Total Root Length Research Articles

Genome-Wide and Transcriptome-Wide Association Analysis Identifies qRS-6D and Its Candidate Genes Regulating Root Development of Wheat Seedlings

Wheat (Triticum aestivum L.) is one of the most important cereal crops worldwide, and its production is challenged by global climate change and a shortage of resources. The root system plays a vital role in uptaking water and nutrients and sensing soil environmental signals, and it has great potential to improve the final yield and stress tolerance of wheat. In order to further explore the genes regulating root development, this study focused on qRS-6D, located on chromosome 6D and spanning from 462,701,391 to 465,068,943, which was significantly associated with the total root length, root volume, root surface, and root fresh weight in our previous GWAS analysis. Firstly, its genetic effects were validated using an F6 segregating population by comparing the root-related traits of homologous lines harboring the alternative haplotypes of this QTL. Then, the number of causal genes of this QTL was narrowed down to four with a transcriptome-wide association study. Additionally, qRS-6D has been demonstrated to have genetic effects on several yield- (kernel length, kernel width, and thousand-kernel weight) and plant structure-related traits (plant height, peduncle length, total tiller number, productive tiller number, flag leaf length, and flag leaf angle). Relatively, the frequency of the favorable haplotype increased with the wheat breeding practice. This study provides a reliable genetic locus to improve root development and structure and evaluate its application potential in wheat breeding improvement.

Dissecting root system architecture traits in durum wheat–goatgrass (Triticum durum–Aegilops speltoides) backcross introgression lines

AbstractA well‐developed root system is essential for efficient nutrient and water uptake. We phenotyped a set of 172 Triticum durum–Aegilops speltoides backcross introgression lines (BILs) for various root architecture traits during 2019–2020 and 2020–2021 cropping seasons. The roots were sampled at the maximum tillering stage, and data on various root architecture traits were recorded. The quantitative trait loci (QTL) mapping was carried out using 5672 polymorphic SNPs obtained from genotyping‐by‐sequencing. A total of 21 QTLs were detected for various root architecture traits on chromosomes 1A, 2A, 2B, 3B, 5A and 6B. Stable QTLs were detected for total root length, number of root tips and root dry weight over the two seasons. Candidate genes were identified by scanning the physical interval corresponding to the linkage disequilibrium (LD) decay flanking the SNPs linked to the stable QTLs. In silico expression studies of postulated candidate genes revealed root‐specific upregulation of some of the genes. These QTLs can be used in breeding programmes after the development and validation of suitable marker assays.

Effects of Bacillus subtilis on Cucumber Seedling Growth and Photosynthetic System under Different Potassium Ion Levels.

Potassium deficiency is one of the important factors restricting cucumber growth and development. This experiment mainly explored the effect of Bacillus subtilis (B. subtilis) on cucumber seedling growth and the photosynthetic system under different potassium levels, and the rhizosphere bacteria (PGPR) that promote plant growth were used to solubilize potassium in soil, providing theoretical support for a further investigation of the effect of biological bacteria fertilizer on cucumber growth and potassium absorption. "Xinjin No. 4" was used as the test material for the pot experiment, and a two-factor experiment was designed. The first factor was potassium application treatment, and the second factor was bacterial application treatment. The effects of different treatments on cucumber seedling growth, photosynthetic characteristics, root morphology, and chlorophyll fluorescence parameters were studied. The results showed that potassium and B. subtilis had obvious promotion effects on the cucumber seedling growth and the photosynthesis of leaves. Compared with the blank control, the B. subtilis treatment had obvious effects on the cucumber seedling height, stem diameter, leaf area, total root length, total root surface area, total root volume, branch number, crossing number, gs, WUE, Ci, and A; the dry weight of the shoot and root increased significantly (p ≤ 0.05). Potassium application could significantly promote cucumber growth, and the effect of B. subtilis and potassium application was greater than that of potassium application alone, and the best effect was when 0.2 g/pot and B. subtilis were applied. In conclusion, potassium combined with B. subtilis could enhance the photosynthesis of cucumber leaves and promote the growth of cucumber.

