Screening,identification And Evaluation Of Potential Biocontrol Actinomycetes Endophytes Against Sporocadus Populinus

Poplar gray leaf spot caused by Sporocadus populinus(Bres.)Orsenigo,Rodondi&B.Sutton?Coryneum populinum Bres.)is one of the momentous diseases in northeast China which is more epidemic in nursery for the present.The prevention and treatment to the poplar gray leaf spot focused on the use of chemical pesticides.There are many microorganism populations in the sphere of plants,among them,for example actinomycetes have antagonism to the phytoPathogen,and can be used as biocontrol agents.Evavluate the potential ability of antistrains is the precondition to use them for biocontrol,and explore the antagonism effect of them is the base to improve their ability for biocontrol.In this study,a Streptomyces strain Syjd3 which has significant antagonism to S.populinus,Alternaria alternate,Drechslera sorokiniana and so on phytopathogenis fungi was isolated from healthy poplar plant.Based on this,the classified appraisal,biocontrol potential and antagonism effect of the strain Syjd3 were studied in this research.The results are as follows:1.S.populinus was separated by single spore separation and S.populinus sporulation meduium was selected.Meanwhile,One hundred and ninety two microorganism strains were isolated from the healthy and disesesd(S.populinus)poplar plants.Though the dual-cultural tests and the fermentation liquid antibacterial test bioassay for inhibition of S.populinus,the Streptomyces strain Syjd3 was selected.2.The strain Syjd3 was classified as Streptomyces cavourensis by observation of its morphological,cultural and physiological characteristics,and by analysis of its 16S rDNA sequence(GenBank accession number KJ918749).3.The effect of different medium conditions and other culture conditions on production of antifungal substances of Streptomyces Syjd3 was investigated.The results showed that among the six tested medium,the best medium for growth and antifungal substances production were LB and G1;The dry weight reached the highest level after incubation at 28? for 7days and the antifungal substances production the highest level after incubation at 28? for 10 days.The antifungal substances produced that the tempreatrue range was 10 to 35?,with optimum of 28?;The favorable pH value for growth and antifungal substance production was 7-9,with optimum of pH6-8.4.The anti-S.populinus activities of the broth were stable in the pH value of 6 to 8 and the temperature range of 30 to 80 ??The inhibition ability of the broth was not affected with ultraviolet radiation and storage-time.5.Culture filtrates of Syjd3 inhibited mycelial growth of S.populinus,and histological ivestigations showed that conidial germination and sppressorial formation of S.populinus were suppressed detached polar leaves.Plot experiment showed that extracts could protect polar plants against S,populinus.The treatment and prevention of gray leaf spot disease of poplar effects were 61.5%and 73.3%,higher than 50%Basdistan 600-fold dilution,prevention is better than treatment.6.By means of the techniques of tracking bioactivity,macrospore absorbed resin and 10-90%ethanol gradient leution,a bioactive substance which could thoroughly inhibit the growth of S.populinus's spore germination was separated out of Streptomyces cavourensis Syjd3 fermenting liquor;its structure was analysed by IR,GC-MS,LC-MC and NMR,its molecular formula is C19H40O,its molecular weight is 284.52,its chemical name is 1-nonadecanol.