of SEQ ID NO: 2, provided that the encoded polypeptide comprises the substitution of phenylalanine (F) to isoleucine (I) at a position corresponding to residue 383 of SEQ ID NO: 2 or 4. Similarly, nucleotide sequence variants will have at least 30, 40, 50, 60, to 70%, e.g., preferably 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, to 79%, generally at least 80%, e.g., 81%-84%, at least 85%, e.g., 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, at least 98%, at least 99% or at least 99.5% nucleotide “sequence identity” to the nucleic acid sequence of SEQ ID NO: 1, provided that the encoded polypeptide comprises the substitution of phenylal- anine (F) to isoleucine (I) at a position corresponding to residue 383 of SEQ ID NO: 2 or 4. In a preferred embodiment, the mutated protoporphyrinogen IX oxidase comprises: an amino acid sequence as shown in SEQ ID NO: 2, or a is a variant thereof being at least 98%, such as at least 99% or at least 99.5% identical to SEQ ID NO: 2, with the proviso that the variant com- prises a substitution of phenylalanine (F) to isoleucine (I) at a position corresponding to residue 383. Further, it is envisaged that the mutated protoporphyrinogen IX oxidase (PPO) gene comprises a) a nucleic acid sequence as shown in SEQ ID NO: 1, or b) a nucleic acid sequence being at least 98%, such as at least 99% or at least 99.5% identical to SEQ ID NO: 1. Moreover, it is envisaged that the mutated PPO polypeptide comprises not more than three, such as not more than two, such as not more than one mutation in addition to the F383I substi- tution. SEQ ID NO: 1 and 3 are coding sequences, i.e. sequences which are translated. The sunflower PPO2 gene comprises many introns. It is to be understood that the sequences of these introns are not comprised by SEQ ID NO: 1 and 3, respectively. Thus, the expression that “the mutated protoporphyrinogen IX oxidase (PPO) gene comprises a nucleic acid sequence” shall mean that plant expresses a transcript comprising said sequence. By “herbicide-tolerant mutated PPO protein” or “herbicide-resistant mutated PPO protein”, it is intended that such a PPO protein displays higher PPO activity, relative to the PPO activity of the wild-type, i.e. the unmutated PPO protein, when in the presence of at least one herbicide that is known to interfere with PPO activity and at a concentration or level of the herbicide that is known to inhibit the PPO activity of the wild-type PPO protein. Furthermore, the PPO activity of such a herbicide-tolerant or herbicide-resistant mutated PPO protein may be referred to herein as “herbicide-tolerant” or “herbicide-resistant” PPO activity. The terms are used interchangeably herein. By a “herbicide-tolerant” or “herbicide-resistant” plant, it is intended that a plant that is tolerant or resistant to at least one herbicide at a level that would normally kill, or inhibit the growth of, a normal or wild-type plant. The term “sunflower” as used herein, shall refer to any plant belonging to the genus Helianthus. In an embodiment, the term refers to a plant of the species Helianthus annuus. L. In some embodiments, the mutated PPO gene is present in homozygous form in the plant (or part thereof). As used herein, the term “homozygous” means a genetic condition existing when two identical alleles reside at a specific locus, but are positioned individually on corresponding pairs of ho- mologous chromosomes in the cell. In contrast, the term “heterozygous” means a genetic condi- tion existing when two different alleles reside at a specific locus, but are positioned individually on corresponding pairs of homologous chromosomes in the cell. As used herein, the term “non-transgenic” refers to a plant or plant cell that does not have DNA derived from another organism inserted into its genome. Thus, the non-transgenic plant shall not have been produced by recombinant means. For example, the mutated PPO gene shall not have been introduced by transformation, such as Agrobacterium-mediated transformation. How- ever, a non-transgenic plant or cell may have been produced by introducing a targeted mutation in the PPO2 gene, e.g. by gene editing. If the plant used in the method of the present invention is non-transgenic, it will be understood that the mutated PPO2 gene shall be at the same position in the sunflower genome as the wildtype PPO2 gene. Thus, the mutated PPO2 gene may be operably linked to the native (i.e. wild-type) promoter of the protoporphyrinogen IX oxidase (PPO2) gene. Typically, a non-transgenic plant