Identification Of Endophytic Diazotroph Bacteria From Maize Seeds And Research Of Its Effects On Wheat Growth And Drought Resistance

Endophytic diazotroph can infect and colonize plants, associative nitrogen fixation topromote plants growth. Humans have done a lot of researches on azotobacter which existswidely in nature, but the understanding of its species and plant interaction mechanism is stilllimited. The tests study on endophytic diazotroph species and their effect of wheat droughttolerance that isolated from maize seeds.This test study on the diversity and function of23strains endophytic diazotroph isolatedfrom maize seeds, PCR amplification of bacterial16S rDNA genes and analysis the diversityof strains16S rDNA gene sequences by RFLP technique to classified strains. According to thetypes of RFLP, strains can be divided into five categories: strain2y and17are divided into aclass; strains of3y,4,20and2-7are divided into a class; strains of3w,5,6,7,9,10,11,13,14,25,27and1-8are divided into a class; strains of16,1-3and2-6are divided into a class;strain18and21are divided into a class.According to the classification results selected strains5,16,17,21, and2-7formorphological identification and molecular authentication.Then according to the result ofstrain morphological identification and phylogenetic tree based on16S rDNA sequences, the16S rDNA sequence similarity of strain17and21with Enterobacteriaceae Pantoea is98%,initially identified as Enterobacter agglomerans; the16S rDNA sequence similarity of strain5and2-7with Enterobacter cloacae (E. cloacae) is98%and99%, initially identified asEnterobacter cloacae; strains16and Acinetobacter haemolyticus of16S rDNA sequencesimilarity is100%, while the other gene sequences with high homology16S rDNA comesfrom uncultured bacteria, but also according to its morphological identification is sphericalbacteria, so suggesting that strain16may be a new strain or Acinetobacter variant whichneeds to be further identified.Measuring morphological characteristics and drought-related physiological andbiochemical indexes of potted wheat after inoculated with strain5,16,17,21and2-7.According to significant analysis of morphological, experimental group inoculated with strain5,16,17,21and2-7played a role in promoting on wheat growth compare with negativecontrol group, and some even better than positive control group poured nitrogen nutrition liquid. Strain2-7showed obvious growth promoting effect on wheat in its seeding stage.Positive control group and the experimental group5,2-7can relieve the impact of thedrought on wheat leaf chlorophyll content. The free proline content of droughts group washigher than normal group in negative control group, the positive control group and fiveexperimental groups were on the contrary, it shows that inoculating endophytic diazotroph onwheat plays a role as applying nitrogen that effectively promote the growth of wheat andresponse to drought effects. The MDA content of negative control group and experimentalgroup2-7increased under drought stress, while the positive control group and experimentalgroup5,16, and21were decreased and the experimental group of17reduced most, so theycan response of wheat leaf MDA content to drought effects. The SOD activity in wheat leavesof normal group in CK1negative control group and experimental groups16,17and21waslarger than that of drought group, and wheat leaves SOD activity of normal group in CK2positive control group and experimental group5,2-7was lower than that of drought group,and the increase of2-7group was significantly. The determination of relative water contentand soluble protein content of wheat leaves both showed that the drought group was lowerthan the normal group. The inhibition rate of RWC is:21<17<CK2<2-7<CK1<5<16,and the inhibition rate of soluble protein content is:5<2-7<16<17<CK2<CK1<21.Thus speculated that the experimental group21and17alleviate the effects of drought onwheat relative water content, and the ease effect is better than the positive control group;Group5,2-7,16and17alleviate the effects of drought on soluble protein content of wheat,and the ease effects better than the positive control group significantly. Conclusion that all thefive endophytic diazotrophs can promote the growth of wheat and enhance the droughtresistance of wheat seedlings to a certain extent, while the effect of strain5,17and2-7ismore obvious.In summary, not only the species of endophytic diazotroph from maize seeds is various,but also they all have a certain degree of growth-promoting effect and enhance the droughtresistance of wheat seedlings. The research provides a basis for diversity study of endophyticdiazotroph, and laid the foundation for the next study of interaction between plants andendophytic diazotroph, and will open the way for its application in agricultural production.