RESUMEN
Consecutive monoculture of crops causes serious diseases and significant decline in yield and quality, and microbes in the rhizosphere are closely linked with plant health. Here we systematically studied the structure dynamics of soil microbiota in the monocropping system of Pseudostellaria heterophlla. The results illustrated that the successive cropping of P. heterophylla shifts the diversity and structure of microbial community in rhizosphere soil of P. heterophylla, showing that the diversity of microbial community in rhizosphere soil of P. heterophylla was decreased with the increase of planting years while the structure of microbial community became more deteriorative. Moreover, the population size of typical pathogens increased and the beneficial bacterial population decreased with the increasing years of monoculture, which resulted in the microecological imbalance in P. heterophylla rhizosphere, thereby caused serious replanting diseases in monocropping system. Our results suggested that structure dynamics of rhizosphere microbial communities were mediated by the richness of replanted P. heterophylla, and thus the replant disease result from the imbalanced microbial structure with a higher ratio of pathogens/beneficial bacteria in rhizosphere soil under monocropping regimes. This finding provides a clue to open a new avenue for modulating the root microbiome to enhance the crop production and sustainability.
Asunto(s)
Biota , Caryophyllaceae/crecimiento & desarrollo , Caryophyllaceae/microbiología , Microbiología del Suelo , Agricultura/métodos , Enfermedades de las Plantas/microbiología , Dinámica PoblacionalRESUMEN
Radix pseudostellariae L. is a common and popular Chinese medication. However, continuous monoculture has increased its susceptibility to severe diseases. We identified two pathogenic microorganisms, Talaromyces helicus M. (KU355274) and Kosakonia sacchari W. (KU324465), and their antagonistic bacterium, Bacillus pumilus Z. in rhizosphere soil of continuously monocultured R. pseudostellariae. Nine types of phenolic acids were identified both in the rhizosphere soil and in culture medium under sterile conditions. A syringic acid and phenolic acid mixture significantly promoted the growth of T. helicus and K. sacchari. T. helicus could utilize eight types of phenolic acids, whereas K. sacchari could only use four phenolic acids. K. sacchari produced protocatechuic acid when consuming vanillin. Protocatechuic acid negatively affected the growth of B. pumilus. The 3A-DON toxin produced by T. helicus promoted the growth of K. sacchari and inhibited growth of B. pumilus at low concentrations. These data help explain why phenolic exudates mediate a microflora shift and structure disorder in the rhizosphere soil of continuously monocultured R. pseudostellariae and lead to increased replanting disease incidence.
RESUMEN
In this study, quantitative real-time PCR (qPCR) was used to determine the amount of Fusarium oxysporum, an important replant disease pathogen in Pseudostellaria heterophylla rhizospheric soil. Moreover, HPLC was used to identify phenolic acids in root exudates then it was further to explore the effects of the phenolic acid allelochemicals on the growth of F. oxysporum f.sp. heterophylla. The amount of F. oxysporum increased significantly in P. heterophylla rhizosphere soil under a consecutive replant system as monitored through qPCR analysis. Furthermore, the growth of F. oxysporum f.sp. heterophylla mycelium was enhanced by root exudates with a maximum increase of 23.8%. In addition, the number of spores increased to a maximum of 12.5-fold. Some phenolic acids promoted the growth of F. oxysporum f.sp. heterophylla mycelium and spore production. Our study revealed that phenolic acids in the root secretion of P. heterophylla increased long with its development, which was closely related to changes in rhizospheric microorganisms. The population of pathogenic microorganisms such as F. oxysporum in the rhizosphere soil of P. heterophylla also sharply increased. Our results on plant-microbe communication will help to better clarify the cause of problems associated with P. heterophylla under consecutive monoculture treatment.