has not been exclusively obtained by means of an essentially biological process. The plant used in the method of the present invention shall be tolerant to PPO-inhibitors. In an embodiment of the present invention, the trait of tolerance to PPO-inhibitors is an endogenous non-transformed trait. Thus, the mutated PPO gene shall not have been introduced by transfor- mation of a transgene. In an embodiment of the present invention, the trait of tolerance to PPO- inhibitors is an endogenous non-transfected trait. Thus, the PPO gene shall not have been mu- tated by gene editing. In an embodiment, the plant has been produced by Ethyl methanesulfonate mutagenesis. Thus, the mutation in the PPO2 gene as referred to herein has been introduced by EMS (ethyl me- thanesulfonate) mutagenesis. Ethyl methanesulfonate (EMS) is a mutagenic compound that produces random mutations in genetic material by nucleotide substitution; particularly through G:C to A:T transitions induced by guanine alkylation. The plant that was tested in the Examples section is derived from plants that were generated by EMS mutagenesis (see Examples in PCT / US2022 / 077037). In another embodiment of the present invention, the plant has been produced by radiation in- duced mutagenesis. Thus, the mutation in the PPO2 gene has been introduced by radiation in- duced mutagenesis. Gene editing techniques may be currently feasible in sunflower, but where available such tech- niques could be used to produce the plants of the invention. In an embodiment of the present invention, the plant may be thus produced by genome editing. Thus, the mutation in the PPO2 gene as referred to herein may be introduced by genome editing. Genome editing, as used herein, refers to the targeted modification of genomic DNA using sequence-specific enzymes (such as endonuclease, nickases, base conversion enzymes) and / or donor nucleic acids (e.g. dsDNA, oligo’s) to introduce desired changes in the DNA. Sequence-specific nucleases that can be programmed to recognize specific DNA sequences include meganucleases (MGNs), zinc- finger nucleases (ZFNs), TAL-effector nucleases (TALENs) and RNA-guided or DNA-guided nu- cleases such as Cas9, Cpf1, CasX, CasY, C2c1, C2c3, certain argonout systems (see e.g. Osakabe and Osakabe, Plant Cell Physiol.2015 Mar; 56(3):389-400; Ma et al., Mol Plant.2016 Jul 6;9(7):961-74; Bortesie et al., Plant Biotech J, 2016, 14; Murovec et al., Plant Biotechnol J. 2017 Apr 1; Nakade et al., Bioengineered 8-3, 2017; Burstein et al., Nature 542, 37–241; Komor et al., Nature 533, 420–424, 2016; all incorporated herein by reference). Donor nucleic acids can be used as a template for repair of the DNA break induced by a sequence specific nucle- ase, but can also be used as such for gene targeting (without DNA break induction) to introduce a desired change into the genomic DNA. By using the above technologies, plants comprising a wild-type sunflower PPO2 can be con- verted to plants comprising the mutated PPO2 gene as referred to herein, thereby increasing the tolerance to PPO-inhibitors. As set forth herein elsewhere, the sunflower plant to be used in the method of the present in- vention shall be also tolerant not only to PPO herbicides, but also to one or more herbicides, in particular to one or more herbicides selected from the group consisting of Auxin mimics, inhibi- tors of Protoporphyrinogen Oxidase (PPO), Acetolactate Synthase (ALS), Acetyl CoA Carbox- ylase (ACCase), Very Long-Chain Fatty Acid (VLCFA) synthesis, Microtubule Assembly and Photosynthesis at PSII. T However, if further herbicide is an ALS-inhibitor, typically, it is required that the ALS-inhibitor tol- erance trait has been added to the plant, thereby generating a sunflower plant that is tolerant to PPO inhibitors and to ALS inhibitors. As compared to wild-type sunflower plants, the plant treated in the method of the present invention thus comprises two additional herbicide tolerance traits. Sunflower plants that are tolerant to ALS inhibitors are well-known in the art. Typically, the trait is conferred by one or more mutations in the acetohydroxyacid synthase (AHAS) gene (R gene). The thus mutated acetohydroxyacid synthase has lower binding to ALS inhibitors (as compared to the wild-type AHAS) which results in a reduced inhibiting efficiency of the ALS in- hibitor. For example, in Clearfield crops, the tolerance trait is conferred by a single point muta- tion in the acetohydroxyacid synthase (AHAS) gene (R gene), with an alanine to valine substitu- tion at position 