Effect Of Corn Straw Returing On Dominant Pathogen Associated With Wheat Crown Rot In Haihe Plain

Wheat crown rot(WCR)occurrence has increased year by year in the Haihe Plain wheat area of the corn straw returning.In order to clarify the group composition of pathogens and causes of severe occurrence of WCR,based on extensive investigation of the extent of WCR in the wheat area of Haihe Plain,this study identified the isolated and purificated pathogens by morphological observation and molecular biology techniques,and clarified the group composition.Furthermore,the effects of corn straw returning and the main chemical substances produced by decomposition on the occurrence of WCR and dominant pathogens were analysised.The aim was to reveal the occurrence mechanism of WCR under straw returning conditions.The main results are as follows:1.The incidence rate and Rate of white heads of WCR in Haihe Plain were between 47.3%~95.9% and 5.2%~19.3%,respectively.He’nan was the most serious,followed by Hebei and Shandong.737 pathogens were separated in the area.Fusarium pseudograminearum was the dominant pathogen(49.7%)of WCR,Followed by F.graminearum(16.0%).The separation frequencies of F.oxysporum,F.equisteti,Multilous genotyping and F.proliferatum were 6.9%,6.1%,5.3%,and 5.0%,respectively.The separation frequencies of F.tricinctum,F.asiaticum,and F.culmorum were all below 5%.2.After vaccinated by F.pseudograminearum,F.graminearum,F.oxysporum,F.equisteti,Multilous genotyping and F.proliferatum,the incidence rate of WCR of Keshi B05-6508,Jimai 22 and Shixin 828 were all up to 100%,the average disease index reached 61.4,26.3 and 29.9,respectively,and the pathogenicity of F.pseudograminearum was significantly stronger than other pathogens.There was no significant difference in the pathogenicity of other pathogens.Based on the analysis of 60 strains of F.pseudograminearum TEF-1α,histone and β-tubulin in Haihe Plain,it was found to be rich in heritage diversity.The genetic relationships among different strains of F.pseudograminearum from Haihe Plain by multigene genealogical analysis based on TEF-1α,histone and β-tubulin gene sequences showed abundant genetic diversity.3.From overwintering stage to heading stage of wheat,the disease index of WCR in corn straw returning field were higher than that in field without corn straw returning by 47.8%~123.1% and 57.9%~250.0% at the the same year,and the incidence rate were improved 18.3%~98.0% and 32.5%~127.7%,respectively.Low concentration corn straw decomposed liquid treatment demonstrated promotion and high concentration corn straw decomposed liquid treatment performance inhibition on mycelial growth and spore germination of F.pseudograminearum when the decomposed liquid 0 days 7 days and 14 days,when the decomposed liquid concentration were 0.0315 g DW/mL and 0.0625 g DW /mL,spore germination rate was higher by 2.0%~5.7% than that of the control.The decomposed maize straw liquid 0.0625 g DW /mL at the decomposed 14 days has the strongest promotion effect on mycelial growth,mycelial growth rate was higher by 17.6% than that of the control.4.O-hydroxybenzoic acid,4-hydroxybenzoic acid and 3,5-dimethoxy-4-hydroxybenzoic acid 4-hydroxy-3-methoxybenzoic acid were detected in the soil of the corn straw returning field.In the whole growth period of wheat,the total content increased first and then decreased.O-hydroxybenzoic acid,4-hydroxybenzoic acid and 3,5-dimethoxy-4-hydroxybenzoic acid exhibited low concentration promotion effect on mycelial growth,spore germination,germ tube elongation,and sporulation ability of F.pseudograminearum was promoted by the three chemical substances at the lower concentrations and inhibited by higher concentrations.Germ tube elongation was promoted obviously by 1.0 mg/L 4-hydroxybenzoic acid with the promotion rate by 105.3%.The effects of O-hydroxybenzoic acid on the mycelial growth,spore germination,sporulation ability were the most significant with the promotion rates by 13.4%,10.7% and 49.5%,respectively.0.5 mg/L to 5.0 mg/L of the above three phenolic acids significantly increased the disease index of WCR,which increased by 6.8% to 33.9%.