Growth-promoting and disease-control effects of Trichoderma and Mortierella synthetic microbial communities on Panax notoginseng （Burk.） F. H. Chen

【Objective】 To compare the effects of synthetic microbial communities composed of Trichoderma and Mortierella mixing with different concentrations and ratios on alleviating continuous cropping obstacles of Panax notoginseng （Burk.） F. H. Chen， and to screen synthetic microbial communities that could significantly promote the growth and strengthen the disease resistance of Panax notoginseng （Burk.） F. H. Chen， which could provide theoretical basis for developing safe and efficient biocontrol agents for Panax notoginseng （Burk.） F. H. Chen root rot. 【Method】 The plate confrontation assay was utilized to screen compatible strains from seven Trichoderma strains （50FZ1， Z2-2-2， 3NG-1， 2ZG-3， 200FN6， 2ZG， and 500FZ1） and four Mortierella strains （B27， B28， B28-1， and NB28） that exhibited no mutual inhibitory but strong antagonism effects against Panax notoginseng （Burk.） F. H. Chen root rot pathogens. The selected Trichoderma and Mortierella strains were treated with single strain and synthetic microbial communities mixed at different concentrations and ratios of the two. Sterile water of the same volume was used as the control （CK）. The effects of the synthetic microbial communities and the corresponding single strains on alleviating the continuous cropping obstacles of Panax notoginseng （Burk.） F. H. Chen and the induced disease resistance of Panax notoginseng （Burk.） F. H. Chen by the synthetic microbial communities and the corresponding single strains were compared and determined. 【Result】 The plate confrontation assay revealed that Trichoderma 3NG-1 and Mortierella B28-1 exhibited good compati-bility and the strongest antagonistic effect against four root rot pathogens （RS6， M， F3， and Z5）， with Trichoderma 3NG-1 showing inhibition rates exceeding 75.00%. After the synthetic microbial communities composed of strains 3NG-1 and B28-1 was applied to the potted continuously cropped Panax notoginseng （Burk.） F. H. Chen， the synthetic microbial communities with varying concentrations and ratios exhibited varying growth-promoting and disease-resist effects. Compared with CK， synthetic communities 6MT41 （mixing at 40 mL B28-1 + 10 mL 3NG-1 when spore suspension concentration was 1.0×10⁶ spore/mL）， 7MT41 （mixing at 40 mL B28-1 + 10 mL 3NG-1 when spore suspension concentration was 1.0×10⁷ spore/mL）， and 7MT14 （mixing at 10 mL B28-1 + 40 mL 3NG-1 when spore suspension concentration was 1.0×10⁷ spore/mL） significantly increased the survival rate of Panax notoginseng （Burk.） F. H. Chen （P<0.05， the same below） and reduced the incidence of root rot， with a notable synergistic effect. In particular， the 7MT41 treatment reduced the incidence of root rot to 42.50%， and 7MT14 treatment also greatly promoted the growth in height and dry weight of Panax notoginseng （Burk.） F. H. Chen. The synthetic microbial communities with varying concentrations and ratios had different effects on saponin content. Compared with CK， 6MT11 （mixing at 25 mL B28-1 + 25 mL 3NG-1 when spore suspension concentration was 1.0×10⁶ spore/mL）， 7MT11 （mixing at 25 mL B28-1 + 25 mL 3NG-1 when spore suspension concentration was 1.0×10⁷ spore/mL）， and 7MT14 significantly increased the total content of five saponins （R1， Rg1， Re， Rb1， and Rd） in Panax notoginseng （Burk.） F. H. Chen， with better results than single strain treatments. Notably， the total saponin content in the 7MT14 treatment reached the highest （2.84%）， which was as 1.47 times as that of CK. Additionally， the treatments 6MT14 （mixing at 10 mL B28-1 + 40 mL 3NG-1 when spore suspension concentration was 1.0×10⁶ spore/mL）， 7MT41， and 7MT14 could induce Panax notoginseng （Burk.） F. H. Chen to resist subsequent infection by the leaf spot pathogen SL17， and the 7MT14 treatment significantly enhanced the activity of four defense enzymes， namely catalase （CAT）， phenylalanine ammonia-lyase （PAL）， peroxidase （POD）， and superoxide dismutase （SOD），in Panax notoginseng （Burk.） F. H. Chen leaves. 【Conclusion】 Synthetic microbial community 7MT14 significantly promotes the growth of Panax notoginseng （Burk.） F. H. Chen， reduces root rot incidence， enhances systemic resistance， and improves quality， demonstrating its potential as a safe and highly effective biocontrol synthetic microbial community， and be developed into compound agent.