Root Traits Research Articles

Phenotyping Seedling Root Biometry of Two Contrasting Bread Wheat Cultivars under Nutrient Deficiency and Drought Stress

Roots play a key role in withstanding wheat abiotic stress. In this work, we phenotyped seedling root morphology of two semi-dwarf bread wheat cultivars, the Chinese cv Lankaodali and the Italian cv Rebelde, under the hypothesis that these two genotypes have contrasting root traits and could be used as donors in breeding programs. Root development was compared in a semi-hydroponic screening, where full-strength (FS) vs. half-strength (HS) complete Hoagland’s solution represented high and moderate nutrient availability, and a screening comparing HS solution with tap water corresponding to a condition of nutrient starvation. Genotypes were further compared in soil under full watering (100% of field capacity) vs. drought stress (50% of field capacity). Lankaodali outperformed Rebelde by producing 50% more leaf mass and 70% more root mass in FS solution, 125% more leaf mass and 106% more root mass in HS solution, and 65% more leaf mass and 36% more root mass under nutrient starvation. This cv also showed a positive correlation between leaf mass and root length and mass (between r = 0.82–0.9 and r = 0.83–0.87, respectively, p < 0.05). In the soil screening experiment, Lankaodali produced more biomass than Rebelde regardless of water availability, 48% more leaf mass, 32% more root mass, and 31% more absolute rhizosheath mass (average across water availability treatments). Lankaodali proved to be more responsive than Rebelde to both water and nutrient availability. High values of broad-sense heritability—ranging between 0.80 for root mass and 0.90 for length in a hydroponic screen and 0.85 for rhizosheath size in soil—indicate that these traits could be useful for breeding.

From acquisitive to conservative: The ontogenetic trajectory of root syndrome of annual and perennial co-generic species

Perennials has been proposed as new crops because their root syndrome offers more ecosystem services and a better use of resources than the annual one. Objective: To compare the ontogenetic trajectory of root syndromes of annual (P. gracilis and P. angustifolia) and perennial (P. pinetorum and P. mendocina) species of Physaria (Brassicaceae) and their root trait relationships. Results and ConclusionRoots became conservative as plants grew, independently of the life cycle of the species. However, perennials invested initially more resources in increasing storage capacity (bigger and thicker roots) while annuals favored increasing the exploration capacity (higher SRL). During first anthesis we found tradeoffs between acquisitive and conservative traits, as expected according to the Root Economic Spectrum (RES), but after the first year, those tradeoffs disappeared and perennials were able to combine a thick and deep taproot and high investment in C reserves with some well-developed acquisitive traits such as higher SRL and total length. This suggest that root traits should be selected during the second year, when no tradeoff exist. Differences between annuals and perennials in most structural taproot traits remained constant along the ontogenetic trajectory, thus the relative position of species in the RES did not change over time. We found a gradient of root strategies supported by the RES theory: from acquisitive in the annual P. gracilis (high SRL, STD and total length) to conservative in the perennial P. mendocina (high root biomass, root diameter, tissue density and storage) with intermediate strategies in P. angustifolia and P. pinetorum.

Metabolic niches in the rhizosphere microbiome: dependence on soil horizons, root traits and climate variables in forest ecosystems.

Understanding belowground plant-microbial interactions is important for biodiversity maintenance, community assembly and ecosystem functioning of forest ecosystems. Consequently, a large number of studies were conducted on root and microbial interactions, especially in the context of precipitation and temperature gradients under global climate change scenarios. Forests ecosystems have high biodiversity of plants and associated microbes, and contribute to major primary productivity of terrestrial ecosystems. However, the impact of root metabolites/exudates and root traits on soil microbial functional groups along these climate gradients is poorly described in these forest ecosystems. The plant root system exhibits differentiated exudation profiles and considerable trait plasticity in terms of root morphological/phenotypic traits, which can cause shifts in microbial abundance and diversity. The root metabolites composed of primary and secondary metabolites and volatile organic compounds that have diverse roles in appealing to and preventing distinct microbial strains, thus benefit plant fitness and growth, and tolerance to abiotic stresses such as drought. Climatic factors significantly alter the quantity and quality of metabolites that forest trees secrete into the soil. Thus, the heterogeneities in the rhizosphere due to different climate drivers generate ecological niches for various microbial assemblages to foster beneficial rhizospheric interactions in the forest ecosystems. However, the root exudations and microbial diversity in forest trees vary across different soil layers due to alterations in root system architecture, soil moisture, temperature, and nutrient stoichiometry. Changes in root system architecture or traits, e.g. root tissue density (RTD), specific root length (SRL), and specific root area (SRA), impact the root exudation profile and amount released into the soil and thus influence the abundance and diversity of different functional guilds of microbes. Here, we review the current knowledge about root morphological and functional (root exudation) trait changes that affect microbial interactions along drought and temperature gradients. This review aims to clarify how forest trees adapt to challenging environments by leveraging their root traits to interact beneficially with microbes. Understanding these strategies is vital for comprehending plant adaptation under global climate change, with significant implications for future research in plant biodiversity conservation, particularly within forest ecosystems.

