Search Results (23)

The einkorn wheat group, comprising ancient diploid species (2n = 14, AA), including Triticum monococcum, Triticum boeoticum, and Triticum urartu, represents a valuable source of genetic variation for improving disease resistance in wheat. To develop a practical platform for introgressing powdery mildew resistance into bread wheat, we screened 21 einkorn accessions with Blumeria graminis f. sp. tritici (Bgt) race E09 and identified seven resistant donors. Because direct hybridization between diploid einkorn (AA) and hexaploid wheat (AABBDD) is constrained by genomic divergence and poor cross-compatibility, we crossed resistant einkorn accessions with susceptible durum wheat and induced chromosome doubling in the F₁ hybrids to generate synthetic durum–einkorn amphiploids. Nine amphiploids were obtained. Chromosome counts and genomic in situ hybridization confirmed the expected genomic constitution (AABBAA) in most lines, with limited variation in chromosome number in two amphiploids. Phenotyping against Bgt race E09 showed that three amphiploids retained high resistance, four showed moderate resistance, and two were moderately susceptible. Marker analysis identified five einkorn accessions contain known Pm genes such as Pm60, Pm60b, and PmNCA6/Pm37, as well as their derived amphipliods. Two einkorn accessions and their derived amphiploids may harbor novel Pm genes. Field evaluation of the agronomic traits of these amphiploids indicated some improvement in tillering, spike length, and seed weight. Moreover, these amphiploids had better seed-setting rates in crosses and backcrosses with common wheat. These synthetic durum–einkorn amphiploids thus offer a new bridging platform for transferring alien genes from diploid einkorn to hexaploid common wheat, providing valuable genetic resources for wheat-breeding programs. Full article

Wheat powdery mildew and stripe rust, caused by Blumeria graminis f. sp. tritici (Bgt) and Puccinia striiformis f. sp. tritici (Pst), respectively, are two devastating diseases that threaten global wheat production. Long-term reliance on a limited number of resistance genes can accelerate resistance breakdown. Triticum urartu (2n = 14, A^uA^u), the progenitor of the wheat A subgenome, serves as a valuable gene pool for disease resistance. In this study, we identified three T. urartu accessions exhibiting high resistance to Bgt and Pst. Molecular marker analysis indicated that PI 428215 and PI 428315 carry Pm60b, whereas CITR 17664 carries both Pm60 and YrU1. Durum–T. urartu amphiploids (AABBA^uA^u) displayed resistance responses identical to their T. urartu parent and were used as bridges to transfer these resistance genes into a common wheat (AABBDD) background. Using marker-assisted selection (MAS), recurrent backcrossing, selfing, and phenotypic screening, we developed wheat lines carrying Pm60, Pm60b, YrU1, or Pm60 + YrU1. Segregation analysis in backcross-derived populations supported the functionality of these genes in the common wheat background. The selected introgression lines have high resistance to Bgt and Pst and showed no obvious adverse agronomic effects, providing useful germplasm for wheat disease resistance breeding. This study used a “multi-resistance, multi-combination” pyramiding strategy by MAS to introduce resistance genes from wild wheat into common wheat. Full article

Background: Ethylene is one of the most important plant hormones. ACC oxidase (ACO) plays a vital role in ethylene synthesis and responses to biotic and abiotic stresses in plants. However, its function in Triticum urartu remains unclear. This study aims to systematically identify the members of the TuACO gene family to elucidate its response characteristics and functions under biotic and abiotic stresses. Methods: Through homologous alignment, phylogenetic evolution analysis, and investigations of gene structure and promoter cis-elements, a total of eight TuACO genes were identified in the T. urartu genome based on their homology to OsACO and AtACO protein sequences. Results: These genes were classified into five ACO subfamilies and distributed across chromosomes 1A, 4A, 5A, 6A, and 7A. TuACO gene families contained 0–3 introns and 1–4 exons. The protein sequence contains 10 different conservative motifs. QRT-PCR expression analysis revealed that the transcript levels of TuACO5a, TuACO5b, and TuACO3a were significantly upregulated at 6 and 24 h after infection with powdery mildew, a biotic stress. Under boron deficiency, an abiotic stress, the expression of TuACO6 and TuACO1b increased, whereas the expression of TuACO5b and TuACO3b was markedly induced under high-boron conditions. Conclusions: These results demonstrate that TuACO genes exhibit functional diversification in response to biotic and abiotic stresses, which lays the foundation for elucidating their gene functions. Full article