Comparative transcriptomic and physiological analyses unravel wheat source root adaptation to phosphorous deficiency

Phosphorus (P) is a crucial macronutrient for plant growth and development. Basic metabolic processes regulate growth; however, the molecular detail of these pathways under low phosphorous (LP) in wheat is still unclear. This study aims to elucidate the varied regulatory pathways responses to LP stress in wheat genotypes. Phenotypic, physiological, and transcriptome analyses were conducted on Fielder (P efficient) and Ardito (P inefficient) wheat genotypes after four days of normal phosphorous (NP) and LP stress. In response to LP, Fielder outperformed Ardito, displaying higher chlorophyll content-SPAD values (13%), plant height (45%), stem diameter (12%), shoot dry weight (42%), and root biomass (75%). Root structure analysis revealed that Fielder had greater total root length (50%), surface area (56%), volume (15%), and diameter (4%) than Ardito under LP. These findings highlight Fielder’s superior performance and adaptation to LP stress. Transcriptome analysis of wheat genotype roots identified 3029 differentially expressed genes (DEGs) in Fielder and 1430 in Ardito, highlighting LP-induced changes. Key DEGs include acid phosphatases (PAPs), phosphate transporters (PHT1 and PHO1), SPX, and transcription factors (MYB, bHLH, and WRKY). KEGG enrichment analysis revealed key pathways like plant hormones signal transduction, biosynthesis of secondary metabolites, and carbohydrate biosynthesis metabolism. This study unveils crucial genes and the intricate regulatory process in wheat’s response to LP stress, offering genetic insights for enhancing plant P utilization efficiency.

Phosphorus uptake and rhizosphere properties of alfalfa in response to phosphorus fertilizer types in sandy soil and saline-alkali soil.

Phosphorus (P) fertilizer is critical to maintain a high yield and quality of alfalfa (Medicago sativa L.). There are several fertilizer types and soil types in China, and the application of a single type of P fertilizer may not be suitable for present-day alfalfa production. In order to select the optimal combination of alfalfa and soil type and fertilizer type for improving P utilization efficiency. We conducted a greenhouse pot experiment, calcium superphosphate (SSP), diammonium phosphate (DAP), ammonium polyphosphate (APP), potassium dihydrogen phosphate (KP), and no-fertilizer control treatments were applied to alfalfa in sandy and saline-alkali soils. The response of alfalfa root morphology and rhizosphere processes to different P fertilizers was investigated. The results showed that shoot biomass of alfalfa was slightly higher in sandy soil than in saline-alkali soil. Shoot biomass of alfalfa increased by 223%-354% in sandy soil under P treatments compared with the control, and total root length increased significantly by 74% and 53% in DAP and SSP treatments, respectively. In saline-alkali soil, alfalfa shoot biomass was significantly increased by 229% and 275% in KP and DAP treatments, and total root length was increased by 109% only in DAP treatment. Net P uptake of alfalfa in DAP treatment was the highest in both soils, which were 0.73 and 0.54 mg plant-1, respectively. Alfalfa shoot P concentration was significantly positively correlated with shoot and root biomass (P < 0.05, 0.01 or 0.001) whereas negatively correlated with acid phosphatase concentration (P < 0.05). Improvement of plant growth and P uptake induced by P fertilizer application was greater in sandy soil than in saline-alkali soil. DAP and KP was the most efficient P fertilizers in both sandy soil and saline-alkali soil.

Response of endophyte‐infected and endophyte‐free tall fescue plants to partial submergence at two developmental stages

AbstractTall fescue (Festuca arundinacea Schreb.) is a perennial C3 grass species usually associated with the endophyte fungus Epichloë coenophiala that enhances tolerance to biotic and abiotic stresses. Given that the proportion of infected tall fescue plants in the grasslands of the Flooding Pampa (Argentina) has been progressively increasing, it is proposed that endophytes confer tolerance to the stresses characteristic of that environment, especially flooding. Plants from a naturalized population and a commercial cultivar were grown, both with and without endophyte (wild type and AR584 respectively). The plants were subjected to two submergence treatments (i.e., control and partial submergence) in two development stages (5‐leaf stage and beginning of the elongation of internodes). Plant performance (aerial and root biomass, root aerenchyma formation, total root length and root diameter, proportion of reproductive tillers, number of panicles and seeds produced) and endophyte transmission to progeny were evaluated. Endophytes did not alter the ecological fitness of plants under partial submergence. Independently of the water condition, the symbiosis was linked to low biomass in plants from the naturalized population, while the opposite occurred in plants from the cultivar. Partial submergence did not affect the germination of the seeds produced, nor the transmission of the endophyte to the seedlings that originated from them. Our work suggests that the invasion ability of tall fescue in the Flooding Pampa grasslands is not related to an endophyte‐mediated improvement of plants to tolerate water excess.

