Effects Of Endophytic Microbial Community Structure In Needles Of Pinus Densiflora On Pine Shoot Blight

Endophytic microorganisms,an indispensable member of the ecosystem,promote the growth of host plants,improve plant resistance,and protect plants from pathogens and leaf-eating insects.Pine shoot blight disease(Sphaeropsis sapinea)is one of the most common and widely distributed diseases on coniferous trees in the world,which seriously endangers the ecological balance of coniferous forests.When diseases occur,endophytic microorganisms,as microorganisms living in host plants,first met and influenced pathogenic bacteria,but the effect was often neglected in previous studies.This study was researched on Kunyushan Mountain,through the study of pine shoot disease on the red pine sample plots of different forest stands,combined with the analysis of the diversity and community structure of the endophytic microorganisms in the needles.First,we analyzed the influence of S.sapinea of shoot blight affected by the microbial diversity of Pinus densiflora needles.Secondly,we predicted the functional characteristics of bacteria and fungi in the needle.Finally,we constructed a microbial molecular ecology network model.We analyzed the interaction mechanism of shoot blight on the endophytic microorganisms in the needles of red pine systematically,providing a theoretical basis for regulating pine shoot blight,and guiding the prevention of pine shoot blight.The main research conclusions are as follows:(1)In the needles of P.densiflora,the community structure of endophytic fungi has an impact on the occurrence of pine shoot.The diversity and composition of the community structure of endophytic fungi in the needles of asymptomatic P.densiflora are significantly different from the infected needles.The dominant phyla of endophytic fungi are Ascomycota,and the unique genus of endophytic fungi in the needles of asymptomatic P.densiflora is higher than the infected needles.The community structure of the endophytic fungi in the needles of P.densiflora is the dominant genera with Lapidomyces and Selenophoma,as well as other genera(including the endophytic fungi Paraconiothyrium and Trichomerium in the sample plot);Among them,the other genera is Lapidomyces(7.39%—11.50%),Catenulostroma(0.3%—0.9%)and Selenophoma(2.53%—4.03%)that have a significant negative correlation with pine shoot blight;the relative abundances of Jattaea taediosa and Aureobasidium pullulans are 0.1%—0.6%.When endophytic fungus community structure in the needle is the above structure,it has a certain inhibitory effect on the pine shoot blight,and the needle is in asymptomatic state.(2)In the needles of P.densiflora,the community structure and diversity of endophytic bacteria affect the infection of S.sapinea,and the composition of endophytic bacteria in the needles of P.densiflora tends to be the same in different forests.The diversity of endophytic bacteria are higher in the asymptomatic needles,and the dominant phyla of endophytic bacteria are Proteobacteria.When the endophytic bacterial community structure of P.densiflora needles is in the following community structure,the dominant species are Massilia,Sphingomonas,Endobacter,and Bryocella,and the other genera are Nitrospira(1.03% — 4.32%),and Pseudomonas(0.22%—0.48%),has a significant inhibitory effect on pine shoot blight.Lactobacillus and Lactobacillus brevis have a slightly lower relative abundance,which is better for inhibiting pine shoot blight.(3)Saprophytic trophic fungi and symbiotic trophic fungi are the main fungi in the asymptomatic needles,while pathological trophic fungi are the main fungi in the infected needles.When the proportion of symbiotic trophic fungi decreases and the proportion of pathological trophic fungi increases,needles appear to be susceptible.There are six metabolic pathways which is the cell processing,environmental information processing,genetic information processing disease,metabolism and tissue systems,which have a certain degree of functional redundancy,and have a certain degree of stability against the infection of the pathogen Sphaeropsis sapinea.(4)In the molecular ecological network structure of fungi and bacteria in the asymptomatic needles,there is a trend of synergetic symbiosis.The molecular ecological network of fungi and bacteria in the asymptomatic needles presents a more complex network structure,which is more stable than the network structure of the infected needles,and the endophytes of the infected needles are more susceptible to the influence of the external environment.By constructing a stable microbial community,the effect of disease control can be achieved.By increasing the abundance of Trichoderma and Pseudomonas,it can inhibit the occurrence of pine shoot blight.