## 1 Introduction  
Italy is the largest rice (_Oryza sativa_ L.) producer in Europe. In 2020, the cultivated area was approximately 500 thousand hectares, providing a yield of 1.5 million tons, representing 53% of Europe's total rice production [1, 2]. Therefore, rice production is one of the main Italian agri-food sectors. The most important agricultural districts suited to rice cultivation are Piedmont and Lombardy (Po Valley, northern Italy). Here, herbicide resistance (HeR) has become a serious problem, causing yield losses [3, 4]. According to the Herbicide Resistance Action Committee (HRAC), resistance to herbicides is an example of the adaptive evolution of weeds in response to human selection pressures, a consequence of the ability of plants to survive the application of chemicals that normally would kill them [5]. Over the years, the increasing prevalence of repeated field applications of an increasingly narrow range of herbicides, as a consequence of the withdrawal of many plant protection products (PPPs) from the EU market due to strict regulations (Reg. EC/1107/2009), and the lack of herbicides with new modes of action (MoAs), has led to a continuous rise in and spread of resistance [6; 7; 8]. Referring to the International Herbicide-Resistant Weed Database, there are currently 523 weed species (272 dicts and 251 monocots) reported as resistant to the most commonly used herbicides. Weeds have evolved resistance to 21 out of the 31 known MoAs and to 167 different herbicides. Herbicide-resistant weeds have been reported for 99 crops in 72 countries [9]. The development and occurrence of herbicide resistance could be due to missense DNA mutations, which cause target site resistance (TSR), or to the physiological degradation processes of the herbicide, which cause non-target site resistance (NTSR). A series of proteins, such as cytochromes P450 (CYP450) and glutathione S-transferase (GST), are involved in the physiological degradation process of herbicides, inactivating and isolating them [10; 11; 12]. The family of cytochromes P450 includes multiple genes that facilitate the denaturation of a wide range of chemicals, encoding heme-dependent enzymes that catalyze oxygen and NADPH-dependent monooxygenation reactions. The substrate specificity of P450 enzymes is high. However, each CYP450 tends to metabolize only a limited number of herbicides, particularly phenylureas. CYP450 belonging to the CYP81A subfamily are an exception, as they are involved in the metabolism of numerous herbicides in _Poaceae_ crops [11; 13]. For instance, _CYP81A6_ is involved in tolerance to bentazone and to several sulfonylurea herbicides in rice (_O. sativa_) [14]; _CYP81A9_ metabolizes sulfonylurea, benzothiadiazinone, and triketone in corn (_Zea mays_ L.) [15; 16]; and _CYP81A63_ is involved in the detoxification of three chemical groups of acetyl-CoA carboxylase (ACCase) inhibitors in barley (_Hordeum vulgare_ L. 'Golden Promise'), namely phenylpyrazololine (pinoxaden), cyclohexanedione (talkoxydim), and aryloxyphenoxypropionate (diclofop-methyl) [17]. Other members of the CYP81A subfamily were reported to be involved in herbicide detoxification in _Echinochla_, particularly in _Echinochlaphylopogon_ (Stapf) Vasc. Specifically, the overexpression of _CYP81A12_ and _CYP81A21_ was responsible for cross-resistance to aceto-lactate-synthease (ALS) and to acetyl CoA carboxylase (ACCase) inhibitors [18]. _CYP81A24_ was found to metabolize pinoxaden and tralkoxydim (ACCase inhibitors) in _E. phyllopogon_, indicating that these enzymes are crucial in the occurrence of herbicide resistance in this weed [19]. Glutathione S-transferases (GST) also act in the herbicide detoxification process, following the oxidation of the substrate by cytochromes P450, by catalyzing the conjugation of the various oxidated substrates with glutathione to form a polar S-glutathionylated product (R-SG), thus reducing the reactiveness of the chemical to be detoxified [11].