Sinigrin content and allyl isothiocyanate concentration of whole ground mustard meal and the ability of allyl isothiocyanate to inhibit growth of \u3cem\u3ePhytophthora parasitica\u3c/em\u3e var. \u3cem\u3enicotianae, Meloidogyne incognita\u3c/em\u3e and possible factors for its action

Abstract

Compounds hydrolyzed from decomposition of glucosinolates have the potential to reduce pest populations and possibly control many soilborne diseases. Sinigrin is a glucosinolate commonly found in Brassica species. Sinigrin concentrations in whole ground oriental mustard seed meal (OMM) obtained from 12 different lots ranged from 101 to 141 μM˙g-1 of OMM. Allyl isothiocyanate (AITC) concentrations evolving from sinigrin in corresponding seed lots ranged from 17 to 33 μM˙g-1. Conversion efficiency of sinigrin to AITC from these 12 lots was approximately 19 percent. Water volume and soil coverings may affect concentrations of AITC evolving from OMM. Increased amounts of water and use of polyethylene soil coverings negatively affected AITC concentrations. The concentrations of commercially obtained AITC and AITC evolved from OMM needed to produce 50% and 90% inhibition (IC50, IC90) of black shank (Phytophthora parasitica var. nicotianae) were calculated. Inhibitory concentrations (IC50, IC90) of AITC were 0.70 and 1.52 μM˙L-1, respectively. Inhibitory concentrations of IC50 and IC90 of AITC from OMM were 0.99 and 1.72 μM˙L-1, respectively. In a similar experiment, the lethal concentrations (LCs) of commercially available AITC, OMM and OMM mixed with soil were determined for root-knot nematode, (Meloidogyne incognita – RKN) eggs. The LC50 and LC90 for AITC were 0.78 and 1.94 μM˙L-1, respectively. The LC50 and LC90 for OMM were 0.44 and 1.22 μM˙L-1 and for OMM mixed with soil they were 0.88 and 1.99 μM˙L-1, respectively. Field tests were conducted to determine the effect of various rates of OMM and commercial fumigants (Telone C-35 and dazomet) on vermiform nematode populations at two locations. Statistical analysis suggested that neither commercially available soil fumigant negatively influencedvermiform nematode populations in the Flethcher or Knoxville location during 2003 or 2004; however, non-significant reductions were observed in nematode populations in plots with Telone or 2,242 kg˙ha-1 of OMM. Effects from OMM treatments were highly variable and were not significantly different from the control. Research from multiple laboratory experiments indicated that AITC has the potential to reduce or inhibit growth of both black shank and eggs of RKN. Results from treatments including OMM in field research, was highly variable and more research is needed to determine the extent of efficacy of this model