Genomic Prediction of Root Traits via Aerial Traits in Soybean Using Canonical Variables

The phenotypic evaluation of root traits in soybeans presents challenges in breeding due to its high cost and the requirement for experimental plot destruction. Establishing relationships between aerial and root traits is crucial, given the relative ease of phenotypic evaluations for aerial traits. Therefore, this study aims to utilize the canonical correlation technique to estimate latent variables, subsequently employing GBLUP for the genomic prediction of the root traits (length, volume, surface area, and dry mass) using phenotypic information from aerial part traits (hypocotyl diameter and dry mass). Our results demonstrate the effectiveness of the technique in predicting the root part, even when not directly evaluated. The agreement observed between the top 10% of individuals selected based on the canonical variable and each root trait individually was considered moderate or substantial. This enables the simultaneous selection of genotypes based on both trait groups, providing a valuable approach for soybean breeding programs.

A case of transdisciplinarity and collaborative decision making: the co-construction of Gendered Food Product Profiles.

Crop breeding in sub-Saharan Africa has made considerable gains; however, postharvest and food-related preferences have been overlooked, in addition to how these preferences vary by gender, social difference and context. This context is changing as participatory approaches using intersectional gender and place-based methods are beginning to inform how breeding programmes make decisions. This article presents an innovative methodology to inclusively and democratically prioritise food quality traits of root, tuber and banana crops based on engagement with food systems actors and transdisciplinary collaboration. The outcome of the methodology is the Gendered Food Product Profile (GFPP) - a list of prioritised food quality characteristics - to support breeders to make more socially inclusive decisions on the methods for trait characterisation to select genotypes closer to the needs of food system actors. This article reviews application of the methodology in 14 GFPPs, presents illustrative case studies and lessons learned. Key lessons are that the transdisciplinary structure and the key role of social scientists helped avoid reductionism, supported co-learning, and the creation of GFPPs that represented the diverse interests of food system actors, particularly women, in situ. The method partially addressed power dynamics in multidisciplinary decision making; however, effectiveness was dependent on equitable team relations and supportive institutions committed to valuing plural forms of knowledge. Actions to address power asymmetries that privilege particular types of knowledge and voices in decision making are crucial in techno-science projects, along with opportunities for co-learning and long-term collaboration and a transdisciplinary structure at higher level. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effects of lianas on forest biogeochemistry during their lives and afterlives.

Climate change and other anthropogenic disturbances are increasing liana abundance and biomass in many tropical and subtropical forests. While the effects of living lianas on species diversity, ecosystem carbon, and nutrient dynamics are receiving increasing attention, the role of dead lianas in forest ecosystems has been little studied and is poorly understood. Trees and lianas coexist as the major woody components of forests worldwide, but they have very different ecological strategies, with lianas relying on trees for mechanical support. Consequently, trees and lianas have evolved highly divergent stem, leaf, and root traits. Here we show that this trait divergence is likely to persist after death, into the afterlives of these organs, leading to divergent effects on forest biogeochemistry. We introduce a conceptual framework combining horizontal, vertical, and time dimensions for the effects of liana proliferation and liana tissue decomposition on ecosystem carbon and nutrient cycling. We propose a series of empirical studies comparing traits between lianas and trees to answer questions concerning the influence of trait afterlives on the decomposability of liana and tree organs. Such studies will increase our understanding of the contribution of lianas to terrestrial biogeochemical cycling, and help predict the effects of their increasing abundance.

