Gaganjit Kaur2020-11-122020-11-122020Gaganjit Kaur (2020). Effect of plant growth promoting Rhizobacteria on germination, antioxidant enzymes and bulb quality in onion (Allium cepa) (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810154993In the present study, ten different PGPR treatments were given to the onion seeds (PRO-6 and ADR). In the first experiment, seeds were sown in the petri-dishes and then analysed for various parameters. The germination percentage (100%) was observed maximum in PRO-6 and ADR. After 7 DAG shoot length (0.53 cm) was same in both varieties and after 14 DAG, it showed maximum in PGPR 7 (2.87 cm) in PRO-6 and ADR (2.97 cm) in PGPR 3. In PRO-6, dry weight of roots and shoots was same 0.08 g and in ADR it was 0.08g in roots and 0.09g in shoots. For peroxidase, PGPR 7 showed maximum activity in roots (0.064-0.028 change in absorbance/min/g FW) in PRO-6 and ADR, respectively. In shoots, PGPR 3 showed maximum activities (0.033-0.14 A OD) in PRO-6 and ADR, respectively. PGPR 3 and PGPR 7 showed maximum activity for catalase in both roots and shoots of PRO-6 and ADR, respectively. PGPR 3 showed maximum activity for superoxide dismutase in both varieties while for ascorbate peroxidase, PGPR 7 showed maximum activity in PRO-6 and ADR. The antioxidant capacity in roots and shoots was observed to be (95.45% and 55.49%) for PRO-6 and (84.38 and 79.65%) for ADR, respectively. On the basis of first experiment, it was observed that the Bacillus cereus (PGPR 7) and Pseudomonas fluoroscens (PGPR 3) were the best plant growth promoters among all the treatments. So, in the second experiment, treatments of PGPR 3 and PGPR 7 were selected and seeds were sown in the field. Shoot length (13.4- 90.3 cm) in PRO-6 and ADR (17.6- 92.0 cm), no. of leaves (1.5-4.5) in PRO-6 and ADR (1.5-4.8) and yield per plot in PRO-6 (0.27 gm/m2) and ADR (0.32 gm/m2) were observed maximum in PGPR 7. The antioxidant enzymes: peroxidase, catalase and superoxide dismutase showed maximum activity in PGPR 7 in roots, leaves and bulb during different intervals of time (45, 90, 135 DAS and at maturity) in PRO-6 and ADR. Total phenol (52.79 and 57.87 mg/100g), anthocyanins (56.10 and 59.23 mg/100g), quercetin (4.6¬6.9 1.1g/100g), pyruvic acid (0.05- 0.07 mmol/g FW) and lachrymatory factor (0.66- 0.53 wnol/100g FW) were observed maximum in PGPR 7 of both PRO-6 and ADR. It was concluded that the treatment given with PGPR 7 led to higher activities of antioxidant enzymes and other biochemical parametersof onion (PRO-6 and ADR).EnglishThesis