Isolation and identification of growth-promoting bacteria of Lactarius deliciosus
[Objective]The present paper aimed to improve the efficiency of mycorrhizal synthesis between Lactarius deliciosus-Pinus spp.,and to screen potential mycorrhizal helper bacteria(MHB)from the soil at the stipe base of Lactarius sp..[Method]Bacterial strains were i-solated from the soil at the stipe base of Lactarius sp..Extracellular metabolites of the purified bacteria were obtained from the centrifuged liquid culture.L.deliciosus was inoculated on the PDA with different concentrations of extracellular metabolites and the ordinary PDA.The diameter and density of the mycelium after 30 days of inoculation at 25 ℃ were detected.Additionally,the potential MHB was identified based on morphological characteristics and 16S rDNA sequences.[Result]Three strains,L1,L2 and L3,were proved to be potential MHB.When extracellular metabolites of L1,L2 and L3 were added at 2.5％,they could promote the mycelium growth significantly(the colony di-ameter increased by 33.6％,55.6％and 75.4％,respectively).When the extracellular metabolites of three strains were mixed in different combinations,at a mixture addition of 5.0％,the combinations L1-L3 and L1-L2-L3 increased the mycelial diameter by 36.9％and 42.5％,respectively.The extracellular metabolites of L3 increased the mycelium density of L.deliciosus when it was added at 2.5％,5.0％and 7.5％,and the best effect was observed at 7.5％.The combinations of L1-L3 and L1-L2-L3 also improved the mycelium density.Based on morphological characteristic and analysis of 16S rDNA gene sequences,L1,L2 and L3 were identified as Bacillus altitudinsis,B.cereus and B.zanthoxyli,respectively.[Conclusion]B.altitudinsis,B.cereus and B.zanthoxyli are proved to be potential mycorrhizal help-er bacteria,and the best potential MHB is B.zanthoxyli in the study.
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