Studies On Mechanism Of Growth Promotion And Disease Resistance Of Tomato Induced By Beauveria Bassiana

Beauveria bassiana is an entomogenic fungus widely used in the biological control of agricultural and forestry pests.Recent studies have shown that B.bassiana has a dual ecological niche,which can not only infect pests,but also colonize plants to promote growth and increase disease resistance.However,the mechanism of action of B.bassiana remains to be further studied.In particular,the effect of endophytic colonization of B.bassiana on the rhizosphere microbial community in plant soil remains unclear.The effects of blastospore colonization of B.bassiana,tomato(Solanum lycopersicum)and B.cinerea on the growth of tomato plants and the resistance to B.cinerea were studied.The effects of the persistence of B.bassiana spores on soil physicochemical properties and bacterial community structure and diversity in rhizosphere soil were measured.The effects of colonization of B.bassiana on differential metabolites in rhizosphere soil of tomato plants were studied.The main research results are as follows:1.Blastospore of B.bassiana can promote the growth of tomato.Total root length,projected area and root surface area of tomato plants in B.bassiana treatment group were significantly increased compared with control group.The number of roots of B.bassiana treated components was 204% higher than that of the control group.Compared with the control group,the plant height of tomato in Bb treatment group increased by 14.2%.Comparing the biomass,we found that the aboveground fresh weight of Bb treatment group increased by 66% compared with the control group.There was no significant difference in the underground fresh weight of Bb treatment group,and the underground dry weight of Bb treatment group was 114% higher than the control group.2.Blastospore of B.bassiana can improve the disease resistance of tomato.The results of experiment on tomato leaves in vitro showed that colonization of B.bassiana could significantly reduce the incidence of botrytis cinerea.The incidence of botrytis cinerea in B.bassiana treatment group was 23.33% lower than that in botrytis cinerea treatment group,and the onset time was late.The results showed that PPO and PAL enzyme activities in tomato leaves were increased after B.bassiana treatment,which indicated that B.bassiana treatment could induce the expression of related defense enzymes in tomato seedlings.Fluorescence quantitative PCR results of different genes showed that the eight target genes were mainly concentrated in plant pathogen interaction,MAPK signaling pathway-plant,steroid biosynthesis,photosynthesis and panquinone biosynthesis pathway of terpenoid compounds,and their expression levels were positively regulated.3.Endophytic colonization of B.bassiana caused changes in the rhizospher e soil microbial community of tomato.There were 958 bacterial OTUs in each treatment group.In the four treatment groups,the dominant bacteria belonged to Pseudomonas 6.6%,Vicinamibacteraceae 7.4%,Pseudarthrobacter 11.5%,M assilia 14.1% and Sphingomonas was 18.4%,and the number of Sphingomonas in Bb treatment group was 0.15% higher than that in CK control group.Anal ysis of the structure and composition of the rhizosphere soil microbial commun ity concluded that anaerobes,Lysobacter＿sp.,Parasegetibacter＿luojiensis,and ac tinobac w WH12 Microvirga＿aerilata and Aquimonas＿sp.,were the dominant spe cies with significant differences,and the relative abundance in the Bb treated g roup was higher than that in the control group.4.Endophytic colonization of B.bassiana had significant effects on rhizosphere soil metabolic characteristics of tomato.The results showed that 79 rhizosphere soil metabolites were annotated to 3 biological metabolic pathways in the B.bassiana treatment group,among which 4 metabolites were annotated to environmental information processing,1 metabolite was annotated to genetic information processing,and 74 metabolites were annotated to metabolism.The results of soil differential metabolites analysis showed that 16 positive ion mode metabolites in rhizosphere soil of B.bassiana treated group were significantly different,among which 14 metabolites were up-regulated and 2 metabolites were down-regulated.Eleven negative ion mode metabolites were significant,four were upregulated and seven were downregulated.By analyzing the correlation of differential metabolites and the relative content of differential metabolites,The results showed that L-Tyrosine,D-Proline,12-Oxo phytodienoic acid,and lndole-3-acrylic were obtained in the B.bassiana treatment group acid was the metabolite with the highest correlation of differential metabolites.The D-Proline,Tributy citrate,and lndole-3-acrylic in the Bb treatment group were acrylic acid,gamma-Glutamyltyrosine and the relative contents of these four metabolites were significantly higher than those of the control group.This study demonstrated that colonization of B.bassiana can promote plant growth and improve disease resistance,and clarified the mechanism of insectogenic fungi in enhancing plant disease resistance from the perspective of changes of soil metabolites and microbial community structure by B.bassiana.This study can lay a theoretical foundation for the study of entomogenous fungus-plant-rhizosphere microorganisms interaction,and provide a theoretical basis for the rational use of entomogenous fungi for biological control.