Microbial-Assisted Wheat Iron Biofortification Using Endophytic Bacillus altitudinis WR10

Microbial-assisted biofortification attracted much attention recently due to its sustainable and eco-friendly nature for improving nutrient content in wheat. An endophytic strain Bacillus altitudinis WR10, which showed sophistical regulation of iron (Fe) homeostasis in wheat seedlings, inspired us to test its potential for enhancing Fe biofortification in wheat grain. In this study, assays in vitro indicated that WR10 has versatile plant growth-promoting (PGP) traits and bioinformatic analysis predicted its non-pathogenicity. Two inoculation methods, namely, seed soaking and soil spraying, with 10⁷ cfu/ml WR10 cells were applied once before sowing of wheat (Triticum aestivum L. cv. Zhoumai 36) in the field. After wheat maturation, evaluation of yield and nutrients showed a significant increase in the mean number of kernels per spike (KPS) and the content of total nitrogen (N), potassium (K), and Fe in grains. At the grain filling stage, the abundance of Bacillus spp. and the content of N, K, and Fe in the root, the stem, and the leaf were also increased in nearly all tissues, except Fe in the stem and the leaf. Further correlation analysis revealed a positive relationship between the total abundance of Bacillus spp. and the content of N, K, and Fe in grains. Seed staining confirmed the enhanced accumulation of Fe, especially in the embryo and the endosperm. Finally, using a hydroponic coculture model, qPCR quantification indicated effective colonization, internalization, translocation, and replication of strain WR10 in wheat within 48 h. Collectively, strain WR10 assisted successful Fe biofortification in wheat in the field, laying a foundation for further large-scale investigation of its applicability and effectiveness.