The domestication and breeding of wheat genotypes through the years has led to the loss in their genetic variation, making them more prone to different abiotic stresses. Boron (B) toxicity is one of the stresses decreasing the wheat cultivars’ yield in arid and semi-arid regions around the world. Wild wheat progenitors, such as Triticum urartu Thumanian ex Gandilyan, possess a broader gene pool that harbors several genes conferring tolerance to various biotic and abiotic stresses. Unfortunately, T. urartu is not well-explored at the molecular level for its tolerance towards B toxicity in soil. In this study, for the first time, we compared the transcriptomic changes in the leaves of a high B-tolerant T. urartu genotype, PI662222, grown in highly toxic B (10 mM B in the form of boric acid) with the ones grown in the control (3.1 μM B) treatment in hydroponic conditions. The obtained results suggest that several mechanisms are involved in regulating the response of the studied T. urartu genotype toward B toxicity. All the growth parameters of T. urartu genotype, including root–shoot length, root fresh weight, and root–shoot dry weight, were less affected by high boron (10 mM) as compared to the boron-tolerant bread wheat cultivar. With a significant differential expression of 654 genes, 441 and 213 genes of T. urartu genotype were down- and upregulated, respectively, in the PI662222 leaves in high B in comparison to the control treatment. While key upregulated genes included those encoding RNA polymerase beta subunit (chloroplast), ATP synthase subunit gamma, chloroplastic, 60S ribosomal protein, and RNA-binding protein 12-like, the main downregulated genes included those encoding photosystem II protein D, ribulose bisphosphate carboxylase small subunit, and peroxidase 2-like. Interestingly, both Gene Ontology enrichment and KEGG pathways emphasized the possible involvement of the genes related to the photosynthetic process and apparatus in the high B tolerance of the T. urartu genotype. The further functional characterization of the identified potential T. urartu genes will facilitate their utilization in crop improvement programs for B toxicity stress. Full article

Aerobic metabolism in plants results in the production of hydrogen peroxide (H₂O₂), a significant and comparatively stable non-radical reactive oxygen species (ROS). H₂O₂ is a signaling molecule that regulates particular physiological and biological processes (the cell cycle, photosynthesis, plant growth and development, and plant responses to environmental challenges) at low concentrations. Plants may experience oxidative stress and ultimately die from cell death if excess H₂O₂ builds up. Triticum dicoccoides, Triticum urartu, and Triticum spelta are different ancient wheat species that present different interesting characteristics, and their importance is becoming more and more clear. In fact, due to their interesting nutritive health, flavor, and nutritional values, as well as their resistance to different parasites, the cultivation of these species is increasingly important. Thus, it is important to understand the mechanisms of plant tolerance to different biotic and abiotic stresses by studying different stress-induced gene families such as catalases (CAT), which are important H₂O₂-metabolizing enzymes found in plants. Here, we identified seven CAT-encoding genes (TdCATs) in Triticum dicoccoides, four genes in Triticum urartu (TuCATs), and eight genes in Triticum spelta (TsCATs). The accuracy of the newly identified wheat CAT gene members in different wheat genomes is confirmed by the gene structures, phylogenetic relationships, protein domains, and subcellular location analyses discussed in this article. In fact, our analysis showed that the identified genes harbor the following two conserved domains: a catalase domain (pfam00199) and a catalase-related domain (pfam06628). Phylogenetic analyses showed that the identified wheat CAT proteins were present in an analogous form in durum wheat and bread wheat. Moreover, the identified CAT proteins were located essentially in the peroxisome, as revealed by in silico analyses. Interestingly, analyses of CAT promoters in those species revealed the presence of different cis elements related to plant development, maturation, and plant responses to different environmental stresses. According to RT-qPCR, Triticum CAT genes showed distinctive expression designs in the studied organs and in response to different treatments (salt, heat, cold, mannitol, and ABA). This study completed a thorough analysis of the CAT genes in Triticeae, which advances our knowledge of CAT genes and establishes a framework for further functional analyses of the wheat gene family. Full article

Wheat powdery mildew (Blumeria graminis f. sp. tritici, Bgt, recently clarified as B. graminis s. str.), is one of the most destructive diseases of wheat. Pm60 is a nucleotide-binding leucine-rich repeat (NLR) gene that confers race-specific resistance to Bgt. Allelic variants (Pm60, Pm60a, and Pm60b) were found in Triticum urartu and T. dicoccoides, the wild progenitors of wheat. In the present study, we studied the diversity of the Pm60 locus in a large set of wheat germplasm and found 20 tetraploid wheats harboring the Pm60 alleles, which correspond to three novel haplotypes (HapI–HapIII). HapI (Pm60 allele) and HapII (Pm60a allele) were present in domesticated tetraploid wheats, whereas HapIII (Pm60a allele) was identified in wild tetraploid T. araraticum. A sequence comparison of HapII and HapIII revealed that they differed by three SNPs and a GCC deletion. Results of the phylogenetic analysis revealed that HapII was more closely related to the functional haplotype MlIW172. Infection tests showed that HapII-carrying lines display a partial resistance response to Bgt#GH, while HapI was susceptible. Our results provide insights into the genetic evolution of the Pm60 locus and potential valuable alleles for powdery mildew resistance breeding. Full article

