Hordeum Marinum Research Articles

Beneficial Effects of Silicon (Si) on Sea Barley (Hordeum marinum Huds.) under Salt Stress

Silicon (Si) plays an important role in providing beneficial effects on plant growth and yield, especially under stressful environments such as salinity. The objective of this work is to study the effects of a fertilizer based on silicon (Na2SiO3 synthesized from Tunisian silica sand) on sea barley (Hordeum marinum Huds.) under salt stress. Due to its forage potentialities, this species presents a very interesting capacity for the rehabilitation of non-productive marginal areas. Forty-two-day-old H. marinum plants were exposed to three concentrations of Na2SiO3 (0, 1, or 2 mM) in the absence or presence of salt (0 or 150 mM NaCl). The examination of the growth parameters, water status, lipid peroxidation, photosynthetic gas exchange, photosynthetic pigment contents, and chlorophyll fluorescence proved that silicon is a great interest support for the remediation of the deleterious effects of salt stress. Therefore, our fertilizer can be considered as an effective solution to cope with salt stress and promote the development of marginal lands. Taking into consideration its high efficiency and its low production cost, this product can compete with other fertilizers.

Phylogenetic analysis of two single-copy nuclear genes revealed origin of tetraploid barley Hordeum marinum.

Sea barley Hordeum marinum is an important germplasm resource. However, the origin of this tetraploid H. marinum subsp. gussoneanum is still unclear, which has caused great perplexity to the exploration and utilization of germplasm resources. We used two single-copy nuclear genes, thioredoxin-like gene (TRX) and waxy1 gene encoding granule-bound starch synthase (WAXY1) to analyze 41 accessions of Hordeum marinum. The phylogenies of different genes told different story of evolution of tetraploids of H. marinum subsp. gussoneanum. The phylogenetic trees showed that two distinct copies of sequences from both genes were detected for some accessions of the tetraploids of H. marinum subsp. gussoneanum, and diploid marinum might also contribute to the origin and evolution of the tetraploid gussoneanum. Our findings suggested that tetraploid more likely originated from the diploids of H. marinum subsp. gussoneanum and another ancestor that might be an extinct unknown diploid species. Homogenization of gene in tetraploids also occurred after polyploidization as both TRX and WAXY1 sequences in some accessions of tetraploid H. marinum subsp. gussoneanum cannot be distinguished, indicating the complicated evolution of this tetraploid.

Use of H. vulgare EST Markers, GISH and C-banding to Study Bread Wheat – H. marinum subsp. gussoneanum (2n = 28) Introgression Lines

Wild barley, Hordeum marinum subsp. gussoneanum (2n = 28) is a valuable source of genes that determine resistance to abiotic stresses. These resistance traits might be transferred to wheat due to the crossability of wild barley with bread wheat. The availability of reliable and rapid methods for the identification of H. marinum subsp. gussoneanum chromatin in a wheat background would facilitate the development of introgression wheat genotypes. For this purpose, we evaluated the applicability of eighty-seven H. vulgare EST markers for studying bread wheat – H. marinum subsp. gussoneanum substitution and addition lines. Of all of the markers studied, forty-three (49%) were amplified in H. marinum ssp. gussoneanum and wheat introgression lines. The identification of wild barley chromosomes using EST markers confirmed the GISH and C-banding data. Thus, it was established that the H. vulgare EST markers can be successfully used to identify the chromosomes of the H. marinum subsp. gussoneanum in introgression lines of wheat.

Do carbohydrate metabolism and partitioning contribute to the higher salt tolerance of Hordeum marinum compared to Hordeum vulgare?

