Hydroponic screening and liquid chromatography–mass spectrometry metabolite profiling of lentil genotypes for tolerance to metribuzin

Abstract Weed pressure threatens lentil ( Lens culinaris Medik.) yields, with metribuzin offering control but risking crop injury. This study used hydroponics to screen metribuzin tolerance in lentils, determining the lethal dose causing 50% mortality (LD 50 ) for lentil cultivar ‘CDC Greenstar’ and profiling metabolites in three genotypes, ‘VIR421’ (susceptible), CDC Greenstar (tolerant), and ‘NZ2022’ (medium tolerant), via liquid chromatography–mass spectrometry (LC-MS). CDC Greenstar plants in a hydroponic deep-water culture system were exposed to metribuzin doses (0.17, 0.25, 0.51, and 2.05 g ai ha⁻ 1 , plus a control) selected based on preliminary trials that identified the effective range for LD 50 estimation in hydroponics, where herbicide bioavailability is higher than in soil due to direct root exposure and absence of soil adsorption. These doses are substantially lower than the recommended field application rate of 205 g ha⁻ 1 as a preemergence treatment for lentils to account for the amplified effects in hydroponics for 24 h, with biomass reductions assessed over 21 d. The LD 50 was 0.4407 g ha⁻ 1 (R 2 = 0.94), with dose strongly reducing shoot/root growth (r = −0.92 to −0.99). Untargeted LC-MS identified seven metabolites in CDC Greenstar and VIR421, including desamino-metribuzin (DA) and conjugates, while targeted LC-MS tracked metribuzin, DA, and desamino-diketo-metribuzin (DADK) over 12 d. VIR421 had higher metribuzin levels (105.70 ng g −1 at dry weight at 12 h) compared with CDC Greenstar and NZ2022, which rapidly metabolized metribuzin to DA (58 and 50.41 ng g −1 dry weight at 2 d), with NZ2022 showing further metabolism by 4 d. DA dominated 59- to 167-fold over DADK, suggesting a primary detoxification pathway. Hydroponics enabled precise tolerance screening, revealing genotype-specific metabolism critical for breeding metribuzin-tolerant lentils and thus enhancing weed management strategies.