Affect Root Development Research Articles

QTL analyses of soybean root system architecture revealed genetic relationships with shoot-related traits.

The genetic basis of soybean root system architecture (RSA) and the genetic relationship between shoot and RSA were revealed by integrating data from recombinant inbred population grafting and QTL mapping. Variations in root system architecture (RSA) affect the functions of roots and thus play vital roles in plant adaptations and agricultural productivity. The aim of this study was to unravel the genetic relationship between RSA traits and shoot-related traits in soybean. This study characterized RSA variability at seedling stage in a recombinant inbred population, derived from a cross between cultivated soybean C08 and wild soybean W05, and performed high-resolution quantitative trait locus (QTL) mapping. In total, 34 and 41 QTLs were detected for RSA-related and shoot-related traits, respectively, constituting eight QTL clusters. Significant QTL correspondence was found between shoot biomass and RSA-related traits, consistent with significant correlations between these phenotypes. RSA-related QTLs also overlapped with selection regions in the genome, suggesting the cultivar RSA could be a partial consequence of domestication. Using reciprocal grafting, we confirmed that shoot-derived signals affected root development and the effects were controlled by multiple loci. Meanwhile, RSA-related QTLs were found to co-localize with four soybean flowering-time loci. Consistent with the phenotypes of the parental lines of our RI population, diminishing the function of flowering controlling E1 family through RNA interference (RNAi) led to reduced root growth. This implies that the flowering time-related genes within the RSA-related QTLs are actually contributing to RSA. To conclude, this study identified the QTLs that determine RSA through controlling root growth indirectly via regulating shoot functions, and discovered superior alleles from wild soybean that could be used to improve the root structure in existing soybean cultivars.

Five NUCLEAR FACTOR-Y subunit B genes in rapeseed (Brassica napus) promote flowering and root elongation in Arabidopsis

Heterologous expression of BnNF-YB2, BnNF-YB3, BnNF-YB4, BnNF-YB5, or BnNF-YB6 from rapeseed promotes the floral process and also affects root development in Arabidopsis. The transcriptional regulator NUCLEAR FACTOR-Y (NF-Y) is a heterotrimeric complex composed of NF-YA, NF-YB, and NF-YC proteins and is ubiquitous in yeast, animal, and plant systems. In this study, we found that five NF-YB proteins from rapeseed (Brassica napus), including BnNF-YB2, BnNF-YB3, BnNF-YB4, BnNF-YB5, and BnNF-YB6 (BnNF-YB2/3/4/5/6), all function in photoperiodic flowering and root elongation. Sequence alignment and phylogenetic analysis showed that BnNF-YB2/3 and BnNF-YB4/5/6 were clustered with Arabidopsis AtNF-YB2 and AtNF-YB3, respectively, implying that these NF-YBs are evolutionarily and functionally conserved. In support of this hypothesis, the heterologous expression of individual BnNF-YB2, 3, 4, 5, or 6 in Arabidopsis promoted early flowering under a long-day photoperiod. Further analysis suggested that BnNF-YB 2/3/4/5/6 elevated the expression of key downstream flowering time genes including CO, FT, LFY and SOC1. Promoter-GUS fusion analysis showed that the five BnNF-YBs were expressed in a variety of tissues at various developmental stages and GFP fusion analysis revealed that all BnNF-YBs were localized to the nucleus. In addition, we demonstrated that the heterologous expression of individual BnNF-YB2/3/4/5/6 in Arabidopsis promoted root elongation and increased the number of root tips formed under both normal and treatment with simulators of abiotic stress conditions.

The locoweed endophyte Alternaria oxytropis affects root development in Arabidopsis in vitro through auxin signaling and polar transport.