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 < .05). In the topsoil (0–10 cm), the large soil aggregate rate (LSAR > 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 > 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.

Contribution of Photosynthetic, Root and Phenotypic Traits to Soybean Plant Height

Breeding new high-yield and high-quality forage soybean cultivars is an effective approach to addressing the shortage of feed protein and sustainable agricultural development. Plant height is a key indicator of forage soybean genotypes and is closely related to forage yield. However, the determinants affecting soybean plant height remain highly uncertain. In order to analyze the factors contributing to plant height differences among soybean cultivars, two tall-stemmed soybean cultivars (“Neinong S001” and “Neinong S002”) and two short-stemmed soybean cultivars (“Neinong 0004” and “Neinong 0005”) were used in this study as test materials for examining aboveground phenotypic characteristics, root traits, and photosynthetic characteristics. The test materials were planted in 2018 at Chakintai Ranch (122°15′ E, 43°38′ N) using the potting method, and the indicators were measured in June. The results showed that the leaf area, root volume, and root surface area of high-stemmed soybean cultivars were significantly (p < 0.05) lower than those of short-stemmed soybean cultivars. Additionally, the dry weight of a single plant and transpiration rate were significantly (p < 0.05) higher in high-stemmed soybean cultivars compared to short-stemmed soybean cultivars. It was found that soybean plant height was significantly (p < 0.05) correlated with leaf area, leaf shape index, intercellular CO2 concentration, transpiration rate, SPAD, root weight, root length, root surface area, and root volume. Further path analyses revealed that intercellular CO2 concentration and root surface area had a direct impact on plant height, with direct effect coefficients of 0.22 and −0.91, respectively. These results provide new insights into the sustainability development and genetic enhancement of plant height characteristics in forage soybean.

Soil Nitrogen and Flooding Intensity Determine the Trade-Off between Leaf and Root Traits of Riparian Plant Species.

The investigation into trade-offs among plant functional traits sheds light on how plants strategically balance growth and survival when facing environmental stress. This study sought to evaluate whether trade-offs observed at both community and individual species levels could indicate adaptive fitness across an intensity of flooding intensity. The study was conducted at 25 sampling sites spanning approximately 600 km along the riparian zone in the Three Gorges Reservoir area, China. The findings revealed that, along the flooding gradient, the overall riparian community did not exhibit significant trade-offs between leaf and root traits. Examining three broadly distributed dominant species (Cynodon dactylon, Xanthium strumarium, and Abutilon theophrasti), perennial plants showed pronounced trade-offs under low flooding intensity, while annuals exhibited trade-offs under moderate and low flooding intensity. The trade-offs were evident in traits related to nitrogen-carbon resources, such as specific leaf area, root tissue density, and photosynthetic rate. However, under strong flooding intensity, the relationship between leaf and root traits of the species studied was decoupled. Furthermore, the study identified a significant correlation between soil nitrogen and the trade-off traits under moderate and low flooding intensity. Integrating results from the CSR (Competitors, Stress-tolerators, Ruderals) strategy model, species niche breath analysis, and nitrogen-regulated trade-off, the study revealed that, in the face of high flooding intensity, perennial species (C. dactylon) adopts an S-strategy, demonstrating tolerance through a conservative resource allocation that decouples leaf-root coordination. Annual species (X. strumarium and A. theophrasti), on the other hand, exhibit niche specialization along the flooding gradient, employing distinct strategies (R- and C-strategy). As flooding stress diminishes and soil nitrogen level decreases, plant strategies tend to shift towards an R-strategy with a competition for reduced N resources. In conclusion, the study highlighted the pivotal roles of soil nitrogen and flooding intensity acting as the dual determinants of species growth and tolerance. These dynamics of growth-tolerance balance were evident in the diverse trade-offs between leaf and root traits of individual plant species with different life histories, underscoring the array of adaptive strategies employed by riparian plants across the flooding intensity gradient.

