Multiomics Reveals Mechanisms of Alternaria oxytropisInhibiting Pathogenic Fungi in Oxytropis ochrocephala

Endophytic fungi can benefit the host plant and increase the plant resistance. Now, there is no in-depth study of how Alternaria oxytropis(A. oxytropis) is enhancing the ability of inhibiting pathogenic fungi in Oxytropis ochrocephala(O. ochrocephala). In this study, the fungal community and metabolites associated with endophyte-infected (EI) and endophyte-free (EF) O. ochrocephalawere compared by multiomics. The fungal community indicated that there was more A. oxytropis, less phylum Ascomycota, and less genera Leptosphaeria, Colletotrichum, and Comoclathrisin the EI group. As metabolic biomarkers, the levels of swainsonine and apigenin-7-O-glucoside-4-O-rutinoside were significantly increased in the EI group. Through in vitro validation experiments, swainsonine and apigenin-7-O-glucoside-4-O-rutinoside can dramatically suppress the growth of pathogenic fungi Leptosphaeria sclerotioidesand Colletotrichum americae-borealisby increasing the level of oxidative stress. This work suggested that O. ochrocephalacontaining A. oxytropiscould increase the resistance to fungal diseases by markedly enhancing the content of metabolites inhibiting pathogenic fungi.