Integrated transcriptome and microRNA profiles analysis reveals molecular mechanisms underlying the consecutive monoculture problem of Polygonatum odoratum.

Polygonatum odoratum is a historically traditional Chinese medicine plant. However, the consecutive monoculture problem (CMP) widespread in other Chinese medicine limiting their cultivation on a large scale. In this study, the physiological data showed the adverse effect of CMP on the growth of P. odoratum under the consecutive cropping (CC) compared with the first cropping (FC). Then the high-throughput sequencing of miRNA and mRNA libraries of leaves and roots from FC and CC P. odoratum plants identified 671 differentially expressed genes (DEGs) and 184 differentially expressed miRNAs and revealed that the DEGs and target genes of the miRNAs were mainly involved in starch and sucrose metabolism, phenylpropanoid and brassinosteroid biosynthesis. The KEGG analysis revealed that the DEGs between CC and FC roots were enriched in the plant-pathogen interaction pathway. This study provided the expression regulation of genes related to CMP of P. odoratum but also suggested that CMP may result in the serious damage of pathogens to roots and cause the slow growth in the consecutive cropping plants.

[Relationships between initial chemical composition of forest leaf litters and their decomposition rates in degraded red soil hilly region of Southern China].

A pot experiment with litter bags was conducted to study the relationships between the initial chemical composition of 8 kind forest leaf litters and 4 kind mixed leaf litters and their decomposition rates in degraded red soil hilly region of Southern China. Comparing with needle-leaf litters, broad-leaf litters had significantly higher contents of N, P, K, and Mg, but significantly lower contents of lignin and C. The decomposition rates of test litters were significantly positively correlated with the litters initial contents of N, P, K, and Mg (P < 0.05), and negatively correlated with the initial contents of lignin and C as well as the lignin/N, lignin/P, and C/P ratios (P < 0. 05). The lignin content explained 54.3% of the variation in litter decomposition rates, being the key affecting factor. Litters C, N, and P contents also had close correlations with the decomposition rates, and together with lignin content, contributed 81.4% of the variation. It was suggested that in the process of vegetation restoration in degraded red soil hilly region of Southern China, introducing broad-leaf trees with lower lignin and higher N and P contents would benefit the acceleration of forest litters decomposition and the restoration of soil fertility.