Reduced tillering and dwarfing genes alter root traits and rhizo-economics in wheat.

The tiller inhibition (tin) and Reduced height (Rht) genes strongly influence the carbon partitioning and architecture of wheat shoots, but their effects on the energy economy of roots have not been examined in detail. We examined multiple root traits in three sets of near-isogenic wheat lines (NILs) that differ in the tin gene or various dwarfing gene alleles (Rht-B1b, Rht-D1b, Rht-B1c and Rht-B1b + Rht-D1b) to determine their effects on root structure, anatomy and carbon allocation. The tin gene resulted in fewer tillers but more costly roots in an extreme tin phenotype with a Banks genetic background due to increases in root-to-shoot ratio, total root length, and whole root respiration. However, this effect depended on the genetic background as tin caused both smaller shoots and roots in a different genetic background. The semi-dwarf gene Rht-B1b caused few changes to the root structure, whereas Rht-D1b, Rht-B1c and the double dwarf (Rht-B1b + Rht-D1b) decreased the root biomass. Rht-B1c reduced the energy cost of roots by increasing specific root length, increasing the volume of cortical aerenchyma and by reducing root length, number, and biomass without affecting the root-to-shoot ratio. This work informs researchers using tin and Rht genes how to modify root system architecture to suit specific environments.

Intraspecific variation in fine root morphology of European beech: a root order-based analysis of phenotypic root morphospace

Fine roots are multifunctional organs that may change function with ageing or root branching events from primarily absorptive to resource transport and storage functions. It is not well understood, how fine root branching patterns and related root functional differentiation along the longitudinal root axis change with soil chemical and physical conditions. We examined the variation in fine root branching patterns (the relative frequency of 1st to 4th root orders) and root morphological and chemical traits of European beech trees with soil depth (topsoil vs. subsoil) and soil chemistry (five sites with acid to neutral/alkaline bedrock). Bedrock type and related soil chemistry had an only minor influence on branching patterns: base-poor, infertile sites showed no higher fine root branching than base-rich sites. The contribution of 1st-order root segments to total fine root length decreased at all sites from about 60% in the topsoil (including organic layer) to 45% in the lower subsoil. This change was associated with a decrease in specific root area and root N content and an increase in mean root diameter with soil depth, while root tissue density did not change consistently. We conclude that soil depth (which acts through soil physical and chemical drivers) influences the fine root branching patterns of beech much more than soil chemical variation across soil types. To examine whether changes in root function are indeed triggered by branching events or result from root ageing and diameter growth, spatially explicit root physiological and anatomical studies across root orders are needed.

Canine sexual dimorphism in crown and root dimensions: a cone-beam computed tomographic study.

The primary step in forensic odontological analysis is sex determination. The present study is one of the few studies that evaluated the accuracy of the combination of canine tooth root length and crown measurements for sex determination. The study sample comprised 196 cone-be am computed tomographic scans of individuals aged 20-80 years distributed in five age categories: 20-29, 30-39, 40-49, 50-59, and 60+ years old. Different parameters, such as width, length, and ratio measurements for the crown and root of each maxillary and mandibular canine tooth, were examined and recorded. The findings indicated that maxillary canines had greater sex dimorphism ability (87.3%) than mandibular canines (80.6%). Total tooth length and root length of maxillary canine were the most pronounced variables in the differentiation of sex groups. When the combination of the mandibular and maxillary measurements was considered, the accuracy for sex dimorphism was 85.7%. By using ratio variables, the accuracy was reduced to 68.9%. According to the findings of this study, total tooth length and root length are the most discriminant variables of canine teeth. These variables are more reliable sex indicators than crown measurements.

Karst fissures mitigate the negative effects of drought on plant growth and photosynthetic physiology.