The aim of the present work was to check whether carbohydrate metabolism and partitioning contribute to the higher salt tolerance of the facultative halophyte Hordeum marinum compared to the glycophyte Hordeum vulgare. Seedlings with the same size from the two species were hydroponically grown at 0 (control), 150, and 300 mM NaCl for 3 weeks. H. marinum maintained higher relative growth rate, which was concomitant with a higher aptitude to maintain better shoot tissue hydration and membrane integrity under saline conditions compared to H. vulgare. Gas exchanges were reduced in the two species under saline conditions, but an increase in their water use efficiency was recorded. H. marinum exhibited an increase in leaf soluble sugar concentrations under saline conditions together with an enhancement in the transglucosidase DPE2 (EC 2.4.1.25) activity at 300 mM NaCl. However, H. vulgare showed a high increase in starch phosphorylase (EC 2.4.1.1) activity under saline conditions together with a decrease in leaf glucose and starch concentrations at 300 mM NaCl. In roots, both species accumulated glucose and fructose at 150 mM NaCl, but H. marinum exhibited a marked decrease in soluble sugar concentrations and an increase in starch concentration at 300 mM NaCl. Our data constitute an initiation to the involvement of carbohydrate metabolism and partitioning in salt responses of barley species and further work is necessary to elucidate how their flexibility confers higher tolerance to H. marinum compared to H. vulgare.

Comparative analysis of salt impact on sea barley from semi-arid habitats in Tunisia and cultivated barley with special emphasis on reserve mobilization and stress recovery aptitude

The considerable genetic variability of salt tolerance in Hordeum vulgare L. and its wild relative species Hordeum marinum Huds. (sea barley) is a potentially useful trait to develop well-adapted varieties to salt-affected areas. Here, two local barley (Manel and Rihane) cultivars and two local sea barley accessions (Kelbia and Soliman) were compared for their response to salt (up to 200 mM NaCl) exposure at the germination and seedling stages. Increasing salinity significantly decreased seed imbibition and seed reserve mobilization parameters (notably amylase activity), resulting in delayed germination, lower germination percentage and altered seedling root length. Interestingly, inter- and intra-specific variability was observed as cultivated barley (especially Rihane) was less salt-affected when considering final germination percentage. Yet, sea barley Soliman accession showed the highest values of seed vigor (seeds reaching the seedling stage) and efficiency of seed reserve mobilization under saline conditions. In addition, even at 200 mM NaCl, salinity impact was reversible on seeds of sea barley, in contrast with cultivated barley. Overall, while confirming the sensitivity of barley at the early developmental stages, this study provides additional criteria that would allow more accurately addressing inter-specific variability of plant behavior at this crucial step of its life cycle.

Comparisons in functions of HKT1;5 transporters between Hordeum marinum and Hordeum vulgare in responses to salt stress

Sea barley (Hordeum marinum) is more salt tolerant than barley (Hordeum vulgare). In our previous study, H. marinum accession H559 showed the superior salt tolerance and K+/Na+ homeostasis than barley cultivar Golden Promise under 400 mM NaCl. However, the molecular mechanism underlying the difference of salt tolerance between the two species remains to be revealed. Here, we characterized a homolog of HvHKT1;5 transporter in sea barley, HmHKT1;5, and compared their functions in salt tolerance. Like HvHKT1;5, HmHKT1;5 also encodes a plasma membrane protein, which is mainly expressed in roots. The expression of both genes was induced by salt stress, but HmHKT1;5 had less increase than HvHKT1;5. When expressed in Xenopus laevis oocytes, both HmHKT1;5 and HvHKT1;5 were permeable to only Na+, but the transport affinity of HmHKT1;5 was lower than that of HvHKT1;5. Moreover, when each of the two genes was introduced into rice cv. Nipponbare, both the HvHKT1;5 and HmHKT1;5 transgenic lines showed greater Na+ uptake than the wild-types, resulting in enhancement of salt stress sensitivity. Besides, the introduction of HvHKT1;5 also increased Na+ translocation from roots to shoots in rice, while the introduction of HmHKT1;5 did not. The results indicate that HvHKT1;5 is involved in Na+ uptake and translocation from roots to shoots and HmHKT1;5 is only involved in Na+ uptake, and the uptake ability of HmHKT1;5 for Na+ is much weaker than that of HvHKT1;5. These findings partially reveal the reasons why H. marinum has higher salt tolerance than H. vulgare.

