Isolation Of Biocontrol Bacteria And Preliminary Determination Of Its Herbicide Activity Digitaria Sanguinalis

Digitaria sanguinalis is one of the important weeds in dryland crop fields in my country,which seriously affects agricultural production.At present,chemical weeding is the most effective way to inhibit Digitaria sanguinalis.However,the long-term application of chemical weeding is easy to pollute the ecological environment,and it is easy to produce drug resistance.The use of weed pathogens for biological control has become the focus of further research on biological herbicides because of its safety and effectiveness.This paper will focus on the isolation,screening and identification of high-efficiency biocontrol strains,and at the same time investigate their host range,crop safety,optimize fermentation conditions,and evaluate their biocontrol potential through preliminary indoor and outdoor weed control activity assays.1.Isolation,purification and identification of Digitaria sanguinalis live.Release bacteria 8 strains were isolated from the naturally occurring weeds and diseased leaves collected from cotton fields in Hunan Province,and 3 strains were suitable for development as Digitaria sanguinalis microbial herbicides.After the identification of Itss,they belong to the genus Phoma,Fusarium,and Curvularia.Through morphological identification and ITS sequence analysis,they were identified as Phoma sp.,Fusanium incamatum,and Curvularia geniculata.2.Pathogenicity determination of strain MT-1.Take the strain MT-1 with better control effect in vitro as the research object,and further study its biological control effect.The results of host range determination showed that the strains had strong pathogenicity to the tested weeds,Eleusine indica and Chloris virgata,and had slight pathogenicity to Barnyard grass and Portulaca oleracea.When dealing with Digitaria sanguinalis in different growth stages,it was found that the smaller the growth stage of the strain MT-1,the better the control effect,which provided the basis for the following experiments.3.Optimization of fermentation conditions of bacterial strain MT-1.In order to clarify the physiological characteristics of the bacteria and provide experimental data for follow-up research,this experiment studied the biological characteristics of the bacterial strain.PSA had the fastest growth rate,and the colony diameter was the largest after 7 days,reaching 5.75 cm;the optimum growth temperature of the colony was 28 ℃;the colony grew the fastest when the p H value was 6.5;full light was beneficial to the growth of mycelium.The results show that the strain has good adaptability to the environment,the mycelium is easy to reproduce,and it has a good biocontrol prospect for the development of microbial herbicides.4.Weed control effect and safety evaluation of strain MT-1 The safety test showed that the strain did not cause disease to the tested crops Cotton and Soybean.In indoor experiments,the control effect of Digitaria sanguinalis was determined by the plate method and the whole plant method.The root length inhibition rate determined by the plate method was better than the shoot length inhibition rate,and the inhibition rates were 88.19% and 94.4%,respectively.The heavy control effects were 94.64% and69.7%,respectively.In the field test,strain MT-1 had the best fresh weight control effect on Digitaria sanguinalis(50.07%),followed by Chloris virgata(35.39%).The overall control effect of the MT-1 strain was weaker than that of the chemical herbicide quizalofop-ethyl EC.In conclusion,Phoma.sp.MT-1 strain is safe and environmentally friendly to Cotton and Soybean,and has the potential to control Digitaria sanguinalis and release fungi.The obtained results have certain theoretical and practical significance for weed biological control.