Root Trait Diversity Research Articles

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.

Unrevalling phenotypic diversity of root system architecture in ancient wheat species versus modern wheat cultivars

Understanding the phenotypic variability in root system architecture and root-shoot relationships across different growth stages of wheat is of utmost importance for the improvement of genotypes with enhanced nutrient uptake and resource-use efficiency. This study focused on identifying variations and relationships in the root and shoot characteristics of seven modern cultivars and twelve ancient wheat accessions of different species, including T. monococcum, T. turanicum, T. polonicum, T. mirabile, T. durum, and T. aestivum, during the early vegetative growth and stem elongation stages. The results demonstrated significant phenotypic variation among the genotypes for shoot traits, root biomass, rooting depth, R/S ratio, and seminal and nodal root numbers. When considering both growth stages, the dry land-adapted cultivar ‘Taner’ and ancient wheat species, such as T. turanicum (2) and T. monococcum (1) accessions, exhibited deeper roots, which can enhance access to water in drought-prone areas. Furthermore, it was observed that modern wheat cultivars and T. turanicum accessions exhibited increased root biomass, suggesting a higher allocation of resources towards root growth, which could potentially enhance nutrient uptake. Conversely, T. monococcum accessions and T. mirabile revealed lower root biomass compared to other ancient species and modern cultivars. Additionally, the unrooted cluster analysis based on root biomass, rooting depth, and root to shoot ratio at both growth stages indicated a distinct separation of T. monococcum accessions and T. mirabile from other genotypes. Overall, these findings underscore the importance of phenotypic diversity in root traits for crop improvement and adaptation to varying environments. Identifying genotypes with desirable root characteristics can enhance nutrient and water uptake efficiencies, leading to increased crop productivity and sustainability.

The combined effects of faba bean and endogeic earthworms on soil microbial activity in intercrops

The rhizosphere is a hotspot of interactions between plants and soil organisms that affect the soil functioning and nutrient cycling. The drilosphere is a hotspot of interactions between earthworms and soil microbial communities affecting plant growth, soil aggregation, and porosity. Central to these interactions are microorganisms, which are affected by both plant species diversity and earthworm activity. Little is known about the effects of earthworms on the microbial community activity under the influence of root-trait diversity in cases of multi-species plant covers. We investigated the impact of plant composition and the presence of endogeic earthworms on the metabolic response of microorganisms to the addition of 10 carbon substrates relevant as rhizodeposition components. A greenhouse experiment was conducted with mesocosms filled with 10 kg of soil, sown with two plants of either the same or different species, chosen based on their contrasting root traits. Five modalities were investigated: 1 faba bean (Vicia faba L. ssp. Minor) intercropped with either 1 rapeseed (Brassica napus L.) or 1 wheat (Triticum aestivum L.) plant, as well as crops of the same species: either 2 rapeseeds, 2 wheats, or 2 faba beans. For each modality, 10 mesocosms were set up, and half of them were inoculated with 5 endogeic earthworms (Aporrectodea caliginosa Savigny). After 91 days, the plants’ dry weight, N content, and 15N:14N ratio were measured. The rhizosphere microbial respiration was assessed using the MicroResp™ method. The results showed that the level of metabolic activity depends on the plant species composition. Faba bean had the highest positive effect on microbial growth and metabolic activity. Microbial activity was also significantly increased by earthworms, but with no specific effect between plant treatments. Our findings suggest that plant traits are the main driver of the metabolic activity of soil microorganisms that is stimulated by earthworms.

Root Trait Diversity in Field Grown Durum Wheat and Comparison with Seedlings

Roots are important for crop adaptation, particularly in dryland environments. We evaluated root development of 37 durum wheat genotypes (modern cultivars and landraces) in the field at the adult plant stage, through a shovelomics approach. Large genotypic variability was found for root traits. Differences between the landraces and modern cultivars were the main driver of this variation, with landraces showing higher plant vigor for roots and shoots. Nonetheless, genotypic variation within groups was also observed, related to different models of root growth, largely independent of total root length. These two models represented root growth were oriented either to occupy more soil volume, or to occupy less soil volume with increased density. The field results were then compared with root data previously collected in seedlings using a filter paper-based method, to assess whether early root anticipated adult root features. Field plants showed a narrower root angle than seedlings. In particular, landraces presented a narrower root angle than cultivars, but only at seedling stage. Potentially useful correlations were found between the two growth stages for root length and number.