Hard limestone substrates, which are extensively distributed, are believed to exacerbate drought and increase the difficulty of restoration in vulnerable karst regions. Fissures in such substrates may alleviate the negative effect of drought on plants, but the underlying mechanisms remain poorly understood. In a two-way factorial block design, the growth and photosynthesis of 2-year-old Phoebe zhennan seedlings were investigated in two water availabilities (high versus low) and three stimulated fissure habitat groups (soil, soil-filled fissure and non-soil-filled fissure). Moreover, the fissure treatments included both small and big fissures. Compared to the soil group, the non-soil-filled fissure group had decreased the total biomass, root biomass, total root length, and the root length of fine roots in the soil layer at both water availabilities, but increased net photosynthetic rate (Pn) and retained stable water use efficiency (WUE) at low water availability. However, there were no significant differences between the soil-filled fissure group and soil group in the biomass accumulation and allocation as well as Pn. Nevertheless, the SF group decreased the root distribution in total and in the soil layer, and also increased WUE at low water availability. Across all treatments, fissure size had no effect on plant growth or photosynthesis. Karst fissures filled with soil can alleviate drought impacts on plant root growth, which involves adjusting root distribution strategies and increasing water use efficiency. These results suggest that rock fissures can be involved in long-term plant responses to drought stress and vegetation restoration in rocky mountain environments under global climate change.

Can Arbuscular Mycorrhizal Fungi Enhance Crop Productivity and Quality in Hydroponics? A Meta-Analysis

Finding environmentally friendly solutions for crop growth and productivity has been gaining more attention recently. This meta-analysis aims to understand the combined application of arbuscular mycorrhizal fungi (AMF) and hydroponic systems compared to AMF in conventional (soil) systems. The analysis of up-to-date studies revealed that the root colonization, calculated as the proportion of colonized root segments relative to the total root length, by AMF in conventional (soil-based) culture exceeded hydroponic (or soilless) culture systems by 16.8%. The mean root colonization by AMF was determined to be 52.3% in hydroponic systems and 61.1% in conventional systems. Within hydroponic systems, the root colonization ranged from 2% to 20% after 10 days of inoculation, and notably, it exceeded 50% after 30 to 65 days, depending on the growing substrate and species. Under hydroponics, AMF application had a higher (compared to none-inoculated) positive effect on crop biomass and yield than fruit and leaf quality (antioxidants, phenols, and sugars) as well as leaf nutrients. However, AMF do not always have the potential to improve crop growth, quality and productivity in hydroponics. Among the studies analyzed in this review, approximately 34% (no effect: 29%; negative: 5%) reported no discernible positive effect on biomass or yield, 37% (no effect: 16%; negative: 21%) on fruit or leaf quality, and 60% (no effect: 47%; negative: 13%) on nutrient levels within plant tissues. To improve the performance of AMF in hydroponic systems, the meta-analysis recommended maintaining phosphorus levels in the nutrient solution within the range of 0.15 to 15.5 mg L−1 as elevated levels (40–75 mg L−1) were found to significantly reduce AMF colonization. Additionally, it was observed that certain hydroponic techniques, such as the presence of air bubbles generated by air pumps in floating hydroponic systems (Deep Flow technique) and continuous circulation of the nutrient solution (Ebb and Flow systems), may create dynamic conditions that could potentially hinder the introduction of AMF spores into hydroponic systems and potentially compromise the integrity of the spores and hyphae.

Antagonistic effect of Bacillus and Pseudomonas combinations against Fusarium oxysporum and their effect on disease resistance and growth promotion in watermelon.

We aimed to develop an effective bacterial combination that can combat Fusarium oxysporum infection in watermelon using in vitro and pot experiments. In total, 53 strains of Bacillus and 4 strains of Pseudomonas were screened. Pseudomonas strains P3 and P4 and Bacillus strains XY-2-3, XY-13, and GJ-1-15 exhibited good antagonistic effects against F. oxysporum. P3 and P4 were identified as Pseudomonas chlororaphis and Pseudomonas fluorescens, respectively. XY-2-3 and GJ-1-15 were identified as B. velezensis, and XY-13 was identified as Bacillus amyloliquefaciens. The three Bacillus strains were antifungal, promoted the growth of watermelon seedlings and had genes to synthesize antagonistic metabolites such as bacilysin, surfactin, yndj, fengycin, iturin, and bacillomycin D. Combinations of Bacillus and Pseudomonas strains, namely, XY-2-3+P4, GJ-1-15+P4, XY-13+P3, and XY-13+P4, exhibited a good compatibility. These four combinations exhibited antagonistic effects against 11 pathogenic fungi, including various strains of F. oxysporum, Fusarium solani, and Rhizoctonia. Inoculation of these bacterial combinations significantly reduced the incidence of Fusarium wilt in watermelon, promoted plant growth, and improved soil nutrient availability. XY-13+P4 was the most effective combination against Fusarium wilt in watermelon with the inhibition rate of 78.17%. The number of leaves; aboveground fresh and dry weights; chlorophyll, soil total nitrogen, and soil available phosphorus content increased by 26.8%, 72.12%, 60.47%, 16.97%, 20.16%, and 16.50%, respectively, after XY-13+P4 inoculation compared with the uninoculated control. Moreover, total root length, root surface area, and root volume of watermelon seedlings were the highest after XY-13+P3 inoculation, exhibiting increases by 265.83%, 316.79%, and 390.99%, respectively, compared with the uninoculated control. XY-13+P4 was the best bacterial combination for controlling Fusarium wilt in watermelon, promoting the growth of watermelon seedlings, and improving soil nutrient availability.

