Biological control of Rhizoctonia solani: use of molecular methods for the characterization of complex interactions among biological control agents, pathogens and the microbial …

In a growth chamber experiment, the effects of the inoculation of Trichoderma viride (strain GB7) and Serratia plymuthica (strain 3Re4), singly or in combination, on the composition of bacterial and fungal communities in the rhizosphere of lettuce infected by R. solani (AG1-IB) were studied. Plant growth promotion and biological control efficiency were measured. The combined inoculation of 3Re4 and GB7-18 in the presence or absence of R. solani had significant effects on the composition of the bacterial and fungal communities in the rhizosphere. The profiles of all treatments with 3Re4 + GB7-18 showed less dominant bands (increased evenness). The increased abundance of a band in all treatments with GB7 indicated that the inoculant strain successfully established in the rhizosphere. The presence of the pathogen significantly stimulated the density of bacterial antagonists. The fungal antagonists had no effect on the cell density of 3Re4 + GB-718. The results suggested the strong interaction between the pathogen and the bacterial inoculant. Both inoculants stimulated the growth of lettuce irrespective of the inoculation strategy. The biological control effect was markedly dependent on the inoculation strategy. Both inoculants were effective in suppressing R. solani. Superior biological control effect was recorded for 3Re4-18 + GB7.