The rhizospheric bacterial diversity of Fritillaria taipaiensis under single planting pattern over five years.

Rhizospheric microorganisms can profoundly influence the nutritional status of soil and the growth of plant. To reveal the change on the bacterial diversity in the rhizosphere of Fritillaria taipaiensis under long-term single planting, the bacterial community structure in the rhizospheric soils of F. taipaiensis with different cultivation years from 1 to 5 were analyzed. The result showed the Chao1 and the ACE indices of the bacterial community had no significant difference among samples while the Shannon and Simpson indices declined with the cutivation year; the intra group beta diversity of the rhizospheric bacteria increased after a initial decline with the cultivation year; in the sample with 1 year of cultivation, the dominant bacterial genera were mainly the species that can improve the soil nutrient status and promote plant growth while with the increase of cultivation year, the dominant genera in samples then gradually reflected the pathogen accumulation and soil nutrient status deterioration; pH was the most significant factor affected by the bacterial community composition. These results indicated long term continuous cropping changed the bacterial community structure and soil nutritional status in the F. taipaiensis rhizospheric soils, which could badly affect its growth.

[Correlation between rhizospheric microorganisms distribution and alkaloid content of Fritillaria taipaiensis].

In order to reveal the relationship between the amount of soil microorganisms and the quality of Fritillaria taipaiensis, both cultivated and wild F. taipaiensis were collected from Chongqing, Wuxi at different stages of their growth as objects of the research. The mycorrhizal infection rate and colonization intensity, peimisine and total alkaloid content in bulbs, the amount of microorganisms and biomass carbon content in rhizospheric soil were all determined using common methods. The results showed that the typical arbuscular-vesicle roots were formed after the AM fungi infected the F. taipaiensis roots which were collected from different origins. The mycorrhizal infection rates were ranged from 78.74% to 98.68% and the colonization intensities were ranged from 13.29% to 37.06%. The rhizospheric microorganisms of F. taipaiensis showed abundant resources. The distribution rule of them in the rhizospheric soil was as follows: the amount of bacteria>the amount of actinomycetes>the amount of fungi. The rhizospheric bacteria, decomposition inorganic phosphorus bacteria, decomposition organic phosphorus bacteria, actinomycetes amount and the total number of microbes increased first and then decreased with the increase of years, while decomposition potassium bacteria showed decreasing trend and fungi showed gradual increasing trend. The soil microbial flora content in the soil changed from "bacterial type" with a high fertility to "fungal type" with a low fertility. The mass fraction of peimisine and total alkaloid content increased first and then decreased with the increase of over the years, the same trend of culturable rhizosphere soil bacteria and actinomycetes indicated that the growth years affected the quality of soil and medicinal materials on different levels. Therefore, the diversity of microbial communities in rhizosphere soil reduced with the increase of years leading to the continuous cropping obstacles and the destruction of medicinal quality of F. taipaiensis.