205 (Arabidopsis alignment). This mutation is also referred to as the “A205(At)V” substitution. The “At” in brackets indicates that that the mutation is at a position corresponding to position 205 in the acetohydroxyacid synthase large subunit from Arabidopsis thaliana. The Clearfield Plus production system is a based on a single gene with higher levels of toler- ance to imidazolinones traits and provides sunflowers with greater crop tolerance regardless of environmental stresses, improved weed control, oil content and grain yield. Therefore, the sunflower plant may also comprise a mutated gene encoding for a mutated AHASL (acetohydroxyacid synthase large subunit) which confers resistance to ALS inhibitors, such as to imidazolinone herbicides. Such mutated genes are described e.g. in WO 2008 / 124431 A1 (incorporated herein by reference). In a preferred embodiment, the sunflower crop, preferably, additionally contains a. a herbicide tolerance trait of (1) an AHASL (acetohydroxyacid synthase large subunit) having an A122(At)T substitution, or (2) an AHASL variant thereof that contains both the A122(At)T substitution and a second substitution that can be one or more of P197(At)Q, P197(At)S, P197(At)L T203(At)I, T203(At)X, A205(At)D, A205(At)V, W574(At)L, A653(At)N, A653(At)T, A653(At)F, or A653(At)V, wherein X may be selected as any natural amino acid; b. two herbicide tolerance traits, the trait with the AHASL A122(At)T substitution and a second trait having an AHASL with an A205(At)V substitution, an AHASL with a P197(At)S substitution, an AHASL with a P197(At)L substitution or an AHASL with a W574(At)L substitution; c. a herbicide tolerance trait having an AHASL with one A205(At)V substitution; d. a herbicide tolerance trait having an AHASL with one P197(At)L substitution; e. a herbicide tolerance trait having an AHASL with one P197(At)S substitution; or f. a herbicide tolerance trait having an AHASL with one W574(At)L substitution. The PPO herbicide tolerance trait and the ALS inhibitor tolerance trait can be combined in a sunflower plant by gene stacking. “Gene stacking”, also referred to as gene pyramiding, is the process of combining two or more genes of interest into a single plant. The combined traits re- sulting from this process are called stacked traits. When a stack is engineered or breed into a crop, the crop has better overall performance since a variety of genes for controlling different problems can in theory be stacked together. Moreover, gene stacking allows for better perfor- mance because if the resistance or tolerance conferred by a single gene breaks down, there is still a remaining gene that confers some benefit. Stacking can be achieved by transgenic ap- proaches, by genome editing but, in particular, by using conventional breeding techniques. For example, a non-transgenic sunflower plant expressing a mutated PPO polypeptide can be crossed with a non-transgenic sunflower plant expressing a mutated AHASL polypeptide in or- der to obtain plants with both herbicide tolerance traits. The present invention relates to a method for weed control. The method comprises the step of applying a composition as set forth herein above to the sunflower crop. The terms “crop” and “ sunflower” or “sunflower plant” are used interchangeably herein. The term “broomrape control” or “control of broomrape” preferably is to be understood as mean- ing the killing of broomrape and, more preferably, retarding or inhibiting the growth of the broomrape. In an embodiment, the growth of broomrape that is attached to a sunflower root is retarded or inhibited (e.g. if the at least one PPO inhibitor is applied to the sunflower crop post- emergence, such as by foliar spraying). The term “broomrape”, preferably refers to Orobanche ssp, more preferably to Orobanche Cu- mana (Orobanche cumana Wallr.). In an embodiment, the “broomrape” is resistant to Acetolac- tate Synthase (ALS) inhibitors. It is to be understood that the sunflower crop and / or the cultivation site to be treated is infested with broomrape. Preferably, broomrape seeds, i.e. viable broomrape seeds, are present in the soil of the cultivation site for the sunflower crop. For example, at least one broomrape organism shall be present at the cultivation. Preferably, at least one broomrape organism should be killed or inhibited in its growth by carrying out the present invention. In some embodiments, the growth of further weeds of sunflower is inhbited, for example, dicoty- ledonous and monocotyledonous weeds. Dicotyledonous