Advances In Difference Of Endophytic Bacteria In Three Tissues Of Pinus Massoniana Seedlings Infected By Bursaphelenchus Xylophilus

Pine wood nematode disease is often referred to as "pine cancer" and is the most harmfuldisease to pine plants.As the largest species in the pines,themasson pine is also the most severely affected by pine wood nematode disease.In recent years,research on endophytic bacteria in the prevention and control of plant diseases has gradually increased.However,there are few reports on the relationship between the changes of endophytic bacterial flora in different parts of Masson pine and pine wood nematode disease.The main results of this research were as follows:(1)Through polymerase chain reaction and denaturing gradient gel electrophoresis(PCR-DGGE),we analyzed the pine needles,pine stems and root samples.Among them,the total number of bands in the root system is the largest,and and the bright bands are also the most;the number of bright bands in the pine needles is less than the root system,but the total number of bands is the least;the total number of bands in the pine stems is in the middle,but the bright bands is the least.Which indicated that the types and quantity of endophytic bacteria in different parts are quite different,root system>pine stems>pine needles.(2)The DGGE electrophoresis band map of the pine dry endophytic bacterial flora was analyzed by using PAST and Quantity One software,the results showed that at 15 days of infection,the types and numbers of endophytic bacterial flora in cadres had shown a significant increase,but the increase was not large;within 30 days of infection,the types and numbers of bacterial flora further increased,and the magnitude of change was largest;at 45 days after infection,its types and numbers further expanded to the highest level,but the range of change was significantly lower than before;by the 60 th day of infection,the type and quantity of the flora remained relatively stable.The pine needles only show significant changes in the types and numbers of bacterial flora after 30 days of infection;although the change of the flora is not obvious after 15 days of infection,but the overall trend is still increasing;within 45 days of infection,the species and quantity of the needle flora reached the maximum,the range of change has also reached the maximum;the number and species of bacteria have been partially reduced by 60 days after infection,but the variation range is relatively stable.Compared with pine stems and pine needles,the types and numbers of endophytic bacterial flora in roots did not change significantly with the prolonged infection time.It can be seen that the structural changes of the endophytic bacterial flora in different parts are significantly different,pine stems>pine needles>root system.(3)Through high-throughput sequencing technology,we analyzed the Analysis of Endophytic Bacteria in Pinus massoniana.There are 442 genera of endophytic bacteria in it,distributed in 35 phyla,49 classes,110 orders,and 210 families.Through the analysis of flora diversity,it was found that the abundance trend of the same flora in different parts is quite different.The relative abundance of Methylobacterium,Pseudomonas,Curtobacterium,and Hymenobacter in the pine stems part showed a gradual increase trend with the prolonged infection time,while the change trend in the pine needles was opposite.The abundance changes of Pantoea and Actinomycetospora are mainly reflected in the pine stems.As the infection time increases,its relative abundance gradually increases,but there is no obvious change pattern in the pine needles.(4)Through the comparative analysis of the endophytic bacteria structure in the pines stem at different infection stages,it can be seen that the relative abundance of Mucilaginibacter 、Gammaproteobacteria、Occallatibacter、Acidobacteria and Lysobacter in the blank control group is weak,but significant increase after 15 days of infection.However,the surface of the seedlings did not show any symptoms.Therefore,real-time monitoring of the dynamic changes of the endophytic bacterial flora in pine stems during the peak period of infection has certain reference value for the early diagnosis of pine wood nematode disease.In conclusion,pine wood nematode infection can have different effects on the endophytic bacterial flora structure in different parts of Masson pine.With the extension of the infection time,the structural differences of the endophytic bacterial flora in different parts are gradually increasing.One of the most fastest response is the pine stems to Bursaphelenchus xylophilus and then pine needles,the roots are basically unaffected.By analyzing the relatively comprehensive dynamic information of bacteria in different parts,it is expected to discover biocontrol bacteria that play a role in the growth and development of Pinaceae,provide a new research direction for the control of pine wood nematode disease.