Mycorrhizal Symbiosis Enhances P Uptake and Indole-3-Acetic Acid Accumulation to Improve Root Morphology in Different Citrus Genotypes

Arbuscular mycorrhizal fungi (AMF) are known to enhance plant growth via stimulation of root system development. However, the extent of their effects and underlying mechanisms across different citrus genotypes remain to be fully elucidated. This study investigates the impact of Funneliformis mosseae (F. mosseae) inoculation on plant growth performance, root morphology, phosphorus (P), and indole-3-acetic acid (IAA) concentrations, as well as the expression of related synthesis and transporter genes in three citrus genotypes: red tangerine (Citrus tangerine ex. Tanaka), kumquat (Fortunella margarita L. Swingle), and fragrant citrus (Citrus junos Sieb. ex. Tanaka). Following 12 weeks of inoculation, significant improvements were observed in plant height, shoot and root biomass, total root length, average root diameter, second-order lateral root development, root hair density, and root hair length across all genotypes. Additionally, F. mosseae inoculation significantly increased root P and IAA concentrations in the three citrus genotypes. Notably, phosphatase activity was enhanced in F. margarita but reduced in C. tangerine and C. junos following inoculation. Gene expression analysis revealed a universal upregulation of the P transporter gene PT5, whereas expressions of the auxin synthesis gene YUC2, transporter gene LAX2, and phosphatase gene PAP1 were commonly downregulated. Specific to genotypes, expressions of YUC5, LAX5, PIN2, PIN3, PIN6, and expansin genes EXPA2 and EXPA4 were significantly upregulated in C. tangerine but downregulated in F. margarita and C. junos. Principal component analysis and correlation assessments highlighted a strong positive association between P concentration, P and auxin synthesis, and transporter gene expressions with most root morphology traits, except for root average diameter. Conversely, IAA content and phosphatase activities were negatively correlated with these root traits. These findings suggest that F. mosseae colonization notably enhances plant growth and root system architecture in citrus genotypes via modifications in P transport and IAA accumulation, indicating a complex interplay between mycorrhizal symbiosis and host plant physiology.

Genome-wide association studies and transcriptomics reveal mechanisms explaining the diversity of wheat root responses to nutrient availability.

Nutrient availability profoundly influences plant root system architecture, which critically determines crop productivity. While Arabidopsis has provided important insights into the genetic responses to nutrient deficiency, translating this knowledge to crops, particularly wheat, remains a subject of inquiry. Here, examining a diverse wheat population under varying nitrogen (N), phosphorus (P), potassium (K), and iron (Fe) levels, we uncover a spectrum of root responses, spanning from growth inhibition to stimulation, highlighting genotype-specific strategies. Furthermore, we reveal a nuanced interplay between macronutrient deficiency (N, P, and K) and Fe availability, emphasizing the central role of Fe in modulating root architecture. Through genome-wide association mapping, we identify 11 quantitative trait loci underlying root traits under varying nutrient availabilities, including homologous genes previously validated in Arabidopsis, supporting our findings. In addition, utilizing transcriptomics, ROS imaging, and antioxidant treatment, we uncover that wheat root growth inhibition by nutrient deficiency is attributed to ROS accumulation, akin to the role of ROS in governing Arabidopsis root responses to nutrient deficiency. Therefore, our study reveals the conservation of molecular and physiological mechanisms between Arabidopsis and wheat to adjust root growth to nutrient availability, paving the way for targeted crop improvement strategies aimed at increasing nutrient use efficiency.

SNP Markers Associated with Some Root, Stolon, and Tuber Traits in Tetraploid Potatoes (Solanum tuberosum L.) Grown Under Diverse Growing Systems

AbstractNumerous loci, environmental factors, and their interactions have an impact on the phenotypic diversity of several significant traits in plants. One approach put forth in recent years for genetic research and finding quantitative trait loci (QTLs) responsible for the specific trait is association mapping. The purpose of the current study was to pinpoint the genetic underpins of significant underground traits in potato. A panel of 192 diverse tetraploid potato genotypes from different countries were grown under different growing conditions (i.e., aeroponics and pot) to study root, stolon and tuber traits. Significant differences (P ≤ 0.01) were found between the genotypes for all examined traits, and the heritability (H2) of the traits ranged from 0.74 to 0.94. Genotyping was carried out using the SolCAP 25K array. 21,226 polymorphic SNPs were used for association mapping of underground traits. A GWASpoly R package was implemented for the marker-trait associations, and 78 genomic regions were found associated with the traits under investigation.. The history of potato breeding was reflected in LD patterns. The identified SNPs have their putative gene functions related to the root and stolon architecture and tuber growth (i.e., WRKY transcription factor, MAPK, the GTP cyclohydrolase 1 (i.e., GTPCHI), Glutathionyl-hydroquinone reductase, and pyrophosphate—fructose 6-phosphate 1-phosphotransferase subunit alpha (PFPase). The results of the present study provides a framework that could be helpful for future potato breeding programs to increase tuber production and reduce the challenges of feeding the world's population in the years to come.

