|HANDISENI, MAZWELL - UNIVERSITY OF IDAHO|
|BROWN, JACK - UNIVERSITY OF IDAHO|
|ZEMETRA, ROBERT - UNIVERSITY OF IDAHO|
Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2013
Publication Date: 10/10/2013
Citation: Handiseni, M., Brown, J., Zemetra, R., Mazzola, M. 2013. Effect of Brassicaceae seed meals with different glucosinolate profiles on Rhizoctonia root rot of wheat. Crop Protection. doi: 10.1016/j.
Interpretive Summary: Organic soil amendments often have been promoted as a means to control soilborne plant diseases. However, the effective use of such an environmentally sensitive method of disease control has been impeded by a lack of understanding concerning the means by which amendments provide disease control. Tissues from plants belonging to the Brassicaceae have been promoted as a soil amendment for the control of soilborne plant diseases due to their production of glucosinolates, which yield anti-microbial compounds upon hydrolysis. In this study, brassicaceae seed meals, a waste residue resulting from oil seed extraction were evaluated for the ability to control multiple soil inhabiting pathogens that limit the productivity of tomato, pepper and wheat production systems. Seed meal amendments effectively controlled damping-off of tomato and pepper caused by the pathogen Pythium ultimum. In most instances, control was the result of chemicals released from the brassicaceae residues after incorporation into soil. In contrast, suppression of the fungal pathogen Rhizoctonia solani was obtained with intact seed meal or seed meal which had been modified in a manner the limited the release of biologically active chemistries after soil incorporation. The white mustard, Sinapis alba, seed meal was also shown to be phytotoxic to pepper and tomato if soils were planted to soon after seed meal amendment. Therefore, use of lower application rates and increased delay in seeding after SM amendment, may be necessary to minimize phytotoxicity.
Technical Abstract: Tissues of plants in the family Brassicaceae contain glucosinolates, compounds whose hydrolysis results in the release of various bioactive products including isothiocyanates. The broad spectrum of biological activity of these glucosinolate hydrolysis products has led to the promotion of brassicaceae plant residues for use as an amendment for the control of soilborne plant diseases. Studies were conducted to determine the effect of Brassicaceae seed meals on suppression of P. ultimum infection of tomato and pepper seedlings, and R. solani AG-8 infection of winter wheat. P. ultimum was consistently suppressed in soils amended with Brassica juncea or Brassica napus intact SM which was reflected by higher tomato and pepper seedling emergence. Seedling emergence in soils amended with denatured B. napus SM was lower when compared to soils amended with intact B.napus SM. In contrast, seedling emergence was higher in soils amended with denatured than intact S. alba SM. All intact brassicaceae seed meals significantly reduced infection by R. solani AG-8 and the quantity of pathogen DNA detected in wheat roots. Likewise, disease rating was reduced significantly in response to denatured seed meal amendments, but only denatured S. alba SM significantly reduced the quantity of R. solani AG-8 DNA detected in wheat root systems. Reduced emergence of pepper and tomato seedlings observed in response to intact S. alba SM amendment can likely be attributed to phytotoxicity. These studies demonstrate that Brassicaceae seed meals can be used to manage disease incited by P. ultimum and R. solani AG-8, however certain strategies, such as use of lower application rates and increased delay in seeding after SM amendment, may be necessary to minimize phytotoxicity.