The Damage Caused by Decline Disease in Bayberry Plants through Changes in Soil Properties, Rhizosphere Microbial Community Structure and Metabolites

Abstract

Decline disease causes serious damage and rapid death in bayberry, an important fruit tree in south China, but the cause of this disease remains unclear. The aim of this study was to investigate soil quality, microbial community structure and metabolites of rhizosphere soil samples from healthy and diseased trees. The results revealed a significant difference between healthy and diseased bayberry in soil properties, microbial community structure and metabolites. Indeed, the decline disease caused a 78.24% and 78.98% increase in Rhizomicrobium and Cladophialophora, but a 28.60%, 57.18%, 38.84% and 68.25% reduction in Acidothermus, Mortierella, Trichoderma and Geminibasidium, respectively, compared with healthy trees, based on 16S and ITS amplicon sequencing of soil microflora. Furthermore, redundancy discriminant analysis of microbial communities and soil properties indicated that the main variables of bacterial and fungal communities included pH, organic matter, magnesium, available phosphorus, nitrogen and calcium, which exhibited a greater influence in bacterial communities than in fungal communities. In addition, there was a high correlation between the changes in microbial community structure and secondary metabolites. Indeed, GC–MS metabolomics analysis showed that the healthy and diseased samples differed over six metabolic pathways, including thiamine metabolism, phenylalanine–tyrosine–tryptophan biosynthesis, valine–leucine–isoleucine biosynthesis, phenylalanine metabolism, fatty acid biosynthesis and fatty acid metabolism, where the diseased samples showed a 234.67% and 1007.80% increase in palatinitol and cytidine, respectively, and a 17.37%–8.74% reduction in the other 40 metabolites compared to the healthy samples. Overall, these results revealed significant changes caused by decline disease in the chemical properties, microbiota and secondary metabolites of the rhizosphere soils, which provide new insights for understanding the cause of this bayberry disease.

Effect of Two Kinds of Fertilizers on Growth and Rhizosphere Soil Properties of Bayberry with Decline Disease

“…Dongkui) from the orchard located in Qianjiang Village (30 • 32 N; 120 • 42 E) of Huangwan Town, Haining City, Zhejiang Province, which was a typical gentle slope mountain area, approximately 50 m above sea level. The soil was acidic yellow in the orchard with the row spacing of 4 m × 5 m, while 65% of the bayberry plants were infected by decline disease with varied grades (1)(2)(3)(4)(5)(6)(7)(8)(9). The field was managed conventionally.…”

“…Paired-end reads were preprocessed as described in our recent publication [3] using Trimmomatic software [35] to cut off ambiguous bases and low-quality sequences and then assembled using FLASH software [36]. Further denoising was obtained by removing the reads with chimera, ambiguous, homologous sequences or less than 200 bp in length.…”

“…The soil sample for GC-MS metabolomics analysis was prepared as described in our recent publication [3]. The reliability of the entire analysis was justified by inserting one quality control (QC) sample among every 10 samples.…”

“…The QC sample was prepared by mixing the extract of all samples in equal volume, and the volume of each QC sample was the same as that of the tested sample. Furthermore, all soil samples were stored at room temperature for GC-MS metabolomics analysis, which was carried out and analyzed as described in our recent publication on a 7890B-5977A GC/MSD GC-MS (Agilent Technologies Inc., Santa Clara, CA, USA) [3]. The obtained data in this study were analyzed by comparing them with that of the standard spectrum library of the National Institute of Standards and Technology, while the obtained metabolite information in this study was searched against the KEGG database.…”

“…Bayberry (Myrica rubra) is an economically important fruit tree and medicinal plant that is grown in southern China [1][2][3]. It is cultivated in about 334,000 hectares each year with an annual output of 950,000 tons.…”