Chromosomal control of the tolerance of gradually and suddenly imposed salt stress in the Lophopyrum elongatum and wheat,Triticum aestivum L. genomes

The facultatively halophytic Lophopyrum elongatum, closely related wheat, Triticum aestivum, and their amphiploid tolerate salt stress better if they are gradually exposed to it than if they are suddenly stressed. Lophopyrum elongatum has greater tolerance of both forms of salt stress than wheat, and its genome partially confers this tolerance on their amphiploid. Chromosomal control of the tolerance of both stress regimes in the L. elongatum and wheat genomes was investigated with disomic and ditelosomic addition lines and disomic substitution lines of L. elongatum chromosomes in wheat and with wheat tetrasomics. The tolerance of the sudden salt stress is principally controlled by L. elongatum chromosomes 3E and 5E and less by 1E, 2E, 6E, and 7E and the tolerance of gradually imposed salt stress principally by chromosomes 3E, 4E, and 5E, and less by chromosome 1E and 7E. Ditelosomic analysis indicated that genes conferring the tolerance of sudden stress are on chromosome arms 1EL, 5ES, 5EL, 6EL, 7ES and 7EL and those controlling the gradual stress regime are on 1ES, 1EL, 5ES, 5EL, 6ES, 7ES, and 7EL. In wheat, chromosomes in homoeologous groups 1, 3, and 7 and chromosomes in homoeologous groups 1, 4, and 6 were shown to enhance the tolerance of suddenly and gradually imposed stress, respectively. The arms of chromosome 3E individually conferred tolerance to neither stress regime. Chromosome 2E and wheat chromosomes 2B and 2D reduce the tolerance of both stress regimes in a hyperploid state. In 2E this effect was associated with arm 2EL. A potential relationship between the tolerance of these stress regimes and the expression of the early-salt induced genes is examined.     

Cytological and molecular characterization of a chromosome interchange and addition lines in Cadet involving chromosome 5B of wheat and 6Ag of Lophopyrum ponticum

Efforts to transfer wheat curl mite (Eriophyes tulipae Keifer) resistance from Lophopyrum ponticum 10X (Podb.) Love to bread wheat (Triticum aestivum L.) have resulted in the production of a number of cytogenetic stocks, including an addition line of 6Ag, a ditelo addition line, and a wheat-Lophopyrum translocation line. Characterization of these lines with C-banding, in situ hybridization with a Lophopyrum species-specific repetitive DNA probe (pLeUCD2), and Southern blotting with pLeUCD2 and a 5S ribosomal DNA probe (pScT7) confirmed that the distal portion of the short arm of 6Ag was translocated onto the distal portion of 5BS (5BL. 5BS-6AgS). It was also determined that the ditelo addition was an acrocentric chromosome of 6AgS.     

Differential stress responses of early salt-stress responding genes in common wheat

Four early salt-stress responding genes (WESR1-4) in common wheat (Triticum aestivum L.) were analyzed for their temporal accumulation of mRNA during salt stress, osmotic stress and abscisic acid (ABA) treatment. All genes showed transient stimulation by 0.15 M NaCl treatment. WESR1 and WESR2 were induced by both osmotic stress and exogenous ABA treatment. WESR3 responded to exogenous ABA, but not to osmotic stress. WESR4 did not show significant response to either osmotic stress or exogenous ABA treatment. These results suggest that wheat has at least two salt stress signal transduction pathways, an ABA-dependent and ABA-independent pathway.     

The effects of NaCl on antioxidant enzyme activities in callus tissue of salt-tolerant and salt-sensitive cotton cultivars (Gossypium hirsutum L.)