weeds include, but are not limited to, weeds of the genera: Sinapis, Lepidium, Galium, Stellaria, Matricaria, Anthemis, Galinsoga, Chenopodium, Erigeron, Hibiscus, Urtica, Senecio, Amaranthus, Portulaca, Xanthium, Convol- vulus, Ipomoea, Polygonum, Sesbania, Ambrosia, Mercuralis, Cirsium, Carduus, Sonchus, So- lanum, Rorippa, Rotala, Lindernia, Lamium, Veronica, Abuthilon, Emex, Datura, Viola, Galeop- sis, Papaver, Centaurea, Trifolium, Ranunculus, Helianthus, and Taraxacum. Monocotyle- donous weeds include, but are not limited to, weeds of the genera: Echinochloa, Setaria, Pani- cum, Digitaria, Phleum, Poa, Festuca, Eleusine, Brachiaria, Lolium, Bromus, Avena, Cyperus, Sorghum, Elymus, Cynodon, Monochoria, Fimbristyslis, Sagittaria, Eleocharis, Scirpus, Paspa- lum, Ischaemum, Sphenoclea, Dactyloctenium, Urochloa, Agrostis, Alopecurus, and Apera. In a preferred embodiment, the further weeds to be controlled are weeds which are common weeds in the cultivation of sunflower, such as one or more weeds selected from Convolvulus arvensis, Cirsium arvense, Xanthium spp., Abuthilon theophrasti, Polygonum spp., Sorghum halepense, Portulaca oleracea, Ambrosia ssp. (e.g. Ambrosia artemisiifolia, Ambrosia trifida), Sonchus oleraceus, Datura stramonium, Chenopodium album, Amaranthus spp. (e.g. Amaran- thus retroflexus, Amaranthus palmeri), Echinochloa crus-galli. Setaria spp. (e.g. Setaria faberi), Sinapis spp. and Matricaria chamomilla. Moreover, preferred weeds to be controlled are one or more weeds of the weeds in Table 2 in the Examples section. The herbicide or composition as set forth herein is applied at the cultivation site of the sunflower plant. The cultivation site may be any site at which the sunflower is grown or will be grown. In an embodiment, it is a greenhouse. In an alternative embodiment, it is a field. In an embodiment, the plant grown at the cultivation site, including the plant of the present invention and weed plants, are contacted with an effective amount of the herbicides, e.g. by spraying. In the method of the present invention, the herbicide or composition can be applied by any method known in the art including, but not limited to, soil treatment, and foliar treatment. Prefer- ably, the herbicide or herbicides present in the composition are applied in an effective amount (as disclosed elsewhere). Prior to application, the herbicide can be converted into the custom- ary formulations, for example solutions, emulsions, suspensions, dusts, powders, pastes and granules. The use form depends on the particular intended purpose; in each case, it should en- sure a fine and even distribution of the composition. A wide variety of formulations can be em- ployed for protecting plants from weeds, so as to enhance plant growth and reduce competition for nutrients. The herbicides as set forth herein can be used by itself for pre-emergence, post- emergence, pre-planting, and at-planting control of weeds in areas surrounding the crop plants described herein. Further, a herbicide formulation can be used that contains other additives. Ad- ditives found in herbicide formulation, detergents, adjuvants, spreading agents, sticking agents, stabilizing agents, or the like. The herbicide containing formulation can be a wet or dry prepara- tion and can include, but is not limited to, flowable powders, emulsifiable concentrates, and liq- uid concentrates. The herbicide containing formulations can be applied in accordance with con- ventional methods, for example, by spraying, irrigation, dusting, or the like. In an embodiment, the herbicide or composition as set forth herein is applied by spraying. According to the method of the present invention, the herbicide or composition is applied to the sunflower crop and / or the cultivation site of the sunflower crop pre-emergence or post-emer- gence of the sunflower crop, preferably post emergence of the sunflower crop, more preferably post-emergence of the sunflower crop and the weeds. In an embodiment of the present invention, the herbicide or composition as set forth herein is applied pre-emergence to the sunflower crop. For example, the herbicide or composition is be applied about 1 to 14 days before emergence of the sunflower crop. In some embodiments, the herbicide or composition is applied before sowing of the sunflower seed. In some embodiments, the composition is applied after sowing of the sunflower seed, but before emergence of the sun- flower crop. If the herbicide is applied before sowing the sunflower seed, the method of the present