Dissertation
WHEAT GENOTYPE-SPECIFIC RECRUITMENT OF RHIZOSPHERE MICROBIOMES THAT ARE SUPPRESSIVE TO RHIZOCTONIA ROOT ROT
Washington State University
Doctor of Philosophy (PhD), Washington State University
01/2021
DOI:
https://doi.org/10.7273/000005399
Handle:
https://hdl.handle.net/2376/119073
Abstract
The soilborne fungal pathogen Rhizoctonia solani AG8 causes root-rot and bare patch disease and is an important disease of wheat especially in the dryland areas of the Pacific Northwest. Despite large scale screening for resistance, resistance is limited in the wheat germplasm. Harnessing suppressive soils with the use of specific wheat genotypes that recruit suppressive rhizosphere microbiomes is a potential alternative in managing the disease. To determine wheat genotype-specific recruitment of microbiomes, growth chamber cycling experiments using six winter wheat genotypes were initially done and suppression assays performed to determine suppression against R. solani AG8. Furthermore, a more diverse wheat panel was assembled for a two-year field cycling experiment to explore more suppressive microbiomes. Disease suppression, observed using field rhizosphere soils, was validated in the growth chamber. PBW343 a spring wheat variety, exhibited more suppressiveness compared with PI561725, a winter wheat breeding line that was identified to have a suppressive microbiome in the initial growth chamber cycling experiment. To identify bacterial taxa that constitute the suppressive microbiome, 16S rRNA sequencing was done and revealed notable abundance of Proteobacteria in more suppressive soils compared to less suppressive soils. Bacterial taxa belonging to Chitinophagaceae, Bradyrhizobiaceae, Rhodospirillaceae, Phyllobacteriaceae, Burkholderiaceae, Caulobacteraceae, Xanthomonadaceae, Glycomycetaceae and Pseudonocardiaceae were differentially more abundant in rhizosphere from PBW343 and were associated with pathogen suppression. Furthermore, bacterial isolation from the rhizosphere soil of PBW343 was done to isolate suppressive bacterial taxa and to determine direct antagonism to the pathogen. Classification of bacterial isolates was done through 16S rRNA amplicon sequencing of colonies and have aided in narrowing down to 13 isolates for antagonism assays. Among the isolates tested, Pseudomonas baetica, Stenotrophomonas maltophilia and Pseudomonas fluorescens significantly inhibited the radial growth of the pathogen. Our research demonstrated that disease suppression elicited by microbiomes are recruited by specific wheat genotypes. With this, specific wheat genotypes can be used to manipulate soil as part of a cropping system to manage root rot and bare patch disease in wheat.
Metrics
Details
- Title
- WHEAT GENOTYPE-SPECIFIC RECRUITMENT OF RHIZOSPHERE MICROBIOMES THAT ARE SUPPRESSIVE TO RHIZOCTONIA ROOT ROT
- Creators
- Christine Jade Dilla Ermita
- Contributors
- Scot H. Hulbert (Advisor)Tarah S. Sullivan (Committee Member)Cynthia A. Gleason (Committee Member)Timothy C. Paulitz (Committee Member)Kimberly G. Campbell (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Plant Pathology
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 190
- Identifiers
- 99900592258301842
- Language
- English
- Resource Type
- Dissertation