Fitness And DON Production Of Three Chemotypes Of Fusarium Graminearum Species Complex From Wheat

Fusarium head blight caused by Fusarium spp.occurs worldwide on small grain cereals.In China,Fusarium head blight is mainly caused by Fusarium graminearum species complex(FGSC).FGSC produces trichothecene toxins and it was divided into 3 chemotypes:nivalenol(NIV),15-acetyldeoxynivalenol(15-AcDON)and 3-acetyldeoxyniva-lenol(3-AcDON).In order to predict the spreading trend of 3 chemotypes of Fusarium spp in China,we randomly selected 20 strains for every chemotype and studied the biological characteristics including mycelial growth rate,conidial production quantity,the perithecia production quantity.Virulence of these strains was also tested in seedling and heading stage of wheat.The results show that the growth rate of 3-AcDON,3-AcDON,15-AcDON and NIV isolates was highest at 15?,20?,25? and 30?.The conidium production of 15-AcDON isolates was the highest and there was no significant difference between 3-AcDON and NIV chemotype.The isolates of 15-AcDON chemotypes formed more peritheciaand earlier at 15?and 18?.The isolates formed more perithecia on the maize straws than that on rice straws.The virulence test results suggested that the average disease index of 3-AcDON,15-AcDON and NIV were 72.71,70.72 and 48.27,respectively.Variance analysis showed that there was no significant difference between 3-AcDON and 15-AcDON,but NIV chemotype was significant lower than 3-AcDON and 15-AcDON.The virulence of three chemotypes in field got the same results.Fusarium graminearum species complex can produce a variety of trichothecene when infected wheat.In order to compare the toxin-producing ability of three chemotypes,we inoculated wheat head on flowering stage with conidia of 60 strains and harvested the inoculated heads and collected the grains.DON content in grains was assayed with HPLC mehod.The DON content that 60 strains produced in liquid media also assayed.The results showed that 3-AcDON strains produced more DON than 15-AcDON and NIV strains.Variance analysis showed that the DON content of three chemotypes strains produced in wheat grains had significant difference.In vitro,the difference of DON content of the three chemotypes were smaller.In China,F.asiaticum and F.graminearum are the major pathogens of Fusarium head blight and they were described to 3 chemotypes.In order to distinguish these two populations and three chemotypes,we amplified partial translation elongation factor 1 alpha gene and Tri8 gene.One pair of designed primers were capable of distinguishing F.asiaticum and F.graminearum.We found that 3 chemotypes can be differentiated according to the size of fragments after Tri8 gene was digested with AvaI enzyme.