The Effect Of Fusarium Graminearum Stress On Physiological And Biochemical Indexes And Genomic DNA Methylation Levels Of Maize Seedling

It is generally known that maize is a type of crop used as food and fodder and playsimportant roles in national economy development.In recent years the maize yield has increasedsignificantly,however,the yield of maize in the world has been impacted negatively as a result ofstem rot disease.In our country the incidence of stem rot can reach70%,the main varieties canbe infected by stem rot pathogen.Therefore,it is of vital importance to study the responsemechanisms of maize under Fusarium graminearum stress.The experimental used two inbredlines Mo17and B73as materials which were infected by the bacterium liquid with differentconcentration of spores.Then the methylation levels were measured and the change ofmethylation pattern was analysed.Biochemical indexes were measured at the stage of maizeseedling.Results are as follows:(1)The results of the content of protein in the seeding leaves of two inbred lines afterFusarium graminearum stress show：the content of protein in the seeding leaves of inbred lineMo17increased affected by the concentration of spores(0-103) and decreased under theconcentration of spores(103-109).The content of protein in the seeding leaves of inbred line B73decreased repeatedly with the Fusarium graminearum stress increased.Under eachconcentration of spores,the content of protein in the seeding leaves of inbred line Mo17washigher than that of protein in the seeding leaves of inbred line B73.(2)The measurement results of the vitality of antioxidant enzyme in the seeding leaves oftwo inbred lines are as follows:the vitality of superoxide dismutase(SOD) increased first andthen decreased after stress.The change of peroxidase(POD) and catalase (CAT) activities havethe same trend.The POD and CAT activities decreased repeatedly with the stress levelsincreased. The POD、SOD and CAT activities of Mo17are higher than those of B73.(3)The measurement results of the content of malonyldialdehyde(MDA) in the seedingleaves of two inbred lines showed that the difference among the contents of MDA under eachconcentration of spores was significant.The content of MDA in the seeding leaves of two inbredlines increased repeatedly with the stress levels increased. The content of MDA of B73washigher than those of Mo17.That indicated that inbred line Mo17better adapted to Fusariumstress environments.(4)The measurement results of the amount of reduction of2,3,5-Triphenyltetrazoliumchloride (TTC) in the seedling roots of two inbred lines are as follows: The vitality of dehydrogenase in the seedling roots of two inbred lines increased with the increase of theintensity of Fusarium stress.The vitality of dehydrogenase in the seedling roots of Mo17washigher than that of dehydrogenase in the seedling roots of B73.That indicated that the inbred lineMo17could keep respiration intensity of roots better and enhance the activity of roots.(5)The measurement results of the content of chlorophyll in the seedling leaves of twoinbred lines are as follows:the content of Chlorophyll a and the value of Chlorophyll a/bincreased significantly first,then decreased with the increasing concentration of spores ofFusarium.The concent of Chlorophyll b and total chlorophyll content decreased significantlywith the increase of stress intension in the range.Under each concentration of spores,theChlorophyll a content,Chlorophyll b content and total Chlorophyll content in the seeding leavesof inbred line Mo17were higher than those in the seeding leaves of inbred line B73.Thisillustrated that The photosynthesis capacity of Mo17was better than that of B73.The value ofChlorophyll a/b of B73was lower than that of Mo17under the higher stress intensity.Thisshowed the leaves of B73aged more easily.(6)The measurement of methylation levels and the analysis of change of methylationpattern:Compared with the control group,the methylation levels of the CCGG locus of twoinbred lines has raised under Fusarium stress. The methylation levels of the CCGG locus ofinbred line Mo17increased repeatedly with the increasing intensity of Fusarium stress.Exceptthe hypomethylation rate and the hypermethylation rate under the sporesconcentration(103spores/ml),the hypermethylation rate of CG locus and CHG locus of Mo17was higher than the hypomethylation rate.Under each concentration of spores,thehypermethylation rate of CHG locus of B73was lower than the hypomethylation rate of CHGlocus significantly.This indicated that under the Fusarium stress the response mechanism of twoinbred lines Mo17and B73were different.