Introgression of early shoot vigour in wheat modifies root systems, increases competitiveness and provides options for integrated weed management

Abstract Background and aims Weeds are a major biotic stressor impacting crop production. Improving the competitiveness of wheat (Triticum aestivum L.) could provide a useful tool in integrated weed management. While wheat typically exhibits conservative early growth, early vigour has been increased through long-term recurrent selection for greater early biomass and leaf area. However, the influence of integrating such vigour into breeding lines for improving competitive ability remains to be explored. Methods In replicated controlled environment experiments, the effect of breeding early shoot vigour on root development and below-ground competitiveness was carefully examined. Physical and chemical characteristics of wheat vigour lines were assessed and compared with commercial cultivars in hydroponics and field soil experiments. Measurements included early root growth, rhizosheath size and growth responses in the presence of annual ryegrass, a major weed in wheat production. Results The vigorous lines exhibited larger leaf widths, increased cell file number, increased total root length and larger rhizosheaths compared with commercial parents. Numerous secondary metabolites with known allelopathic effects on weeds were detected in the roots and the rhizosphere, and significant allelochemical level differences observed between distilled water and soil water extract-treated plants. Although the vigour lines were significantly more competitive than the commercial cultivars against ryegrass, they produced similar levels of phytotoxic secondary metabolites. Conclusion Competition below-ground was strongly suppressive of ryegrass for the more vigorous genotypes suggesting that breeding with shoot vigour had pleiotropic effects on key root traits for below-ground wheat competitiveness.

Neighbour-induced changes in root exudation patterns of buckwheat results in altered root architecture of redroot pigweed

Roots are crucial in plant adaptation through the exudation of various compounds which are influenced and modified by environmental factors. Buckwheat root exudate and root system response to neighbouring plants (buckwheat or redroot pigweed) and how these exudates affect redroot pigweed was investigated. Characterising root exudates in plant–plant interactions presents challenges, therefore a split-root system which enabled the application of differential treatments to parts of a single root system and non-destructive sampling was developed. Non-targeted metabolome profiling revealed that neighbour presence and identity induces systemic changes. Buckwheat and redroot pigweed neighbour presence upregulated 64 and 46 metabolites, respectively, with an overlap of only 7 metabolites. Root morphology analysis showed that, while the presence of redroot pigweed decreased the number of root tips in buckwheat, buckwheat decreased total root length and volume, surface area, number of root tips, and forks of redroot pigweed. Treatment with exudates (from the roots of buckwheat and redroot pigweed closely interacting) on redroot pigweed decreased the total root length and number of forks of redroot pigweed seedlings when compared to controls. These findings provide understanding of how plants modify their root exudate composition in the presence of neighbours and how this impacts each other’s root systems.

C-terminally encoded peptide-like genes are associated with the development of primary root at qRL16.1 in soybean.

Root architecture traits are belowground traits that harness moisture and nutrients from the soil and are equally important to above-ground traits in crop improvement. In soybean, the root length locus qRL16.1 was previously mapped on chromosome 16. The qRL16.1 has been characterized by transcriptome analysis of roots in near-isogenic lines (NILs), gene expression analysis in a pair of lines contrasting with alleles of qRL16.1, and differential gene expression analysis in germplasm accessions contrasting with root length. Two candidate genes, Glyma.16g108500 and Glyma.16g108700, have shown relatively higher expression in longer root accessions than in shorter rooting accessions. The C-terminal domain of Glyma.16g108500 and Glyma.16g108700 is similar to the conserved domain of C-terminally encoded peptides (CEPs) that regulate root length and nutrient response in Arabidopsis. Two polymorphisms upstream of Glyma.16g108500 showed a significant association with primary root length and total root length traits in a germplasm set. Synthetic peptide assay with predicted CEP variants of Glyma.16g108500 and Glyma.16g108700 demonstrated their positive effect on primary root length. The two genes are root-specific in the early stage of soybean growth and showed differential expression only in the primary root. These genes will be useful for improving soybean to develop a deep and robust root system to withstand low moisture and nutrient regimes.