Locoweeds are leguminous forbs known for their toxicity to livestock caused by the endophytic fungi Alternaria sect. Undifilum. Unlike the defensive mutualisms reported in many toxin-producing endophytes and their plant hosts, the benefits that A. sect. Undifilum can confer to it host plants remains unclear. Here, we conducted physiological and genetic analyses to show that A. (sect. Undifilum) oxytropis influences growth, especially root development, in its locoweed host Oxytropis ochrocephala and Arabidopsis. The presence of A. oxytropis significantly decreased primary root length while increasing the numbers of lateral roots and root hairs, and increasing plant leaf area and fresh weight. The fungus also increased the concentrations of plant endogenous auxin, and the expression of key genes for auxin biosynthesis, signaling, and transport. These effects on root development were abolished in mutants deficient in auxin signaling and polar transport. Alternaria oxytropis down-regulated expression of PIN1 but increased expression of PIN2, PIN7, and AUX1, which might reflect alterations in the spatial accumulation of auxin responsible for the changes in root architecture. Plant growth was insensitive to A. oxytropis when naphthylphthalamic acid was applied. Our findings indicate a function of A. oxytropis in promoting the growth and development of Arabidopsis via the regulation of auxin, which in turn suggests a possible role in benefiting its locoweed hosts via a process independent of its toxin production.

RESÍDUOS DE PLANTAS DE COBERTURA E Pochonia chlamydosporia NO CONTROLE DE Meloidogyne javanica EM SOJA

ABSTRACT Pochonia chlamydosporia (Pc) is a nematophagous fungus with saprotrophic activity. However, little is known about the interaction between Pc and green manure. This study aimed to investigate the interaction effects of different green manures and Pc on the control of Meloidogyne javanica in soybean. Two greenhouse experiments were conducted in different periods using a 6 × 2 factorial design, with six replicates. The first factor was green manure application (oat, brachiaria, crotalaria, millet, buckwheat, and untreated control) and the second factor was treatment with Pc (in-furrow application and untreated control). Cover crops were grown separately and applied to pots as green manure 15 days before soybean sowing. At 5 days after sowing, soybean was inoculated with 2 000 eggs and juveniles of M. javanica. At 60 days after inoculation, nematode and vegetative variables were determined. All green manures reduced nematode population levels, especially oat, crotalaria, and buckwheat. Pc treatment did not influence nematode population levels. Soybean plants treated with oat or crotalaria green manure had greater height than untreated plants in both experiments. The effects of factors on shoot fresh and dry weights differed between experiments, and green manure application did not affect root development. The findings confirmed the potential of plant residues to control M. javanica.

Plant growth promoting rhizobacteria increased canola yield and root system

Decreasing the use of synthetic chemicals including nitrogen fertilizers is a top priority worldwide for the establishment of sustainable agriculture and high productivity. Using plant growth promoting rhizobacteria (PGPR) can help in this regard. Identification of PGPRs associate with canola can be of great importance to produce sustainable and low-cost biodiesel also in less favored areas. The objective of this study was to evaluate the growth, and grain yield of canola grown with five different PGPRs. The treatments Azospirillum brasiliense, Methylobacterium komagatae, Rhizobium sp., Azomonas sp., mixture of microorganisms from 1 to 4, and control (no inoculation), in the canola (Brassica napus L) were evaluated. The experiment was performed in a clay soil with six replicates. Plants height and diameter were evaluated at 15, 50, 80, and 110 days after the sowing. At the end of the cycle, root area and grain yield were also calculated. The PGPRs significantly affect root development, shoot dry weight, and grain yield of canola. M. komagacae increased rooting area in 44%. M. komagacae and A. brasiliense resulted in 56 e 53% more grain yield compared to un-inoculated canola, respectively, indicating that PGPRs holds high potential to promote canola productivity.

Symplastic communication in the root cap directs auxin distribution to modulate root development.

