Abstract
BackgroundThis study analyzed the effect of silicon (Si) application on the occurrence of ginseng black spot caused by Alternaria panax. We explored the differences in soil physical and chemical factors and microbial community structure following Si application as well as the key factors that affected the occurrence of ginseng black spot in soil. Potted Panax ginseng plants were used to assess the effect of Si treatment on ginseng black spot. Soil physical and chemical properties were comprehensively analyzed. Bacterial communities were analyzed using Illumina HiSeq sequencing targeting the 16S rRNA gene.ResultsAfter inoculation with A. panax, the morbidity (and morbidity index) of ginseng with and without Si was 52% (46) and 83% (77), respectively. Soil physical and chemical analysis showed that under the ginseng black spot inoculation, bacterial communities were mainly affected by pH and available potassium, followed by ammonium nitrogen and available Si. NMDS and PLS-DA analyses and the heat maps of relative abundance revealed that Si application elevated the resistance of ginseng black spot as regulated by the abundance and diversity of bacterial flora in rhizosphere soils. Heatmap analysis at the genus level revealed that A. panax + Si inoculations significantly increased the soil community abundance of Sandaracinus, Polycyclovorans, Hirschia, Haliangium, Nitrospira, Saccharothrix, Aeromicrobium, Luteimonas, and Rubellimicrobium and led to a bacterial community structure with relative abundances that were significantly similar to that of untreated soil.ConclusionsShort-term Si application also significantly regulated the structural impact on soil microorganisms caused by ginseng black spot. Our findings indicated that Si applications may possibly be used in the prevention and treatment of ginseng black spot.
Highlights
This study analyzed the effect of silicon (Si) application on the occurrence of ginseng black spot caused by Alternaria panax
Additional studies have indicated that Si is related to plant-pathogen interactions for the control in diseases in different plant species [3], and aids in the enhancement of plant resistance against disease caused by viruses, fungi, bacteria, and nematodes
Significant differences were observed in the severity of A. panax infections under Si treatment (Fig. 1)
Summary
This study analyzed the effect of silicon (Si) application on the occurrence of ginseng black spot caused by Alternaria panax. Ginseng black spot, caused by Alternaria panax Whetz, is a common soil-borne disease and one of the most serious diseases affecting the above-ground parts, especially the leaves, of Panax ginseng This pathogen is distributed widely in the Changbai Mountains of China and other ginseng production regions, and accounts for more than 20—30% of the annual incidence, which is very common. It was suggested that the deposition of Si in the apoplast may prevent fungal effectors from entering the target cells, altering the development of the pathogens [4] Another recently study showed that Si treatment conferred an effective protection of soybean plants against Phytophthora sojae in a hydroponic experiment [5]. A pot experiment demonstrated that Si addition decreased the concentrations of water-soluble and exchangeable arsenic in soil and, decreased the bioavailability of red soil arsenic in Panax notoginseng [11]
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