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theses

Poaceae grass root associated ACC-deaminase producing bacteria were collected from four locations in New Jersey pine barrens. A total of 186 bacterial isolates were obtained, belonging to 6 orders, 9 families and 10 genera based on 16S rDNA sequencing. The most prevalent genus was Burkholderia (71.5%), followed by Herbaspirillum (9.1%), Pseudomonas (8.6%) and Paenibacillus (5.4%). A high throughput method was employed to quantify the ACC deaminase activity, which ranged from 0 to as high as 40024 nmol ketobutyrate/mg/h among all the isolates. A root elongation assay showed three isolates promoted root elongation significantly under well-watered condition and one isolate was able to promote root elongation under salinity condition. ACC-deaminase producing bacteria may play an important role in assisting the establishment of Poaceace grasses in the dry and infertile pine barrens ecosystem. The second part of this study tested the potential of ACC-deaminase bacteria inoculation in promoting plant growth and salinity stress tolerance and examined growth traits, nutrition status, and physiological changes associated with the ACC-deaminase bacteria inoculation. Perennial ryegrass (Lolium perenne L.) were inoculated with two ACC-deaminase bacteria, Burkholderia phytofirmans and Burkholderia gladioli under well-watered or salinity condition. The inoculums suppressed ACC production in both shoots and roots. Shoot and root growth was inhibited by salinity stress whereas the bacteria inoculation increased turf quality, tiller number, and promoted root development and biomass accumulation of both roots and shoots under well-watered and salinity stress. The inoculation also promoted physiological tolerance of plant to salinity stress, as manifested by higher leaf relative water content and photochemical efficiency, as well as lower electrolyte leakage of plants exposed to salinity stress. The inoculated plants had significantly lower Na content and higher K+/Na+ ratio in shoots under both well-watered and salinity conditions. The inoculation increased nitrogen content in shoot and root and potassium content in shoot under both well-watered and salinity conditions, but caused reduction in Ca, Mg, Fe, and Al content in shoots and roots under salinity conditions. The results demonstrated ACC-deaminase bacteria had beneficial roles in promoting perennial ryegrass growth and salinity tolerance, which could be potentially used in turfgrass establishment and maintenance.

ETD_6379

M.S.

Includes bibliographical references

by Liang Cheng

doi:10.7282/T3PR7XTG

ETD graduate

The author owns the copyright to this work.