Diversity Of Endophytic Diazotrophs From Different Varieties Of Maize In Songliao Area And Their Growth-Promoting Characteristics

The beneficial microorganism plays an important role in improving the environment and increasing the yield of food.In this study,the diversity of endophytic nitrogen-fixing bacteria was studied by culture and non-culture methods of maize in Songliao area.The endogenous nitrogen-fixing bacteria in maize were isolated and identified,and a batch of strains with high nitrogenase activity,ACC deaminase,iron carrier and phosphorus-soluble ability were screened.The main results are as follows:(1)A total of 762 isolates of endophytic nitrogen-fixing bacteria were isolated from the roots,stems and leaves of 7 maize varieties(samples)by using 4 kinds of media.The 16 S rDNA sequence identification revealed that these strains belonged to 4 families,7 classes,10 orders,13 families,29 genera,107 species in taxonomic status.In particular,Actinobacteria,Bacteroides,Firmicutes and Proteobacteria are the main endogenous nitrogen-fixing bacteria,accounting for 91.2 % of total isolated endogenous nitrogen-fixing bacteria.Klebsiella,Enterobacter,Pseudomonas were dominant genera,accounting for 32 %,22 % and 16 % of isolates respectively,a total of 70 %.(2)The diversity of endophytic bacteria and endophytic nitrogen-fixing bacteria in 7 maize varieties was studied by Illumina Miseq high throughput sequencing with 16 S rDNA V5-V7 and nifH as molecular markers.It was found that total kinds of 7 maize varieties at family level was 56,70,59,63,57,68 and 73,so the diversity of endophytic bacteria was 575>570>574>572>571>569.In the same corn sample,the diversity of bacteria in root was highest,followed by leaf,and the endophytic bacteria in stem has the lowest diversity.There were 19,21,20,13,19,16 and 20 kinds of endo-nitrogen-fixing bacteria in 7 maize varieties at the family level respectively,the diversity of endophytic diazotrophs is570>571=575>569=573>574>572.In all maize varieties,there are 37 families of endophytic nitrogen-fixing bacteria in stems,35 families of roots and 32 families of leaves.(3)The activity and promoting characteristics of 762 isolated endophytic nitrogen-fixing bacteria were studied.The activity of nitrogenase was 0~836 nmol /(mg·h),and the activity of ACC deaminase was 0~19.275 ?-butanoic acid /(h·mg protein).(4)The plant test was performed on 61 strains of corn with high ACC deaminase activation.It was found that 10 strains with significant probiotics could increase the height of maize by 3% ~ 11%,the weight of dry matter by 10 %~36 %,and the SPAD value by 5% ~ 16.1 %.The 10 strains were569JA21-2,569JC5-1,569YA28-3,569YA27-1,569YA5-2,569YC12-2,569YC10-2,569YC14-1,570JAS5-3,570YD2-2.And they belonged to Klebsiella pneumoniae?Klebsiella pneumoniae?Enterobacter ludwigii ? Klebsiella michiganensis ? Klebsiella michiganensis ? Klebsiella pneumoniae subsp.Pneumoniae?Kosakonia cowanii?Pseudomonas oryzihabitans?Klebsiella michiganensis?Pseudomonas taiwanensis,respectively.