Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: May 9, 2011
Publication Date: June 9, 2011
Citation: Mazzola, M. 2011. Particle size affects Brassica seed meal-induced pathogen suppression of Rhizoctonia solani AG-5. Phytopathology. 101:S249. Technical Abstract: R. solani AG-5 is a component of the pathogen complex that incites apple replant disease, and is suppressed via multiple mechanisms in response to B. juncea seed meal (SM) amendment. Allyl isothiocyanate (AITC) functions in suppression of this pathogen during the initial 24 h period post-seed meal amendment, but thereafter soil biology and specifically resident Streptomyces spp. have the dominant functional role in disease suppression. AITC emission was initiated earlier and reached higher maximal concentrations in soils amended with fine particle (<1mm dia) than coarse particle (2-4 mm dia) SM. This corresponded with the level of disease suppression obtained when R. solani AG-5 and SM were introduced concurrently into soils and plant to apple; fine particle but not coarse particle SM suppressed apple root infection when applied to soil at a rate of 0.3% (wt/wt). Both fine and coarse particle SM amendment elevated resident Streptomyces approximately an order of magnitude by eight weeks post-application. When soil was infested with R. solani AG-5 subsequent to this eight week incubation period and planted to apple, both SM types effectively suppressed Rhizoctonia root rot. These findings demonstrate that particle size will affect the efficacy of chemistry-based, but not biologically-based, suppression of R. solani in response to B. juncea SM soil amendment.