Analysis of genetic diversity and spatial structure in Tunisian populations ofHordeum marinumssp.marinumbased on molecular markers

AbstractHordeum marinumcommonly known as sea barley is a salinity-tolerant species of grass. In the current study, 150 lines from ten populations ofH. marinumssp.marinumcollected from five Tunisian bioclimatic sites were screened for polymorphism with 13 selected random amplified polymorphic DNA primers. Results exhibited a high level of polymorphism (160 polymorphic bands with an average of 12.46 per primer) and a high level of genetic diversity in all the studied populations (on averageUHe= 0.247 andI= 0.358). High discrimination capacity was found for the 13 primers and a combination of three allowed assignation of a unique profile for each of the 150 lines. The partition of genetic diversity with Analysis of Molecular Variance suggested that the majority of genetic variation (67%) was within populations. The components between-populations within ecoregions and between-ecoregions explained 21 and 12%, respectively, of the total genetic variance. There was no significant association of population differentiation (ФPT) with geographical distance or altitudinal difference. Results also showed that the 150 lines grouped into three clusters with no respect to geographic origin. A sub-set of 13 lines was identified, which captured the maximum genetic diversity of the entire collection. The genetic variation found in this collection ofH. marinumis deemed to be useful in formulating conservation strategies for this species.

Evolutionary mechanism of genome duplication enhancing natural autotetraploid sea barley adaptability to drought stress

The evolutionary mechanism where autopolyploid tolerate abiotic stresses better than its diploid ancestor is poorly known. Large-scale gene-expression changes were not observed in synthetic autopolyploids compared to their respective diploids. However, natural autopolyploids with longer evolutionary periods might have experienced major changes that resulted in greater adaptation of autopolyploids, which might contribute to gene expression in natural autopolyploid differently from that in synthetic autopolyploid, and explain why genome doubling can help plants develop a stronger ability to adapt to various environmental stresses. However, information on this is still lacking. Here, diploid and autotetraploid sea barley tolerance to drought stress were analyzed. Our data showed that autotetraploids showed higher tolerance to drought stress than diploids. The results of GO enrichment and KEGG pathway enrichment showed that diploid and tetraploid would alter their physiological and biochemical process, even morphology to respond to drought stress via different molecular mechanism. Genome duplication resulted in more differentially expressed drought-related genes and higher expression level of those genes in autopolyploid than in diploid, 186 drought-related genes with 97 genes up-regulated in comparison of DiH826Dr_vs_DiH826Ck, while 297 drought-related genes with 126 up-regulated in TetraH832Dr_vs_TetraH832Ck. Among these drought-related genes, 81 of them were specific significantly expressed in DiH826Dr_vs_DiH826Ck, 192 genes were specific significantly expressed in TetraH832Dr_vs_TetraH832Ck. Although our results indicated that the autopolyploid does not seem to undergo major changes of gene expression over long periods (2.84%) and under drought stress, more DEGs and more up-regulated DEGs between autotetraploid and diploid were observed than those in the CK. Furthermore, genome duplication also resulted in gain or loss of drought-related genes, which might offer potential for autopolyploid to survive better under drought environment.

Variability in response to salinity stress in natural Tunisian populations of Hordeum marinum subsp. marinum.

