ARS | Publication request: Natural suppression of Rhizoctonia root rot by soil microbial communities in wheat from a Rhizoctonia decline site.

Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: April 1, 2012
Publication Date: July 1, 2012
Citation: Yin, C., Hulbert, S., Schroeder, K.L., Mavrodi, O., Mavrodi, D., Schillinger, W., Paulitz, T.C. 2012. Natural suppression of Rhizoctonia root rot by soil microbial communities in wheat from a Rhizoctonia decline site. Phytopathology. 102:S4.141.

Technical Abstract: Rhizoctonia root rot, caused by Rhizoctonia solani AG-8, limits yield in direct-seeded wheat, which develops distinct patches of stunted plants. At a cropping systems study near Ritzville, WA with continuously cropped wheat, bare patch reached a peak after 5 years of direct-seeding and then declined by year 11. From replicated plots, bacterial communities from bulk soil and rhizospheres of plants from inside, outside, and recovered patches, were analyzed by pyrosequencing with primers designed to the 16S rDNA. A total of 56,102 high-quality reads were generated in 2008 and 2010 field samples. Mesorhizobium, Burkholderia, Dyella and Acidobacteria Gp3 and Gp7 showed a trend with higher frequencies in the rhizosphere of healthy plants outside of the patches and from recovered patches, compared to diseased plants from inside patches. Oxalobacteriaceae (Herbaspirillum and Massilia), Chitinophaga, Flavobacterium, Pedobacter and Enterobacteriaceae were higher in the rhizosphere of diseased plants from inside patches. For selected taxa, pyrosequencing results were validated by real-time quantitative PCR. Furthermore, the shifts of some microbial communities in the rhizosphere over time were duplicated with cycling experiments in the greenhouse, with successive plantings of wheat in Rhizoctonia-inoculated soil. Chryseobacterium soldanellicola and Pseudomonas sp. were isolated from the rhizosphere of plants inside patches and exhibited significant antagonism against AG-8 in vitro in dual culture experiments and in greenhouse tests. In conclusion, this study identified novel bacterial taxa which respond to conditions affecting bare patch symptoms and may be involved in suppression of Rhizoctonia root rot