To identify new sources of effective resistance to four foliar diseases of wheat, 173 accessions of four wheat species, Triticum boeoticum, T. urartu, T. araraticum, and T. dicoccoides, from the VIR collection were tested at the juvenile and adult growth stages for resistance to leaf rust (Pt = Puccinia triticina), powdery mildew (Bgt = Blumeria graminis tritici), Septoria nodorum blotch (SNB), and dark-brown leaf spot blotch (HLB = Helminthospjrium leaf blotch). The accessions included new additions to the collection, some old samples that had never been tested before, as well as earlier tested samples noted for high levels of juvenile resistance to some fungal diseases. Natural populations of Puccinia triticina and Blumeria graminis f. sp. tritici, mixture of Parastagonospora nodorum and Bipolaris sorokiniana isolates were used to inoculate and to evaluate resistance to Pt, Bgt, SNB, and HLB, respectively. Two samples of T. boeoticum, three of T. urartu, and one of T. araraticum were resistant to leaf rust at both tested stages. Further tests (phytopathological and molecular analyses) excluded Lr9, Lr19, Lr24, Lr41, or Lr47 as single genes controlling resistance; hence, these accessions likely carry new effective leaf rust resistance genes. High level of Bgt resistance was identified in three entries of T. boeoticum, one of T. araraticum, and eleven of T. dicoccoides. All tested accessions were susceptible to HLB and SNB at both tested stages. Accessions identified as resistant are valuable plant material for introgressive hybridization in bread and durum wheat breeding. The results are discussed in the context of N.I. Vavilov’s concept of crop origin and diversity, and the laws of plant natural immunity to infectious diseases. Full article

Triticum urartu Thum. ex Gandil. is a wild diploid wheat species (2n = 2x = 14) that is an A^u genome donor of modern polyploid cultivars of durum and bread wheat. In the last decade, this relict species has attracted breeders as donors of various agronomically important characteristics to broaden the genetic diversity of cultivated wheat. In addition, T. urartu can be considered as a model species for studying the evolution, biology and genomics of wheat without the cross-influence of homologous sub-genomes. Various genetic engineering technologies, including transgenesis and genome editing, may be applied to facilitate the functional characterization of genes located in A chromosomes. Such biotechnological techniques are still required for the efficient tissue culture systems to allow easy plant regeneration. The objective of our study was to assess the abilities of in vitro plant regeneration from zygotic immature embryo-derived tissues of spring and winter types of T. urartu. Three synthetic auxins, 2,4-D, Dicamba and Picloram, at four concentrations were studied to stimulate morphogenic responses in spring T. urartu. The induction medium supplemented with 4 mg·L⁻¹ Dicamba stimulated the highest frequency of regenerable callus production (65.8%), promoting the generation of 5.7 plants. Although the presence of 2 mg·L⁻¹ 2,4-D was less effective in stimulating regenerable callus formation (53.2%) than Dicamba, it allowed the regeneration of more plants from one regenerable callus (9.3 plants). These two treatments also successfully initiated morphogenesis in winter assertions; however, their regenerative capacity was generally lower. The frequency of regenerable callus production was accession-dependent and fluctuated within 31.3 to 49.2%, with a formation of an average 2.2–5.8 plants per callus. The relatively simple and fast regeneration system described in this study could be further used as the basis for regenerating transgenic plants of T. urartu. Full article

Wheat is one of the world’s crucial staple food crops. In turn, einkorn wheat (Triticum monococcum L.) is considered a wild relative of wheat (Triticum aestivum L.) and can be used as a source of agronomically important genes for breeding purposes. Cultivated T. monococcum subsp. monococcum originated from T. monococcum subsp. aegilopoides (syn. T. boeticum). For the better utilization of valuable genes from these species, it is crucial to discern the genetic diversity at their cytological and molecular levels. Here, we used a fluorescence in situ hybridization toolbox and molecular markers linked to the leaf rust resistance gene Lr63 (located on the short arm of the 3A^m chromosome—3A^mS) to track the polymorphisms between T. monococcum subsp. monococcum, T. boeticum and T. urartu (A-genome donor for hexaploid wheat) accessions, which were collected in different regions of Europe, Asia, and Africa. We distinguished three groups of accessions based on polymorphisms of cytomolecular and leaf rust resistance gene Lr63 markers. We observed that the cultivated forms of T. monococcum revealed additional marker signals, which are characteristic for genomic alternations induced by the domestication process. Based on the structural analysis of the 3A^mS chromosome arm, we concluded that the polymorphisms were induced by geographical dispersion and could be related to adaptation to local environmental conditions. Full article