Soil salinity is one of the most serious environmental factors affecting crop productivity around the world. In this study, we analysed morpho-physiological variation in responses to salt stress in Tunisian populations of Hordeum marinum subsp. marinum. The plants were grown under two treatments (0 and 200mm NaCl) until maturity. A total of 19 quantitative traits were measured before and during the harvest. It was observed that most studied traits are influenced by the increasing salinity. High to moderate broad-sense heritability (H2 ) were noted for most of parameters under control and salt treatment, implying that salt tolerance is moderately heritable and environmental variation plays an equally important role. The majority of correlations between measured traits under the two treatments are positive, where the strongest correlations were between spike number (SN) and weight (SW). Based on the salt response index (SRI) values, SN and SW are the most affected by salinity. The 150 studied lines formed three groups according to the SRI values of the 19 quantitative parameters, of which 101 were moderately sensitive, 27 tolerant and 22 highly tolerant. Overall genetic variation of H.marinum in response to salt stress may provide novel insight to identify genes responsible for salt tolerance.

Compensation Ability between the Chromosomes of Homoeologous Group 7 of Triticum aestivum L. and Hordeum marinum ssp. gussoneanum Hudson (2n = 28) and Analysis of the Transmission Frequency of Alien 7H1Lmar Chromosome through Gametes in the Progeny of Wheat–Barley Substitution Lines

On the basis of directed chromosome substitution, ditelosomic (DT) wheat–barley substitution lines (2n = 42 = 40 + 2t) with participation of wild tetraploid barley Hordeum marinum ssp. gussoneanum Hudson (2n = 28) were first obtained and analyzed. GISH analysis of the substitution lines showed that they carried a pair of telocentric barley chromosomes. With the help of ditelosomic analysis, the lines were identified as DT7HILmar(7A) and DT7HILmar(7B). On the basis of the compensation test and the study of meiotic stability of substitution lines, it was demonstrated that 7HILmar chromosome of H. marinum was homoeologous to the group 7 chromosomes of common wheat. Analysis of the gamete transfer frequency in the progeny of reciprocal hybrids between F1 7A-7HILmar, 7B-7HILmar, 7D-7HILmar and Saratovskaya 29 cultivar showed that the gamete with alien chromosome n = 20 + t successfully competed with euploid gamete n = 21 in both macrosporogenesis and microsporogenesis.

Metabolomic and transcriptomic analyses reveal the reasons why Hordeum marinum has higher salt tolerance than Hordeum vulgare

Sea barley (Hordeum marinum) is a wild species belonging to halophytes, while other Hordeum species are glycophytes. In this study, we aimed to understand molecular differences of transcriptomic and metabolomic responses and uncover complex mechanisms underlying salt tolerance between H. marinum and H. vulgare. Physiological studies revealed that sea barley accession H559 had less growth inhibition, higher root K+ concentration, lower shoot Na+ accumulation and higher shoot osmotic potential than barley genotypes XZ113 and Golden Promise under 400 mM salinity stress. The superior Na+/K+ homeostasis in H559 may depend on the regulation of ion transporters including SOS1, HKT1;1, HKT1;5 and HKT2;2 according to RNA-seq analysis. The comparison of metabolite and transcript profiles among three genotypes indicated that H559 used less energy-consuming strategies including a larger scale gene down-regulation and utilization of inorganic ions (i.e. Na+ and K+) as “cheap” osmotica for root tolerance, and enhanced glycolysis and the TCA cycle for energy supply and compatible solutes accumulation for shoot tolerance. Moreover, some genes involved in the ROS detoxification were also identified in H559. We propose that the salt tolerance in the halophyte sea barley is correlated with superior Na+/K+ homeostasis, energy-saving strategy and osmotic adjustments in tissues. The present results provide the fundamental evidences at molecular level for explaining why H. marinum has higher salt tolerance than H. vulgare.

