Narinder SinghSuma, Moka2020-10-232020-10-232020Moka, Suma (2020). Potential of native strains of bioagents for the management of damping off in onion and tomato (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810153708Damping off is a destructive disease in onion and tomato caused by Fusarium oxysporum f.sp.cepae and Rhizoctonia solani in nursery growing areas of Punjab. Rhizospheric soil samples were collected from onion and tomato growing nurseries of Sangrur, Ludhiana and Amritsar districts of Punjab and analysed for antagonistic microflora. Seventeen isolates of Trichoderma and fifteen isolates of Pseudomonas were isolated and screened in vitro against the Fusarium oxysporum f.sp.cepae and Rhizoctonia solani causing damping off in onion and tomato respectively through dual culture technique, volatile and non-volatile compounds. Among all tested isolates Trichoderma isolate (T8) has shown maximum inhibition of Fusarium oxysporum f.sp.cepae (71.42%) and Rhizoctonia solani (84.22%) by dual culture. This isolate also showed maximum inhibition to Fusarium oxysporum f.sp. cepae and Rhizoctonia solani by volatile and non volatile metabolites of Trichoderma isolates. Pseudomonas isolate Pf10 has showed maximum mycelial inhibition of Fusarium oxysporum f.sp.cepae (64.37%) and Rhizoctonia solani (65.93%) by dual culture. It also showed mycelial inhibition of Fusarium oxysporum f.sp.cepae and Rhizoctonia solani by volatile and non volatile compounds released from Pseudomonas isolates. Biochemical tests for estimation of cell wall degrading enzymes has shown the ability of the Trichoderma isolate (T8) and Pseudomonas isolate (Pf10) to produce high level of chitinase (17.57 and 14.20 unit/ml respectively) and β-1,3-glucanase (1.42 and 1.52 unit/ml respectively). Pf10 also showed highest siderophore production of 33.67mm. The efficacy of talc based bioformulations of Trichoderma (T8) and Pseudomonas isolate (Pf10) when applied alone as well as in combination under pot and field conditions was checked against damping off of onion and tomato. In onion under field conditions, Pseudomonas (Pf10) and Trichoderma (T8) when applied as seed+soil treatment @15g/kg showed maximum inhibition of disease (89.99 and 88.75 percent respectively). They also acted as plant growth promoters with root length (14.64 and 14.17 cm), shoot length (25.33 and 25.00cm), fresh weight (4.51 and 4.45g), dry weight (1.82 and 1.80g) and finally yield (195.76 and 193.94 q/acre) of the crop. In tomato under field conditions Pf10 and T8 when applied as seed+soil treatment@15g showed maximum inhibition of damping off disease (88.89 and 85.71 per cent) with yield of 221.86 and 221.40 q/acre respectively. Pf10 and T8 (seed+soil treatments@15g) also acted as plant growth promoters with pooled root length (23.67 and 22.50 cm), shoot length (34.49 and 33.79cm), fresh weight (4.53 and 4.49g) and dry weight (2.22 and 2.19g) respectively during 2018 and 2019. Rhisosphere soil sampling from treated onion and tomato nursery up to 45 days showed decrease in antagonistic population up to 15 days and then it started increasing. The selected antagonists showed promising rhizospheric competency throughout the growing season that was enough to control damping off disease of onion and tomato in both pot and field conditions. Molecular identification of the Trichoderma T8 using endochitinase ech42 gene specific primers was done and found that it is closely related to Trichoderma asperellum and Pseudomonas isolate Pf10 using universal primer and sequence analysis showed similarity with Pseudomonas fluorescens. Study of shelf life of the talc based bioformulation revealed that antagonist Trichoderma asperellum (T8) and P. fluorescens (Pf10) can remain potent for 6 months when stored at room temperature while at low temperature storage (4° and 0°C) they can remain potent upto one year. For Mass multiplication sugarcane press mud, rice leaves and wheat bran supported rapid, maximum growth and sporulation of Trichoderma asperellum T8 at 25°CEnglishThesis