Imazethapyr and weed interference-induced oxidative stress change the dynamics of the antioxidant defence system in lentil (Lens culinaris Medik.)

Weeds prevent the growth of the lentil crop, which significantly reduces yield. Imazethapyr (IM), a post-emergence herbicide, primarily inhibited acetolactate synthase activity by reducing branched-chain amino acid contents which had an impact on plant growth. IM application has a secondary impact of increasing oxidative stress due to ALS inhibition. The objective of the present study was to elucidate the role of antioxidant defence mechanisms in mitigating oxidative stress induced by IM treatment and weed interference in IM-tolerant (LL1397 & LL1612) and susceptible (FLIP2004-7 L & PL07) lentil genotypes that were grown under control, weedy check, and IM-treated conditions. Lower H2O2 and MDA content in tolerant genotypes after IM spray were due to increased NOX (NADPH oxidase), SOD (superoxide dismutase), CAT (catalase), peroxidase (POX), GR (glutathione reductase), APX (ascorbate peroxidase), MDHAR (monodehydroascorbate reductase) and DHAR (dehydroascorbate reductase) along with higher ascorbate (AsA) and lower DHA (dehydroascorbate) content, helped plants recover from herbicide stress. However, in susceptible genotypes, higher H2O2 and MDA contents due to reduced CAT, APX, MDHAR, DHAR and NOX activities led to loss of membrane integrity by lipid peroxidation that adversely affected the plant growth. Increased SOD, GR, MDHAR, and DHAR activities in tolerant genotypes under weedy check treatment tried to cope with weed interference-induced oxidative stress, but a lower magnitude of increase in enzyme activities and decreased H2O2-detoxifying enzyme activities led to incomplete detoxification of ROS, which affected plant development. This is the first in-depth investigation of the IM tolerance mechanism in lentil. The identified tolerance mechanism during herbicide stress and weed interference in lentil will be useful in integrated herbicide weed management.