invention may further comprise the step of sowing the sunflower seed after applying the herbicide. In another embodiment, the herbicide or composition as set forth herein is applied post-emer- gence to the sunflower crop. For example, the herbicide or composition is applied at BBCH stages 10 to 32 (of the sunflower crop), for example at BBCH stage 11, 12, 13, 14, 15, 16, 17 or 18 of the sunflower crop. The BBCH-scale (BBCH: Biologische Bundesanstalt, Bun- dessortenamt und CHemische Industrie) is used to identify the phenological development stages of plants. The scale is e.g. described by Meier, U. (2001). "Growth stages of mono- and dicotyledonous plants". BBCH Monograph. doi:10.5073 / bbch0515, incorporated by reference herein. Further, the scale is described in LANCASHIRE et al. (Annals of Applied Biology. Vol- ume 119, Issue3. Available in: https: / / doi.org / 10.1111 / j.1744-7348.1991.tb04895.x). The definitions and explanations given herein above preferably apply mutatis mutandis to the following. The present invention further relates to the use of at least one PPO inhibitor for broomrape con- trol in transgenic or non-transgenic PPO-inhibitor tolerant sunflower crop. The present invention further relates to a method for producing a product from sunflower seeds, said method comprising a) growing the sunflower plant as set forth in connection with the method of broomrape control at a plant cultivation site, b) harvesting seeds from said plant, and c) producing a product from the seeds harvested in step b. Step a) of the above method, preferably, comprise the step of applying an effective amount of the PPO herbicide to said cultivation site as described elsewhere herein. In an embodiment, the composition is applied pre-emergence. In another embodiment, the composition is applied post- emergence. Preferably, the plant grown at the cultivation site, including the plant of the present invention and weed plants, are contacted with an effective amount of the composition, e.g. by spraying. In an embodiment of the method, the product is bird feed. In another embodiment, the product is seed meal. In another embodiment, the product is sunflower oil. Accordingly, the above methods may com- prise the extraction of sunflower oil from the harvested or provided seeds. All patents, patent applications, and publications or public disclosures referred to or cited herein are incorporated by reference in their entirety. The invention will be further described with reference to the examples described herein; how- ever, it is to be understood that the invention is not limited to such examples. Example 1: The sunflower mutant PPO2_F420I is described in the international patent application PCT / US2022 / 077037. Seeds of the non-transgenic mutant (Helianthus annuus L., HA452 in- bred line, designated “21LHHA000892”) have been deposited on April 22, 2022 at the National Collections of Industrial, Food and Marine Bacteria (NCIMB, full address: Ferguson Building, Craibstone Estate, Bucksburn, Aberdeen, AB219YA Scotland (United Kingdom)). Broomrape seeds were mixed in greenhouse potting substrate at a 1:1 ratio (g / L) to produce a broomrape infested condition to sow the PPO2_F420I sunflower seeds. One pot was consid- ered as one replication, and 8 total replications per treatment were considered (Table 1). When sunflower plants were at the 2-4 leaf stage, saflufenacil was sprayed at 2.5g / ha plus MSO at 1% (v / v) on plants from the treated group. All plants were kept in the phytotron under standard maintenance regime. Thirty days after treatment (30 DAT), soil wash-out was per- formed on the roots of every plant, and broomrape tubercules were counted. Table 1. Plant material, treatments and substrate conditions used in the phytotron experiment. Plant Material Treatment Untreated with broomrape seeds P PO2_F420I Mutant Saflufenacil at 2.5g a.i. / ha + MSO 1% (v / v) with broomrape seeds A significant difference in number of broomrape tubercules present in the roots of PPO2_F420I mutant plants grown in substrate infested with broomrape seeds was observed between un- treated and saflufenacil-treated plants (Figures 1, 2 and 3). While the average number of tuber- cules per plant root was 20 in the plants without saflufenacil application, surprisingly an average of less than 4 tubercules per plant root was found in PPO2_F420I mutant plants treated with saflufenacil, leading to the conclusion that PPO herbicides in combination with PPO tolerance in sunflowers has an added value to broomrape control.