Summary To determine NaCl effects on callus growth and antioxidant activity, callus of a salt-tolerant and a salt-sensitive cultivar of cotton was grown on media amended with 0, 75, and 150 mM NaCl. Callus of the salt-tolerant cultivar, Acala 1517-8 8, grown at 150 mM NaCl, showed significant increases in superoxide dismutase, catalase, ascorbate peroxidase, peroxidase and glutathione reductase activities compared to callus tissue grown at 0 mM NaCl. In contrast, callus tissue of the salt-sensitive cultivar, Deltapine 50, grown at 0, 75, and 150 mM NaCl, showed no difference in the activities of these enzymes. At the 150 mM NaCl treatment, peroxidase was the only antioxidant enzyme from Deltapine 50 with an activity as high as that observed in Acala 1517-88. The NaCl-induced increase in the activity of these enzymes in Acala 1517-88 indicates that callus tissue from the more salt-tolerant cultivar has a higher capacity for scavenging and dismutating superoxide, an increased ability to decompose H₂O₂, and a more active ascorbate-glutathione cycle when grown on media amended with NaCl.     

Synthesis and cytological characterization of trigeneric hybrids involving durum wheat,Thinopyrum bessarabicum,and Lophopyrum elongatum

Summary In an attempt to transfer genes for salt tolerance and other desirable traits from the diploid wheatgrasses, Thinopyrum bessarabicum (2n=2x=14; JJ genome) and Lophopyrum elongatum (2n=2x=14; EE genome), into durum wheat cv Langdon (2n=4x=28; AABB genomes), trigeneric hybrids with the genomic constitution ABJE were synthesized and cytologically characterized. C-banding analysis of somatic chromosomes of the A, B, J, and E genomes in the same cellular environment revealed distinct banding patterns; each of the 28 chromosomes could be identified. They differed in the total amount of constitutive heterochromatin. Total surface area and C-banded area of each chromosome were calculated. The B genome was the largest in size, followed by the J, A, and E genomes, and its chromosomes were also the most heavily banded. Only 25.8% of the total chromosome complement in 10 ABJE hybrids showed association, with mean arm-pairing frequency (c) values from 0.123 to 0.180 and chiasma frequencies from 3.36 to 5.02 per cell. The overall mean pairing was 0.004 ring IV + 0.046 chain IV + 0.236 III + 0.21 ring II + 2.95 rod II + 20.771. This is total pairing between chromosomes of different genomes, possibly between A and B, A and J, A and E, B and J, B and E, and J and E, in the presence of apparently functional pairing regulator Ph1. Because chromosome pairing in the presence of Ph1 seldom occurs between A and B, or between J and E, it was inferred that pairing between the wheat chromosomes and alien chromosomes occurred. The trigeneric hybrids with two genomes of wheat and one each of Thinopyrum and Lophopyrum should be useful in the production of cytogenetic stocks to facilitate the transfer of alien genes into wheat.     

The genetic control of grain esterases in hexaploid wheat

Summary A comparison of EST-5 grain esterase phenotypes from wheat-alien amphiploid, addition and substitution genotypes, resolved by flat-bed isoelectric focusing identified homoeologous Est-5 loci on chromosome 3H of Hordeum vulgare, 3H^ch of H. chilense, 3S^b of Aegilops bicornis, 3S¹ of Ae. sharonensis and Ae. longissima and 6R of Secale cereale and 6R^m of S. montanum. The Est-5 genes in alien species provide evidence for chromosome homoeology with wheat.     

Comparison of categories of resistance in wheat and barley genotypes against biotype 2 of the Russian wheat aphid, Diuraphis noxia (Kurdjumov)

