DES Seminar by Mirja Guldner (PhD candidate)

27 June 2014

Impact of farm management on the diversity of desulfonation genes and 16S rRNA genes in wheat rhizospheres


Worldwide the resources for mineral fertilizer are diminishing. Growth of healthy, high-yielding crop plants requires a stable input not only of nitrogen and phosphorus, but also of sulfur (S). In natural ecosystems, nutrient cycling is mainly mediated by soil microorganisms, and much research is devoted to optimization of microbial nutrient cycling for agricultural ecosystems. Several rhizosphere microorganisms are able to mobilize plant-unavailable soil S, and two bacterial genes that may be involved in the process are atsA, which encodes arylsulfatase, and ssuD which encodes alkanesulfonatemonooxygenase.

This study investigated the impact of agricultural practices on the overall rhizosphere microbial community and on functional diversity of S-mobilizing organisms. Five wheat genotypes with different root-structures were inoculated with different strains of Azospirillum brasilense to determine the influence of wheat genotype and inoculation treatment in a continuous wheat field trial at Narrabri, New South Wales (Australia). Pot trials with vertisol soil from the field-site were carried out to investigate the effect of wheat variety and different inoculation treatments under controlled conditions. For the analysis of the ssuD-gene diversity degenerate primers were designed and tested for specificity through cloning and sequencing. Both, exploratory NMDS-Analysis and redundancy analysis (RDA) of fingerprinting profiles obtained by T-RFLP (Terminal restriction fragment length polymorphism) showed that wheat variety has a significant (p< 0.05) impact on the ssuD gene diversity in the rhizosphere. A comparison of two crop rotations, (field pea/sorghum/wheat or mustard/sorghum/wheat) also showed clear differences between the 16S rRNA-gene and ssuD-gene diversity in the two treatments. Furthermore T-RFLP fingerprints of the ssuD gene diversity in wheat and canola rhizospheres were obtained across NSW and Victoria major environmental factors driving changes in ssuD-gene diversity were assessed. Optimizing farm management by taking into account the genetic potential of rhizosphere microorganisms can help to tailor more resource-efficient crop production systems.

Time: 4-5PM

Location: Rom 422, Biomedical Building (C81), ATP

Contact: Dr Uta Stockmann

Phone: 02 8627 1147

Email: 0422147e1420361a0e17275f3e023c130b0423487b4a2d3c4b1321