Detection of plant cadmium toxicity by monitoring dielectric response of intact root systems on a fine timescale.

The root dielectric response was measured on a minute scale to assess its efficiency for monitoring short-term cadmium (Cd) toxicity non-destructively. Electrical capacitance (CR), dissipation factor (DR) and electrical conductance (GR) were detected during the 24 to 168 h after Cd treatment (0, 20, 50 mg Cd2+ kg-1 substrate) in potted maize, cucumber and pea. Stress was also evaluated by measuring leaf chlorophyll content, Fv/Fm and stomatal conductance (gs) in situ, and shoot and root mass and total root length after harvest. CR showed a clear diurnal pattern, reflecting the water uptake rate, and decreased significantly in response to excessive Cd due to impeded root growth, the reduced tissue permittivity caused by accelerated lignification, and root ageing. Cd exposure markedly increased DR, indicating greater conductive energy loss due to oxidative membrane damage and enhanced electrolyte leakage. GR, which was coupled with root hydraulic conductance and varied diurnally, was increased transiently by Cd toxicity due to enhanced membrane permeability, but declined thereafter owing to stress-induced leaf senescence and transpiration loss. The time series of impedance components indicated the comparatively high Cd tolerance of the applied maize and the sensitivity of pea cultivar, which was confirmed by visible shoot symptoms, repeated physiological investigations and biomass measurements. The results demonstrated the potential of single-frequency dielectric measurements to follow certain aspects of the stress response of different species on a fine timescale without plant injury. The approach can be combined with widely used plant physiological methods and could contribute to breeding crop genotypes with improved stress tolerance.

Wastewater-Derived Struvite has the Potential to Substitute for Soluble Phosphorus Fertiliser for Growth of Chickpea and Wheat

Phosphorus (P) recycling from wastewater can reduce the reliance on the primary source for P fertilisers―rock phosphate reserves. In light of this, we compared the effects of struvite (ST), a sparingly soluble P product derived from wastewater, and readily soluble KH2PO4 (KP) on chickpea (Cicer arietinum L.) and wheat (Triticum aestivum L.) growth and P acquisition. Plants were grown in a temperature-controlled glasshouse in plastic pots containing a soil mixture with low P availability, with ST or KP applied at five P rates (7, 14, 28, 56 and 112 µg P g− 1 dry soil). Plants were harvested 56 days after sowing when there were visible differences in above-ground growth. Chickpea and wheat growth positively responded to increasing P rates of KP and ST. At low and medium P rates (7, 14, 28 and 56 µg P g− 1 dry soil) of KP and ST, the plants acquired similar amounts of P, while at a higher P rate (112 µg P g− 1 dry soil), plants supplied with ST, accumulated 1.2- to ~ 2.0- fold higher P than KP. Rhizosheath soil pH increased by ~ 0.1–0.7 units under ST than KP for both species. Wheat produced greater total root length but lower amount of rhizosheath carboxylates than chickpea under KP and ST, and wheat accumulated more P than chickpea under KP and ST. Chickpea and wheat can well access P from ST, indicating the great potential of ST as an alternative P fertiliser.

Soil amendment incorporation increases organic carbon by improving soil agglomerate and soil microbial biomass carbon in the alpine grassland