The Russian wheat aphid Diuraphis noxia (Kurdjumov) (Homoptera: Aphididae) is a global pest of wheat and barley. This arthropod is difficult to manage with pesticides or biological control agents due to the aphid’s ability to seek shelter in rolled leaves and also to develop virulent biotypes. During the past 20 years, the use of aphid-resistant cereal cultivars has proven to be an economically and ecologically beneficial method of protecting crops from D. noxia damage. Our research reports the results of experiments to determine the categories of D. noxia biotype 2 resistance present in Cereal Introduction Triticeae (CItr) 2401, and a barley genotype (IBRWAGP4-7), compared to control resistant and susceptible wheat and barley genotypes. CItr2401 and IBRWAGP4-7 exhibit no antixenosis, but both genotypes demonstrated antibiosis to D. noxia in the form of reduced aphid populations. Reduced leaf dry weight change, a measure of plant tolerance of D. noxia feeding, was significantly less in CItr2401 and IBRWAGP4-7 plants than in plants of susceptible control varieties. However, tolerance was negated when a tolerance index was calculated to correct for differences in aphid populations. Barley IBRWAGP4-7 is a new source of D. noxia biotype 2 resistance. D. noxia foliar leaf damage and population growth were significantly less on IBRWAGP4-7 plants than on plants of the susceptible barley variety Morex. IBRWAGP4-7 plants were equal in resistance to plants of the resistant barley STARS 9301 and wheat genotype CItr2401. Handling editor: Heikki Hokkanen     

Multidisciplinary approach to genome analysis in the diploid species,Thinopyrum bessarabicum and Th. elongatum (Lophopyrum elongatum), of the Triticeae

Summary The J and E genome species of the Triticeae are invaluable sources of salt tolerance. The evidence concerning the phyletic relatedness of the J genome of diploid Thinopyrum bessarabicum and the E genome of diploid Th. elongatum (=Lophopyrum elongatum) is discussed. Low level of chromosome pairing between J and E at different ploidy levels, suppression of J-E pairing by the Ph1 pairing regulator that inhibits homoeologous pairing, complete sterility of the diploid hybrids (JE), karyotypic divergence of the two genomes, differences in total content and distribution of heterochromatin along their chromosomes, and marked differences in gliadin proteins, isozymes, 5S DNA, and rDNA indicate that J and E are distinct genomes. Well-defined biochemical markers have been identified in the two genomes and may be useful in plant breeding. The level of distinction between J and E is comparable to that among the universally accepted homoeologous genomes A, B, and D of wheat. Therefore, the J and E genomes are homoeologous and not homologous, although some workers continue to call them homologous. The previous workers' data on chromosome pairing in diploid hybrids and/ or karyotypic differences in the conventionally stained chromosomes do not provide sufficient evidence for the proposed merger of J and E genomes (and, hence, of the genera Thinopyrum and Lophopyrum) specifically and for establishing genome relationships generally. Extra precautions should be exercised before changing the designation of an established genome and before merging two genera. A uniform, standardized system of genomic nomenclature for the entire Triticeae is proposed, which should benefit cytogeneticists, plant breeders, taxonomists, and evolutionists.Cooperative investigations of the USDA-Agricultural Research Service and the Utah Agricultural Experiment Station, Logan, UT 84322, USA. Approved as Journal Paper no. 3832     

LMW-GS genes in Agropyron elongatum and their potential value in wheat breeding

To study the usefulness of low-molecular-weight glutenin subunits (LMW-GS) of Agropyron elongatum (Host) Nevski to wheat (Triticum aestivum L.) quality improvement, we characterized LMW-GS genes of A. elongatum. Nine LMW-GS genes of A. elongatum, which were named AeL1 to AeL9, were cloned by genomic PCR. After sequencing, we obtained complete open reading frames from AeL2 to AeL8 and partial genes of AeL1 and AeL9. All nine sequences are homoeologous to those of wheat and related grasses. Comparison of the deduced amino acid sequences with those of published LMW-GS suggests that the basic structures of all the subunits are very similar. However, except for AeL4 and AeL5, which contain the identical N-terminal sequence with LMW-m, other LMW-GS sequences separated from A. elongatum cannot be classified according to previous criteria for the three types: LMW-m (methionine), LMW-s (serine), and LMW-i (isoleucine), and then 12 groups. In addition, there are some characters in the LMW-GS sequences of A. elongatum: AeL2, AeL3, and AeL6 involve a Cys residue in the signal peptide respectively, which is absent in most of LMW-GS; AeL3, AeL6, AeL8, and AeL9 start their first Cys residues in the N-terminal repetitive domains, respectively; both AeL2 and AeL5 have nine Cys residues, with an extra Cys residue in the N-terminal repetitive domain and the repetitive and glutamine-rich domain; AeL2, AeL3, AeL6, and AeL9 comprise long repetitive domains. Phylogenetic analysis indicates that there is a relatively weak sequence identity between the LMW-GS genes from A. elongatum cloned in this study and those reported from other plants. Three LMW-GS sequences, AeL2, AeL3, and AeL6, are clustered to Glu-A3 from wheat than to those from other plants. The possible use of these genes in relation to the high quality of hybrid wheat is discussed.     

