The effect of canola (Brassica napus) as a biofumigant on soil microbial communities and plant vitality: a pot study

Abstract

Canola (Brassica napus) may be incorporated into soil as a biofumigant for control of pathogens such asSclerotinia sclerotiorum. Yet, the effect of biofumigants on natural microbial communities required to maintain soil functions is still unclear. A pot experiment with sunflowers as the crop plant was conducted to assess the biofumigation effect of canola on the soil microbial community. The study consisted of 32 pots containing four treatments of eight replicates each. Each pot contained one sunflower plant. The treatments included (1) soil only, (2) soil incorporated with canola, (3) soil incorporated with canola and inoculated with S. sclerotiorum, and (4) soil inoculated with S. sclerotiorum. Microbial community function and structure were assessed through assays of dehydrogenase activity, substrate utilisation profiles and signature biomarker analysis. Chlorophyll a fluorescence measurements were performed as a measure of sunflower vitality. Canola incorporation brought about transient changes in the soil microbial community, none of which were detrimental. Plant vitality showed no negative effects due to the biofumigant or the inoculated pathogen. Canola can be suitable as a biofumigant, without having harmful effects on the indigenous soil microbial community.

Interactions between Brassica Biofumigants and Soil Microbiota: Causes and Impacts

“…Alternatively, Fusarium spp. were found to be less responsive to BBF at different sampling time points. ,, The temporal variation may be attributed to the degradation effect of applied organic matter in the soil . Such microbial dynamics could have positive effects on the long-term suppression of plant pathogens.…”

“…53 It influences the carbon (C) cycling patterns, and storage of C and N. 54,55 In several BBF experiments, BBF had fewer bacteria effects than fungi. 31,36,37,47,48,51 In Hu et al's 36 study, an approximate 85% reduction in the fungal population was reported. In contrast, a decrease in bacterial copy number and enhancement of fungal copy number following mustard BBF have also been documented.…”

“…10,36,37 The temporal variation may be attributed to the degradation effect of applied organic matter in the soil. 51 Such microbial dynamics could have positive effects on the long-term suppression of plant pathogens. Mazzola et al 52 investigated whether BBF efficacy varies in a time-dependent manner through changes in the resident soil microbial population.…”

“…94 The increase in nutrient supply and organic matter to microbes after BBF increased the total mobilizing and dehydrogenase activities. 51,91 Subsequently, the microbial activity and the available nutrients positively affected plant growth and improved the control of plant diseases induced by Fusarium and Cylindrocarpon. 91 Furthermore, biofumigation enhances dissolved organic carbon, which potentially increases the abundance of saprophytic fungi, resulting in enhanced fungal/bacterial ratio.…”

Plant Volatiles Reduce the Viability of the Root-Knot NematodeMeloidogyne incognitaEither Directly or When Retained in Water

“…Examples include the use of mustard meal to control M. chitwoodi in potato and forage turnip (Brassica rapa var. rapa) and canola (B. napus) to control soilborne pathogens, including nematodes (Al-Rehiayani et al 1999;Henderson et al 2009;Potgieter et al 2013). Thousands of VOC produced by plants are already known, representing around 1% of their secondary metabolites (Dudareva et al 2006;Loreto et al 2014).…”