The quinoa crop (Chenopodium quinoa Willd) has gained global relevance due to its nutritional profile and adaptability to diverse agroecological zones. However, yield potential remains constrained by weed pressure and the lack of selective herbicides registered for quinoa. This research aimed to develop herbicide-tolerant varieties through chemical mutagenesis using ethyl methanesulfonate (EMS). In the first phase, three varieties (Nieves, Chucao, and Pincoya) were exposed to EMS at varying concentrations to identify the optimal mutagenic dose. A 2.5% EMS concentration was selected based on median lethal dose analysis, with Pincoya showing suitable sensitivity. Subsequently, seven post-emergent herbicides were applied to assess phytotoxicity and identify tolerant mutants. Survival rates ranged from 0.25% to 17.8%, with partial tolerance observed for sulfonylureas and photosystem II inhibitors.

In the second phase, 7 M1 lines derived from EMS-treated Pincoya plants were evaluated for the phenotypic behavior of herbicide tolerance. The herbicides applied according to their active ingredient were bentazon (Basagran®), phenmedipham, desmedipham, ethofumesate (Betanal expert®), fomesafen (Flex®), triflusulfuron-methyl (Safari®), and lenacil (Venzar®), representing diverse modes of action. Survival and visual toxicity were assessed 7, 14, 21, 30, and 90 days post-application, revealing differential responses among lines and suggesting heritable mutations conferring partial tolerance.

These approaches demonstrate the potential of EMS mutagenesis to generate heritable herbicide tolerance in quinoa, offering a viable pathway for integrating chemical weed control into sustainable production systems. Molecular validation and field trials are currently underway to confirm genetic stability and agronomic performance.