Modification of the salinity response of wheat by the genome ofElytrigia elongatum

Summary Triticum aestivum cv. Chinese Spring wheat,Elytrigia elongatum (tall wheatgrass), and theTriticum-Elytrigia amphiploid were grown in complete nutrient culture containing, in addition, 0, 40, 80 and 120 mM NaCl. The 3 genotypes responded quite differently to increasing salinity; the Na concentration of wheat shoots increased in direct proportion to the increase in salinity of the external medium whereas the Elytrigia response was interpreted as showing high affinity for Na at low external Na (40 mM) but comparative exclusion of Na at high salinities (120 mM). In contrast, Na levels of the amphiploid were less than those of either wheat or Elytrigia under both low and high salinities. Thus the amphiploid behaved like wheat at 40 mM NaCl but more like Elytrigia at 120 mM NaCl because Na transport to the amphiploid shoot was restricted over the whole salinity range. The K concentration of the amphiploid shoot at high salinities was significantly greater than the K concentrations of either wheat or Elytrigia.     

Molecular cytogenetic analysis of Agropyron elongatum chromatin in wheat germplasm specifying resistance to wheat streak mosaic virus

Summary Three lines derived from wheat (6x) x Agropyron elongatum (10x) that are resistant to wheat streak mosaic virus (WSMV) were analyzed by chromosome pairing, banding, and in situ hybridization. Line CI15321 was identified as a disomic substitution line where wheat chromosome 1D is replaced by Ag. elongatum chromosome 1Ae-1. Line 87-94-1 is a wheat-Ag. elongatum ditelosomic addition 1Ae-1L. Line CI15322 contains an Ag. elongatum chromosome, 1Ae-2, that substitutes for chromosome 1D. The short arm of 1Ae-2 paired with the short arm of 1Ae-1 at metaphase I (MI) in 82% of the pollen mother cells (PMCs). However, the long arms of these two chromosomes did not pair with each other. In CI15322, the long arm of chromosome 4D has an Agropyron chromosome segment which was derived from the distal part of 1Ae-1L. This translocation chromosome is designated as T4DS·4DL-1L. T4DS·4DL-1Ae-1L has a 0.73 m distal part of the long arm of 4D replaced by a 1.31 m distal segment from 1Ae-1L. The major WSMV resistance gene(s) in these lines is located on the distal part of 1Ae-1L.Contribution No. 92-599-J from the Kansas Agricutural Experiment Station, Kansas State University, Manhattan, Kansas, USA     

Partitioning of carbohydrates in salt-sensitive and salt-tolerant soybean callus cultures under salinity stress and its subsequent relief

Salt tolerant (R100) and sensitive (S100) cell lines of Glycine max (L.) that differ in their ability to accumulate sodium (Na) and chloride (Cl) under 100 mM salt stress, were used to compare the contribution of carbohydrates in osmotic adjustment. Calliwere exposed to a 100 mM NaCl concentrations for 12 days followed by 16 days of relief from stress to determine the effect of salinity changes of sugar content in the two cell lines. The salt-tolerant and the salt-sensitive cell lines differed in the time at which, and the type of sugar, that increased during salt stress. However, recovery in sugar content parameters during relief from stress were similar in the two cell lines. The concentration of glucose and fructose increased at a rate closely corresponding to the increase in fresh weight, while the concentration of sucrose decreased to the control level coincident with relatively rapid growth.     