Marker-trait association study for root-related traits in chickpea (Cicer arietinum L.)

<p class="042abstractstekst">Root structure modification can improve important agronomic traits including yield, drought tolerance and nutrient deficiency resistance. The aim of the present study was to investigate the diversity of root traits and to find simple sequence repeat (SSR) markers linked to root traits in chickpea (<em>Cicer arietinum </em>L.). This research was performed using 39 diverse accessions of chickpea. The results showed that there is significant variation in root traits among chickpea genotypes. A total of 26 alleles were detected 26 polymorphic bands were produced by 10 SSR markers in the eight linkage groups (LG). The results indicated that there is substantial variability present in chickpea<strong> </strong>germplasm for root traits.<strong> </strong>By analyzing the population structure, four subpopulations were identified.<strong> </strong>PsAS2, AF016458, 16549 and 19075 SSR markers on LG1, LG3, LG2 and LG1 linkage group respectively were<strong> </strong>associated with root traits<strong>.</strong> The research findings provide valuable information for improving root traits for chickpea breeders.</p>

Marker-trait association study for root-related traits in chickpea (Cicer arietinum L.)

Root structure modification can improve important agronomic traits including yield, drought tolerance and nutrient deficiency resistance. The aim of the present study was to investigate the diversity of root traits and to find simple sequence repeat (SSR) markers linked to root traits in chickpea (Cicer arietinum L.). This research was performed using 39 diverse accessions of chickpea. The results showed that there is significant variation in root traits among chickpea genotypes. A total of 26 alleles were detected 26 polymorphic bands were produced by 10 SSR markers in the eight linkage groups (LG). The results indicated that there is substantial variability present in chickpea germplasm for root traits. By analyzing the population structure, four subpopulations were identified. PsAS2, AF016458, 16549 and 19075 SSR markers on LG1, LG3, LG2 and LG1 linkage group respectively were associated with root traits. The research findings provide valuable information for improving root traits for chickpea breeders.

Groundwater and root trait diversity jointly drive plant fine root biomass across arid inland river basin

Groundwater and root trait diversity jointly drive plant fine root biomass across arid inland river basin

Structural and Functional Organization of the Root System: A Comparative Study on Five Plant Species

Plants are affected by soil environments to the same extent that they affect soil functioning through interactions between environmental and genetic factors. Here, five plant species (broad bean, pea, cabbage, fennel, and olive) grown under controlled pot conditions were tested for their ability to differently stimulate the degradation of standard litter. Litter, soil C and N contents were measured for evaluating chemical changes due to plant presence, while soil microbial abundance was evaluated to assess if it had a positive or negative catalyzing influence on litter decomposition. The architecture and morphological traits of roots systems were also evaluated by using specific open-source software (SmartRoot). Soil chemical and microbiological characteristics were significantly influenced by the plant species. Variations in soil C/N dynamics were correlated with the diversity of root traits among species. Early stage decomposition of the standard litter changed on the basis of the plant species. The results indicated that key soil processes are governed by interactions between plant roots, soil C and N, and the microbial metabolism that stimulate decomposition reactions. This, in turn, can have marked effects on soil chemical and microbiological fertility, both fundamental for sustaining crops, and can promote the development of new approaches for optimizing soil C and N cycling, managing nutrient transport, and sustaining and improving net primary production.

