Interactive Effects of Epichloë Endophyte, Dormancy-Breaking Treatments and Geographic Origin on Seed Germination of Achnatherum inebrians

Early inoculation and bacterial community assembly in plants: A review

The relationship between plants and early colonizing microbes is crucial for regulating agricultural ecosystems. Recent evidence strongly suggests that by introducing beneficial microbes during the seed or seedling stages, the diversity and assembly structure of the plant-related microbial community during later plant development can be altered, recruiting beneficial bacteria to enhance plant protection. However, the mechanisms of community assembly and their effects on plant growth are still not fully understood. To deepen our understanding of the importance of early inoculation for improving plant performance, this review comprehensively summarizes recent research advancements on the effects of early introduction on plant growth and adaptability. The mechanisms and ecological significance of early inoculation in the assembly of plant-related bacterial communities are discussed, with particular emphasis on the importance of seed endophytes, plant growth-promoting rhizobacteria (PGPR), and synthetic microbial consortia as microbial inoculants in enhancing plant health and productivity. Additionally, this review proposes a new strategy: sequential inoculation during the seed and seedling stages, aiming to maximize the effects of microbes.

Host-endophyte (Epichloë occultans) interaction impacts on annual ryegrasses (Lolium persicum and Lolium rigidum): ecological and breeding implications

MAIN CONCLUSION

Grass endophytic symbionts interact with the host depending on the host's genetic background and environmental pressures, aiming for survival. Lolium persicum, a self-pollinating annual grass, is suggested for studying such an interaction. Most grasses host endophytic fungi, co-evolved organisms that can interact with their hosts from antagonism to mutualism. This study examined the impact of mating systems on host-endophyte interactions by utilizing endophyte-infected (E+) and endophyte-free (E-) populations of self-pollinating Lolium persicum and open-pollinating Lolium rigidum, collected from three regions of Iran. The evaluations in a pre-breeding process and two experiments were conducted on 1400 plants screened to select 126 half-sib (L. rigidum) and full-sib (L. persicum) families based on a limited space stress, morphological traits, and seed dormancy, respectively. It was found that endophytes generally have a significant and positive effect on reproductive traits and promoting effects in plants to strive for survival. Their impacts were population-dependent, and the E+ plants were superior when a population had higher biomass production and seed yield-related traits. Endophytes help to maintain the host's genetic structure over generations, particularly in L. persicum. In this way, E+ populations exhibited the highest heritability and genetic advance for endophyte-host survival traits such as seed weight, number of seeds, plant height, and days to tillering in both species. In L. persicum, this also included acid-detergent fiber, neutral detergent fiber, crude protein, fat content, phosphorus content, number of tillers, and days to emergence. We demonstrated that artificial selection of morphological traits influenced plant-fungal fitness, such that selecting against seed dormancy significantly increased seed shattering but decreased fungal fitness.

Endophytic fungi in buckwheat seeds: exploring links with flavonoid accumulation

Buckwheat is a famous edible and medicinal coarse cereal which contain abundant of bioactive flavonoids, such as rutin. In this study, the composition and diversity of endophytic fungi in eight different buckwheat seeds were analyzed by high-throughput sequencing of ITS rDNA. Results showed that, the fungal sequences reads were allocated to 272 OTUs, of them, 49 OTUs were shared in eight buckwheat seeds. These endophytic fungi could be classified into 6 phyla, 19 classes, 41 orders, 79 families, 119 genera, and 191 species. At genus level, Alternaria sp. was the domain fungal endophyte. Besides, fungal endophytes belonged to the genera of Epicocum, Cladosporium, Botrytis, Filbobasidium, Stemphylium, and Vishniacozyma were highly abundant in buckwheat seeds. The total flavonoids and rutin contents in tartary buckwheat cultivars (CQ, XQ, CH, K2) were much higher than those in common buckwheat cultivars (HT, T2, T4, T8). For tartary buckwheat cultivars, the total flavonoids and rutin contents were ranging from 2.6% to 3.3% and 0.9% to 1.3%, respectively. Accordingly, the tartary buckwheat samples displayed stronger antioxidant activity than the common buckwheat. Spearman correlation heat map analysis was successfully found that certain fungal species from the genera of Alternaria, Botryosphaeria, Colletorichum and Diymella exhibited significant positive correlation with flavonoids contents. Results of this study preliminary revealed the fungi-plant interaction relationship at secondary metabolite level, and could provide novel strategy for increasing the flavonoids accumulation of buckwheat seeds, as well as improving their quality.

Seed fungal endophytes as biostimulants and biocontrol agents to improve seed performance

Seed germination is a major determinant of plant development and final yield establishment but strongly reliant on the plant's abiotic and biotic environment. In the context of global climate change, classical approaches to improve seed germination under challenging environments through selection and use of synthetic pesticides reached their limits. A currently underexplored way is to exploit the beneficial impact of the microorganisms associated with plants. Among plant microbiota, endophytes, which are micro-organisms living inside host plant tissues without causing any visible symptoms, are promising candidates for improving plant fitness. They possibly establish a mutualistic relationship with their host, leading to enhanced plant yield and improved tolerance to abiotic threats and pathogen attacks. The current view is that such beneficial association relies on chemical mediations using the large variety of molecules produced by endophytes. In contrast to leaf and root endophytes, seed-borne fungal endophytes have been poorly studied although they constitute the early-life plant microbiota. Moreover, seed-borne fungal microbiota and its metabolites appear as a pertinent lever for seed quality improvement. This review summarizes the recent advances in the identification of seed fungal endophytes and metabolites and their benefits for seed biology, especially under stress. It also addresses the mechanisms underlying fungal effects on seed physiology and their potential use to improve crop seed performance.'

