Screening And Plant Growth Promoting Activity Of Biocontrol Streptomyces SSD49

Due to the increasing seriousness of environmental pollution, biological control of green and environmental is the trend of future development and urgent demand. Many of plant growth-promoting rhizobacteria (PGPR) are able to transcend the endodermis barrier, cross from the root cortex to the vascular system, and subsequently thrive as endophytes in plant organs. This study pay attention to microbial species lived inside medicinal plant tissue such particular habitat, screening and identification of isolates that have inhibitory effect on several pathogen; detection of bacteriostatic effect and promoting characteristics.This study detect bacteriostatic spectrum, chitinase and glucanase activity, production of IAA and siderophores, presence of polyketone synthetase related gene clusters of endophytes; biocontrol plant growth-promoting efficiency of selected five multi-functional bio-control strains tested by pot experiments; colonization of green fluorescent protein marked endogenous Streptomyces sp. SSD49 in Populus tomentosa somaclone; transcriptome sequencing of P. tomentosa somaclone inoculated by Streptomyces sp. SSD49 to analysis the mechanism of plant microbe interactions.Results indicated that 94 isolates had inhibitory effect on pathogen were screened from 412 endophytes, among these 47 isolates had inhibitory effect on at least three kinds of indicator bacteria; 23 isolates had chitinase activity, none of the isolates had glucanase activity; 55 and 32 isolates contained polyketone synthase related gene clusters and polyene compounds gene clusters; 34 isolates produced IAA and 2 isolates produced siderophores. Pot experiments indicated that Streptomyces sp. SSD49 and Streptomyces sp.SSD60 significantly improved the growth of soybean and tomato, Streptomyces sp. SSD41 and Streptomyces sp. SSD49 had great control effect on Sclerotinia sclerotiorum and Botryosphaeria dothidea. Green fluorescent protein marked Streptomyces sp. SSD49 colonized in stems and leaves of P. tomentosa. The somaclones in control (CK) and infected treatment (IN) were sent to sequencing, joining together and received 69652 Final Unigene. Gene function classification showed that 19618 genes were categorized into GO classification; 25995 unigenes were annotated on KEGG database, participated in 284 pathways. 256 transcripts were identified as differentially expressed under biotic stress, of which 141 transcripts increased and 115 decreased in abundance. Expression changes of 14 candidate genes were validated by real-time PCR, indicating significant differences between the controls and Streptomyces infected treatments.This study obtain multifunctional bio-control endogenous Streptomyces sp. SSD49 through multi-angle screening, provide theoretical basis for application of this strain to prevent poplar canker and develop bio-control bacteria agent.