Cytoplasmic and cytogenetic relationships among tetraploid Triticum species

Summary The F₁ hybrids from crosses of 59 accessions of wild and cultivated Triticum types including amphidiploids T. boeoticum-Ae. squarrosa, T. timopheevi-Ae. squarrosa, T. timopheevi-T. monococcum, T. boeoticum (4n), T. macha, and T. Zhukovskyi with T. durum Sel. 56-1 and/or T. aestivum were examined for male sterility and chromosome pairing at metaphase I of meiosis in pollen mother cells. Those hybrids which produced male-sterile F₁'s were recurrently backrossed with pollen from T. durum or T. aestivum to study segregation for male sterility and/or to confirm cytoplasmic male sterility.All T. timopheevi and T. araraticum accessions and several T. dicoccoides types, including T. dicoccoides var. nudiglumis from the Turkey-Iran-Iraq area, had male sterility inducing cytoplasm. The chromosome pairing in the F₁ hybrids indicated that all tetraploid Triticum accessions with male sterility inducing cytoplasm had genome AAGG. T. dicoccoides Körn types from the Turkey-Iran-Iraq area had genomes AABB and did not have male sterility inducing cytoplasm. Therefore, T. dicoccoides Körn and the T. timopheevi complex differ from each other cytoplasmically and cytogenetically and occur sympatrically in the Turkey-Iran-Iraq area.Possibly, the cytoplasm of the emmers was not derived from the putative diploid progenitors, T. boeoticum, Ae. speltoides, or Ae. bicornis as indicated by their nucleo-cytoplasmic and cytogenetic relationships with the tetraploid Triticum species. The cytoplasmic differences among Ae. speltoides, T. araraticum and T. timopheevi are of a relatively smaller magnitude than the cytoplasmic differences among T. timopheevi, T. boeoticum, and the emmers. A complete analysis of nucleo-cytoplasmic relationships among Triticum and Aegilops species may indicate the cytoplasmic donor(s) to the two tetraploid Triticum species complexes.Authorized for publication 19 July, 1972 as Paper No 397 in the Journal Series of the North Dakota Agricultural Experiment Stations.     

Wheat pre-breeding using wild progenitors

To facilitate the use of wheat wild relatives in conventional breedingprograms, a wheat pre-breeding activity started at ICARDA in 1994/1995season. Preliminary results of gene introgression from wild diploidprogenitors, Triticum urartu, T. baeoticum, Aegilops speltoides andAe. tauschii and tetraploid T. dicoccoides are described. Crosseswith wild diploid Triticum spp. yielded high variation in plant andspike morphology. Synthetic hexaploids were produced from crosses of alocal durum wheat landrace `Haurani' with two Ae. tauschiiaccessions. Both Ae. tauschii accessions carry hybrid necrosis allelesthat gave necrotic plant phenotypes in crosses with some bread wheats.Backcross progenies with agronomical desirable traits, i.e. high spikeproductivity, short plant stature, earliness, drought tolerance and highproductive tillering, were identified in crosses of durum wheat with wild Triticum spp. and in a cross of one of the hexaploid synthetics with alocally adapted bread wheat cv. `Cham 6'. Resistance to yellow rust wasfound in durum wheat crosses with the three wild Triticum spp. andAe. speltoides and leaf rust resistance was identified in crosses withT. baeoticum and Ae. speltoides. The results show that wheatimmediate progenitors may be a valuable and readily accessible source ofnew genetic diversity for wheat improvement.     

Variation for resistance to head blight caused by Fusarium graminearum in wild emmer (Triticum dicoccoides) originating from Israel

Head blight of wheat (FHB, scab) caused by Fusarium spp. has been associated with yield and quality losses in many wheat-growing regions. In tetraploid wheat sources of resistance are scarce. In the search for novel sources of resistance, 151 Triticum dicoccoides genotypes, originating from 16 habitats in Israel and one habitat in Turkey together with several control genotypes, were evaluated for reaction to fungal spread (Type II resistance) in replicated greenhouse experiments. Significant genetic diversity was found among the tested genotypes, the broad sense heritability for Type II FHB resistance was 0.71. Most of the tetraploid accessions were highly susceptible, only a few showed moderate resistance. Among the eight T. dicoccoides lines with the lowest relative infection rates, five originated from the Mt. Gerizim population, and three from the Mt. Hermon population. None of the T. dicoccoides lines reached the level of resistance present in the common wheat cultivar Sumai3. This revised version was published online in July 2006 with corrections to the Cover Date.     