AbstractSoil amendments aiming to enhance soil quality and bolster carbon sequestration have been extensively investigated. However, the specific impacts of diverse soil amendment types on soil total organic carbon content (TOC), soil aggregate and the growth of ryegrass remain largely unexplored, particularly within the unique context of alpine grassland soils in northwest Sichuan. For this, four soil amendments (CK: no soil amendment, CM: cattle manure 2000 kg ha−1, CS: straw amendment 12,000 kg ha−1 and MS: mushroom substrate 18,000 kg ha−1) were applied to alpine grassland soils over a 2‐year duration, conducted in situ during 2017 and 2018, to investigate the influences of these soil amendments on 0–30 cm soil of TOC, total nitrogen (TN), microbial biomass carbon (MBC), soil aggregation, the above‐ground biomass (DMA) and root traits of ryegrass. Compared to CK, the above‐ground biomass exhibited an average of 348.78% in MS, 287.18% in CS and 115.54% in CM, all reaching statistical significance (p &lt; .05). In the topsoil (0–10 cm), the large soil aggregate rate (LSAR &gt; 0.25 mm) showed a significant increase in CM, CS and MS, particularly in 2018, compared to CK. Our findings further indicated that the improvement in alpine grassland LSAR &gt; 0.25 mm was correlated with a rise in TOC by over 69.89% and MBC by more than 27.14%. The MS treatment resulted in a significant increase in above‐ground biomass and TRL (total root length), while also increasing the levels of TN, MBC and soil aggregates (0.25 ~ 0.5 mm) within the 0–10 cm soil. A similar result of CS treatment was observed to increase the total chlorophyll content and RD (root diameter), as well as an increase in SWC and TOC levels. The TN, MBC, TOC and LSAR contributed 44.77%, 20.87%, 6.46% and 6.45% for ryegrass growth. The SEM indicated that soil amendments promote the growth of ryegrass by improving soil agglomerate and increasing MBC, TOC and TN. Our analysis revealed that ryegrass biomass production was limited by soil nutrients in the alpine grassland of northwest Sichuan. The study also highlights the potential impact of soil amendments on future management practices, contributing to a more comprehensive understanding of the subject.

Reduced Strigolactone Synthesis Weakens Drought Resistance in Tall Fescue via Root Development Inhibition

Drought stress significantly hampers plant growth and productivity. Strigolactones (SLs), a class of carotenoid-derived plant hormones, are recognized for their pivotal role in modulating plant morphology and enhancing drought resistance. Nonetheless, the underlying mechanisms through which SLs influence drought tolerance in tall fescue remain largely unexplored. In this study, we employed TIS108 to inhibit SL biosynthesis under drought conditions and assessed a range of morphological and physiological parameters in tall fescue, including biomass both above and below ground, antioxidase activities, proline and soluble sugar contents, and survival rates, across treatments of drought and drought coupled with TIS108 inhibition. Our findings demonstrate that the suppression of SL synthesis detrimentally affects the drought resilience of tall fescue. Through comprehensive transcriptome sequencing and subsequent qRT-PCR analyses of samples subjected to drought with and without TIS108 treatment, we identified a marked downregulation of genes involved in auxin metabolism and root development. This downregulation correlated with significant reductions in total root length, root surface area, and the number of root tips under drought stress conditions. Collectively, our research elucidates that the inhibition of SL synthesis impairs drought tolerance in tall fescue by constraining root growth and development, mediated through the modulation of auxin metabolism.

Improved bacterial composition and co-occurrence patterns of rhizosphere increased nutrient uptake and grain yield through cultivars mixtures in maize

Crop diversification contributes to agricultural productivity and resources efficient utilization. However, whether cultivar mixtures in maize affects soil bacterial community, nutrient uptake, plant growth and yield remains unknown. A two-year lysimetric experiment was conducted using two maize cultivars (LY16 and JS501) with different root system architectures planted in monoculture or in mixture under normal fertilization (NF), reduced fertilization (RF) or no addition of fertilizer (CK) and was assessed at the silking stages. Cultivar mixtures and monoculture of LY16 had higher shoot biomass, nutrient uptake and total root length at silking stage, and grain yield than monoculture of JS501 under NF and RF conditions. Under NF and RF conditions, cultivar mixtures and monoculture of LY16 led to an increase in bacterial diversity, significant changes in community structure, and a high abundance of Bacteroidia and biomarkers of Chitinophagaceae and Saprospiraceae (Bacteroidia). Cultivar mixtures showed specific responses from modules of the rhizosphere bacterial community co-occurrence network, and the relative abundance of keystone taxa of cultivar mixtures was higher than that of monoculture of JS501. The keystone taxa had a broad and significant positive correlation with plant nutrient accumulation and grain yield. Cultivar mixtures showed similar assembly processes of Bacteroidia with monoculture of LY16, and the increased abundance of Chitinophagaceae may lead to a healthy rhizosphere bacterial community. Overall, our findings indicate that cultivar mixtures significantly affects the assembly and composition of the rhizosphere bacterial community, and thus benefits plant nutrient acquisition and plant growth. These findings could deepen our understanding of the facilitating effect of rhizosphere functional microbial community (e.g. plant nutrition uptake or immunity)of cultivar mixtures.