Rhizobacterial communities and red pepper (Capsicum annum) yield under different cropping systems

The intensive cropping of red pepper (Capsicum annuum L.) negatively affects the soil environment and reduces crop yield. The red pepper plant's rhizospheric bacterial communities under different cropping methods (intensive cropping or crop rotation) were investigated over three years (2010 to 2012). The red pepper yield and bacterial communities were also investigated under agrochemical treatment or microbial agent treatment against Phytophthora blight disease. Pyrosequencing of 16S rRNA gene amplicon libraries were constructed to characterize the bacterial communities. Bacterial richness and red pepper yield increased 65% and 55%, respectively under the crop rotation method combined with the microbial agent treatment, whereas the intensive cropping method with the agrochemical treatment resulted in low richness and diversity. The dominant bacterial phylogenetic phyla present were Acidobacteria, Proteobacteria, Gemmatimonadetes, Chloroflexi, and Planctomycetes, ranging from 5% to 38% of the sequences. In conclusion, crop rotation and microbial agent has a synergistic positive effect not only on rhizobacterial diversity, but also on red pepper yield.