Herbicidal Activity Of Granules And Metabolites Of Serratia Marcescens Ha1

In this study, a strain Ha1with the herbicidal activity were isolated from479marinemicroorganisms. Biological activity assay indicated that the crude extracts from the strainHa1performed strong inhibitory effects on Digitaria sanguinalis and Chlamydomonasreinhardtii (algal cells number×107mL-1culture, algal cells dry weight mg·mL-1cultureand algal chlorophyll mg·mL-1culture). The crude extracts were isolated and purified usingthe Silica gel column chromatography and HPLC. Granule formulation of the strain Ha1was developed and its herbicidal activity was detected.1. Four strains, which showed stronger herbicidal activity were selected from479bacterial strains and were named as Ha1, Ha17, Ha38, Ha384, respectively. The strain Ha1showed the strongest herbicidal activity.2. The strain Ha1was identified as Serratia marcescens by using the methods of16SrDNA sequence analysis and the physiological and biochemical assay. The mainly resultsof its physiological and biochemical assay were: Gram-negative bacteria, which showednegative in sugar and alcohol fermentation and hydrolysis of starch test. The indole, VP,MR, sulfureted hydrogen and hydrogen peroxide detection were positive. The Ha1was theglucose oxidative fermentation bacteria. Analysed with blastN software, it showedhomology with several other Serratia marcescens, especially the Serratia marcescensWW4, with whom the homology rate is100%. The phylogenetic tree was constructed,respectively.3. The metabolites of the Ha1strain had certain degree of inhibition on D. sanguinalis,as well as the C. reinhardtii. The IC50of the culture filtrate extracts for the radicula andcoleoptile of Digitaria sanguinalis were2828mg·L-1and3332mg·L-1, respectively. Andthe IC50of the metabolites on C. reinhardtii was628mg·L-1. When the concentration of thecrude toxin was between0to0.5mg·mL-1, it had obvious stimulation on C. reinhardtii.The toxin had strong inhibition on C. reinhardtii growth when its concentration reached0.5mg·mL-1, which showed positive correlation. The influence on the chlorophyll of C.reinhardtii was dose dependent.4. The crude extracts of strain Ha1were isolated using silica gel columnchromatography, the biological assay result as an index, and the active components weredetected by HPLC, mobile phase:70%methanol, monitored at280nm, flow rate:1.0 mL·min-1, sample:10μL, temperature:25℃. According to the biological assay and HPLCdetection results, we merged the similar components, eight components were acquired andthe component3and component4showed higher herbicidal activity than others. Thecomponent3and component4were isolated and purified by HPLC, the active substanceⅠfrom the component4was thought to be the weeding activity substance.5. The semolina-kaolin granular formulation of strain Ha1was developed. And theinfluence of the storage temperature and the adjuvant maize oil on living bacterium andherbicidal activity in granular formulation were detected. It showed that the viability ofbacteria in granular formulation was preserved, and the herbicidal activity was improvedwhen the granules were stored at4℃and the maize oil was added as the adjuvant. Aftereight weeks storage, the living bacterium of those at4℃and room temperature stored ingranular formulation were decreased by4.3units and5.5units, respectively. The granularformulation stored at4℃, which inhibit rate was reduced to23%from83%, showedhigher inhibit activity compared with the granules stored at room temperature, whoseinhibit rate was reduced to17%from70%. The living bacterium of those at4℃stored ingranular formulation with adjuvant were reduced by3.55units, while the granularformulation without adjuvant were reduced by4.95units. The inhibit rate on Digitariasanguinalis of granular formulation with adjuvant were reduced to50%from90%, whilethe granular formulation without adjuvant were reduced to23%from83%.