Root cap not only protects root meristem, but also detects and transduces the signals of environmental changes to affect root development. The symplastic communication is an important way for plants to transduce signals to coordinate the development and physiology in response to the changing enviroments. However, it is unclear how the symplastic communication between root cap cells affects root growth. Here we exploit an inducible system to specifically block the symplastic communication in the root cap. Transient blockage of plasmodesmata (PD) in differentiated collumella cells severely impairs the root development in Arabidopsis, in particular in the stem cell niche and the proximal meristem. The neighboring stem cell niche is the region that is most sensitive to the disrupted symplastic communication and responds rapidly via the alteration of auxin distribution. In the later stage, the cell division in proximal meristem is inhibited, presumably due to the reduced auxin level in the root cap. Our results reveal the essential role of the differentiated collumella cells in the root cap mediated signaling system that directs root development.

Silicon Application Differentially Modulates Root Morphology and Expression of PIN and YUCCA Family Genes in Soybean (Glycine max L.).

Silicon (Si) is absorbed and accumulated by some plant species; it has been shown to improve plant growth and performance. The beneficial role of Si in plants is based on the fundamental assumptions, and the biological function of Si is still being researched due to its complex nature, distinctiveness, and interaction. The present study included two distinct experiment sets: a screening test and an advanced test. In the initial examination, we used 21 soybean (Glycine max L.) cultivars. Following the evaluation, we chose four cultivars to investigate further. In particular, the positive response cultivars, Taeseon and Geomjeongsaeol, showed a 14% increase in net photosynthesis (PN), and a 19–26% increase in transpiration in Si-treated plants when compared to the control plants. Si-treated Taeseon, Geomjeongsaeol, and Somyongkong, Mallikong cultivars showed significant differences in root morphological traits (RMTs) and root system architecture (RSA) when compared to the control plants. Taeseon and Geomjeongsaeol showed a 26 and 46% increase in total root length (TRL) after Si application, respectively, compared to the control, whereas Mallikong and Somyongkong showed 26 and 20% decrease in TRL after Si treatment, respectively, compared to the control. The Si application enhanced the overall RMTs and RSA traits in Taeseon and Geomjeongsaeol; however, the other two cultivars, Somyongkong and Mallikong, showed a decrease in such RMTs and RATs. Furthermore, to understand the underlying molecular mechanism and the response of various cultivars, we measured the Si content and analyzed the gene expression of genes involved in auxin transport and root formation and development. We showed that the Si content significantly increased in the Si-treated Somyongkong (28%) and Taeseon (30%) compared to the control cultivars. Overall, our results suggested that Si affects root development as well as the genes involved in the auxin synthesis, transport pathway, and modulates root growth leading to cultivar-dependent variation in soybeans.

Phloem iron remodels root development in response to ammonium as the major nitrogen source

Plants use nitrate and ammonium as major nitrogen (N) sources, each affecting root development through different mechanisms. However, the exact signaling pathways involved in root development are poorly understood. Here, we show that, in Arabidopsis thaliana, either disruption of the cell wall-localized ferroxidase LPR2 or a decrease in iron supplementation efficiently alleviates the growth inhibition of primary roots in response to NH4+ as the N source. Further study revealed that, compared with nitrate, ammonium led to excess iron accumulation in the apoplast of phloem in an LPR2-dependent manner. Such an aberrant iron accumulation subsequently causes massive callose deposition in the phloem from a resulting burst of reactive oxygen species, which impairs the function of the phloem. Therefore, ammonium attenuates primary root development by insufficiently allocating sucrose to the growth zone. Our results link phloem iron to root morphology in response to environmental cues.

Supernumerary roots in maxillary deciduous canines: A rare anomaly with a long history

