Screening And Field Control Effect Evaluation Of Biocontrol Strains Against Corn Sheath Blight And Stalk Rot

As the worldwide soil-borne diseases,increasingly serious corn sheath blight and stalk rot have brought great losses to agricultural production in recent years.In this study,Rhizoctonia solani and Fusarium graminearum,the dominant strains of corn sheath blight and stalk rot in Jilin province,were used as indicator bacteria to isolate microorganisms from rhizosphere soil of perennial ginseng.The biocontrol strains of corn sheath blight and stalk rot were screened through confrontation culture and identified by physiological,biochemical and molecular biology.The inhibation mechanism of biocontrol strains and the potential of their combined application with water and fertilizer integration technology of drip irrigation under film were explored,providing new strategies for biocontrol of corn sheath blight and stalk rot.The results of this study are as follows:1.Isolation and identification of biocontrol strainsThe rhizosphere soil of perennial ginseng was used as the material for microbial isolation,and 32 strains were obtained after purification,including 23 strains of bacteria,6 strains of filamentous fungi and 3 strains of actinomycetes.The isolated strains were subjected to confrontation culture with R.solani and F.graminearum,and finally two strains GsBv1 and GsAl2 with obvious inhibation effects were obtained.GsBv1inhibition rates of R.solani and F.graminearum were 35.74%and 33.33%respectively,and the inhibition rates of Setosphaeria turcica,Pyricularia oryzae,Sclerotinia sclerotiorum and Botrytis cinerea were 69.50%,60.10%,38.03%and 40.33%respectively.GsAl2 inhibition rates of R.solani and F.graminearum were 48.56%and46.27%respectively,and the inhibition rates of S.turcica,P.oryzae,S.sclerotiorum and B.cinerea were 62.30%,54.90%,34.60%and 34.60%respectively.Biochemical,molecular biological identification and phylogenetic analysis of GsBv1 and GsAl2showed that GsBv1 was Bacillus velezensis and GsAl2 was Asaia lannensis.2.Inhibition mechanism of biocontrol strains GsBv1 and GsAl2The inhibition mechanism was explored through the effects of biocontrol strains GsBv1 and GsAl2 on mycelial growth,cell membrane permeability and lipid peroxidation of R.solani and F.graminearum.The results showed that GsBv1 and GsAl2 fermentation significantly inhibited the mycelial growth of R.solani and F.graminearum,and the inhibitory effect on R.solani was stronger.Mycelial branches of R.solani increased and the hyphae tips curved.F.graminearum hypha is uneven in thickness and its contents are leaked out.Mycelial conductivity of R.solani and F.graminearum treated with GsBv1 fermentation was not different from the control.Mycelial cell membrane permeability was not significantly changed,MDA(malondialdehyde)content was increased,and lipid peroxidation degree of mycelia was significantly increased.Mycelial conductivity of R.solani and F.graminearum increased under the treatment of GsAl2 fermentation,hyphal cell membrane permeability increased,MDA content also increased,so the hyphal lipid peroxidation degree increased.The results showed that GsBv1 and GsAl2 had effects on mycelial growth,mycelial morphology,mycelial cell membrane permeability(GsBv1 had no effect on it)and mycelial lipid peroxidation of R.solani and F.graminearum.3.Combination of biocontrol strains and integrated water,fertilizer and drug technologies for drip irrigation under mulch for cornThe biocontrol strains fermentation was added into pipelines of water,fertilizer and drug system,and was slowly dripped into a test area along with the flowing of drip irrigation water,and comprehensively prevent and control diseases in the test area and improve the resistance of corn sheath blight and stalk rot.The inoculation period are the early sowing period?the 3-leaf period and the 8-10-leaf period of corn.The concentration of fermentation is 1.5×10~8 CFU/mL.The inoculation method is drip irrigation.The results showed that the control effect of GsBv1 on corn sheath blight and corn stalk rot are 69.64%and 47.64%respectively in field.The control effect of GsAl2 on corn sheath blight and corn stalk rot are 52.34%and 58.68%respectively.At the same time,the application of biocontrol strain GsBv1 and GsAl2 did not increase the apparent of corn disease.These results showed that it was feasible to combine biological control with drip irrigation under film to prevent and control soil-borne diseases such as corn sheath blight and stalk rot.