Relationships between rhizosphere microbial communities, soil abiotic properties and root trait variation within a pine species

Abstract Rhizosphere microbes play important roles in plant performance and ecosystem functioning. It is becoming increasingly clear that rhizosphere communities vary with soil properties and variation in root traits among plant species. However, less is known about whether and how variation in root traits within plant species influences the rhizosphere microbial communities. We evaluated the intraspecific root traits variation and explored their associations with bacterial and fungal communities in rhizosphere by focusing on an ectomycorrhizal tree species, that is Pinus massoniana, in 22 sites in subtropical China. The first dimension of the principal component analysis on root traits revealed evidence for the ‘conservation’ gradient of the root economics space. Overall, root traits explained more variation in fungal communities than in bacterial communities in the rhizosphere. Functional composition of rhizosphere microbial communities changed significantly along the ‘conservation’ gradient, with fast‐growing copiotrophic bacteria and symbiotic ectomycorrhizal fungi were significantly enriched on the ‘acquisition’ side, while slow‐growing oligotrophic bacteria were significantly enriched on the ‘conservation’ side of the gradient. Synthesis: Our study demonstrates that intraspecific variation in plant roots significantly influence rhizosphere microbial communities, which in turn can influence plant nutrition and therefore plant performance within the community.

Root traits and biomass production of drought‐resistant and drought‐sensitive arabica coffee varieties growing under contrasting watering regimes

AbstractDrought is a major factor affecting coffee production, and different genotypes exhibit varying degrees of resistance to drought stress. We examined root traits and biomasses of drought‐resistant (74110, Angafa, Bultum, Chala, and Gawe) and drought‐sensitive (75227, Koti, Melko CH2, Menasibu, and Mokah) Coffea arabica varieties at seedling stage under contrasting watering regimes (water stressed and well watered) for 30 days followed by 15 days of recovery to identify the association between drought resistance and root traits and dry matter partitioning, and the impact of drought stress on growth performance of arabica coffee varieties. We used a split‐plot design with three blocks, where watering regime was the whole‐plot factor and variety was the subplot factor. During water‐stress and recovery periods, the interaction effect between watering regime and variety significantly affected root traits and dry matter partitioning, while the watering‐regime main effect affected biomass. We observed a higher (1) tap root diameter (0.34 cm), lateral root number (80.7), and root volume (4.7 cm−3) for 74110; (2) lateral root number (79.3), specific root length (24.8 cm g−1), and root‐mass ratio (0.41 g g−1) for Bultum; and (3) root length density (3.3–5.2 cm cm−3), root angle (42.6°–47.8°), root‐mass ratio (0.40–0.42 g g−1), and root‐shoot ratio (0.67–0.72 g g−1) for Angafa, Chala, and Gawe under water‐stressed condition. During both study periods, biomasses were much lower under water‐stressed than under well‐watered condition. The findings show the association between drought resistance and root traits and dry matter partitioning, and the impact of drought stress on growth performance of young arabica coffee.

Phosphate bio-solubilization and cadmium tolerance interplay in the root-microbe interface and consequences on root P absorption in wheat