Root Trait Variability in Coffea canephora Genotypes and Its Relation to Plant Height and Crop Yield

Coffee breeding based on root traits is important to identify productive genotypes under adverse environmental conditions. This study assessed the diversity of root traits in Coffea canephora and its correlation with plant height and crop yield. Undisturbed soil samples were collected down to 60 cm from 43 coffee genotypes, in which one of them was propagated by seed and all others by stem cutting. The roots were washed, scanned, and processed to quantify root length density, root volume, root superficial area, and root diameter. Additionally, plant height and crop yield were also assessed. Root length density ranged from 40 to 1411 mm cm−3, root volume from 6 to 443 mm3 cm−3, root superficial area from 61 to 1880 mm2 cm−3, and root diameter from 0.6 to 1.1 mm. Roots were concentrated in the topsoil (0–20 cm) for most genotypes. In deeper depths (30–60 cm), root length density, root volume, and root superficial area were higher in genotypes 14, 25, 31, and 32. Positive correlations were found between root traits and both plant height and crop yield. The results of this work may contribute to the overall cultivation of C. canephora, specially for crop breeding in adverse environmental conditions.

Durum Wheat Seminal Root Traits within Modern and Landrace Germplasm in Algeria

Seminal roots are known to play an important role in crop performance, particularly under drought conditions. A set of 37 durum wheat cultivars and local landraces was screened for variation in architecture and size of seminal roots using a laboratory setting, with a filter paper method combined with image processing by SmartRoot software. Significant genetic variability was detected for all root and shoot traits assessed. Four rooting patterns were identified, with landraces showing overall steeper angle and higher root length, in comparison with cultivars, which presented a wider root angle and shorter root length. Some traits revealed trends dependent on the genotypes’ year of release, like increased seminal root angle and reduced root size (length, surface, and volume) over time. We confirm the presence of a remarkable diversity of root traits in durum wheat whose relationship with adult root features and agronomic performance should be explored.

Rhizosphere bacteria are more strongly related to plant root traits than fungi in temperate montane forests: insights from closed and open forest patches along an elevational gradient

Heterogeneous canopies in temperate montane forests affect microclimate and soil characteristics, with important effects on soil microbial communities and related processes. Here, we studied the interactions between plant root traits and soil bacterial and fungal communities in closed forest and open gaps in a mixed forest along an elevational gradient in the French Alps (1400, 1700 and 2000 m). Samples were separated into three fractions (plant root, rhizosphere and bulk soil), to further investigate the influence of plant zones on microbial communities. Bacterial (16S) and fungal (ITS) biodiversity was determined using high throughput sequencing, along with standard measures of soil, litter and root traits. We found that (i) microbial community diversity was higher in gaps than in closed forest because of increased root trait diversity and density; (ii) open versus closed forest patches affected phylogenetic dispersion despite differences in elevations with phylogenetic clustering in closed forest; (iii) the interaction between root traits and microbial communities was stronger for rhizosphere and root fractions than for bulk soil and (iv) bacterial community composition was better explained by root traits than for fungi. Our findings highlight the importance of open gaps versus closed forest patches and associated root traits affecting microbial community structure, particularly for bacterial assemblages that exhibited a stronger interaction with root traits than for fungi.

Root traits and carbon input by sweet sorghum genotypes differs in two climatic conditions

Response of sweet sorghum [Sorghum bicolor (L.) Moench] root traits and carbon (C) input under two different climatic condition is not well understood. The aims of this study were to characterize and compare root biomass and root traits of several sweet sorghum genotypes at field condition and to estimate their C input to into soil. Roots and shoots were analyzed for C concentration and CO2 was calculated. Root samples were collected through monolith root sampling techniques. Root morphological characteristics like root surface area and root volume were differed between locations as well as locations × genotypes interactions. Root surface area varies from 423,800 to 887,800 m2 ha-1 in Mediterranean soil and 339,100 to 579,600 m2ha-1 for Harran soil. All sweet sorghum genotypes inputs root and shoot C as well as CO2 higher in Mediterranean than Harran soil. Root C input varies from 140 to 386 Mg ha-1 in Mediterranean soil and 112 to 224 Mg ha-1 for Harran soil. A greater diversity of root traits was found on several sweet sorghum genotypes irrespective to plant biomass C inputs into the soil. However, compared to several sweet sorghum genotypes, their lower C input to soil needs to be recognized to ensure a balanced C budget. This study concluded that several sweet sorghum genotypes can be a good source of soil C sequestration under different climatic conditions of Turkey.

