The Mechanism Research Of Pochonia Chlamydosporia PC-170 In Inducing Plant Systemic Resistance And Its Application In Grapes

Pochonia chlamydosporia has been applied as a promising biological control agent of nematodes in many economically important crops for a long time.In the process of research,it was discovered that P.chlamydosporia has the ability to colonize in the roots of both monocotyledonous and dicotyledonous plants.The colonization of P.chlamydosporia can not only promote plant growth and increase yield,but also induce plant resistance to root-knot nematodes.However,it is not clear that the mechanism of the interaction between P.chlamydosporia and plants and how it affects the resistance of plants to pathogens.The applied research of P.chlamydosporia has been extended to fruit trees.Grape is a perennial plant.The growth of the root system,the environment,and diseases and insect pests are all factors that restrict the production of grapes.Whether the positive effects of P.chlamydosporia on plants can be transferred from model plants or annual plants to other perennial horticultural plants needs more research to prove.In this study,the PC-170 strain of P.chlamydosporia was used to study the colonization of P.chlamydosporia and its effect on plant growth,and the way of PC-170 in inducing plant resistance.P.chlamydosporia PC-170 was applied to grapes to explore the role of P.chlamydosporia in the production of grapes.It provides a basis for clarifying the molecular mechanism of P.chlamydosporia inducing plant resistance,and also provides more theoretical support for the application of P.chlamydosporia to fruit trees as a biocontrol bacteria or biological fertilizer.The main conents are listed as following:1.It was observed that P.chlamydosporia PC-170 can colonize the roots of tomatoes,cucumbers,and promote plant growth.But this promotion depends on the concentration and dose of the inoculation.Too high inoculum concentration will inhibit the growth of plants.The colonization of PC-170 is regulated by the jasmonic acid signaling pathway(JA)in plants and the amount of colonization finally reaches a dynamic equilibrium.2.The anti-nematode effect of PC-170 on plants was tested,and the results showed that the number of root knots,egg masses and eggs on the roots of plants inoculated with PC-170 decreased significantly.PC-170 can reduce the infection of nematodes and affectaffect the development and reproduction of nematodes.This shows that PC-170 has the potential as a biological control agent.3.The split-root experiment proved that PC-170 can induce tomato resistance to root-knot nematodes,without direct contact with root-knot nematodes.At the same time,it can improve tomato resistance to other soil-borne diseases and some foliar diseases.This shows that PC-170 can induce tomato systemic resistance and improve the overall tomato resistance.4.The related marker genes of salicylic acid(SA)signal pathway and JA signal pathway of tomato were analyzed,and it was found that JA signal pathway related marker genes are first to be up-regulatedregulated during the colonization process,and after nematode inoculation,the related marker genes of the SA signal pathway are up-regulated.The activation of signaling pathways becomes more intense under the action of PC-170,and the gene was up-regulated and duration are significantly improved.Using tomato mutant materials,it was verified that the JA signal pathway plays an indispensable role in tomato resistance to nematodes.The absence of JA completely lost the resistance induced by PC-170,and it would over-colonize the roots,which is not conducive to plant growth.The lack of SA signal pathway will affect the induced resistance of PC-170,but it has not been completely lost.PC-170 can induce plant resistance by affecting the immune signal pathways in plants.5.PC-170 can be colonized in the roots of Arabidopsis thaliana to promote the growth of Arabidopsis thaliana.In the transcriptome data of the interaction with Arabidopsis thaliana,some genes that were up-regulated in the process of interaction with plants were found,and the No.3 gene cluster was screened,which may be involved in the process of interaction between bacteria and plants.According to genome data and transcriptome data,it is predicted that there are 24 genes in this gene cluster,including two key biosynthetic genes and three transcription factors.The synthesized secondary metabolites are non-ribosomal peptide synthase(NRPS).Five mutant strains were obtained through molecular techniques such as gene knockout and overexpression.Compared with the PC-170 strain,the effect of the mutant strain on plants has undergone some changes,indicating that the secondary metabolites synthesized by the gene cluster are likely to function in the bacteria-plant-nematode interaction.By comparing the secondary metabolites of the PC-170 strain and the mutant strain in different media,the No.2 medium suitable for further separation of the synthesis products of the No.3 gene cluster was screened.At the same time,it was also verified that the direct use of crude extraction could not play the role of promoting growth and inducing resistance well,and further separation and purification of secondary metabolites was required.6.Using three varieties of Summer black,Kyoho and Shine Musca,the influence of PC-170 on grapes was explored under greenhouse and field.It was observed that PC-170 can colonize grape roots.PC-170 can promote the growth of the root system and above-ground part of grapes,no matter in the greenhouse conditions or in the field conditions.Three grape varieties have shown the effect of promoting growth.At the same time,PC-170 can improve the soil conditions of grapes and promote the absorption of soil nutrients and minerals by the roots.PC-170 can also improve the resistance of grapes to root-knot nematodes.Under greenhouse conditions,the biocontrol effect of nematodes can reach about 40%,and under natural conditions,the biocontrol effect of nematode can reach 20%.Above,it shows that PC-170 can be used as a biological agent in the production of grapes.It was also observed under field conditions that Moldova’s root system itself is resistant to nematodes,but PC-170 can also promote the growth of Moldova.