The bacterial microbiomes of Saskatchewan crops and potential for plant growth promotion
Date
2019-02-26
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
ORCID
Type
Thesis
Degree Level
Doctoral
Abstract
Bacteria associated with the rhizosphere and plant tissues may contribute to host crops by providing nutrients, stimulating growth and/or controlling phytopathogens. These beneficial plant × bacteria associations may have a key role in the establishment and production of agricultural ecosystems. This research thesis investigated the bacterial communities associated with canola (Brassica napus L.), wheat (Triticum aestivum L.), lentil (Lens culinaris L.) and field pea (Pisum sativum L.) grown in agricultural fields in Saskatchewan and assessed the potential of some of these bacteria for plant growth promotion. Analysis of bacterial communities associated with these crops suggested a selection of the root endophytic microbiome from the rhizosphere. In contrast, endophytic bacteria associated with aboveground plant organs varied greatly among crops, soils and plant organs. Furthermore, Denaturing Gradient Gel Electrophoresis (DGGE) and high throughput-sequencing analyses of baterial profiles in wheat and canola suggested that each crop may select specific bacterial taxa at different plant growth stages and within different plant compartments. Pseudomonas and Stenotrophomonas were predominant genera in the rhizosphere and root interior of all crops, suggesting a generalist distribution of these bacteria. Relative abundance of specific bacterial groups in the rhizosphere, as well as bacterial Phospholipid Fatty Acids (PLFA) in the bulk soil, were significantly correlated with soil pH, silt and organic matter content. There was, however, no correlation between soil properties and the most abundant endophytic bacterial genera, thus suggesting that soil characteristics may not influence bacterial communities within plant roots. Culturable bacteria (n=157) isolated from the root interior of the studied crops were tested for their effect on seed germination, root elongation and plant growth promotion. A total of nine bacterial strains, isolated from the root interior of field grown crops, stimulated seed germination and root elongation when inoculated to canola and wheat plants, and five of these bacterial strains also promoted shoot growth in canola. Overall, these results suggest the bacterial microbiomes of the rhizosphere and plant tissues were modulated by soil properties and host crop, respectively. In addition, several endophytic bacteria demonstrated potential for use as bioinoculants in agriculture.
Description
Keywords
crops, bacteria, microbiome
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Soil Science
Program
Soil Science