Root litter diversity and functional identity regulate soil carbon and nitrogen cycling in a typical steppe

Root litter decomposition is the dominant source of soil organic carbon (C) and nitrogen (N) in grasslands. Few studies, however, have explored the effect of root litter diversity on soil C and N cycling. This study investigated the effects of species diversity and functional traits of root litter on soil CO2 and N2O release, net ammonification, net nitrification, and net N mineralization based on a 56-day incubation of grassland soils with root litter mixtures containing one, two, or four native plant species. The increasing species richness of root litter decreased the cumulative CO2 and N2O release in the soil, but enhanced the net ammonification, nitrate immobilization, and N mineralization. Root litter diversity has a predominant non-additive antagonistic effect on the release of soil CO2 and N2O, and a synergistic effect on the net ammonification, nitrate immobilization, and N mineralization in the soil. The functional identity rather than functional diversity of root traits explains most of the variation in soil C and N cycling. A high C: N ratio and low concentrations of N, P, K, and Di-O-alkyl-C (characteristic of celluloses) were found to be key to the antagonistic effects associated with cumulative release of CO2 from the soil. For net N ammonification and mineralization, the synergistic effect was principally induced by the high levels of carbohydrate-C and N and the low C: N ratios in root litter mixtures. Our study highlights the role and mechanisms of increased root litter diversity in decreasing soil CO2 and N2O release and in increasing the net N mineralization via non-additive antagonistic and synergistic effects of dominant root traits.

Screening for Sugarcane Root Phenes Reveals That Reducing Tillering Does Not Lead to an Increased Root Mass Fraction.

Sugarcane root systems are poorly studied and understood due to the perennial nature, tall stature, and the long cropping cycle. Whilst some field studies gave insights into sugarcane root traits, there is no detailed description of root and root system traits available. The objectives of our work were to establish a baseline of sugarcane root trait values that will serve for future studies, and to characterize the degree of root system resilience when restricting tiller number. We first conducted an initial screening for root trait diversity on a collection of twenty cultivars representative of sugarcane breeding from 1930 to now. Then we investigated the effect of reduced tillering, via manual de-tillering, on the plant root and root system traits of five varieties grown under optimal conditions in a glasshouse for 1700°Cd. In addition to establishing baseline means and variation for sugarcane root trait values that could serve as a reference for crop models, we demonstrated that the sugarcane root mass fraction was extremely resilient to drastic reduction in tiller number. Restricted plants were effectively maintaining their root system configuration (opening angle) by dramatically increasing the number of nodal roots produced per tiller as well as maximizing total root length by increasing the specific root length. Using this knowledge of sugarcane root traits in combination with the specific agronomic constraints for sugarcane will now underpin the development of a root system ideotype for sugarcane to enable targeted root trait selection for improving crop productivity.

Using root traits to understand temporal changes in biodiversity effects in grassland mixtures

Biodiversity–ecosystem functioning (BEF) studies typically show that species richness enhances community biomass, but the underlying mechanisms remain debated. Here, we combine metrics from BEF research that distinguish the contribution of dominant species (selection effects, SE) from those due to positive interactions such as resource partitioning (complementarity effects, CE) with a functional trait approach in an attempt to reveal the functional characteristics of species that drive community biomass in species mixtures. In a biodiversity experiment with 16 plant species in monocultures, 4‐species and 16‐species mixtures, we used aboveground biomass to determine the relative contributions of CE and SE to biomass production in mixtures in the second, dry year of the experiment. We also measured root traits (specific root length, root length density, root tissue density and the deep root fraction) of each species in monocultures and linked the calculated community weighted mean (CWM) trait values and trait diversity of mixtures to CE and SE. In the second year of the experiment, community biomass, CE and SE increased compared to the first year. The contribution of SE to this positive effect was greater than that of CE. The increased contribution of SE was associated with root traits: SE increased most in communities with high abundance of species with deep, thick and dense roots. In contrast, changes in CE were not related to trait diversity or CWM trait values. Together, these results suggest that increased positive effects of species richness on community biomass in a dry year were mainly driven by increased dominance of deep‐rooting species, supporting the insurance hypothesis of biodiversity. Positive CE indicates that other positive interactions did occur, but we could not find evidence that belowground resource partitioning or facilitation via root trait diversity was important for community productivity in our biodiversity experiment.

