[Objective] The screening method and the pathogenic function of pathogenic bacteria X46（Micromonospora）of crabgrass was studied.[Method] Improved Gaoshi No.I medium was adopted to isolate a strain of pathogenic bact...[Objective] The screening method and the pathogenic function of pathogenic bacteria X46（Micromonospora）of crabgrass was studied.[Method] Improved Gaoshi No.I medium was adopted to isolate a strain of pathogenic bacteria X46 of crabgrass from the rhizosphere soil of crabgrass and barnyardgrass,the optimal toxin production condition was determined,and the preliminary assessment of its security was conducted.[Result] Pathogenic bacteria X46（Micromonospora）of crabgrass was identified to be Micromonospora.When the liquid volume of 300 ml flask was 30 ml,initial pH was 6.0-6.5,inoculation amount was 10%,fermentation was conducted at 180 r/min,28 ℃ for 120 h,the production amount of toxin in improved Gaoshi No.I medium was the largest,these were the optimum culture condition.The bacteria had significant promotion effect on the growth of maize,tomato and soybean,which had slight inhibition effect on wheat growth and significant inhibition effect on cucumber growth.[Conclusion] X46 is a potential strain that can be developed as the biological herbicide in North China.展开更多
Weed tolerance of UV-B radiation varies with species, and the radiation could affect weed ecology and management. Variations In growth, photosynthesis and defense system among four important agronomic weeds, Abutllon ...Weed tolerance of UV-B radiation varies with species, and the radiation could affect weed ecology and management. Variations In growth, photosynthesis and defense system among four important agronomic weeds, Abutllon theophrastl Medlk, Amaranthus retroflexus L., Digitaria sanguinalis （L.） Scop and Chloris virgata Swartz, under Increased UV-B radiation （ambient and increased radiation at 2.7, 5.4 and 10.8 kJ.m^-2.d-1） were studied In the greenhouse experiment. After 2 weeks of radiation, the shoots＇ dry mass decreased with increasing UV-B radiation except for D. sanguinalis. The reduction in biomass was the result of changes in morphology and physiology. Higher levels of UV-B treatment decreased the leaf area, plant height, net photosynthetic rate and chlorophyll contents, while it increased the contents of wax and UV-B absorbing compound in all species, except for A. retroflexus, which did not increase significantly. The activity of superoxide dismutase, catalase, ascorbate peroxide and the content of ascorblc acid changed differently among the weed species as UV-B radiation increased. D. sangulnalls was the most tolerant and A. retroflexus the most sensitive to increased UV-B radiation. The results also show that the two grass species （D. sanguinalis and C. virgata） were more tolerant to UV-B radiation than the two broadleafed species （A. theophrasti and A. retroflexus）. The UV-B absorbing compound and leaf wax played Important roles against UV-B damages in the two grass weeds. The overall results suggest that weed community, competition and management will be altered by continuous ozone depletion.展开更多
基金Supported by Funded Project in Department of Education,Hebei Province:Research on Microorganism Herbicide of Crabgrass Pathogenic bacteria(No.Z2007443)~~
文摘[Objective] The screening method and the pathogenic function of pathogenic bacteria X46（Micromonospora）of crabgrass was studied.[Method] Improved Gaoshi No.I medium was adopted to isolate a strain of pathogenic bacteria X46 of crabgrass from the rhizosphere soil of crabgrass and barnyardgrass,the optimal toxin production condition was determined,and the preliminary assessment of its security was conducted.[Result] Pathogenic bacteria X46（Micromonospora）of crabgrass was identified to be Micromonospora.When the liquid volume of 300 ml flask was 30 ml,initial pH was 6.0-6.5,inoculation amount was 10%,fermentation was conducted at 180 r/min,28 ℃ for 120 h,the production amount of toxin in improved Gaoshi No.I medium was the largest,these were the optimum culture condition.The bacteria had significant promotion effect on the growth of maize,tomato and soybean,which had slight inhibition effect on wheat growth and significant inhibition effect on cucumber growth.[Conclusion] X46 is a potential strain that can be developed as the biological herbicide in North China.
基金Supported by the National Natural Science Foundation of China （30370940）.
文摘Weed tolerance of UV-B radiation varies with species, and the radiation could affect weed ecology and management. Variations In growth, photosynthesis and defense system among four important agronomic weeds, Abutllon theophrastl Medlk, Amaranthus retroflexus L., Digitaria sanguinalis （L.） Scop and Chloris virgata Swartz, under Increased UV-B radiation （ambient and increased radiation at 2.7, 5.4 and 10.8 kJ.m^-2.d-1） were studied In the greenhouse experiment. After 2 weeks of radiation, the shoots＇ dry mass decreased with increasing UV-B radiation except for D. sanguinalis. The reduction in biomass was the result of changes in morphology and physiology. Higher levels of UV-B treatment decreased the leaf area, plant height, net photosynthetic rate and chlorophyll contents, while it increased the contents of wax and UV-B absorbing compound in all species, except for A. retroflexus, which did not increase significantly. The activity of superoxide dismutase, catalase, ascorbate peroxide and the content of ascorblc acid changed differently among the weed species as UV-B radiation increased. D. sangulnalls was the most tolerant and A. retroflexus the most sensitive to increased UV-B radiation. The results also show that the two grass species （D. sanguinalis and C. virgata） were more tolerant to UV-B radiation than the two broadleafed species （A. theophrasti and A. retroflexus）. The UV-B absorbing compound and leaf wax played Important roles against UV-B damages in the two grass weeds. The overall results suggest that weed community, competition and management will be altered by continuous ozone depletion.
