Screening And Identification Of Biocontrol Fusarium Strains Against Soybean Root Rot Disease

Fusarium spp.is widely distributed and important fungi in nature,and most of Fusarium species are devastating pathogens that cause a variety of plant diseases.However,some of Fusarium species were also used as biocontrol agents to prevent and control various plant diseases.The purpose of this study was to screen out biocontrol Fusarium spp.that can control soybean root rot.Fungal strains were isolated from soybean rhizosphere soil in the most representative soybean fields,including Langfang,Lankao,Harbin,Heihe and Yichun in China.Antagonistic test were then assayed by culturing these strains with the pathogic Fusarium oxysporum and Fusarium graminearum strains,which both strains cause obvious soybean root rot disease.Molecular and morphological identification were subsequently conducted for classification of these antagonistic strains.To obtain the effective biocontrol Fusarium strains exhibiting harmless effect on host plant,safety assay of the antagonistic Fusarium was evaluated by pot experiment and infection experiment,respectively.The main findings of this study are listed as follows:A total of 529 fungal strains were isolated,including 158 antagonistic Fariarium strains.During these 158 antagonistic Fusarium strains,71 strains were F.oxysporum with the first rank percentage 45%.F.solani were followed by 37 strains,accounting for 23%;While 33 F.equiseti strains were isolated with the third rank percentage at 21%.Another six Fusarium species including F.proliferatum,F.verticillioides,F.acuminatum,F.merismoides,F.redolens and F.graminearum were also identified with four,four,four,two,two and one strains,respectively.The results isolation and identification of strains showed that the dominant antagonistic Fusarium spp.in each area was the same as the dominant Fusarium spp.In Langfang of Hebei Province,Lankao of Henan Province,Harbin of Heilongjiang Province were F.solani,F.proliferatum and F.equiseti,respectively.In Heihe and Yichun of Heilongjiang Province,were F.oxysporum.The results showed that the predominant species of Fusarium spp.were different in soybean rhizosphere soils in different regions,and dominant antagonistic Fusarium spp.were mostly from dominant species.According to evaluation the safety effect on the host,three strains of Fusarium strain,namely 2017-141,2017-106 and 2017-119,were found to be non-pathogenic to the soybean cultivar Zhonghuang 13.Therefore,these three strains of Fusarium were considered as the safely potential biocontrol strains to control soybean root rot disease.Combined with molecular characteristics and morphological examinations,it was determined that 2017-141 was F.equiseti,2017-106 was F.redolens,and 2017-119 was F.acuminatum,respectively.The result that the predominant Fusarium species differs in the field will contribute to the prevention and control of soybean root rot theoretically in different regions.In addition,the three isolated Fusarium strains will lay solid foundation for the development of biocontrol preparations.