Dominant Bacterial Phyla in Soils Under 18-114 Years of Wheat Cultivation.

The diversity and structure of a microbial community often reflect cultivation history and vegetation cover as well as soil type. Studies were conducted to evaluate the soil bacterial community in agroecosystems under different years of wheat cultivation on three soil types. Soil samples were obtained from five experimental sites that were under continuous winter wheat (Triticum aestivum L.) cultivation from 18 to 114 years without fertilization.  A total of 136,462 sequences of 16S rRNA gene fragments were obtained. Acidobacteria and Proteobacteria were the two most dominant phyla, comprising 42.5~68.4% and 11.8~17.2% of the community in four of the five tested soils. In the fifth soil, Firmicutes and Chloroflexi were the two most dominant phyla, comprising 53.1% and 19.5% respectively. The obtained result suggested that the distribution of bacterial phyla was affected by soil type and duration under wheat cultivation, supporting our hypothesis that the ratio of Proteobacteira/Acidobacteria indicates nutritional status; the ratio of Actinobacteria/Firmicutes indicates stress resistance ability; and the ratio of Firmicutes/Bacteroidetesindicates metabolic capacity and cultivation age of a system.