Characterization of Seed Endophytic Microbiota in Pinus massoniana

Seed endophytic microbiota are crucial for plant early development and stress resistance. <i>Pinus massoniana</i> is a key ecological and economic tree species in China, yet it is severely threatened by pine wilt disease (PWD). However, the community composition of <i>P. massoniana</i> seed endophytic microbiota and the persistent symbiosis formed via vertical transmission in seeds remain unclear. We analyzed the endophytic bacterial and fungal microbiota of <i>P. massoniana</i> seeds from four geographic regions using high-throughput 16S rRNA and ITS sequencing to characterize community structure, diversity, and functional potential, providing a basis for endophytic microbiota-based strategies to enhance resistance to PWD. Results showed that both alpha and beta diversity analyses indicated that seed endophytic microbial communities of <i>P. massoniana</i> differed among regions. Bacterial communities were dominated by Pseudomonadota (phylum), Gammaproteobacteria (class), and the genera <i>Klebsiella</i>, <i>norank_f_Pectobacteriaceae</i>, and <i>Lactobacillus</i>. Fungal communities were primarily composed of Ascomycota and Basidiomycota (phylum), Sordariomycetes (class), and the genera <i>Rosellinia</i>, <i>Aspergillus</i>, and <i>Coniophora</i>. Correlation network analysis revealed that fungal networks were characterized by a higher proportion of positive correlations, whereas bacterial networks were more complex. Notably, several genera detected in seeds, including <i>Pseudomonas</i>, <i>Bacillus</i>, and <i>Trichoderma</i>, have also been reported in mature <i>P. massoniana</i> tissues, indicating a potential for putative vertical transmission from mother plants. Functional prediction further suggested that these taxa were enriched in pathways related to terpenoid and polyketide metabolism and saprotrophic functions, which have been implicated in PWD resistance and have been previously reported to exert nematode-suppressive or plant growth-promoting effects. Overall, this study elucidates the community structure and ecological characteristics of seed endophytic microbiota in <i>P. massoniana</i> and identifies potentially beneficial microbial taxa, providing potential support for the future utilization of <i>P. massoniana</i> endophytic microbiota in PWD research.