关键词: 植物免疫调节剂, 多粘类芽孢杆菌, 枯草芽孢杆菌, 当归

Abstract: The rhizosphere soil fungal community comprises both biocontrol fungi and pathogenic fungi. Understanding its composition and functions helps reveal the mechanisms underlying plant diseases and provides new insights for the green control of continuous cropping obstacles. In this study, continuous cropping of Angelica sinensis was used as the research subject, with four treatments: salicylic acid group (S.RH), methyl jasmonate group (M.RH), composite microbial agent group (DK.RH), and control group (C.RH). Disease incidence and yield were assessed with conventional methods. The contents of endogenous plant hormones, including auxins, cytokinins, gibberellins, abscisic acid, ethylene, melatonin, jasmonic acid, and salicylic acid, were detected via high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The diversity of rhizosphere soil fungi was evaluated using Illumina Miseq high-throughput sequencing, and the composition, diversity, species differences, function and correlation prediction of soil fungal communities were analyzed. The results showed that both salicylic acid and methyl jasmonate treatments reduced the incidence of root rot and yield. Compared with the control, the methyl jasmonate treatment decreased root rot incidence by 43.6% and the average weight per hundred plant individuals by 17.4%, while the salicylic acid treatment reduced root rot incidence by 46.2% and the average weight per hundred plant individuals by 20.6%. The composite microbial agent treatment reduced the endogenous levels of salicylic acid and jasmonic acid in plants, while increased the abscisic acid content. The log₂FC value of methyl salicylate glucoside was negative infinity (-Inf). The log_2-FC values for 12-hydroxyjasmonic acid, jasmonoyl isoleucine, and jasmonic acid were -1.25, -2.02, and -2.10, respectively, whereas those for abscisic acid, abscisic aldehyde, and abscisic acid glucosyl ester were 1.49, -Inf, and 1.03, respectively. Both salicylic acid and methyl jasmonate treatments promoted the enrichment of Trichoderma fungi, with salicylic acid additionally enhancing the enrichment of mycorrhizal fungi. In contrast, the composite microbial agent treatment led to the enrichment of Fusarium and Rhizoctonia fungi in the rhizosphere soil, whereas the control group primarily exhibited enrichment of Aspergillus fumigatus and Cladosporium cladosporioides. In conclusion, foliar spraying can modulate the composition of rhizosphere microbial communities and disease incidence by regulating endogenous hormone levels, particularly through altering the balance among abscisic acid, salicylic acid, and jasmonic acid.

Key words: plant immune modulator, Paenibacillus polymyxa, Bacillus subtilis, Angelica sinensis