Diversity and Recruitment Strategies of Rhizosphere Microbial Communities by Camellia fascicularis, a Plant Species with Extremely Small Populations in China: Plant Recruits Special Microorganisms to Get Benefit out of Them

Camellia fascicularis belongs to the family Theaceae and is a plant species with extremely small populations. It is also a second-class national protected plant in China. In recent years, the anti-inflammation, antioxidation, and antitumor effects of C. fascicularis polyphenols and flavonoids have been reported. However, changes in the soil chemistry and microbes after artificial cultivation of C. fascicularis have not been well studied. Therefore, three healthy plants from each different artificial planting year’s plot (Age_3, Age_5, and Age_7) were selected, and the chemical properties of the rhizosphere soil and root endophytic microbial communities for different cultivation years of C. fascicularis were studied in Hekou County, China. The accumulation of pathogenic and beneficial microbes in the rhizosphere of C. fascicularis was also discussed. The results show that (1) the alpha diversity in rhizosphere soil was significantly higher than that in roots, and roots recruited more Actinobacteria, which might produce beneficial secondary metabolites for the plant; (2) the total nitrogen in the rhizosphere soil of C. fascicularis cultivated for 7 years was significantly higher than that in the soil cultivated for 3 years; (3) there was no significant difference in the alpha and beta diversity in the rhizosphere soil and root endophytes of C. fascicularis in different cultivation years; (4) there was no difference in the abundance of plant-growth-promoting rhizobacteria (PGPR) in either the rhizosphere soil or roots, but the number of PGPR in roots was higher than that in rhizosphere soil; and (5) the changes in pathogenic fungi and biocontrol fungi in rhizosphere soil were greater than those of endophytic fungi in roots. The results show that there are no significant differences in microbial communities among 3, 5, and 7 years, but the influence of the outside environment on the soil and fungi was greater than that of the roots and bacteria. These results can help us to understand the soil chemical and microbial community changes during the artificial cultivation of C. fascicularis and play an important role in its artificial conservation and breeding, as it is a plant species with extremely small populations.