ObjectiveTo describe two maxillary deciduous bi-rooted canines, one archeological and one modern, and examine the possible etiology of this condition. DesignTwo cases of bi-rooted canines were described and compared to published examples. Both specimens were radiographed and measured and compared to one-rooted samples. The archeological specimen was scanned using CBCT to facilitate detailed examination of the deciduous teeth. The extracted modern tooth was embedded in epoxy resin and two coronal sections were cut, one through the crown and one through the roots and examined with a light microscope. ResultsThe bi-rooted canines were larger than the control samples. They showed none of the features commonly associated with gemination. The radiographs and scans showed that the canine roots in the archeological case diverged mesio-distally like the buccal roots in the adjacent first deciduous molar. In the clinical case, the root trunk was elongated mesio-distally and the furcation was located very close to the apex with a C-shaped root canal. ConclusionsBoth variants of the condition described above are rare in deciduous canines. They do not seem to be associated with fusion or gemination. However, as the teeth are relatively flattened bucco-lingually and we tentatively propose that this form results from spatial constraints during the early stages of crown development that have contributed to the development of additional roots. The megadont dimension of the recent bi-rooted deciduous canine may affect root development and the necessity of two mesio-distally located roots for anchorage in the maxilla.

Initial development of tomato plants in response to biostimulants

The objective of this work was to evaluate the efficiency of biostimulants in the initial development of tomato plants. The experiment was carried out in a greenhouse at the Goiano Federal Institute (IFGoiano), campus Urutaí, Brazil. The treatments consisted of applying four biostimulants (Raizer, NK+ Aminosoil, Rootex, and Booster) in six doses (0, 25, 75, 100, 125, and 150% of the recommended dose). Height (cm), fresh root weight (FRW, g), dry root weight (DRW, g), aerial part fresh weight (APFW, g), and aerial part dry weight (APDW, g) were evaluated 30 days after transplanting. We also evaluated the content of nitrogen (N), phosphorus (P), and sulfur (S) in the leaves. Data were subjected to analysis of variance (F-test, 5% probability), and treatments were compared using Student's t-test. The treatment with NK+Aminosoil promoted increment in plant height, MSPA, and N-content in leaves, with the best doses varying between 75 and 100% of the recommended dose. Rootex promoted increases in FRW, APFW, APDW, and N-content, when using 125 and 150% of the recommended dose. The Booster positively affected root development (FRW and DRW), increasing P and S-contents in applications ranging from 125 to 150% of the recommended dose. Raizer promoted greater shoot development (APFW and APDW), increasing N-contents when 125% of the recommended dose was used. It could be inferred that the evaluated biostimulants affected the initial development of tomato plants.

The Modulation of Auxin-Responsive Genes, Phytohormone Profile, and Metabolomic Signature in Leaves of Tomato Cuttings Is Specifically Modulated by Different Protein Hydrolysates

Protein hydrolysates (PHs) are employed in agriculture to increase the sustainability of farming systems, with positive results on crop productivity and response against environmental stressors. Nevertheless, the molecular mechanism(s) triggered by their specific activity is not clearly understood. In this work, five PHs obtained by enzymatic hydrolysis of different vegetal protein sources were tested for their root-promoting activity on tomato cuttings. All the treatments improved both root length and number when compared to negative controls. Distinctive metabolomic signatures were highlighted in response to treatments, indicating the triggering of different molecular processes in leaf tissues of tomato cuttings. PHs differentially modulated the biosynthesis of plant stress-protectants, such as alkaloids and phenylpropanoids. Moreover, metabolites involved in phytohormone biosynthesis were significantly impacted. In this context, a clear modulation of several compounds related to auxin homeostasis was observed. In addition, the differential modulation of SlIAA2 and SlIAA9 genes, which are involved in the IAA signalling pathway, might further suggest the auxin-like activity elicited by the PHs tested. Here we provide evidence that PHs can impact plant molecular level, positively affecting root development, most likely by affecting the signalling cascades activated in leaf tissues. The biostimulant activity was sustained by PH-specific response at the molecular level, likely ascribable to their heterogeneous botanical origins. In fact, our findings did not point out a clear universal response to PHs, and specific effects are to be investigated.

