Abstract
Seeds play key roles in the acquisition of plant pioneer microbiota, including the transmission of microbes from parent plants to offspring. However, the issues about seed microbial communities are mostly unknown, especially for their potential origins and the factors influencing the structure and composition. In this study, samples of rice seed and rhizosphere were collected from northeast and central-south China in two harvest years and analyzed using a metabarcoding approach targeting 16S rRNA gene region. A higher level of vertical transmission (from parent seed microbiota to offspring) was revealed, as compared to the acquisition from the rhizosphere (25.5 vs 10.7%). The core microbiota of the rice seeds consisted of a smaller proportion of OTUs (3.59%) than that of the rice rhizosphere (7.54%). Among the core microbiota, species in Arthrobacter, Bacillus, Blastococcus, Curtobacterium, Pseudomonas, and Ramlibacter have been reported as potential pathogens and/or beneficial bacteria for plants. Both the seed and the rhizosphere of rice showed distance-decay of similarity in microbial communities. Seed moisture and winter mean annual temperature (WMAT) had significant impacts on seed microbiota, while WMAT, total carbon, available potassium, available phosphorus, aluminum, pH, and total nitrogen significantly determined the rhizosphere microbiota. Multiple functional pathways were found to be enriched in the seed or the rhizosphere microbiota, which, to some extent, explained the potential adaptation of bacterial communities to respective living habitats. The results presented here elucidate the composition and possible sources of rice seed microbiota, which is crucial for the health and productivity management in sustainable agriculture.
Highlights
Seeds, the most remarkable vectors in plants’ life, enable plants to give rise to new generations (Gundel et al, 2011; Mitter et al, 2017)
The FEAST analysis revealed that the former had higher contribution (25.5% in average, from 10.1 to 34.2%) to the seed microbiota in 2016 than the latter did (10.7% in average, from 5.6 to 17.8%) (Supplementary Table S2), suggesting that the microbiota of the parent seeds is the main source of the offspring seed microbiota
In an agricultural ecosystem with homogenized landscape and biodiversity evenness, the FEAST analysis suggested that about 25.5% of the seed microbiota was likely inherited from the parent seed and about 10.7% of the seed microbiota was likely acquired from the rhizosphere soil microbiota
Summary
The most remarkable vectors in plants’ life, enable plants to give rise to new generations (Gundel et al, 2011; Mitter et al, 2017). Seed may acquire soilor airborne microorganisms (horizontal transmission) from the surrounding environments, which play important roles for plant health (Gundel et al, 2011; Shade et al, 2017). When germinating, the seed releases nitrogen-rich compounds, which may attract microbial inhabitants from the surrounding environment in establishing the spermosphere (Nelson, 2004). These attracted microbiota could promote plant germination and growth by producing phytohormone, and/or protect seedlings from soil-borne pathogens at the vulnerable stage (BacilioJiménez et al, 2001). The relative importance of horizontal and vertical transmissions that contribute to the rice seed microbiota remains unclear (Shade et al, 2017)
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