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Background The development and dispersal of seeds as well as their transition to seedlings represent perhaps the most critical stages of a plant's life cycle. The endophytic and epiphytic microbial interactions that take place in, on, and around seeds during these stages of the plant's life cycle may have profound impacts on plant ecology, health, and productivity. While our understanding of the seed microbiota has lagged far behind that of the rhizosphere and phyllosphere, many advances are now being made. Scope This review explores the microbial associations with seeds through various stages of the plant life cycle, beginning with the earliest stages of seed development on the parent plant and continuing through the development and establishment of seedlings in soil. This review represents a broad synthesis of the ecological and agricultural literature focused on seed-microbe interactions as a means of better understanding how these interactions may ultimately influence plant ecology, health, and productivity in both natural and agricultural systems. Our current understanding of seed-microbe associations will be discussed, with an emphasis on recent findings that specifically highlight the emerging contemporary understanding of how seed-microbe associations may ultimately impact plant health and productivity. Conclusions The diversity and dynamics of seed microbiomes represent the culmination of complex interactions with microbes throughout the plant life cycle. The richness and dynamics of seed microbiomes is revealing exciting new opportunities for research into plant-microbe interactions. Often neglected in plant microbiome studies, the renaissance of inquiry into seed microbiomes is offering exciting new insights into how the diversity and dynamics of the seed microbiome with plant and soil microbiomes as well as the microbiomes of dispersers and pollinators. It is clear that the interactions taking place in and around seeds indeed have significant impacts on plant health and productivity in both agricultural and natural ecosystems.

Background and aims To assess the impacts of soil microbes and plant genotype on the composition of maize associated bacterial communities. Methods Two genotypes of Brazilian maize were planted indoors on sterile sand, a deep underground subsoil, and a nutrient-rich topsoil from the Amazon jungle (terra preta). DNA was extracted from rhizospheres, phyllospheres, and surface sterilized roots for 16S rDNA fingerprinting and next generation sequencing. Results Neither plant genotype nor soil type appeared to influence bacterial diversity in phyllospheres or endospheres. Rhizospheres showed strikingly similar 16S rDNA ordination of both fingerprinting and sequencing data, with soil type driving grouping patterns and genotype having a significant impact only on sterile sand. Rhizospheres grown in non-sterile soils contained greater bacterial diversity than sterile-sand grown ones, however the dominant OTUs (species of Proteobacteria and Bacteroidetes) were found in all rhizospheres suggesting seeds as a common source of inoculum. Rhizospheres of the commercial hybrid appeared to contain less bacterial diversity than the landrace. Conclusions Maize rhizospheres receive diverse bacteria from soil, are influenced by the genotype or treatment of the seed, and are dominated by species of Proteobacteria, Actinobacteria, Bacteroidetes, and Firmicutes. As many dominant 16S rDNA sequences were observed in rhizospheres grown in both sterile and non-sterile substrate, we conclude that the most common bacterial cells in juvenile maize rhizospheres are seed transmitted.

Macroorganisms are colonized by microbial communities that exert important biological and ecological functions, the composition of which is subject to host control and has therefore been described as “an ecosystem on a leash”. However, domesticated organisms such as crop plants are subject to both artificial selection and natural selection exerted by the agricultural ecosystem. Here, we propose a framework for understanding how host control of the microbiota is influenced by domestication, in which a double leash acts from domesticator to host and host to microbes. We discuss how this framework applies to a plant compartment that has demonstrated remarkable phenotypic changes during domestication: the seed.Soldan and co-authors propose an evolutionary framework for understanding how host control of the microbiota is influenced by artificial selection. They go on to discuss the potential effect of domestication syndrome on the seed microbiome and plant-microbe interactions in the spermosphere.