Tests for the presence of gametoclonal variation in barley and wheat doubled haploids produced using the Hordeum bulbosum system

Summary To investigate whether the Hordeum bulbosum system of doubled haploid production generates gametoclonal variation, populations of second generation doubled haploid lines were developed from first generation doubled haploid lines of two barley varieties and three wheat genotypes. In barley, no variation between doubled haploids from doubled haploids was detected for a range of quantitative characters, suggesting the absence of any gametoclonal effects. However, the original selfed-seed stocks were shown to contain cryptic allelic variation for some of the characters investigated. In wheat, gametoclonal variation was detected for ear emergence time, plant height and yield, and its components for two out of the three genotypes investigated. The type and range of variation was similar to that reported from studies of somaclonal variation from immature embryos and gametoclonal variation from anther culture. Generally, the effects appeared to reduce the yield performance of individual lines. The difference in response between the two species and the consequences for the use of the doubled haploid system in breeding programmes are discussed.     

Screening salt-tolerant barley genotypes via F1 anther culture in salt stress media

Summary Anthers of two six-row barley cultivars Diamond (a germination salt sensitive cultivar) and Men Yuan Liang Lan (a germination salt tolerant cultivar), and their F₁ reciprocal crosses were cultured in liquid media containing 0, 0.4, 0.6, and 0.8% Na₂SO₄. A total of 138 green pollen plants were obtained: 7 from Na₂SO₄ media, 128 from Na₂SO₄ free medium. Seeds of two successive generations of 61 pollen plants were germinated in a series of Na₂SO₄ solution (0 to 5.5%). It was found that among 37 progenies from F₁ pollen in Na₂SO₄ free medium, 11 were as sensitive as Diamond, 12 were intermediate to the two parents, 7 were equal to the salt tolerant parent and 7 were more tolerant to Na₂SO₄ than Men Yuan Liang Lan. Whereas, no progeny from F₁ pollen in high salt media was as susceptible as the susceptible parent; 2 were intermediate, 2 were equal to the salt tolerant parent and 2 were more tolerant than the salt tolerant parent. The results indicate that culturing anthers in Na₂SO₄ media effectively eliminated salt susceptible progenies. All 16 microspore-derived lines of Diamond were as susceptible as Diamond to Na₂SO₄. The 5 lines from Men Yuan Liang Lan microspores were as resistant to Na₂SO₄ as Men Yuan Liang Lan. All of the lines breed-true. The results indicate that the lines exhibiting elevated levels of tolerance to salt probably resulted from recombination of genes rather than from spontaneous mutation.     

Salt stress induces changes in amounts and localization of the mitogen-activated protein kinase SIMK in alfalfa roots

Summary SIMK is an alfalfa mitogen-activated protein kinase (MAPK) that is activated by salt stress and shows a nuclear localization in suspension-cultured cells. We investigated the localization of SIMK in alfalfa (Medicago sati a) roots. Although SIMK was expressed in most tissues of the root apex, cells of the quiescent center and statocytes showed much lower SIMK protein amounts. In cells of the elongation zone, SIMK was present in much higher amounts in epidermal than in cortex cells. In dividing cells of the root tip, SIMK revealed a cell cycle phase-dependent localization, being predominantly nuclear in interphase but associating with the cell plate and the newly formed cell wall in telophase and early G₁ phase. In dividing cells, salt stress resulted in an association of part of the SIMK with the preprophase band. Generally, salt stress resulted in much higher amounts of SIMK in dividing cells of the root apex and epidermal cells of the elongation zone. These data demonstrate that amounts and subcellular localization of SIMK in roots is highly regulated and sensitive to environmental stress.Dedicated to Professor Walter Gustav Url on the occasion of his 70th birthday     

Comparison of rates of natural senescence of the root cortex of wheat (with and without mildew infection), barley,oats and rye

Summary In comparative tests in a glasshouse, the cortex of oat and rye roots senesced more slowly than the cortex of wheat and barley roots. Of the cereals tested, wheat showed the most rapid rate of root cortical senescence, and the rate was unaffected by inoculation of leaves withErysiphe graminis. The results are discussed in relation to infection by root pathogens.