Seed Bacterial Microbiome in Spring Bread Wheat Varieties of the Ural-Siberian Forest-Steppe Ecogeographical Group

Abstract This study investigated three varieties of spring bread wheat (Triticum aestivum L.): Omskaya 35, Uralosibirskaya, and Uralosibirskaya 2 from the Ural-Siberian forest-steppe ecogeographical group, which occupies one of the northernmost wheat cultivation areas in the world. These wheats are characterized by a unique adaptation strategy to early drought, involving slow growth during the germination-heading period, followed by accelerated development fueled by late-summer rains. We hypothesized that this adaptation, combined with the low mean annual temperature of the group’s cultivation area, would shape the composition of its seed bacterial microbiome. Here we present the first metagenomic analysis of the seed bacterial endophyte community in these varieties, using 16S rRNA gene metagenomic sequencing. Our main finding is that the key taxon in all varieties was the genus Pantoea, which appears to be associated with the plants' adaptation to the local agroclimatic conditions. Surprisingly, no bacteria of the genus Bacillus were detected in any cultivar. We propose that the absence of Bacillus may be a consequence of the drought resistance strategy, as the host plant’s slow initial growth may require alternative symbiotic mechanisms. These findings highlight the unique microbiome structure of this ecogeographical group and open new questions about the functional roles of its dominant taxa.