Mineral nutrients, such as manganese (Mn) and iron (Fe), play essential roles in many biological processes in plants but their over-enrichment is harmful for the metabolism. Metal tolerance proteins (MTPs) are involved in cellular Mn and Fe homeostasis. However, the transporter responsible for the transport of Mn in wheat is unknown. In our study, TuMTP8, a Mn-CDF transporter from diploid wheat (Triticum urartu), was identified. Expression of TuMTP8 in yeast strains of Δccc1 and Δsmf1 and Arabidopsis conferred tolerance to elevated Mn and Fe, but not to other metals (zinc, cobalt, copper, nickel, or cadmium). Compared with TuVIT1 (vacuole Fe transporter), TuMTP8 shows a significantly higher proportion in Mn transport and a smaller proportion in Fe transport. The transient analysis in tobacco epidermal cells revealed that TuMTP8 localizes to vacuolar membrane. The highest transcript levels of TuMTP8 were in the sheath of the oldest leaf and the awn, suggesting that TuMTP8 sequesters excess Mn into the vacuole in these organs, away from more sensitive tissues. These findings indicate that TuMTP8, a tonoplast-localized Mn/Fe transporter, functions as a primary balancer to regulate Mn distribution in T. urartu under elevated Mn conditions and participates in the intracellular transport and storage of excess Mn as a detoxification mechanism, thereby conferring Mn tolerance. Full article

The mechanism and course of Triticum plastome evolution is currently unknown; thus, it remains unclear how Triticum plastomes evolved during recent polyploidization. Here, we report the complete plastomes of two polyploid wheat species, Triticum sphaerococcum (AABBDD) and Triticum turgidum subsp. durum (AABB), and compare them with 19 available and complete Triticum plastomes to create the first map of genomic structural variation. Both T. sphaerococcum and T. turgidum subsp. durum plastomes were found to have a quadripartite structure, with plastome lengths of 134,531 bp and 134,015 bp, respectively. Furthermore, diploid (AA), tetraploid (AB, AG) and hexaploid (ABD, AGA^m) Triticum species plastomes displayed a conserved gene content and commonly harbored an identical set of annotated unique genes. Overall, there was a positive correlation between the number of repeats and plastome size. In all plastomes, the number of tandem repeats was higher than the number of palindromic and forward repeats. We constructed a Triticum phylogeny based on the complete plastomes and 42 shared genes from 71 plastomes. We estimated the divergence of Hordeum vulgare from wheat around 11.04–11.9 million years ago (mya) using a well-resolved plastome tree. Similarly, Sitopsis species diverged 2.8–2.9 mya before Triticum urartu (AA) and Triticum monococcum (AA). Aegilops speltoides was shown to be the maternal donor of polyploid wheat genomes and diverged ~0.2–0.9 mya. The phylogeny and divergence time estimates presented here can act as a reference framework for future studies of Triticum evolution. Full article

Stripe rust is one of the most devastating diseases in wheat. Nucleotide-binding site (NBS) and leucine-rich repeat (LRR) domain receptors (NLRs) recognize pathogenic effectors and trigger plant immunity. We previously identified a unique NLR protein YrU1 in the diploid wheat Triticum urartu, which contains an N-terminal ANK domain and a C-terminal WRKY domain and confers disease resistance to stripe rust fungus Puccinia striiformis f. sp. Tritici (Pst). However, how YrU1 functions in disease resistance is not clear. In this study, through the RNA-seq analysis, we found that the expression of a NAC member TuNAC69 was significantly up-regulated after inoculation with Pst in the presence of YrU1. TuNAC69 was mainly localized in the nucleus and showed transcriptional activation in yeast. Knockdown TuNAC69 in diploid wheat Triticum urartu PI428309 that contains YrU1 by virus-induced gene silencing reduced the resistance to stripe rust. In addition, overexpression of TuNAC69 in Arabidopsis enhanced the resistance to powdery mildew Golovinomyces cichoracearum. In summary, our study indicates that TuNAC69 participates in the immune response mediated by NLR protein YrU1, and likely plays an important role in disease resistance to other pathogens. Full article