Functional soil microbial communities, including phosphate solubilizing bacteria (PSB), are known for their ability to enhance P availability along with additional properties such as the immobilization of trace elements like cadmium (Cd). Bacterial P solubilization and tolerance to Cd are important biological processes that might occur simultaneously with positive influence on plant growth, thus physiological mechanisms controlling both processes need to be deciphered. This interplay was investigated in three PSB isolates (Bacillus siamensis "B. Siam", Rahnella aceris "R. Acer" and Bacillus cereus "B. Cer") and their consortium (PSBCs) with contrasting P solubilizing capacities (high-medium-low), through bacterial culture-based and plant inoculation experiments under increasing Cd concentrations and low P availability conditions (Tri-calcium P "TCP" and Rock P "RP"). Results show that PSB, particularly R. Acer and PSBCs, significantly increased P bioavailability (from TCP) under increasing Cd2+ concentrations (33 ppm “Cd33”, 67 ppm “Cd67”, 134 ppm “Cd134” and 201 ppm “Cd201”). The enhanced bioavailable P strongly correlated (B. Siam and PSBCs) with Cd bioaccumulation capacity, phosphatase enzyme activity, and organic acids (OA) production. Co-application of RP and PSB inoculation under Cd2+ stress (Cd8 and Cd16) improved wheat seedling root growth, P acquisition, and root hairs density in the piliferous zone and root cap. Moreover, inoculation with B. Cer significantly improved root inorganic P (Pi) (384 and 752%) and root acid phosphatases (176 and 131%) under Cd8 and Cd16 compared to uninoculated Cd-stressed seedlings. Such a beneficial root adaptation mechanism could be explained by the significant correlations (mainly under Cd16) between Pi content and morphological traits of wheat roots. Findings from this study demonstrate that P solubilization and Cd tolerance are likely interconnected rhizosphere processes triggered by inoculation that presumably induced the elongation of root hairs and likely the rigidity of the root cell wall to reduce Cd entrance while increasing P acquisition.

Are high-throughput root phenotyping platforms suitable for informing root system architecture models with genotype-specific parameters? An evaluation based on the root model ArchiSimple and a small panel of wheat cultivars.

Given the difficulties in accessing plant roots in situ, high-throughput root phenotyping (HTRP) platforms under controlled conditions have been developed to meet the growing demand for characterizing root system architecture (RSA) for genetic analyses. However, a proper evaluation of their capacity to provide the same estimates for strictly identical root traits across platforms has never been achieved. In this study, we performed such an evaluation based on six major parameters of the RSA model ArchiSimple, using a diversity panel of 14 bread wheat cultivars in two HTRP platforms that had different growth media and non-destructive imaging systems together with a conventional set-up that had a solid growth medium and destructive sampling. Significant effects of the experimental set-up were found for all the parameters and no significant correlations across the diversity panel among the three set-ups could be detected. Differences in temperature, irradiance, and/or the medium in which the plants were growing might partly explain both the differences in the parameter values across the experiments as well as the genotype × set-up interactions. Furthermore, the values and the rankings across genotypes of only a subset of parameters were conserved between contrasting growth stages. As the parameters chosen for our analysis are root traits that have strong impacts on RSA and are close to parameters used in a majority of RSA models, our results highlight the need to carefully consider both developmental and environmental drivers in root phenomics studies.

Unraveling root and rhizosphere traits in temperate maize landraces and modern cultivars: Implications for soil resource acquisition and drought adaptation.

A holistic understanding of plant strategies to acquire soil resources is pivotal in achieving sustainable food security. However, we lack knowledge about variety-specific root and rhizosphere traits for resource acquisition, their plasticity and adaptation to drought. We conducted a greenhouse experiment to phenotype root and rhizosphere traits (mean root diameter [Root D], specific root length [SRL], root tissue density, root nitrogen content, specific rhizosheath mass [SRM], arbuscular mycorrhizal fungi [AMF] colonization) of 16 landraces and 22 modern cultivars of temperate maize (Zea mays L.). Our results demonstrate that landraces and modern cultivars diverge in their root and rhizosphere traits. Although landraces follow a 'do-it-yourself' strategy with high SRLs, modern cultivars exhibit an 'outsourcing' strategy with increased mean Root Ds and a tendency towards increased root colonization by AMF. We further identified that SRM indicates an 'outsourcing' strategy. Additionally, landraces were more drought-responsive compared to modern cultivars based on multitrait response indices. We suggest that breeding leads to distinct resource acquisition strategies between temperate maize varieties. Future breeding efforts should increasingly target root and rhizosphere economics, with SRM serving as a valuable proxy for identifying varieties employing an outsourcing resource acquisition strategy.