Purpose The study was conducted for exploring efficacy of a prebiotic seed coating formulation on soil microbial communities and it’s potential to enhance soil health and crop productivity. Methods The blackgram seeds were coated with prebiotic seed coating formulation at 4, 6, and 8 g kg −1 of seeds and screened based on the seedling characteristics, rhizosphere activity and root exudates. Two best treatments were forwarded to field trials along with control to examine the spermosphere, rhizosphere activity, crop growth and soil health characteristics. Results In laboratory, prebiotic seed coating formulation at 8 g kg −1 significantly improved blackgram germination (92%), and soil microbial activity. Seedlings from seeds coated with prebiotic formulation released a greater number of unique compounds in root exudates. Field evaluation with t he prebiotic seed coating formulation at 8 g kg −1 , exhibited higher field emergence (90.0%), plant population (19.6 no. m −2 ), and other growth attributes. Spermosphere, rhizosphere microbial activity, dehydrogenase, alkaline phosphatase activity were increased at different growth stages (30 and 60 days after sowing) at 8 g kg −1 . Prebiotic film coating of blackgram seeds at 8 g kg −1 resulted in higher number of pods plant −1 (30.14) and 100 seed weight (4.019 g), which resulted in increased seed yield plant −1 (8.750 g). Conclusion Results demonstrated that prebiotic seed coating of blackgram seeds at 8 g kg −1 improved seed germination, seedling vigour, spermosphere, rhizosphere microbial population, enzyme activity leading to improved soil health and crop productivity. Through the research, prebiotic seed coating technology can be introduced as a novel technology to enhance rhizosphere activity and improve soil health. 

Background: Exposure of seeds to high salinity can cause reduced germination and poor seedling establishment. Improving the salt tolerance of peanut (Arachis hypogaea L.) seeds during germination is an important breeding goal of the peanut industry. Bacterial communities in the spermosphere soils may be of special importance to seed germination under salt stress, whereas extant results in oilseed crop peanut are scarce. Methods: Here, bacterial communities colonizing peanut seeds with salt stress were characterized using 16S rRNA gene sequencing. Results: Peanut spermosphere was composed of four dominant genera: Bacillus, Massilia, Pseudarthrobacter, and Sphingomonas. Comparisons of bacterial community structure revealed that the beneficial bacteria (Bacillus), which can produce specific phosphatases to sequentially mineralize organic phosphorus into inorganic phosphorus, occurred in relatively higher abundance in salt-treated spermosphere soils. Further soil enzyme activity assays showed that phosphatase activity increased in salt-treated spermosphere soils, which may be associated with the shift of Bacillus. Conclusion: This study will form the foundation for future improvement of salt tolerance of peanuts at the seed germination stage via modification of the soil microbes.

Abstract During germination, the seed releases nutrient-rich exudates into the spermosphere, thereby fostering competition between resident microorganisms. However, insight into the composition and temporal dynamics of seed-associated bacterial communities under field conditions is currently lacking. This field study determined the temporal changes from 11 to 31 days after sowing in the composition of seed-associated bacterial communities of winter wheat as affected by long-term soil fertilization history, and by introduction of the plant growth-promoting microbial inoculants Penicillium bilaiae and Bacillus simplex. The temporal dynamics were the most important factor affecting the composition of the seed-associated communities. An increase in the relative abundance of genes involved in organic nitrogen metabolism (ureC and gdhA), and in ammonium oxidation (amoA), suggested increased mineralization of plant-derived nitrogen compounds over time. Dynamics of the phosphorus cycling genes ppt, ppx and cphy indicated inorganic phosphorus and polyphosphate cycling, as well as phytate hydrolysis by the seed-associated bacteria early after germination. Later, an increase in genes for utilization of organic phosphorus sources (phoD, phoX and phnK) indicated phosphorus limitation. The results indicate that community temporal dynamics are partly driven by changed availability of major nutrients, and reveal no functional consequences of the added inoculants during seed germination. Development of the wheat seed-associated microbiome and its functional potential of nitrogen and phosphorous cycling.

Thermal seed treatment can be used as an alternative method to prevent infection by seed-borne diseases, but exposure duration and temperature during thermal treatment are important to maintain high seed viability and emergence whilst decreasing infection rate. A method for predicting suitable treatment parameters to maintain viability and eliminate seed-borne pathogens is therefore needed. Seeds of winter wheat were subjected to thermal treatment at four levels of intensity and pre-treatments with or without imbibition. Treatment impact was measured by metabolome analysis using LC-MS and GC-MS, analysis of spermosphere bacterial and fungal metagenomes using Illumina MiSeq, and detection of presence of Fusarium spp. and Microdochium spp. using ddPCR. The results showed that moderate treatment intensity reduced signs of infection and increased seedling emergence. In imbibed samples, myo-inositol concentration and myo-inositol: glucose ratio were positively correlated with treatment intensity, whereas concentrations of glucose and citric acid were negatively correlated. No correlations were found for non-imbibed samples. Imbibition had a large significant impact on microbial community composition of the wheat spermosphere. Imbibition of wheat seeds prior to thermal treatment altered wheat spermosphere microbiota. The concentration of myo-inositol, potentially in combination with glucose, could be a candidate predictor for suitable thermal treatment intensity of wheat seeds.

