Study On Herbicidal Activity Of Streptomyces Sp.D15 And Polyphasic Taxonomy On Glycomyces Luteolus Sp.nov.

Weed damage,which is the first of the three hazards of farmland,can cause the world's crop yield reduced by 9.7%every year.The farmland weeds have the characteristics of fast reproduction and strong adaptability,and weed control has become a very difficult problem in the farmland management system.The birth of chemical herbicides has brought new hope to field managers.Chemical herbicides are widely used for their advantages such as fast,high efficiency,and manpower-free.However,with the use of chemical herbicides,their disadvantages such as environmental pollution,weed resistance and excessive chemical residues have gradually emerged.Therefore,more and more attention has been paid to the microbial herbicides which are environmentally friendly,not easy to make weeds resistant and come from a wide range of sources.In this study,the rhizosphere soil of wheat was used as the source of separation,and 5 kinds of media were used to separate actinomycetes.These actinomycetes were screened for herbicidal activity,and a strain D15 with strong herbicidal activity was obtained through the preliminary screening of spores and rescreening of fermentation broth.The herbicidal activity of the fermentation broth of strain D15 on Echinochloa crusgalli(L.)Beauv,Amaranthus retroflexus L.and Setaria viridis L.was studied by plate test and pot test(closed stage and seedling stage),and the effect of the fermentation broth on the growth of a variety of crops was also analyzed.The physiological characteristics of herbicidal activity strain D15 were analyzed,and the secondary metabolites of herbicidal activity strain D15 were isolated after the optimal fermentation conditions were determined,and the activities of the secondary metabolites(herbicidal activity,antifungal activity)were verified.Finally,the isolated rare actinomycete Glycomyces luteolus was identified by polyphasic taxonomy.The main results of this experiment are as follows:(1)134 actinomycetes were screened for herbicidal activity.Through spore screening,7strains were found to have an inhibitory effect on root and shoot of Amaranthus retroflexus L..After the fermentation broth was rescreened,strain D15 showed the highest inhibitory effect on the root and shoot of Amaranthus retroflexus L..Therefore,strain D15 was selected for subsequent herbicidal activity studies.(2)The plate test showed that strain D15 fermentation supernatant could inhibit the germination of Echinochloa crusgalli(L.)Beauv and Amaranthus retroflexus L.when diluted 10times.When the fermentation supernatant was diluted 100 times,the inhibition rate of root of Echinochloa crusgalli(L.)Beauv and Amaranthus retroflexus L.was higher than 78%,and the inhibition rate of shoot of these two weeds was higher than 61%,and the inhibitory effect on Setaria viridis L.was weak.(3)The pot experiment showed that the application of D15 fermentation supernatant in the closed stage could inhibit the germination of weed seeds.At seedling stage,strain D15fermentation supernatant was sprayed after dilution of 100 times,and the inhibition rates of above-ground plant height of Setaria viridis L.and Amaranthus retroflexus L.were 45.2%and62.1%,and the fresh weight inhibition rate of Setaria viridis L.and Amaranthus retroflexus L all higher than 57%.When fermentation supernatant dilution of 10 times,the inhibition rates of above-ground plant height of Setaria viridis L.and Amaranthus retroflexus L.were 56.1%and69.8%,and the above-ground fresh weight inhibition rate of E.crusgalli(L)Beauv and A.retroflexus L.all higher than 73%.The pot experiment further confirmed that strain D15fermentation supernatant had an inhibitory effect on the growth of weeds.(4)The effect of strain D15 on crop growth showed that the supernatant had a heavy effect on tomato and soybean,and the inhibition rate of fresh weight was about 40%.The production of new leaves of coriander decreased significantly,and the leaves of rape turned yellow.The damage to corn and wheat was small,and the inhibition rate of fresh weight was less than 10%.It indicates that the herbicide active substance of strain D15 is not safe for some crops and will affect the growth of crops,so it should be used selectively.(5)Borrelidin,a herbicide active compound,was isolated by fermentation of strain D15 under optimal fermentation conditions,When the concentration was 0.08 mg/m L,the germination of Echinochloa crusgalli(L.)Beauv and Amaranthus retroflexus L.was inhibited 100%.When the concentration was 0.04 mg/m L,the seed germination rates of Echinochloa crusgalli(L.)Beauv,Amaranthus retroflexus L.and Setaria viridis L.were 42.6%,73.3%and 80.8%,respectively,the inhibition rates of the root of Echinochloa crusgalli(L.)Beauv,Amaranthus retroflexus L.and Setaria viridis L.were 73.6%,94.4%and 84.7%,respectively,and the inhibition rates of the shoot were 66.9%,89.1%and 67.3%,respectively.It showed effective herbicidal activity to these three kinds of weeds.(6)The strains NEAU-A15~T,NEAU-A13 and NEAU-C4 isolated from the rhizosphere soil of wheat were identified as a novel species of the genus Glycomyces by polyphasic taxonomic analysis,for which the name Glycomyces luteolus sp.nov.is proposed.