Preparation Of Compound Microbial Inoculant And Its Application In Control Of Weeds In Wheat Fields

Weed is huge harm to agricultural production.Chemical herbicides are the most widely used method of weeding in farmland,but people are beginning to realize the problems caused by chemical herbicides,such as environmental pollution and drug resistance in weeds.Microbial herbicides have become a research hotspot because of safety and environment-friendly.Microbial herbicides are currently in the development stage,few studies have been commercialized.In this thesis,we mainly isolated,screened,identified,optimized the fermentation process and compounded the fermentation broth with herbicidal active fungi,in order to obtain microbial herbicides that can have a good control effect on various weeds.Isolation of 19 fungi from soil and diseased weeds,Based on herbicidal activity experiment of fungus fermentation broth,Z-5 has a good control effect on crabgrass,abutilon and echinochloa frumentacea;Z-6 has a good control effect on crabgrass,barnyard grass and purslane.Use Morphological identification and ITS sequence analysis,Z-5 belongs to aspergillus tubingensis,Z-6 belongs to aspergillus niger.By the studies on Fermentation Process of Z-5 and Z-6,the optimal medium for Z-5 is 1000 m L of potato extract,3.08% of starch,0.31% of potassium nitrate and 0.15% of magnesium sulfate.The optimum culture conditions are: culture temperature 30.3?,initial p H 5,liquid volume 100 m L(250m L conical flask),inoculation amount 8%,rotating speed 150r/min,seed age 48h;The optimal medium formula for Z-6 is 1000 m L potato leaching solution,starch 3.11%,ammonium sulfate 0.21%,dipotassium hydrogen phosphate 0.1%.The optimal culture conditions are: culture temperature 27.8?,initial p H 5,liquid filling 100 m L(250m L conical flask),inoculation amount 9%,rotating speed 140r/min,seed age 36 h.After the fermentation broths of herbicide fungi Z-5 and Z-6 were reconstituted in a ratio of 1:1,a pot application experiment was conducted.It was found that the best application method was foliar spraying,Use 4×105spore/m L fermentation broth to have 80% control effect on crabgrass,abutilon,echinochloa frumentacea and purslane.Safety test on the mixed fermentation broth show the fermentation broth has no effect on wheat growth,it is safe for earthworm,brachydanio rerio and chlorella.After applying the fermentation broth to the soil,the number of microorganisms in the soil including bacteria,fungi,and actinomycetes will increase significantly.Through the analysis of crabgrass and purslane after spraying fermentation broth,we can find that,after spraying the fermentation broth,the chlorophyll content in the weeds decreased rapidly,and the content of MDA and O2-began to rise,The activity of peroxidase-protected enzymes(SOD,CAT,POD)showed a tendency to increase first and then decrease rapidly,continued increase in malondialdehyde and reactive oxygen species can cause severe damage to plant membrane lipids and proteins,which is why the soluble protein content drops dramatically.As the degree of damage to plant membrane lipids and proteins increases,weeds eventually die.