Responses of community traits and soil characteristics of Achnatherum inebrians-type degraded grassland to grazing systems in alpine meadows on the Qinghai-Tibet Plateau

Introduction

Scientific grazing management is of great significance for the ecological health and sustainable use of alpine meadows.

Methods

To explore appropriate management methods of alpine grasslands of the Qinghai-Tibet Plateau degraded by Achnatherum inebrians (Hance) Keng ex Tzvele presence, we studied the effects of different grazing systems on the A. inebrians population, grassland vegetation community traits, soil characteristics and soil microbial community structure for cold- season grazing plus supplementary feeding pasture (CSF) and four-season open public pasture (FOP) in Tianzhu County, Gansu Province.

Results

Compared with FOP, the CSF site showed significantly inhibited reproduction of A. inebrians, especially the crown width, seed yield and number of reproductive branches per plant were as high as 50%, significantly increased the aboveground biomass of edible forage and soil water content by 57% and 43-55%, better soil nutrients, and significantly reduced soil bulk density by 10- 29%. Different grazing systems affected the composition and diversity of soil microbial communities, with a greater effect on fungi than on bacterial flora. The most abundant phyla of bacteria and fungi were Proteobacteria and Ascomycota for CSF (by 30-38% and 24-28%) and for FOP (by 67-70% and 68-73%), and the relative abundance and species of bacterial and fungal genera were greater for CSF than FOP. The α-diversity indexes of fungi were improved, and the β-diversity of fungi was significant difference between CSF and FOP. However, the grazing utilization time was prolonged in FOP, which reduced the diversity and abundance of soil bacteria and increased soil spatial heterogeneity. The use of A. inebrians-type degraded grassland in the cold season, and as a winter supplementary feeding and resting ground, could effectively inhibit expansion of A. inebrians, promote edible forage growth, enhance grassland productivity and community stability, and improve soil structure.

Discussion

The results guide healthy and sustainable utilization of A. inebrians-type degraded grassland in the Qinghai-Tibet Plateau.

Special Issue “Microbial Endophytes: Functional Biology and Applications”: Editorial

Plants harbour various microbial communities, including bacteria, fungi, actinomycetes, and nematodes, inside or outside their tissues [...]

Effects of Seed Endophytic Bacteria on Life History and Reproductive Traits in a Cosmopolitan Weed, Capsella bursa-pastoris

Diverse bacteria inhabit plant seeds, and at least some of them can enhance plant performance at the early developmental stage. However, it is still inconclusive whether seed bacteria can influence post-germination traits and their contribution to plant fitness. To explore the evolutionary and ecological consequences of seed endophytic bacteria, we isolated four bacterial strains from the seeds of an annual weedy plant species, Capsella bursa-pastoris, and conducted a common garden experiment using seeds inoculated by isolated bacteria. Seeds infected by bacteria tended to germinate in spring rather than in autumn. Bacterial treatment also altered the expression of plant life history and reproductive traits, including flowering dates, rosette diameter at bolting, number of inflorescences, and fruit production. The results of the path analyses suggested that such effects of bacterial treatments were due to bacterial inoculation as well as germination delayed until spring. Spring germinants with bacterial infection showed a weaker association between post-germination traits and relative fitness than those without bacterial infection. These results suggest that seed bacteria likely affect the expression of post-germination traits directly or indirectly by delaying the germination season. An altered contribution of plant traits to relative fitness implies the influence of seed bacteria on the strength of natural selection.

Mowing Facilitated Shoot and Root Litter Decomposition Compared with Grazing

Shoot and root litter are two major sources of soil organic carbon, and their decomposition is a crucial nutrient cycling process in the ecosystem. Altitude and land use could affect litter decomposition by changing the environment in mountain grassland ecosystems. However, few studies have investigated the effects of land use on litter decomposition in different altitudes. We examined how land-use type (mowing vs. grazing) affected shoot and root litter decomposition of a dominant grass (Bromus inermis) in mountain grasslands with two different altitudes in northwest China. Litterbags with 6 g of shoot or root were fixed in the plots to decompose for one year. The mass loss rate of the litter, and the environmental attributes related to decomposition, were measured. Litter decomposed faster in mowing than grazing plots, resulting from the higher plant cover and soil moisture but lower bulk density, which might promote soil microbial activities. Increased altitude promoted litter decomposition, and was positively correlated with soil moisture, soil organic carbon (SOC), and β-xylosidase activity. Our results highlight the diverse influences of land-use type on litter decomposition in different altitudes. The positive effects of mowing on shoot decomposition were stronger in lower than higher altitude compared to grazing due to the stronger responses of the plant (e.g., litter and aboveground biomass) and soil (e.g., soil moisture, soil bulk density, and SOC). Soil nutrients (e.g., SOC and soil total nitrogen) seemed to play essential roles in root decomposition, which was increased in mowing plots at lower altitude and vice versa at higher altitude. Therefore, grazing significantly decreased root mass loss at higher altitude, but slightly increased at lower altitude compared to mowing. Our results indicated that the land use might variously regulate the innate differences of the plant and edaphic conditions along an altitude gradient, exerting complex impacts in litter decomposition and further influencing carbon and nutrient cycling in mountain grasslands.