Dissertation
GENETIC CHARACTERIZATION AND RHIZOSPHERE MICROBIAL COMMUNITY ANALYSIS ASSOCIATED WITH ROOT ROT DISEASE OF WHEAT
Doctor of Philosophy (PhD), Washington State University
01/2017
Handle:
https://hdl.handle.net/2376/112321
Abstract
Yield losses associated with soilborne pathogens Rhizoctonia solani AG8 and R. oryzae are a significant problem for farmers that adopt minimal tillage systems in the PNW. Genetic resistance could reduce this problem and provide an economic and sustainable management strategy. To identify resistance, synthetic and synthetic-derived genotypes were screened in field and growth chamber environments under high and low inoculum densities. Genotypes varying in resistance were found by measuring stunting and root disease scores. SPCB-3104 was identified as having moderate levels of resistance. A BC1-derived population consisting of 190 recombinant inbred lines (RILs) were used to map loci in a cross between ‘Louise,’ and SPCB-3104. QTL derived from SPCB-3104 were found on chromosomes 1BL, 2AS, and 2DL.
In a collection of synthetic genotypes, SYN-172 was observed to have low levels of Rhizoctonia root damage, and no stunting in a high inoculum field nursery. A mapping population of 150 BC1-derived RILs were created by crossing into Louise. QTL were found on 1AL, 2AL, 5BL, 7DS, and 7DL. When the parental roots were compared, differences in total root length and projected surface area were observed when grown in artificially infested soils. Louise, the susceptible parent was found to have a significant reduction in total root length as compared to SYN-172.
Minimal tillage practices can provide significant benefits such as soil erosion, water retention, and beneficial microbial populations. To investigate the long-term rhizosphere community of wheat, wheat cultivars were grown for two years at different locations. Amplicon sequencing of the population identified 26,604 operational taxonomic units (OTUs). Significant community differences in relative abundances were found for cultivars and location. A small number of OTUs (24) were found to differ by cultivar; these differences were consistent at both locations. Co-occurrence networks demonstrated positive correlations amongst most of the OTUs. However, in some instances, OTUs co-excluded each other, and these negative correlations were found to be cultivar-specific. Significant differences by cultivar for metabolic functions of the communities were found using PICRUSt analyses. These functions associated with plant beneficial services, such as nitrogen, sulfur, phosphorus, and malate metabolisms.
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Details
- Title
- GENETIC CHARACTERIZATION AND RHIZOSPHERE MICROBIAL COMMUNITY ANALYSIS ASSOCIATED WITH ROOT ROT DISEASE OF WHEAT
- Creators
- Aaron Mahoney
- Contributors
- Scot H Hulbert (Advisor)Pat Okubara (Advisor)Timothy Paulitz (Committee Member)Arron Carter (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Program in Molecular Plant Sciences
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 132
- Identifiers
- 99900581629801842
- Language
- English
- Resource Type
- Dissertation