Abstract: This study aimed to investigate the composition and metabolic pathways of endophytic microbial communities in Chaenomeles speciosa (Sweet) Nakai from different genuine production areas and to analyze the correlation between endophytic microbial metabolism and active substance accumulation in C. speciosa (Sweet) Nakai in order to provide a reference for developing geographical origin-specific markers and exploring functional endophytic microbial communities in this plant. Fresh papaya fruits from three genuine production areas were analyzed for endophytic microbial communities and active substance contents using high-throughout sequencing and high-performance liquid chromatography (HPLC). The results revealed that the geographical origin of C. speciosa (Sweet) Nakai affected endophytic bacterial diversity less than endophytic fungi diversity. The closer the geographical distance between two production areas, the smaller the difference in the diversity of endophytic microbial communities. The geographical origin had little effect on the major flora types and relative abundance of endophytic bacteria in C. speciosa (Sweet) Nakai, with the main bacterial genera being Lactobacillus, Photobacterium, Lachnospiraceae_NK4A136_group. However, the geographical origin significantly affected the major flora types and relative abundance of endophytic fungal communities, with the genera Candida, Ramularia, Cladosporium, Humicola, and Phialocephala being significantly enriched in papaya samples from one or two production areas. The total content of oleanolic acid and ursolic acid varied significantly among different production areas, while it showed a small correlation with the accumulation of the terpenoid precursor isopentenyl pyrophosphate synthesized by endophytic microorganisms. The main endophytic bacterial communities involved in the synthesis of isopentenyl pyrophosphate were Lachnospiraceae_NK4A136_group, Photobacterium, and Lactobacillus, and the main fungal communities involved in the synthesis of isopentenyl pyrophosphate were Candida, Ramularia, and Cladosporium. This study lays the foundation for establishing a method for the geographical origin identification of C. speciosa (Sweet) Nakai and for developing a microbial consortium that synthesizes terpene precursors in this plant.

Key words: Chaenomeles speciosa (Sweet) Nakai; endophytic microorganisms; genuine production areas; oleanolic acid; ursolic acid