Abstract
Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, is a devastating disease in rapeseed. The objective of this study was to investigate the role and the mechanism of silicon (Si) in alleviating the disease severity of S. sclerotiorum in rapeseed. In the absorption assays, the rapeseed that absorbed 10 mM of K2SiO3 exhibited an 86% decrease in lesion size on infected leaves as compared with controls. In the spray assay, the lesion length on rapeseed stems was reduced by 30.5–32.9% with the use of 100 mM of a foliar Si fertilizer as compared with controls. In the pot assay, the lesion length on rapeseed stems was reduced by 34.9–38.3% when using the Si fertilizer as basal fertilizer. In the field assay, both the disease incidence and disease index of sclerotinia stem rot were significantly reduced with the usage of a solid Si fertilizer, Si foliar fertilizer, and the application of both, without negative affection on the main agronomic traits and seed quality of rapeseed. The transcriptome sequencing, quantitative reverse transcription PCR (qRT-PCR), and biochemical assays between K2SO4- and K2SiO3- treated rapeseed leaves revealed that Si promoted the biosynthesis of defense-related substances and enhanced the antioxidation and detoxification abilities of rapeseed after infection. Thus, this study concluded that Si can alleviate the disease severity of S. sclerotiorum in rapeseeds, partially due to the induced defense responses.
Highlights
Rapeseed (Brassica napus L., AACC, 2n = 38) is widely cultivated in Canada, Europe, China, and other parts of the world as an important source of both biofuel and edible oil
The plants supplemented with K2SiO3 showed higher Si content in the leaves (Csi = 38.5 ± 2.53 mg/kg·fresh weight [FW]) as compared with plants cultured with ddH2O (Csi = 12 ± 1.77 mg/kg·FW) and K2SO4, (Csi = 10.3 ± 3.92 mg/kg·FW) (p < 0.001)
This study provided evidence on the positive role of Si in alleviating the disease severity caused by S. sclerotiorum in rapeseed
Summary
Rapeseed (Brassica napus L., AACC, 2n = 38) is widely cultivated in Canada, Europe, China, and other parts of the world as an important source of both biofuel and edible oil. The production of rapeseed suffers from the fungal pathogen Sclerotinia sclerotiorum (del Río et al, 2007; Koch et al, 2007), which infects over 600 plant species worldwide (Liang and Rollins, 2018). The disease caused by S. sclerotiorum, which is termed as sclerotinia stem rot (SSR), usually results in 10–70% yield losses in rapeseed cultivation (del Río et al, 2007; Koch et al, 2007). Development of resistant lines or cultivars is a cost-effective and sustainable strategy to control to this disease, the breeding of resistant rapeseed has been difficult due to the lack of resistant germplasms. A few fungicides are available, the low efficiency, environmental contamination, and economic costs cannot be ignored (del Río et al, 2007).
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