Root characteristics of an elite spring wheat panel under contrasting water treatments and their genome-wide association study

Wheat occupies the largest global harvested area of any crop, most of which has been affected by abiotic stress. Root features are challenging to enhance through conventional selection strategies, and therefore, molecular approaches such as genome-wide association studies (GWAS) may help overcome some of the limitations. In the current study, 170 elite spring wheat lines were studied for root and shoot characteristics under water-stress and non-stress environments in two replications of field soil tubes. Root and shoot phenotypes especially network root length, network root volume and plant highest showed significant decrease under water-stress in contrast with well-watered condition. Also, the studied factors revealed distinct aspects of the population, which are called “root development”, “deep rooting system”, “plant vigor”, and “spike properties” via principal component analysis (PCA). The population was genotyped using 90 K Illumina SNPs and a total of 14,968 markers used in GWAS. In total, 186 significant marker-trait associations were identified on 16 chromosomes, some of which confirmed previously reported loci for root length. Several new loci affecting root development in wheat were identified in the present study. Several MTAs on specific chromosomes were identified exclusively under well-watered condition as well as water-stress environment, particularly 58 significant ones related to the root development component. The most significant associations were found for the deep rooting component. Also, candidate loci were identified having significant effect on different aspects of the studied population particularly the deep rooting system and the root development under water-stress environment. The candidate SNPs identified in the current study were validated by the whole WAMI population's field data, emphasizing the reliability of performed GWAS for identifying loci affecting root quantitative-related traits. These results improve our understanding of the genetic basis of root system architecture under well-watered and water-stressed environments.

Cold response and tolerance in cereal roots.

Cold stress adversely affects plant growth and is a limiting factor in crop productivity. Temperature volatility as a consequence of climate change will increase the effects of cold stress on crop cultivation. Low temperatures frequently occur early after planting in temperate climates and severely affect root development in cereals. In this review we address the question how cereal root systems respond to cold on different scales. First, we summarize the morphological, physiological and cellular responses of cereal roots to cold stress and how these processes are regulated by phytohormones. Subsequently, we highlight the status of the genetic and molecular dissection of cold tolerance with emphasis on the role of cold-responsive genes in improving cold tolerance in cereal roots. Finally, we discuss the role of beneficial microorganisms and mineral nutrients in ameliorating the effects of cold stress in cereal roots. A comprehensive knowledge of the molecular mechanisms underlying cold tolerance will ensure yield stability by enabling the generation of cold-tolerant crop genotypes.

Microcystin-LR, a cyanobacterial toxin affects root development by changing levels of PIN proteins and auxin response in Arabidopsis roots

Microcystin-LR (MCY-LR) is a heptapeptide toxin produced mainly by freshwater cyanobacteria. It strongly inhibits protein phosphatases PP2A and PP1. Functioning of the PIN family of auxin efflux carriers is crucial for plant ontogenesis and their functions depend on their reversible phosphorylation. We aimed to reveal the adverse effects of MCY-LR on PIN and auxin distribution in Arabidopsis roots and its consequences for root development.Relatively short-term (24 h) MCY-LR treatments decreased the levels of PIN1, PIN2 and PIN7, but not of PIN3 in tips of primary roots. In contrast, levels of PIN1 and PIN2 increased in emergent lateral roots and their levels depended on the type of PIN in lateral root primordia. DR5:GFP reporter activity showed that the cyanotoxin-induced decrease of auxin levels/responses in tips of main roots in parallel to PIN levels. Those alterations did not affect gravitropic response of roots. However, MCY-LR complemented the altered gravitropic response of crk5-1 mutants, defective in a protein kinase with essential role in the correct membrane localization of PIN2. For MCY-LR treated Col-0 plants, the number of lateral root primordia but not of emergent laterals increased and lateral root primordia showed early development. In conclusion, inhibition of protein phosphatase activities changed PIN and auxin levels, thus altered root development. Previous data on aquatic plants naturally co-occurring with the cyanotoxin showed similar alterations of root development. Thus, our results on the model plant Arabidopsis give a mechanistic explanation of MCY-LR phytotoxicity in aquatic ecosystems.

Modulation of Arabidopsis root growth by specialized triterpenes.

