Title: GENERAL SUPPRESSION OF FREE-LIVING NEMATODES BY BRASSICACEAE SEED MEAL Authors
Submitted to: Microbial Ecology International Symposium
Publication Type: Proceedings
Publication Acceptance Date: May 10, 2010
Publication Date: N/A
Technical Abstract: Biologically-based management systems such as soil-organic residue amendments or “biofumigation” are promoted as alternatives for control of soil-borne pathogens in agro-ecosystems. Brassica plant residues contain glucosinolates which upon hydrolysis by endogenous myrosinase yields broadly-active biocidal compounds such as isothiocyanates (ITC). Incorporation of brassicaceae seed meal (BSM), a waste product of oil extraction processes (including biofuel), has been shown to suppress plant pathogenic fungi, oomycetes and nematodes. Although effective control of lesion (Pratylenchus) and root knot (Meloidogyne) nematodes is advantageous and well documented, the impact on plant beneficial or free-living populations is not well defined. Suppression of free-living bacterivorous nematodes may be detrimental to overall soil health since these populations contribute significantly to the process of nitrogen mineralization and plant bioavailability. Terminal restriction fragment length polymorphism and quantitative polymerase chain reaction analyses were utilized to determine the effect of BSM amendment on nematode community structure and abundance in orchard soils. The study employed BSMs with high (B. juncea) and low (B. napus) glucosinolate content, as well as the corresponding autoclaved BSMs possessing inactivated myrosinase function and subsequently diminished levels of ITC. As evidenced by decreased nematode abundance and diversity in lab-scale studies, B. juncea seed meal (SM) was an effective nematicide against free-living populations and performed equivalent to a commercially available product. The biocidal activity was dependent on generation of allyl ITC since both B. napus SM and heat-inactivated B. juncea SM enhanced overall nematode community diversity. This study indicates that the biocidal activity of B. juncea SM is non-specific to plant parasitic nematodes and further studies are required to assess the impact on N-mineralization and overall soil health.