Establishment of Kentucky bluegrass inoculated with the novel nitrogen fixing bacterial endophyte, Gluconacetobacter diazotrophicus

Open Access
- Author:
- Sebring, Ryan L
- Graduate Program:
- Agronomy
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 07, 2017
- Committee Members:
- Maxim J Schlossberg, Thesis Advisor/Co-Advisor
Ray Bryant, Committee Member
John Michael Regan, Committee Member - Keywords:
- Bacterial nitrogen fixation
bnf
poa pratensis
gluconacetobacter diazotrophicus
G. diaz
nitrogen fixation - Abstract:
- Applications of exogenous nitrogen fertilizers to turfgrass systems are subject to losses via leaching, volatilization, and/or denitrification, negatively impacting effective cultural and environmental practices. Biological nitrogen fixation (BNF) by bacterial endosymbionts has been confirmed to reduce external N requirements and thus loss potential in several non-leguminous plant species, and may potentially satisfy, to some degree, nitrogen fertilizer requirements in turfgrasses. The objective of this field experiment was to assay the inoculation of Kentucky bluegrass (Poa pratensis) with the BNF bacteria Gluconacetobacter diazotrophicus and measure normalized difference vegetation index (NDVI), dark green color index (DCGI), and biomass accumulation as N correlating plant responses. A 2x5 factorial of seed treatment (inoculated or virgin) by N fertility (0, 33, 67, 100, or 133% recommended yearly N rates) was arranged in a randomized complete block design. Seedlings were randomly sampled 18 days after establishment (DAE) to test for successful inoculation, and then yearly for bacterial persistence. Nitrogen fertilizer treatments were initiated in the 4th month post seeding, when all plots were established and mowing had been initiated. Beginning in the establishment year and for two years thereafter, canopy reflectance measured via multispectral radiometers was used to quantify K. blue canopy density and color. Clippings were collected in the first post-establishment season to assess shoot biomass accumulation. PCR analysis of surface-sterilized leaf and crown tissue confirmed full colonization of plant tissues by G. diazotrophicus in the establishment year but demonstrated a 70% loss after one wintering and 100% loss after two. NDVI measurements reported a significant (+2.6%) canopy density difference main effect in inoculated tissues over non-inoculated and a significant inoculation by fertilization interaction at N fertility 33 and 133%. DGCI and biomass were not impacted.