Effects Of Rhizosphere Growth-promoting Strains On The Growth And Quality Of Chrysanthemum ‘Hongxinju’

Chrysanthemum(Chrysanthemum morifolium Ramat.)is a kind of plant with ornamental value,medicinal value,edible value and tea value.However,at present,the chrysanthemum tea industry can’t meet the requirements of market for high yield and high quality,and the traditional methods of fertilizer and pesticide application have caused huge environmental pressure on the soil,and will also bring about pesticide residues in chrysanthemum tea,which will endanger human health.Therefore,it is urgent to find a green and effective method to improve the yield and quality of chrysanthemum tea.Rhizosphere growth-promoting bacteria is a kind of natural soil microbes,and it is a hotspot of current research.This article used Bacillus subtilis,Bacillus amyloliquefaciens,Bacillus velezensis,Pseudomonas aeruginosa and Trichoderma harzianum as materials to study their effects on the growth and quality of chrysanthemum ‘Hongxin’.The main research results are as follows:1.A large number of bacterial strains were isolated from the rhizosphere soil of healthy chrysanthemum.After screening,four strains(BA,BS,BV,PA)with significant growth-promoting effect were obtained,and a fungal strain(TH)with significant growth-promoting effect was obtained from the rhizosphere soil of healthy cucumber.Bacteria were identified as Bacillus amyloliquefaciens(BA),Bacillus subtilis(BS),Bacillus velezensis(BV),Pseudomonas aeruginosa(PA)and Trichoderma harzianum(TH).2.Set four treatments with Bacillus amyloliquefaciens and Bacillus subtilis as experimental materials,including blank control(CK),Bacillus subtilis single inoculation treatment group(BS),Bacillus amyloliquefaciens single inoculation treatment group(BA),Bacillus amyloliquefaciens and Bacillus subtilis mixed inoculation treatment group(BA-BS).Appearance and root index were measured at different growth stages.Yield and quality indexes were measured at flowering stage.The results showed that the growth promotion effect of mixed inoculation treatment group(BA-BS)was better than that of single inoculation of the two strains.In seeding stage,compared with CK,the crown width,fresh weight of aboveground,dry weight of aboveground and fresh weight of underground,dry weight of increased by 25.23%,86.64%,161.71%,128.57% and 80.00%,respectively.In flowering stage,compared with CK,the plant height,crown width,fresh weight of aboveground,dry weight of aboveground increased by 21.75%,51.74%,53.88% and56.79%,respectively,and the flower number per plant and estimated yield increased by111.29% and 152.00%,respectively,which were significantly higher than those of other treatments.All quality indexes of the treatment group reached significant level compared with the control group.The content of flavonoids of mixed inoculation treatment group(BA-BS)increased by 15.64%,which was significantly higher than that of other treatments.3.Set five treatments with Bacillus velezensis,Pseudomonas aeruginosa,Trichoderma harzianum as experimental materials,including blank control(CK),Bacillus velezensis single inoculation treatment group(BV),Pseudomonas aeruginosa single inoculation treatment group(PA),Trichoderma harzianum single inoculation treatment group(TH),Bacillus velezensis,Pseudomonas aeruginosa and Trichoderma harzianum mixed inoculation treatment group(BV-PA-TH).Untargeted metabonomics analysis was carried out at the flowering stage to study the changes of secondary metabolites in the head inflorescence of the main application parts of Chrysanthemum ‘Hongxinju’.1781 and 1432 metabolites were identified in the positive and negative ion modes,respectively,which mainly included organic acids,lipids,flavonoids,alkaloids and other metabolites,and they mainly concentrated in carbohydrate,amino acid and flavonoid metabolic pathways.Principal component analysis(PCA)showed that the Bacillus velezensis single inoculation treatment group(BV)was the most discrete from the control group.There was no significant difference between the two treatment groups containing Trichoderma harzianum and the control group.The content of differential metabolites was the highest in the treatment group of Bacillus velezensis single inoculation treatment group(BV),followed by Pseudomonas aeruginosa single inoculation treatment group(PA).The results of cluster heat map showed that there was significant difference between the control group and the inoculation treatment group,while there was no significant difference between the four inoculation treatment groups.