Claims

Claims 1. A method for broomrape (Orobanche cumana) control in Protoporphyrinogen Oxidase (PPO)-inhibitor tolerant sunflower crop, comprising applying to said sunflower crop and / or the cultivation site of said sunflower crop an effective amount of at least one PPO-inhibitor.

2. The method of claim 1, wherein said sunflower crop and / or the cultivation site of said sun- flower crop is infested with broomrape.

3. The method of claim 1 or 2, wherein the at least one PPO-inhibitor is selected from the group consisting of Saflufenacil, Flumioxazin, Bifenox, Fomesafen, Pyraflufen-ethyl, Sul- fentrazone, Trifludimoxazin and combinations thereof.

4. The method of claim 3, wherein the at least one PPO-Inhibitor is Saflufenacil, Flumioxa- zin, or a combination thereof.

5. The method of any one of claims 1 to 4, wherein the at least one PPO-inhibitor is applied in the range of from 0.1 to 100 g / ha.

6. The method of any one claim 1 to 4, wherein the at least one PPO-inhibitor is applied pre- emergence to the PPO inhibitor tolerant sunflower crop.

7. The method of any one claim 1 to 4, wherein the at least one PPO-inhibitor is applied post- emergence to the PPO inhibitor tolerant sunflower crop.

8. The method of claim 7, wherein the at least one PPO-inhibitor is applied during BBCH stages 10 to 32 (of the sunflower crop), for example at BBCH stage 11, 12, 13, 14, 15, 16, 17 or 18 of the sunflower crop.

9. The method of any one of claims 1 to 8, wherein the PPO-inhibitor tolerant sunflower crop is a transgenic PPO-inhibitor tolerant sunflower crop.

10. The method of any one of claims 1 to 8, wherein the PPO-inhibitor tolerant sunflower crop is a non-transgenic PPO-inhibitor tolerant sunflower crop.

11. The method of any one claims 1 to 10, wherein the sunflower crop comprises a mutated protoporphyrinogen IX oxidase (PPO) gene encoding a mutated sunflower protoporphyrin- ogen IX oxidase, wherein the mutated sunflower Protoporphyrinogen IX Oxidase com- prises a substitution of phenylalanine (F) to isoleucine (I) at a position corresponding to residue 383 relative to SEQ ID NO: 2 (F383I substitution).

12. The method of claim 11, wherein the mutated protoporphyrinogen IX oxidase comprises: an amino acid sequence as shown in SEQ ID NO: 2, or a variant thereof being at least 98%, or at least 99% or at least 99.5% identical to SEQ ID NO: 2, with the proviso that the variant comprises a substitution of phenylalanine (F) to isoleucine (I) at a position corre- sponding to residue 383.

13. The method of any one of claims 1 to 12, wherein the at least one PPO-inhibitor is applied by spraying to said sunflower crop and / or the cultivation site of said sunflower crop.

14. The method of claim 13, wherein the at least one PPO-inhibitor is applied by foliar spraying to said sunflower crop.

15. Use of at least one PPO inhibitor for broomrape control in transgenic or non-transgenic PPO-inhibitor tolerant sunflower crop.

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