Interaction Effect of Symbiotic Microorganisms on Seedling Growth of Dendrobium catenatum Lindley (Orchidaceae)

Complex micro-ecosystems exist between plants and rhizosphere,where various symbiotic microorganisms with complicated interactions jointly influence the growth and deve-lopment of the plant.To better understand the interaction effect of fungi and bacteria on orchid growth,we screened four endophytic fungi that beneficially promote growth,among which two strains were isolated from Dendrobium catenatum and two from Dendrobium loddigesii.Three growth-promoting endophytic bacteria were also screened from D.catenatum,and combinations of tested fungi and bacteria were inoculated on the roots of seedlings for 120 days to investigate the growth effect on D.catenatum.Inocula combinations C22+TX-19,L28+TX-16,and L28+TX-19 demonstrated the best growth effect on the host,showing additive effects on the number of tillers and root tips of seedlings.Moreover,C22+TX-19 and L28+TX-19 combinations synergistically increased seedling biomass,and L28+TX-19 inocula synergistically promoted root branching.Results indicated that interactions between endophytic fungi and endophytic bacteria had significant growth promoting effects on the host.It may be possible to develop endophytic inocula for orchid growth.