Plant roots are specialized belowground organs that spatiotemporally shape their development in function of varying soil conditions. This root plasticity relies on intricate molecular networks driven by phytohormones, such as auxin and jasmonate (JA). Loss-of-function of the NOVEL INTERACTOR OF JAZ (NINJA), a core component of the JA signaling pathway, leads to enhanced triterpene biosynthesis, in particular of the thalianol gene cluster, in Arabidopsis thaliana roots. We have investigated the biological role of thalianol and its derivatives by focusing on Thalianol Synthase (THAS) and Thalianol Acyltransferase 2 (THAA2), two thalianol cluster genes that are upregulated in the roots of ninja mutant plants. THAS and THAA2 activity was investigated in yeast, and metabolite and phenotype profiling of thas and thaa2 loss-of-function plants was carried out. THAA2 was shown to be responsible for the acetylation of thalianol and its derivatives, both in yeast and in planta. In addition, THAS and THAA2 activity was shown to modulate root development. Our results indicate that the thalianol pathway is not only controlled by phytohormonal cues, but also may modulate phytohormonal action itself, thereby affecting root development and interaction with the environment.

Loss of Arabidopsis matrix metalloproteinase-5 affects root development and root bacterial communities during drought stress.

Matrix metalloproteinases (MMPs) are zinc‐dependent endo‐peptidases that in mammals are known to be involved in remodeling the extracellular matrix (ECM) in developmental and pathological processes. In this study, we report At5‐MMP of Arabidopsis thaliana to be important for root development and root bacterial communities. At5‐MMP is mainly localized in the root vasculature and lateral root, an At5‐MMP T‐DNA insertion mutant (mmp5 KO) showed reduced root growth and a lower number of root apexes, causing reduced water uptake from the soil. Subsequently, mmp5 KO is sensitive to drought stress. Inhibited auxin transport was accompanied with resistance to indole‐3‐acetic acid (IAA), 2, 4‐dichlorophenoxyacetic acid (2, 4‐D), and 1‐naphthaleneacetic acid (NAA). The content of endogenous abscisic acid (ABA) was lower in roots of mmp5 KO than in wild type. Genes responsive to ABA as well as genes encoding enzymes of the proline biosynthesis were expressed to a lower extent in mmp5 KO than in wild type. Moreover, drought stress modulated root‐associated bacterial communities of mmp5 KO: the number of Actinobacteria increased. Therefore, At5‐MMP modulates auxin/ABA signaling rendering the plant sensitive to drought stress and recruiting differential root bacterial communities.

Crosstalk among hydrogen sulfide (H2S), nitric oxide (NO) and carbon monoxide (CO) in root-system development and its rhizosphere interactions: A gaseous interactome

Root development in higher plants is achieved by a precise intercellular communication which determines cell fate in the primary embryonic meristem where the gasotransmitters H2S, NO and CO participate dynamically. Furthermore, the rhizosphere interaction of these molecules with microbial and soil metabolism also affects root development. NO regulates root growth and architecture in association with several other biomolecules like auxin indole-3-acetic acid (IAA), ethylene, jasmonic acid (JA), strigolactones, alkamides and melatonin. The CO-mediated signal transduction pathway in roots is closely linked to the NO-mediated signal cascades. Interestingly, H2S acts also as an upstream component in IAA and NO-mediated crosstalk during root development. Heme oxygenase (HO) 1 generates CO and functions as a downstream component in H2S-mediated adventitious rooting and H2S–CO crosstalk. Likewise, reactive oxygen species (ROS), H2S and NO crosstalk are important components in the regulation of root architecture. Deciphering these interactions will be a potential biotechnological tool which could provide benefits in crop management in soils, especially under adverse environmental conditions. This review aims to provide a comprehensive update of the complex networks of these gasotransmitters during the development of roots.

Potassium Deficiency Significantly Affected Plant Growth and Development as Well as microRNA-Mediated Mechanism in Wheat (Triticum aestivum L.).