The Proteome Response of \u201cHordeum marinum\u201d to Long-term Salinity Stress

Salinity is a major constraint to crop productivity and mechanisms of plant responses to salinity stress are extremely complex. “Hordeum marinum” is a salt tolerant barley species, which could be a good source to evaluate salt-tolerance patterns. Proteomics is a powerful technique to identify proteins involved in plant adaptation to stresses. We applied a proteomic approach to better understanding the mechanism of plant responses to salinity in a salt-tolerant genotype of barley. At the 4-leaf stage, plants were exposed to 0 (control treatment) or 300 mM NaCl (salt treatment). Salt treatment was maintained for 3 weeks. Total proteins of leaf 4 were extracted and separated by two-dimensional gel electrophoresis. More than 290 protein spots were reproducibly detected. Of these, 20 spots showed significant changes to salt treatment compared to the control: 19 spots were upregulated and 1 spot was absent. Using MALDI-TOF/TOF MS, we identified 20 cellular proteins which represented 11 different proteins and were classified into five categories. These proteins were involved in various cellular functions. Upregulation of proteins which involved in protein processing (ribosomal protein, cullin family, cp31AHv protein and RNA recognition motif (RRM) superfamily), photosynthesis (Ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) and Ribulose bisphosphate carboxylase/oxygenase activase (rubisco activase)), energy metabolism (cytosolic malate dehydrogenase (cyMDH) and fructokinase), oxygen species scavenging and defense (cystatin and thioredoxin) may increase plant adaptation to salt stress.

On the allopolyploid origin and genome structure of the closely related species Hordeum secalinum and Hordeum capense inferred by molecular karyotyping.

To provide additional information to the many phylogenetic analyses conducted within Hordeum , here the origin and interspecific affinities of the allotetraploids Hordeum secalinum and Hordeum capense were analysed by molecular karyotyping. Karyotypes were determined using genomic in situ hybridization (GISH) to distinguish the sub-genomes and , plus fluorescence in situ hybridization (FISH)/non-denaturing (ND)-FISH to determine the distribution of ten tandem repetitive DNA sequences and thus provide chromosome markers. Each chromosome pair in the six accessions analysed was identified, allowing the establishment of homologous and putative homeologous relationships. The low-level polymorphism observed among the H. secalinum accessions contrasted with the divergence recorded for the sub-genome of the H. capense accessions. Although accession H335 carries an intergenomic translocation, its chromosome structure was indistinguishable from that of H. secalinum . Hordeum secalinum and H. capense accession H335 share a hybrid origin involving Hordeum marinum subsp. gussoneanum as the genome donor and an unidentified genome progenitor. Hordeum capense accession BCC2062 either diverged, with remodelling of the sub-genome, or its genome was donated by a now extinct ancestor. A scheme of probable evolution shows the intricate pattern of relationships among the Hordeum species carrying the genome (including all H. marinum taxa and the hexaploid Hordeum brachyantherum ).

Anatomical and biochemical characterisation of a barrier to radial O2 loss in adventitious roots of two contrasting Hordeum marinum accessions.

A barrier to radial O2 loss (ROL) in roots is an adaptive trait of waterlogging-tolerant plants. Hordeum marinum Huds. is a waterlogging-tolerant species that, in contrast to its waterlogging-sensitive cultivated relatives, forms a tight barrier to ROL in basal root zones. To evaluate the nature of the barrier to ROL in roots, we combined measurements of ROL with histochemical and biochemical studies of two contrasting H. marinum accessions. H21 formed greater aerenchyma (up to 38% of cross-sectional area) and a tight barrier to ROL when grown under deoxygenated stagnant conditions, whereas the barrier was only partially formed in roots of H90 and aerenchyma was up to 26%. A tight barrier to ROL in roots of H21 corresponded with strong suberisation of the exodermis. In agreement with anatomical studies, almost all aliphatic suberin quantities were greater in roots of H21 grown under stagnant conditions compared with roots from aerated controls, and also to those in H90. By contrast to suberin, no differences in root lignification were observed between the two accessions raised in either aerated or stagnant conditions. These findings show that in adventitious roots of H. marinum, suberisation rather than lignification restricts ROL from the basal root zones.