Soil quality reflects microbial resource availability and drives rhizosphere microbiome variation in Ghanaian cocoa farms

Cocoa (Theobroma cacao L.) is an important crop in Ghana and the source of livelihood for hundreds of thousands of smallholder farmers. Maintaining soil quality on these farms is critical to ensuring the long-term viability of cocoa farming and preventing deforestation to meet rising demand. However, increasing attention to soil health has revealed a significant knowledge gap related to the soil microbiome in cocoa production systems. Using a nested design of sixteen smallholder cocoa farms in agroforestry or monoculture, on different soil quality classes and in different agroecological zones, a study was conducted to identify 1) drivers of rhizosphere microbial diversity and community composition across scales and 2) the extent of microbial differentiation between soil quality classes. Soil quality had far greater impacts than agroecological zone or agroforestry vs. monoculture management on microbial diversity and community composition, accounting for 17 % of variation in prokaryotes and 10 % in fungi. Good-quality and poor-quality soils contrasted in soil and root parameters, creating variable microbial resources, which led to differences in microbial community composition and the relative abundance of specific taxa. Soil organic matter and root traits were key drivers of community composition in good-quality soils, while permanganate-oxidizable carbon was relatively more important in poor-quality soils. These results underscore the importance of considering rhizosphere microbial communities in assessments of soil quality and highlight taxa that may serve as biological indicators of soil health in cocoa agroforestry systems.

Durum wheat (Triticum turgidum L. var. durum) root system response to drought and salt stresses and genetic characterization for root-related traits.

Abiotic stresses such as drought and salt are significant threats to crop productivity. The root system adaptation and tolerance to abiotic stresses are regulated by many biochemical reactions, which create a complex and multigenic response. The present study aims to evaluate the diversity of root responses to cyclic abiotic stress in three modern durum wheat varieties and one hydric stress-tolerant landrace in a pot experiment from seedling to more advanced plant development stages. The genotypes responded to abiotic stress during the whole experiment very differently, and at the end of the experiment, nine out of the 13 traits for the landrace J. Khetifa were significantly higher than other genotypes. Moreover, single sequence repeat (SSR) genetic analysis revealed high polymorphism among the genotypes screened and interesting private alleles associated with root system architecture traits. We propose that the markers used in this study could be a resource as material for durum wheat breeding programs based on marker-assisted selection to increase the vegetal material with high drought and salt stress tolerance and to identify candidates with strong early vigor and efficient root systems. This study provides appropriate genetic materials for marker-assisted breeding programs as well as a basic study for the genetic diversity of root traits of durum wheat crops.

Root system architecture change in response to waterlogging stress in a 448 global collection of rapeseeds (Brassica napus L.).

A novel image-based screening method for precisely identifying genotypic variations in rapeseed RSA under waterlogging stress was developed. Five key root traits were confirmed as good indicators of waterlogging and might be employed in breeding, particularly when using the MFVW approach. Waterlogging is a vital environmental factor that has detrimental effects on the growth and development of rapeseed (Brassica napus L.). Plant roots suffer from hypoxia under waterlogging, which ultimately confers yield penalty. Therefore, it is crucially important to understand the genetic variation of root system architecture (RSA) in response to waterlogging stress to guide the selection of new tolerant cultivars with favorable roots. This research was conducted to investigate RSA traits using image-based screening techniques to better understand how RSA changes over time during waterlogging at the seedling stage. First, we performed a t-test by comparing the relative root trait value between four tolerant and four sensitive accessions. The most important root characteristics associated with waterlogging tolerance at 12 h are total root length (TRL), total root surface area (TRSA), total root volume (TRV), total number of tips (TNT), and total number of forks (TNF). The root structures of 448 rapeseed accessions with or without waterlogging showed notable genetic diversity, and all traits were generally restrained under waterlogging conditions, except for the total root average diameter. Additionally, according to the evaluation and integration analysis of 448 accessions, we identified that five traits, TRL, TRSA, TRV, TNT, and TNF, were the most reliable traits for screening waterlogging-tolerant accessions. Using analysis of the membership function value (MFVW) and D-value of the five selected traits, 25 extremely waterlogging-tolerant materials were screened out. Waterlogging significantly reduced RSA, inhibiting root growth compared to the control. Additionally, waterlogging increased lipid peroxidation, accompanied by a decrease in the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). This study effectively improves our understanding of the response of RSA to waterlogging. The image-based screening method developed in this study provides a new scientific guidance for quickly examining the basic RSA changes and precisely predicting waterlogging-tolerant rapeseed germplasms, thus expanding the genetic diversity of waterlogging-tolerant rapeseed germplasm available for breeding.