Abstract: Based on morphological characters and 16S rRNA gene sequence，actinomycete strain D74 was identified as Streptomyces rochei. D74 showed antagonistic activity against soft rot pathogens in petri dish trials，and the diameter of growth inhibition zones ranged from 11.0 to 18.3 mm. Fermentation filtrate of D74（10-fold dilution）significantly increased germination rate，condensed vigor index，hypocotyl length，and radicle length of melon seeds by 34.9%，82.4%，66.4%，and 31.5%，respectively（P < 0.05）. In the pot experiment，individual inoculation of D74 and combined inoculation of D74 with Pectobacterium chrysanthemi（a bacterial pathogen）respectively achieved 100% and 17.0% relativebiocontrol effect on A.konjac during the harvest stage. Either individual or combined treatment with D74 improved photosynthetic rate，SPAD value，biomass，yield，and corm quality of A. konjac. In the plot experiment，hole application of D74 increased photosynthetic indexes，biomass，and yield of A. konjac compared with control. This study indicates that Streptomyces rochei D74 strongly inhibits the growth of soft rot pathogens. Its viable preparation（powder formulation）has a great effect on A. konjac regarding disease prevention and growth promotion，as well as corm quality improvement.

Key words: Amorphophallus konjac, soft rot disease, biocontrol agent, Streptomyces rochei