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ThesisItem Restricted Integrated weed management in wheat and characterization of herbicide resistance in Phalaris minor Retz.(Punjab Agricultural University, Ludhiana, 2022) Gurpreet Kaur; Tarundeep KaurThe study ―Integrated weed management in wheat and characterization of herbicide resistance in Phalaris minor Retz.‖, consisted of two field and one pot experiment. Expt I: Integrated weed management in relation to paddy straw levels, nitrogen rates in wheat under rice -wheat cropping system was conducted in split plot design with paddy straw levels i.e. 0 t ha-1 , 7.5 t ha-1 and 10 t ha-1 paddy straw in main plots, nitrogen doses i.e. 100 % , 125 % and 150 % recommended nitrogen in sub plots and weed control i.e. without herbicide (control) and metribuzin 42% + clodinafop propargyl 12% at 270 g ha-1 (POST) in sub-sub plots with three replications. Significant reduction in viable weed seeds and density of Phalaris minor, Medicago denticulata and Rumex dentatus was recorded in 7.5 and 10 t ha-1 than 0 t ha-1. An increase of 9.3 & 8.1 % and 9 & 5.9 % in grain yield was recorded in 7.5 and 10 t ha-1 paddy straw level than 0 t ha-1 paddy straw level during 2018-19 and 2019-20, respectively. Grain yield slightly enhanced with increasing 100 to 125 % recommended nitrogen and started decreasing with further increasing nitrogen to 150 % recommended nitrogen. Lower density of weeds and higher grain yields (38.1-51.3%) were produced in metribuzin + clodinafop (pre-mix) at 270 g ha-1 than without herbicide. Expt II: Integrated weed management with crop establishment methods and row spacing in wheat under rice -wheat cropping system was conducted in split plot design with crop establishment methods i.e. mechanically transplanted rice and manual transplanted rice in main plots, row spacing i.e. 18.25 cm (7.3 inches) and 22.5 cm (9 inches) in sub plots and weed control i.e. without herbicide (control), pyroxasulfone at 127.5 g ha-1 (PRE), metsulfuron 10% + carfentrazone 40% at 25 g ha-1 (POST) and metribuzin 42% + clodinafop 12% at 270 g ha-1 (POST) in sub-sub plots with three replications. Closer row spacing of 18.25 cm had better smothering effect on weeds and gave 9.2 and 12.5% increased grain yields than row spacing of 22.5 cm. Metribuzin + clodinafop at 270 g ha-1 and pyroxasulfone at 127.5 g ha-1 reduced grass and broad leaf weeds effectively. Metsulfuron + carfentrazone at 25 g ha-1 managed broad leaf weeds efficiently but it did not control grass weeds and their biomass. Metribuzin + clodinafop at 270 g ha-1 and pyroxasulfone at 127.5 g ha-1 gave higher grain and straw yield than without herbicide. Expt III: Characterization of herbicide resistance in Phalaris minor was carried out using five post emergence herbicides viz clodinafop, mesosulfuron + iodosulfuron, pinoxaden, sulfosulfuron and isoproturon, and three pre-emergence herbicides namely pendimethalin, pendimethalin+metribuzin and pyroxasulfone at 0, 0.25X, 0.50X, X, 2X and 4X doses of recommended field use of herbicides with three replications tested against 95 populations of Phalaris minor alongwith two susceptible population. It was found that 13 populations had homozygous resistant alleles (404bp band), 41 populations had homozygous sensitive alleles (169 and 235 bp band) whereas 12 populations had heterozygous resistant alleles (169, 235 and 404bp band). T to A nucleotide transversion was observed in amplfied region of ACC gene which is responsible for resistance to Acetyl CoA Carboxylase enzyme in Phalaris minor. Non-enzymatic antioxidant components and antioxidant enzymes played an important role in defence mechanism of Phalaris minor resistant populations under herbicide stress. H2O2 produced during the oxidative stress was detoxified in resistant Phalaris minor populations either by peroxidase enzyme and/or catalase enzyme and/or ascorbate peroxodase and/or glutathione reductase in combination of two or more enzymes along with superoxide dismutate enzyme.