Root dynamics and survival in a nutrient-poor and species-rich woodland under a drying climate

In Australia’s Mediterranean hyperdiverse vegetation, species that produce cluster roots to mobilise poorly-available nutrients (e.g. Banksia spp.) are an important functional and structural component. Cluster roots are only active during the wet season, indicating a strong dependence on suitable surface soil moisture conditions. Winter rainfall in this region is declining due to global climate change, with a delayed commencement of rains and a decline in precipitation. It is unknown how lower soil moisture levels will affect the root dynamics of these globally-significant plant communities. We determined the root dynamics and root lifespan with minirhizotrons with or without irrigation to simulate reduced rainfall scenarios. We found a major effect of irrigation on the early production (0.24 m m−2 d−1 increase), occurrence (97% increase) of cluster roots and only slight effects on lifespan (~10 days less) of all root types. With irrigation, the resultant greater soil moisture levels increased the deployment of cluster roots. Apart from cluster roots, the dynamics of other roots did not decline at lower soil moisture levels, suggesting that this system shows some resilience to decreased rainfall. Future research should focus on assessing if climate-altered cluster-root activity may be promoting compositional shifts in plant communities with additional restraining effects on root trait diversity.

Taxonomic and ecological patterns in root traits of Carex (Cyperaceae)

Plants can develop various root traits which may contribute to their nutrient acquisition. We investigated the occurrence of five root traits among species of genus Carex to determine their frequency, mutual associations and dependence on taxonomy (subgenus) or habitat. Root samples of 40 species were collected in their natural habitats within Russia and Belarus. They were examined microscopically to quantify the abundance of AM-fungal hyphae (H), arbuscules (A) and vesicles (V), dark septate endophyte (DSE), typical (long) root hairs (TRH), bulbous (shortened) root hairs (BRH) and dauciform roots (DR). The frequency of root traits decreased in the order TRH (100% of the species), DSE (80%), BRH (43%), A and V (25%) and DR (23%). Most species possessed 2–4 different traits, but up to five were possible, even on a single plant. Traits occurred largely independently of each other. DR were only found in subgenus Carex and mainly in grasslands. DSE and BRH were more abundant in subgenus Carex. BRH were most abundant in wetlands, TRH were shortest and thinnest in grasslands. A diversity of root traits exists in the genus Carex, with variation both among and within species. The abundance and size of traits exhibits some taxonomic and ecological patterns, which differ for each trait.

GrowScreen-PaGe, a non-invasive, high-throughput phenotyping system based on germination paper to quantify crop phenotypic diversity and plasticity of root traits under varying nutrient supply.

New techniques and approaches have been developed for root phenotyping recently; however, rapid and repeatable non-invasive root phenotyping remains challenging. Here, we present GrowScreen-PaGe, a non-invasive, high-throughput phenotyping system (4 plants min-1) based on flat germination paper. GrowScreen-PaGe allows the acquisition of time series of the developing root systems of 500 plants, thereby enabling to quantify short-term variations in root system. The choice of germination paper was found to be crucial and paper☓root interaction should be considered when comparing data from different studies on germination paper. The system is suitable for phenotyping dicot and monocot plant species. The potential of the system for high-throughput phenotyping was shown by investigating phenotypic diversity of root traits in a collection of 180 rapeseed accessions and of 52 barley genotypes grown under control and nutrient-starved conditions. Most traits showed a large variation linked to both genotype and treatment. In general, root length traits contributed more than shape and branching related traits in separating the genotypes. Overall, results showed that GrowScreen-PaGe will be a powerful resource to investigate root systems and root plasticity of large sets of plants and to explore the molecular and genetic root traits of various species including for crop improvement programs.