Assessment of Genetic Variability among Tunisian Populations of Hordeum marinum Using Morpho‐Agronomic Traits

Sea barely (Hordeum marinum Huds.) is known as a salinity‐tolerant annual grass species. Its use in the rehabilitation of degraded arid and semiarid rangelands or in crop plant improvement programs is of great interest. In this study, we investigated the phenotypic variation within and among 150 single‐seed descent families representing 10 Tunisian populations of H. marinum using eight quantitative traits. The experiment was conducted under greenhouse conditions. For each population, seeds from 15 mother plants were evaluated with five replicates per mother plant. Our results showed significant variation within and between populations for most measured traits. Most phenotypic variation was found to occur within populations. The QST measurement of differentiation between populations varied according to traits from 0.03 for number of tillers to 0.309 for the weight of aerial part, with an average of 0.149. Pairwise QST grouped studied populations into three major clusters; the first group included Tabarka and Sidi Othman populations showing the lowest values for spike number and weight. The second group included Lessouda, Bouficha, and Mouthul having the highest values for the number and weight of spikes, while the third group included populations Lac de Bizerte, Sebkhet Ferjouna, Bkalta, Medjez El Bab, and Soliman and had moderate spike number and weight. Furthermore, there was no significant association between population differentiation and ecogeographical parameters.

Evaluation of root porosity and radial oxygen loss of disomic addition lines of Hordeum marinum in wheat.

Hordeum marinum Huds. is a waterlogging-tolerant wild relative of wheat (Triticum aestivum L.). Greater root porosity (gas volume per root volume) and formation of a barrier to reduce root radial O2 loss (ROL) contribute to the waterlogging tolerance of H. marinum and these traits are evident in some H. marinum-wheat amphiploids. We evaluated root porosity, ROL patterns and tolerance to hypoxic stagnant conditions for 10 various H. marinum (two accessions) disomic chromosome addition (DA) lines in wheat (two varieties), produced from two H. marinum-wheat amphiploids and their recurrent wheat parents. None of the DA lines had a barrier to ROL or higher root porosity than the wheat parents. Lack of a root ROL barrier in the six DA lines for H. marinum accession H21 in Chinese Spring (CS) wheat indicates that the gene(s) for this trait do not reside on one of these six chromosomes; unfortunately, chromosome 3 of H. marinum has not been isolated in CS. Unlike the H21-CS amphiploid, which formed a partial ROL barrier in roots, the H90-Westonia amphiploid and the four derived DA lines available did not. The unaltered root aeration traits in the available DA lines challenge the strategy of using H. marinum as a donor of these traits to wheat.

Proteomic Response of Hordeum vulgare cv. Tadmor and Hordeum marinum to Salinity Stress: Similarities and Differences between a Glycophyte and a Halophyte.

Response to a high salinity treatment of 300 mM NaCl was studied in a cultivated barley Hordeum vulgare Syrian cultivar Tadmor and in a halophytic wild barley H. marinum. Differential salinity tolerance of H. marinum and H. vulgare is underlied by qualitative and quantitative differences in proteins involved in a variety of biological processes. The major aim was to identify proteins underlying differential salinity tolerance between the two barley species. Analyses of plant water content, osmotic potential and accumulation of proline and dehydrin proteins under high salinity revealed a relatively higher water saturation deficit in H. marinum than in H. vulgare while H. vulgare had lower osmotic potential corresponding with high levels of proline and dehydrins. Analysis of proteins soluble upon boiling isolated from control and salt-treated crown tissues revealed similarities as well as differences between H. marinum and H. vulgare. The similar salinity responses of both barley species lie in enhanced levels of stress-protective proteins such as defense-related proteins from late-embryogenesis abundant family, several chaperones from heat shock protein family, and others such as GrpE. However, there have also been found significant differences between H. marinum and H. vulgare salinity response indicating an active stress acclimation in H. marinum while stress damage in H. vulgare. An active acclimation to high salinity in H. marinum is underlined by enhanced levels of several stress-responsive transcription factors from basic leucine zipper and nascent polypeptide-associated complex families. In salt-treated H. marinum, enhanced levels of proteins involved in energy metabolism such as glycolysis, ATP metabolism, and photosynthesis-related proteins indicate an active acclimation to enhanced energy requirements during an establishment of novel plant homeostasis. In contrast, changes at proteome level in salt-treated H. vulgare indicate plant tissue damage as revealed by enhanced levels of proteins involved in proteasome-dependent protein degradation and proteins related to apoptosis. The results of proteomic analysis clearly indicate differential responses to high salinity and provide more profound insight into biological mechanisms underlying salinity response between two barley species with contrasting salinity tolerance.