Powdery mildew, caused by the fungus Blumeria graminis f. sp. tritici (Bgt), has limited wheat yields in many major wheat-production areas across the world. Introducing resistance genes from wild relatives into cultivated wheat can enrich the genetic resources for disease resistance breeding. The powdery mildew resistance gene Pm60 was first identified in diploid wild wheat Triticum urartu (T. urartu). In this study, we used durum as a ‘bridge’ approach to transfer Pm60 and Pm60b into hexaploid common wheat. Synthetic hexaploid wheat (SHW, AABBA^uA^u), developed by crossing T. urartu (A^uA^u) with durum (AABB), was used for crossing and backcrossing with common wheat. The Pm60 alleles were tracked by molecular markers and the resistance to powdery mildew. From BC₁F₁ backcross populations, eight recombinant types were identified based on five Pm60-flanking markers, which indicated different sizes of the introgressed chromosome segments from T. urartu. Moreover, we have selected two resistance-harboring introgression lines with high self-fertility, which could be easily used in wheat breeding system. Our results showed that the durum was an excellent ‘bridge’ for introducing the target gene from diploid T. urartu into the hexaploid cultivated wheat. Moreover, these introgression lines could be deployed in wheat resistance breeding programs, together with the assistance of the molecular markers for Pm60 alleles. Full article

Phenylalanine ammonia-lyase (PAL) is the first enzyme in the phenylpropanoid pathway and plays a vital role in adoption, growth, and development in plants but in wheat its characterization is still not very clear. Here, we report a genome-wide identification of TaPAL genes and analysis of their transcriptional expression, duplication, and phylogeny in wheat. A total of 37 TaPAL genes that cluster into three subfamilies have been identified based on phylogenetic analysis. These TaPAL genes are distributed on 1A, 1B, 1D, 2A, 2B, 2D, 4A, 5B, 6A, 6B, and 6D chromosomes. Gene structure, conserved domain analysis, and investigation of cis-regulatory elements were systematically carried out. Chromosomal rearrangements and gene loss were observed by evolutionary analysis of the orthologs among Triticum urartu, Aegilops tauschii, and Triticum aestivum during the origin of bread wheat. Gene ontology analysis revealed that PAL genes play a role in plant growth. We also identified 27 putative miRNAs targeting 37 TaPAL genes. The high expression level of PAL genes was detected in roots of drought-tolerant genotypes compared to drought-sensitive genotypes. However, very low expressions of TaPAL10, TaPAL30, TaPAL32, TaPAL3, and TaPAL28 were recorded in all wheat genotypes. Arogenate dehydratase interacts with TaPAL29 and has higher expression in roots. The analysis of all identified genes in RNA-seq data showed that they are expressed in roots and shoots under normal and abiotic stress. Our study offers valuable data on the functioning of PAL genes in wheat. Full article

Durum wheat (Triticum turgidum subsp. durum) is mostly grown in Mediterranean type environments, characterized by unpredictable rainfall amounts and distribution, heat stress, and prevalence of major diseases and pests, all to be exacerbated with climate change. Pre-breeding efforts transgressing adaptive genes from wild relatives need to be strengthened to overcome these abiotic and biotic challenges. In this study, we evaluated the yield stability of 67 lines issued from interspecific crosses of Cham5 and Haurani with Triticum dicoccoides, T. agilopoides, T. urartu, and Aegilops speltoides, grown under 15 contrasting rainfed and irrigated environments in Morocco, and heat-prone conditions in Sudan. Yield stability was assessed using parametric (univariate (e.g., Bi, S²di, Pi etc) and multivariate (ASV, SIPC)) and non-parametric (Si1, Si2, Si3 and Si6) approaches. The combined analysis of variance showed the highly significant effects of genotypes, environments, and genotype-by-environment interaction (GEI). The environments varied in yield (1370–6468 kg/ha), heritability (0.08–0.9), and in their contribution to the GEI. Several lines derived from the four wild parents combined productivity and stability, making them suitable for unpredictable climatic conditions. A significant advantage in yield and stability was observed in Haurani derivatives compared to their recurrent parent. Furthermore, no yield penalty was observed in many of Cham5 derivatives; they had improved yield under unfavorable environments while maintaining the high yield potential from the recurrent parent (e.g., 142,026 and 142,074). It was found that a limited number of backcrosses can produce high yielding/stable germplasm while increasing diversity in a breeding pipeline. Comparing different stability approaches showed that some of them can be used interchangeably; others can be complementary to combine broad adaption with higher yield. Full article