Screening Of Biocontrol Bacteria Against Corn Stalk Rot And Maize Leaf Blight And Their Growth Promotion

Corn stalk rot and maize leaf spot are common plant diseases affecting the quality and yield of maize.Corn stalk rot causes a series of problems,such as short and small fruits,dry and unsaturated maize grains,dim color,difficult threshing,and a significant decrease in 1000-grain weight,which reduces the yield by 50%-60% in severe cases.Maize leaf blight is characterized by yellowing and early withering of plants,turning over straw,and often withering in the field,resulting in serious loss of maize yield.These two maize diseases have become epidemic diseases that restrict the quality and yield of maize.However,at present,chemical fertilizers and pesticides are mainly used to control maize diseases in the world,but the excessive use of chemical fertilizers and pesticides has caused many problems.For example,the re tention of chemical fertilizers and pesticides poses a threat to the health of humans and animals;pollutes the environment and destroys the ecological balance;biological control,a new method of plant disease control,will not cause harm to humans and animals,will not produce resistance to pesticides,and maintain the ecological balance.It meets people's demand for green non-polluting food and conforms to the sustainable development of green agriculture,which is gradually recognized by everyone.In this study,microorganisms with biological control function were isolated and screened from soil.Molecular biological identification of the screened biocontrol microorganisms and pathogenic microorganisms was carried out,and their biological control function was determined.Then the growth promoting ability of the screened biocontrol microorganisms was determined,including the determination of indole acetic acid,iron carrier and phosphorus release.At the same time,through pot experiment in greenhouse,the biological control effect and promotion effect of selected biocontrol microorganisms on maize seedlings were studied,in order to provide effective control ways for the prevention of maize diseases and the promotion of maize seedlings.The main results are as follows:1.Fifty-seven strains with biological control effect against corn stalk rot disease or large leaf spot disease were screened out through preliminary screening.One actinomycete,six bacteria and five fungi were screened out through further screening,which had good biological control effect on corn stalk rot disease and corn leaf spotdisease.The screened biocontrol microorganisms were identified by morphology and molecular biology.The biocontrol effects of actinomycetes and bacteria on corn stalk rotdisease and maize leaf spot disease were antagonistic,while those of fungi were antagonistic,competitive and parasitic.Bacteria B.subtilis Y21 had a good biocontrol effect.The inhibition rates of B.subtilis Y21 on corn stalk rot and leaf spot were 73% and 88%respectively.Fungus T.harzianum YZ9 had a good biocontrol effect,and its inhibition rates on corn stalk rot and leaf spot were 64% and 79%,respectively.2.The screened biocontrol microorganisms were tested for their growth-promoting function,and the screened biocontrol microorganisms showed different degrees of growth-promoting ability.Among them,T.harzianum YZ9 can secrete iron carrier.The type of iron carrier is hydroxamic acid iron carrier.The content of iron carrier is 87.80 mg/l.The strains B.amyloliquefaciens Q1,B.subtilis Y21 and F.oxysporum Y10 had the ability to produce indole acetic acid(IAA)with IAA contents of 82.5 mg/l,80.5 mg/l and 71.3 mg/l,respectively.Fungi T.harzianum 6,P.bilaiae YZ12,T.harzianum YZ9 and F.oxysporum Y10 have the ability to dissolve phosphorus.After 7 days of incubation,the content of soluble phosphorus and phosphorus reached 578.22 mg/l,87.09 mg/l,286.61 mg/l and 118.35 mg/l,respectively.3.Pot experiments were carried out in a constant temperature incubator to study the effects of selected biocontrol microorganisms on maize stem rot disease and maize leaf blight disease,and on the growth and development of maize seedlings.In the biocontrol pot experiment,the biocontrol effect of bacteria B.subtilis Y21 was better,and the biocontrol effect could reach 70%.In the growth promotion pot experiment,the plant height,fresh weight and dry weight,root,stem and leaf length of Maize Treated by B.subtilis Y21 suspension were significantly higher than those of the control.