Collinearity of homoeologous group 3 chromosomes in the genus Hordeum and Secale cereale as revealed by 3H-derived FISH analysis.

Crop wild relatives are considered as important genetic resources of allelic diversity for domesticated crop species. Their utilization in breeding programs, however, is often limited due to crossing barriers and genome incompatibilities. Wild relatives of barley possess attractive properties and hence allelic diversity for adapting barley better to changing environmental conditions. Therefore, gaining a better knowledge about genomic synteny between cultivated barley and wild relatives of the same genus is an important task. To visualize genomic collinearity in related species, 22 genomic single-copy and 14 complementary DNA (cDNA) chromosome 3H-specific probes were mapped to the chromosomes of Hordeum bulbosum, Hordeum marinum, Hordeum pubiflorum, Hordeum murinum, and Secale cereale by fluorescent in situ hybridization (FISH). Most probes showed reliable signals confirming homoeology between cultivated barley and related species. Differences in order and position of FISH markers demonstrated sequence movements or small-scale chromosomal rearrangements within genus Hordeum and confirmed interchromosomal rearrangements between barley and rye. Comparison between repeat-free genomic and cDNA probes showed that gene-containing single-copy genomic DNA (gDNA) probes are performing more reliably for FISH-based analysis of synteny.

A Novel Itera-Like Densovirus Isolated by Viral Metagenomics from the Sea Barley Hordeum marinum.

Densoviruses (DVs) infect arthropods and belong to the Parvoviridae family. Here, we report the complete coding sequence of a novel DV isolated from the plant Hordeum marinum (Poaceae) by viral metagenomics, and we confirmed reamplification by PCR. Phylogenetic analyses showed that this novel DV is related to the genus Iteradensovirus.

Potential new sources of wheat curl mite resistance in wheat to prevent the spread of yield-reducing pathogens

The wheat curl mite (WCM), Aceria tosichella Keifer (Trombidiformes: Eriophyidae), is a major pest in cropping regions of the world and is recognised as the primary vector of several yield-reducing pathogens, primarily affecting wheat. Management of WCM is complicated due to several aspects of the mite's biology and ecology; however, commercially viable mite resistant wheat varieties may offer practical long-term management options. Unfortunately, mite populations have adapted to previously identified sources of resistance, highlighting the need for further sources of resistance and the value of stacking different resistances to give greater degrees and longevity of control. In this study we assessed the susceptibility of 42 wheat-derived genotypes to mite population growth using a new experimental method that overcomes methodological limitations of previous studies. Experimental wheat lines included a variety of wheat genotypes, related Triticeae species, wheat-alien chromosome amphiploids, and chromosome addition or substitution lines. From these we identify new promising sources of WCM resistance associated with Thinopyrum intermedium, Th. ponticum and Hordeum marinum chromosomes. More specifically we identify group 1J and 5J chromosomes of the L3 and L5 wheat-Th. intermedium addition lines as new sources of resistance that could be exploited to transfer resistance onto homoeologous wheat chromosomes. This study offers new methods for reliable in situ estimations of mite abundance on cereal plants, and new sources of WCM resistance that may assist management of WCM and associated viruses in wheat.