Effects of Bacillus amyloliquefaciens FZB42 on Lettuce Growth and Health under Pathogen Pressure and Its Impact on the Rhizosphere Bacterial Community

Abstract

The soil-borne pathogen Rhizoctonia solani is responsible for crop losses on a wide range of important crops worldwide. The lack of effective control strategies and the increasing demand for organically grown food has stimulated research on biological control. The aim of the present study was to evaluate the rhizosphere competence of the commercially available inoculant Bacillus amyloliquefaciens FZB42 on lettuce growth and health together with its impact on the indigenous rhizosphere bacterial community in field and pot experiments. Results of both experiments demonstrated that FZB42 is able to effectively colonize the rhizosphere (7.45 to 6.61 Log 10 CFU g−1 root dry mass) within the growth period of lettuce in the field. The disease severity (DS) of bottom rot on lettuce was significantly reduced from severe symptoms with DS category 5 to slight symptom expression with DS category 3 on average through treatment of young plants with FZB42 before and after planting. The 16S rRNA gene based fingerprinting method terminal restriction fragment length polymorphism (T-RFLP) showed that the treatment with FZB42 did not have a major impact on the indigenous rhizosphere bacterial community. However, the bacterial community showed a clear temporal shift. The results also indicated that the pathogen R. solani AG1-IB affects the rhizosphere microbial community after inoculation. Thus, we revealed that the inoculant FZB42 could establish itself successfully in the rhizosphere without showing any durable effect on the rhizosphere bacterial community.

Biological control in the microbiome era: Challenges and opportunities

“…Plating and low-throughput molecular techniques showed that BCA treatment altered microbial community diversity and abundance. (Buddrus-Schiemann et al, 2010;Chowdhury et al, 2013;Teixidó et al, 1998;Yin et al, 2013;Zhang et al, 2008). These results show that a BCA has an impact on the plant microbiome.…”

“…Several studies evidenced that factors like soil properties, experimental conditions and physiological state had a deeper and more durable effect on the rhizosphere microbiota than BCA application (Chowdhury et al, 2013;Grosch et al, 2006;Kröber et al, 2014;Scherwinski et al, 2007;Schreiter et al, 2014b). The effect of a BCA can also depend on its interaction with other factors: amplicon sequencing analysis revealed significant modifications of the bacterial community composition of lettuce rhizosphere following application of the BCA P. jessenii RU47 in alluvial loam, but not in diluvial sand or loess loam (Schreiter et al, 2014a).…”

“…R. solani severely affected the bacterial and fungal community structure of lettuce rhizosphere, while the BCA Pseudomonas jessenii RU47 had a much smaller effect (Adesina et al, 2009). Application of B. amyloliquefaciens FZB42 to the soil did not cause major shifts in the microbial communities of lettuce rhizosphere, while R. solani inoculation affected the rhizosphere bacterial population structure (Chowdhury et al (2013). The impact of the pathogen R. solani and/or of the BCA strain FZB42 on phyllosphere and rhizosphere bacterial communities of lettuce was also studied more in depth by amplicon sequencing (Erlacher et al, 2014).…”

The science, development, and commercialization of postharvest biocontrol products

“…Previous studies, using plating and low-throughput molecular techniques, reported that the introduction of a biocontrol agent or a pathogen to the system had a marked impact on the plant microbiome (Teixidó et al, 1998;Zhang et al, 2008;BuddrusSchiemann et al, 2010;Chowdhury et al, 2013;Yin et al, 2013). Erlacher et al (2014) demonstrated shifts in the microbiota of lettuce as a result of introducing a pathogen (Rhizoctonia solani) and/or a biocontrol agent.…”

Cucumber Rhizosphere Microbial Community Response to Biocontrol Agent Bacillus subtilis B068150

“…The ability of members of the Gram-positive genus Bacillus to form spores is advantageous for controlling a variety of soil-borne phytopathogenic fungi [23][24][25][26][27], and some are commercially marketed as biopesticides, biofertilizers and soil amendments because of their easy colonization, good competition and broad antimicrobial spectrum [28][29][30][31][32]. For example, these bacteria: B. subtilis B579 [33], B. subtilis N7 [34], B. amyloliquefaciens SQR-9 [35], Pseudomonas fluorescens [15,36] are effective biocontrol agents.…”