茅苍术叶片可培养内生细菌多样性及其促生潜力

Abstract

Atractylodes lancea is a medicinal plant grown in Jiangsu Province,China.The diversity of the endophytic bacteria culturable from the leaves of A.lancea and their plant growth-promoting potential,including nitrogen fixation,phosphorus solubilization,potassium solubilization and indole acetic acid(IAA) production were investigated.According to morphological characteristics of bacterial colonies,52 endophytic bacterial strains were obtained and 45 could be subcultured normally in vitro and subjected to amplified ribosomal DNA restriction analysis(ARDRA).Based on the ARDRA fingerprints,the 45 subculturable endophytic bacterial strains could be classified into 14 clusters.The 16S rDNA fragments of representative strains from different clusters were sequenced and deduced by a BLAST search to identify similar strains.The results showed that the isolated endophytic bacteria most likely belong to Pantoea sp.,Microbacterium sp.,Curtobacterium sp.,Agrobacterium sp.,Pseudomonas sp.,or Bacillus sp.Among them,the Pseudomonas sp.was the most dominant genera.BOX-PCR was then used to study the diversity of the endophytic bacteria in the main ARDRA clusters.The BOX-PCR fingerprints showed that the endophytic bacteria in the same cluster were not similar,indicating a broad genetic diversity within the same genera.Ten of the 45 subculturable endophytic bacteria could grow normally on Burk′s medium,which indicates their potential to fix nitrogen.We also amplified the nifH genes in these strains and all strains generated a band of the expected size except for ALEB 33.Among all subculturable endophytic bacteria,19 and 15 strains could dissolve insoluble calcium phosphate and lecithin,respectively,and then release dissociative phosphorus into the medium.ALEB 43 could dissolve the largest amount of phosphorous from calcium phosphate,reaching(251.43±6.55) mg/L.Furthermore,ALEB 4A could dissolve the largest amount of phosphorous from lecithin,reaching(23.63±1.46) mg/L.After comparing the amount of phosphorous dissolved from calcium phosphate by the endophytic bacteria and the pH of the bacterial inoculum,we deduced that some phosphate-solubilizing bacteria dissolve insoluble calcium phosphate by secreting certain types of acids.However,the pH of the fermentation solution of endophytic bacteria capable of dissolving lecithin was not related to the release of dissociative phosphorus.There were 24 strains that could grow on silicate medium,indicating these strains had the potential to dissolve insoluble potassium feldspar and release dissociative potassium,which was available to plants.Forty three endophytic bacterial strains could produce and release IAA into the medium.The amount of IAA released by ALEB 44 was the highest,reaching(268.44±10.12) μg/mL.These endophytic bacteria could promote the growth of host plants by increasing the amounts of available nutrients or phytohormones.This paper is the first to reveal the diversity of endophytic bacteria in A.lancea and their plant growth-promoting potential.Continued research will be needed to clarify the interactions between A.lancea and its endophytes.