It is well studied that potassium (K+) deficiency induced aberrant growth and development of plant and altered the expression of protein-coding genes. However, there are not too many systematic investigations on root development affected by K+ deficiency, and there is no report on miRNA expression during K+ deficiency in wheat. In this study, we found that K+ deficiency significantly affected wheat seedling growth and development, evidenced by reduced plant biomass and small plant size. In wheat cultivar AK-58, up-ground shoots were more sensitive to K+ deficiency than roots. K+ deficiency did not significantly affect root vitality but affected root development, including root branching, root area, and root size. K+ deficiency delayed seminal root emergence but enhanced seminal root elongation, total root length, and correspondingly total root surface area. K+ deficiency also affected root and leaf respiration at the early exposure stage, but these effects were not observed at the later stage. One potential mechanism causing K+ deficiency impacts is microRNAs (miRNAs), one important class of small regulatory RNAs. K+ deficiency induced the aberrant expression of miRNAs and their targets, which further affected plant growth, development, and response to abiotic stresses, including K+ deficiency. Thereby, this positive root adaption to K+ deficiency is likely associated with the miRNA-involved regulation of root development.

Nitrogen application improved the growth and yield performance of sweetpotato (lpomoea batatas (L.) Lam.)

Nitrogen is one of the most critical nutrients affecting sweetpotato yield. This study was conducted to 1) evaluate the growth and yield response of sweetpotato NSIC SP 33 to different levels of N; and 2) determine the relationship between N level and root yield. A screenhouse experiment laid out in Completely Randomized Design (CRD) was carried out using five (5) N levels: 0,40, 80, 120 and 160kg ha-1, each replicated thrice.Thetotal amount of N (as urea) was applied twice, one-half at planting and the other half at six weeks after planting (6 WAP) along with a blanket application of solophos and muriate of potash at 40 and 60kg ha-1 P2O5and K2O. An alluvial Umingan sandy loam soil (lnceptisol) was used as medium. Levels of N significantly increased the leaf area, fresh herbage, total root yield, biomass, dry matter yield, shoot-root ratio, weight and number of marketable roots. Harvest index (HI) of plants applied with 40 and 80kg N ha-1 were comparable to those applied with 0 N. Increasing levels of N from 0 to 1 60kg ha-1 resulted in higher total crude protein (CP) and total N in the leaves. N uptake was higher in N-applied plants. Application of 40 and 80kg ha-1 N produced the highest root yield, above which root yield declined. Relationship between N level and root yield developed through regression analysis showed a quadratic function of Y=111.1794+1.2098x-0.00897x2 and R-square of 0.9904 which suggest that inherent soil N affected root development.

Exploring the Genetic Architecture of Root-Related Traits in Mediterranean Bread Wheat Landraces by Genome-Wide Association Analysis

Background: Roots are essential for drought adaptation because of their involvement in water and nutrient uptake. As the study of the root system architecture (RSA) is costly and time-consuming, it is not generally considered in breeding programs. Thus, the identification of molecular markers linked to RSA traits is of special interest to the breeding community. The reported correlation between the RSA of seedlings and adult plants simplifies its assessment. Methods: In this study, a panel of 170 bread wheat landraces from 24 Mediterranean countries was used to identify molecular markers associated with the seminal RSA and related traits: seminal root angle, total root number, root dry weight, seed weight and shoot length, and grain yield (GY). Results: A genome-wide association study identified 135 marker-trait associations explaining 6% to 15% of the phenotypic variances for root related traits and 112 for GY. Fifteen QTL hotspots were identified as the most important for controlling root trait variation and were shown to include 31 candidate genes related to RSA traits, seed size, root development, and abiotic stress tolerance (mainly drought). Co-location for root related traits and GY was found in 17 genome regions. In addition, only four out of the fifteen QTL hotspots were reported previously. Conclusions: The variability found in the Mediterranean wheat landraces is a valuable source of root traits to introgress into adapted phenotypes through marker-assisted breeding. The study reveals new loci affecting root development in wheat.