Stellera chamaejasme has become a problematic weed in northern and south-western grasslands of China. To evaluate a possible role of endophytes in its strong competitive capacity, the endophytic bacterial community of S. chamaejasme was investigated by culture-dependent and independent methods, and the growth-promoting traits of some culturable isolates as well as the benefit of endophyte ST3CS3 (Brevundimonas sp.) on host plants growth were studied. The results showed that 823 OTUs were generated with a 97% similarity level in the cultureindependent study. They were classified into 29 phyla, 61 classes, 147 orders, 237 families and 440 genera. Among them, Pseudomonas and Ralstonia were the most dominant genera in belowground parts (G) (64.25%) and aboveground parts (S) (26.54%) respectively. The diversity and species richness of endophytes in S were significantly higher than that of G (P < 0.001, t-test). Contrary to this, the number of culturable bacteria in S was a little lower than that of G (P > 0.05, t-test). Totally, 176 isolates belonging to 30 morphotypes were obtained in the culturedependent study. Among them, Acinetobacter was the most dominant genus in G (51.30%), then followed by Pseudomonas (6.09%) and Brevundimonas (6.09%), while Lysinibacillus (21.31%) was the most dominant genus in S, followed by Pseudomonas (11.48%). Growth-promoting trait tests indicated that 93.65% of the tested isolates (63) exhibited nitrogen-fixing, IAA-synthesizing, phosphorus or potassium solubilizing capacity, in which 77.97% belonged to Proteobacteria, a phylum found to contain more active isolates. Pot experiments demonstrated that endophyte ST3CS3 can significantly improve host plants growth and increase its nitrogen and chlorophyll content (P < 0.01, t-test). Therefore, we suggest that strong competitiveness of S. chamaejasme may in part be due to possession of high ratios of plant growth-promoting proteobacterial endophytes such as Pseudomonas, Acinetobacter and Brevundimonas.

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Stellera chamaejasme L. is a widely distributed poisonous plant in Chinese degraded grasslands. To investigate the role of endophytic fungi (EF) in S. chamaejasme’s quick spread in grasslands, the endophytic fungal community of S. chamaejasme was studied through culture-dependent and culture-independent methods, and the plant-growth-promoting (PGP) traits of some culturable isolates were tested. Further, the growth-promoting effects of 8 isolates which showed better PGP traits were evaluated by pot experiments. The results showed that a total of 546 culturable EF were isolated from 1114 plant tissue segments, and the colonization rate (CR) of EF in roots (33.27%) was significantly higher than that in shoots (22.39%). Consistent with this, the number of specific types of EF was greater in roots (8 genera) than in shoots (1 genus). The same phenomenon was found in culture-independent study. There were 95 specific genera found in roots, while only 18 specific genera were found in shoots. In addition, the dominant EF were different between the two study methods. Cladosporium (18.13%) and Penicillium (15.93%) were the dominant EF in culture-dependent study, while Apiotrichum (13.21%) and Athelopsis (5.62%) were the dominant EF in culture-independent study. PGP trait tests indicated that 91.30% of the tested isolates (69) showed phosphorus solubilization, IAA production, or siderophores production activity. The benefit of 8 isolates on host plants’ growth was further studied by pot experiments, and the results indicated that all of the isolates can improve host plants’ growth. Among them, STL3G74 (Aspergillus niger) showed the best growth-promotion effect; it can increase the plant’s shoot and root dry biomass by 68.44% and 74.50%, respectively, when compared with the controls. Our findings revealed that S. chamaejasme has a wide range of fungal endophytic assemblages, and most of them possess PGP activities, which may play a key role in its quick spread in degraded grasslands.

H igh concentration of h eavy metal (HM) is toxic to the plant and endophytes can improve host plants HM tolerance. In the present study, the role of endophytes FT2G7 (Phomopsis columnaris) and FT2G24 (Setophoma terrestris) on host plant Dysphania ambrosioides HM tolerance was evaluated under m ulti-HMs stress through pot experiments. The results showed that regardless at lower or higher multi-HMs stress, inoculation of isolate(s) improved host plants growth and HM tolerance through regulating their antioxidant capacities etc., and inoculation of multi-isolates (ME+) had better effects on host plants than inoculation of single isolate (SE+). Particularly, the malondialdehyde (MDA) of ME+ decreased 50% under the lower multi-HMs stress and the glutathione (GSH) increased 169.55% under the higher multi-HMs stress when compared with ME-. Both inoculation of single isolate and multi-isolates increased host plants HM accumulation when compared with non-inoculation. However, different isolates had different effects: under the lower multi-HMs stress, the accumulation of multi-HMs in ME+ plants was higher than that of FT2G7-inoculated plants but lower than that of F T2G24-inoculated plants, w ith a few e xceptions, such as Zn in underground parts of ME+ was higher than that of FT2G24-inoculated plants. The bioaccumulation factor (BAF) of ME+ was higher than that of SE+, but the translocation factor (TF) was lower than that of SE+, e xcept Pb of FT2G24 inoculated plants. Under the higher multi-HMs stress, Zn and Cd in ME+ plants were lower but Pb was higher than that of SE+, with a few exceptions, such as Pb in underground parts of ME+ plants was lower than that of FT2G24-inoculated plants. The BAF and TF of ME+ were lower than that of SE+, except that of Pb.