Effects of consecutive monoculture of Pseudostellaria heterophylla on soil fungal community as determined by pyrosequencing

Abstract

Under consecutive monoculture, the biomass and quality of Pseudostellaria heterophylla declines significantly. In this study, a three-year field experiment was conducted to identify typical growth inhibition effects caused by extended monoculturing of P. heterophylla. Deep pyrosequencing was used to examine changes in the structure and composition of soil fungal community along a three-year gradient of monoculture. The results revealed a distinct separation between the newly planted plot and the two-year, three-year monocultured plots. The Shannon and Simpson diversity indices were significantly higher in the two-year and three-year monoculture soils than in the newly planted soil. Consecutive monoculture of this plant led to a significant increase in relative abundance of Fusarium, Trichocladium and Myrothecium and Simplicillium, etc., but a significant decrease in the relative abundance of Penicillium. Quantitative PCR analysis confirmed a significant increase in Fusarium oxysporum, an agent known to cause wilt and rot disease of P. heterophylla. Furthermore, phenolic acid mixture at a ratio similar to that found in the rhizosphere could promote mycelial growth of pathogenic F. oxysporum. Overall, this study demonstrated that consecutive monoculture of P. heterophylla can alter the fungal community in the rhizosphere, including enrichment of host-specific pathogenic fungi at the expense of plant-beneficial fungi.

Insights into the Regulation of Rhizosphere Bacterial Communities by Application of Bio-organic Fertilizer in Pseudostellaria heterophylla Monoculture Regime

“…Our field experiment showed that consecutive monoculture of P. heterophylla resulted in a significant decline in the yield of tuberous roots ( Figure 2 ). Many factors have been thought to be responsible for the consecutive monoculture problem of P. heterop hylla, including soil physical and chemical properties, accumulation of allelochemicals released by roots, and shifts in the soil microbial community (Wu L. et al, 2016). In this study, we found that the content of most of the soil nutrients were significantly higher in the unhealthy samples (SP and MO) than in the healthy samples (NP and MT) ( Table 1 ).…”

“…Our previous studies by culture-dependent and culture-independent analysis demonstrated that F. oxysporum and other Fusarium spp. are the main causative agents of wilt and rot disease of this plant (Zhao Y. et al, 2015; Wu L. et al, 2016). Our previous studies have demonstrated that the phenolic acids identified in the root exudates of P. heterophylla could significantly inhibit the growth of beneficial Burkholderia sp.…”

“…Li et al (2014) attributed the problems associated with consecutive monoculture in peanut to the changes in the structure of the soil microbial community induced by root exudates rather than to direct allelopathy. Wu L. et al (2016) found that P. heterophylla monoculture can significantly increase the amount of Fusarium oxysporum in the rhizosphere, and root exudates could promote the growth of this soil-borne pathogen. Besides, previous studies demonstrated that a decrease in soil microbial diversity or the population size of antagonistic bacteria could result in the occurrence of soil-borne diseases (Latz et al, 2012; Shen et al, 2014).…”

“…that have shown strong antagonistic activities against F. oxysporum were used as inocula to fortify organic fertilizer for the purpose of suppressing P. heterophylla Fusarium wilt (Supplementary Figure S1). In addition, our previous studies found that phenolic acids in the root exudates of medicinal plants mediated the increase of soil-borne pathogens (Wu H. et al, 2016; Wu L. et al, 2016). Some Bacillus spp.…”

“…However, consecutive monoculture of this plant has led to a serious decline of biomass and quality of its underground tubers. Fields used for P. heterophylla cultivation can only be replanted once every 4 years (Wu H. et al, 2016; Wu L. et al, 2016). In addition, farmers generally apply a copious amount of pesticides and fertilizers to maintain production levels under this monoculture regime, but such application raises production costs, causes excessive pesticide residues, and leads to environmental pollution.…”