Pandove, GulabJagjot Kaur2023-12-112023-12-112023Jagjot Kaur(2023). Appraisal of seed priming with liquid microbial inoculants on agronomic and fibre quality traits of cotton (Unpublished Ph.D. Dissertation). Punjab Agricultural University, Ludhiana, Punjab, India.https://krishikosh.egranth.ac.in/handle/1/5810202506Cotton (Gossypium hirsutum L.) is an important commercial cash crop. In India, north-western zone majorly Punjab, Haryana and Rajasthan are highly known for cotton cultivation. Thus, the present investigation was undertaken for the appraisal of seed priming with liquid microbial inoculants on agronomic and fibre quality traits of cotton. A total of 124 cotton plants and 124 rhizospheric soil samples were collected mainly from the different cotton fields of Bathinda, Punjab, India and a total of 243 bacterial isolates (148 rhizospheric and 95 endophytic isolates) based upon distinct colony morphology were isolated. Further, prominent 27 rhizospheric and 35 endophytic isolates were selected on the basis of quantitative phosphate solubilization assay and were further evaluated for other PGP traits such as siderophore production, exogenous phytohormones production (IAA, gibberellic acid), ammonia production, HCN production and ACC deaminase activity. Consequently, five potential isolates i.e., 31LN, 43RN, 35TP, 34RN and 43TN were selected on the basis of multiple PGP traits and identified by the sequencing of 16S rRNA gene as Acinetobacter lwoffii, Bacillus thaon-hiensis, Klebsiella pneumoniae subsp. ozaenae, Pseudomonas brassicacearum and Pseudomonas fluorescens respectively. The identified bacterial strains were analysed for the presence of accds, alps, gdh and pqqE gene using gene specific universal primers. Further, the medium composition for liquid inoculant of potential bacterial strains was optimized as yeast extract: 4.5g/L, peptone: 5g/L, NaCl: 5g/L and food- grade trehalose: 12.5mM by using RSM. The liquid inoculants of each promising bacterial strain showed shelf stability upto 180th day of storage at room and refrigerated conditions. Also, the root colonization assay by scanning electron microscopy demonstrated the successful establishment of bacterial strains PAU_43RN, PAU_35TP, PAU_34RN and PAU_43TN with roots of cotton seedlings developed from the bio-primed seeds. During the in-vitro studies for abiotic stress tolerance, the bacterial strains reported to maintain a constant viability at 150mM NaCl and 10% PEG concentration. The bacterial strains were also evaluated for the production of PGP traits and found positive for IAA, gibberellic acid, ammonia, siderophore production, phosphate solubilization and ACC deaminase activity under the varying saline and drought stress conditions. The in vitro plant growth assay demonstrated that seed bio-priming with B. thaonhiensis improved the seedling length (6.50cm shoot and 3.60cm root length), dry shoot and root biomass (0.037g and 0.0023g respectively), vigor index (765.9), and germination percentage (79%) under 150mM salt content. Furthermore, at 10% PEG concentration, the B. thaonhiensis treatment improved the germination% (75%), shoot length (5.30cm), root length (4.60cm), fresh and dry; shoot (0.19g and 0.014g) and root weight (0.013g and 0.003g) and vigor index (SVI: 350.35) of the in-vitro grown cotton seedlings. The field experiments were also conducted at PAU, Ludhiana and PAU, RRS, Bathinda during the kharif 2021. The experiments were laid in the RCBD with 12 treatments of liquid bacterial inoculants in combination with 100% RDF and replicated thrice. The maximum seed cotton yield was measured in the treatment T12: RDF+ B. thaonhiensis followed by the treatment T7: RDF + Sphingobacterium sp. with the percentage increment of 16.13% and 13.97% respectively over the control (T1) in the pooled data. The lint yield (39.09 g/plant), GOT% (36.51), lint index (5.25), boll weight (4.30 g), number of bolls (33.5 per plant), seed index (9.10), sympodial branches (25.51) and plant biomass (1116.9 g/plant) were also found maximum in the treatment T12. The quality attributes of cotton fibre affected non-significantly with the application of liquid bacterial inoculants. The impro -vement in the soil physico-chemical and microbiological parameters was observed with the application of liquid bacterial inoculants over the control (T1: RDF). Therefore, the study concludes that the seed bio-priming with liquid bacterial inoculants can escalate the yield of cotton crop in an environment-friendly manner under arid and semi- arid agro-ecosystem.EnglishThesis