Microbial diversity formed by ages of evolution in soils plays an important role in sustainability of crop production by enriching soil and alleviating biotic and abiotic stresses. This diversity is as an essential part of the agro-ecosystems, which is being pushed to edges by pumping agrochemicals and constant soil disturbances. Consequently, efficiency of cropping system has been decreasing, aggravated further by the increased incidence of abiotic stresses due to changes in climatic patterns. Thus, the sustainability of agriculture is at stake. Understanding the microbiota inhabiting phyllosphere, endosphere, spermosphere, rhizosphere, and non-rhizosphere, and its utilization could be a sustainable crop production strategy. This review explores the available information on diversity of beneficial microbes in agricultural ecosystem and synthesizes their commercial uses in agriculture. Microbiota in agro-ecosystem works by nutrient acquisition, enhancing nutrient availability, water uptake, and amelioration of abiotic and abiotic stresses. External application of such beneficial microbiota or microbial consortia helps in boosting plant growth and provides resistance to drought, salinity, heavy metal, high-temperature and radiation stress in various crop plants. These have been instrumental in enhancing tolerance to diseases, insect pest and nematodes in various cropping system. However, studies on the microbiome in revolutionary production systems like conservation agriculture and protected cultivation, which use lesser agrochemicals, are limited and if exploited can provide valuable input in sustainable agriculture production.

Seeds are crucial for plant reproduction, dispersal and agriculture. Seed quality and vigour greatly impact crop production by enabling rapid and uniform germination under various environmental conditions. This leads to healthy seedlings that can withstand both biotic and abiotic stresses, which are particularly important in the context of the accentuation of global climate change. Upon imbibition during germination sensu stricto , seeds release exudates, complex mixtures of organic and inorganic molecules, into the microenvironment surrounding them, known as the spermosphere. These exudates play a pivotal role in seedling development and overall plant fitness by influencing microbial selection, growth and interactions in the spermosphere, ultimately shaping the plant's microbiome. Proteins such as enzymes with protection properties have previously been demonstrated to be released by the seeds in their exudates. However, limited information is available pertaining to peptides in seed exudates. Here, we developed an experimental protocol to extract and identify peptides in the spermosphere of germinating common bean seeds. We showed that our methodology was successful in identifying a broad spectrum of peptides and that extraction solvent choice impacts peptide identification both qualitatively and quantitatively. We also show the possibility of using online prediction tools to predict the properties of identified peptides based on their amino acid sequence. We propose that this approach may be used to identify potential molecules that could be used as candidates for developing strategies to enhance seed quality and improve crop productivity.

Agricultural products such as tea, chocolate, coffee and wine are valued for their sensorial and nutritional qualities. Variation in the growing conditions of a crop can influence the plant’s phenotype, thus it behooves agriculturalists to optimize the conditions on their farms to grow the highest quality product. The set of growing conditions associated with a certain geographic location and its influence on the product’s chemistry is known as terroir. Although terroir plays a significant role in marketing and consumer appreciation as well as product identity and valorization, rarely are the biochemical differences or the factors creating them very well understood. The word derives from the Latin for “land”, suggesting terroir is simply a function of the geographical location where a plant grew, while in its modern usage, terroir is understood to be the result of soil type, climate, landscape, topography, biotic interactions and agricultural practice. Except for fermented food products like wine and chocolate, plant associated microbiomes have been little studied for their contribution to a crop’s terroir; however, modern metagenomics and metabolomics technologies have given scientists the tools to better observe how microbial diversity can impact the chemical variation in plant products. Differences in the microbiomes inhabiting plant organs can change phytochemistry by altering host metabolism, for example increasing the nutrients absorbed by roots that then are deposited in leaves, seeds and fruits. Plant associated microbes can consume plant molecules, removing them from the metabolome, or they can contribute smells and flavors of their own. This review aims to synthesize research into rhizosphere, endosphere, phyllosphere, spermosphere, carposphere, and anthosphere microbiome influences on plant biochemistry and crop derived products, while helping to increase the appreciation that beneficial microbes are able to contribute to agriculture by improving phytochemical quality.