Can root trait diversity explain complementarity effects in a grassland biodiversity experiment?

Aims The positive relationship between plant biodiversity and community productivity is well established. However, our knowledge about the mechanisms underlying these positive biodiversity effects is still limited. One of the main hypotheses is that complementarity in resource uptake is responsible for the positive biodiversity effects: plant species differ in resource uptake strategy, which results in a more complete exploitation of the available resources in space and time when plant species are growing together. Recent studies suggest that functional diversity of the community, i.e. the diversity in functional characteristics ('traits') among species, rather than species richness per se, is important for positive biodiversity effects. However, experimental evidence for specific trait combinations underlying resource complementarity is scarce. As the root system is responsible for the uptake of nutrients and water, we hypothesize that diversity in root traits may underlie complementary resource use and contribute to the biodiversity effects. Methods In a common garden experiment, 16 grassland species were grown in monoculture, 4-species mixtures differing in root trait diversity and 16-species mixtures. The 4-species mixtures were designed to cover a gradient in average rooting depth. Above-ground biomass was cut after one growing season and used as a proxy for plant productivity to calculate biodiversity effects. Important Findings Overall, plant mixtures showed a significant increase in biomass and complementarity effects, but this varied greatly between communities. However, diversity in root traits (measured in a separate greenhouse experiment and based on literature) could not explain this variation in complementarity effects. Instead, complementarity effects were strongly affected by the presence and competitive interactions of two particular species. The large variation in complementarity effects and significant effect of two species emphasizes the importance of community composition for positive biodiversity effects. Future research should focus on identifying the traits associated with the key role of particular species for complementarity effects. This may increase our understanding of the links between functional trait composition and biodiversity effects as well as the relative importance of resource complementarity and other underlying mechanisms for the positive biodiversity effects.

Mean root trait more than root trait diversity determines drought resilience in native and cultivated Mediterranean grass mixtures

Grasslands provide numerous ecosystem services but their sustainability is threatened by climate change. As plant functional diversity is expected to stabilize ecosystem functions, we tested whether mixing species with contrasting root systems could improve the resilience of Mediterranean grasslands under increasing aridity. We hypothesized that root functional identity (RFI) and diversity (RFD) respectively determines and improves soil water uptake capacity, aboveground biomass (AGB) production and resilience after drought stress (=post-stress AGB/pre-stress AGB). Monocultures, two- and three species mixtures of two groups of perennial grasses (cultivars and native species) were compared in a twin 3-years field experiment under two levels of summer drought in southern France. RFI and RFD were assessed as the mean and variance of multiple root traits (rooting depth, deep root mass fraction, root tissue density, root diameter and specific root length) measured in species monocultures. AGB and resilience were assessed from annual harvests; total transpirable soil water (TTSW) and evapotranspiration in summer (ET_sum) were assessed through the monitoring of soil water content. For both groups of species, RFI was a major predictor of TTSW and resilience, but not of AGB or ET_sum. Greater water uptake, especially from deep soil layers, increased resilience. Rooting depth distribution determined the potential depth of water uptake while root morphology influenced the precision of water uptake along the soil profile. However, RFD only marginally improved AGB production and resilience, although long-term effects of RFD should be tested. Designing artificial plant communities under water-limited conditions should therefore prioritize the maximization of rooting depth and root distribution along the soil profile. Diversifying root morphological traits associated with resource acquisition could also have a positive impact. The similarity of results between cultivars and native species suggests that agro-ecological guidelines for species assembly can be based on advances of functional ecology in natural ecosystems.