Vertically transmitted seed core endophytes enhance the drought resistance of Ambrosia artemisiifolia

To identify the vertically transmitted core endophytes in common ragweed, seed microbial communities from 5 geographic populations were compared and seedlings were cultivated in a sterile system. To assess the distribution of vertically transmitted core endophytes in leaf and root microbial communities, the common garden experiment was conducted. To investigate their role in plant growth and drought resistance, the transmitted core endophytes were isolated and inoculated in the pot experiment. The results demonstrated that Bacillus and Pseudomonas were vertically transmitted core endophytic bacteria, which served as keystone taxa in leaf and root microbial networks. The pot experiment showed that Pseudomonas and Bacillus, isolated from seeds, roots, and rhizosphere, promoted common ragweed growth by increasing the indole-3-acetic acid (IAA) content and improved its resistance to drought by increasing the soluble sugar content, augmenting antioxidant enzyme activities, and reducing the accumulation of malondialdehyde (MDA). The vertically transmitted core endophytic bacteria play critical roles in the growth of common ragweed and its