Resistance of wild emmer wheat to stem rust: Ecological,pathological and allozyme associations

Summary Seedling resistance to wheat stem rust was determined in populations of wild emmer wheat, Triticum dicoccoides, and characterized by means of ecological factors and allozyme genotypes. Reactions to wheat stem rust were studied in 102 single plant accessions of T. dicoccoides from ten populations by inoculation with Puccinia graminis tritici race 14, isolate GSR-739. Six populations displayed different degrees of response polymorphism with reactions ranging from high resistance to complete susceptibility, whereas four populations contained only susceptible plants. In some of the accession, unexplained intrasib variation in resistance and intraplant variation of infection-types were found. Resistance to stem rust was negatively correlated with two ecological factors, altitude and number of Sharav (hot-dry) days which are unfavorable to disease development. Variation in stem rust response was shown to exist in ecogeographic regions where climatic variables enhanced the development of the fungus, conceivably maintained by natural selection. Likewise, allozyme genotypes, single or in multiple loci combinations, appeared to be associated with resistance or susceptibility to rust. Such association need to be verified by genetic studies in order to become established as useful markers.     

Utilisation of <Emphasis Type="Italic">Aegilops</Emphasis> (goatgrass) species to widen the genetic diversity of cultivated wheat

Wild Aegilops species related to cultivated wheat (Triticum spp.) possess numerous genes of agronomic interest and can be valuable sources of resistance to diseases, pests and extreme environmental factors. These genes can be incorporated into the wheat genome via intergeneric crossing, following, where necessary, the development of chromosome addition and substitution lines from the resulting hybrids. The transfer of a single segment from an alien chromosome can be achieved by translocations. The Aegilops (goatgrass) species, which are the most closely related to wheat, exhibit great genetic diversity, the exploitation of which has been the subject of experimentation for more than a century. The present paper gives a survey of the results achieved to date in the field of wheat–Aegilops hybridisation and gene transfer. The Aegilops genus consists of 11 diploid, 10 tetraploid and 2 hexaploid species. Of these 23 Aegilops species, most of the diploids (Ae. umbellulata Zhuk., Ae. mutica Boiss., Ae. bicornis (Forssk.) Jaub. & Spach, Ae. searsii Feldman & Kislev ex Hammer, Ae. caudata L., Ae. sharonensis Eig, Ae. speltoides Tausch, Ae. longissima Schweinf. & Muschl.) and several polyploids (Ae. ventricosa Tausch, Ae. peregrina (Hack. In J. Fraser) Marie & Weiller, Ae. geniculata Roth, Ae. kotschyi Boiss., Ae. biuncialis L.) have been used to develop wheat–Aegilops addition lines. Wheat–Aegilops substitution lines were developed using several species, including Ae. umbellulata, Ae. caudata, Ae. tauschii, Ae. speltoides, Ae. sharonensis, Ae. longissima and Ae. geniculata. Translocations carrying genes responsible for useful agronomic traits were developed with Ae. umbellulata, Ae. comosa, Ae. ventricosa, Ae. longissima, Ae. speltoides and Ae. geniculata. A large number of genes were transferred from Aegilops species to cultivated wheat, including those for resistance to leaf rust, stem rust, yellow rust and powdery mildew, and various pests (cereal cyst nematode, root knot nematode, Hessian fly, greenbug). Many molecular markers are linked to these resistance genes. The development of new molecular markers is also underway. There are still many untapped genetic resources in Aegilops species that could be used as resistance sources for plant breeding.     

Growth dependency of wild,primitive and modern cultivated wheat lines on vesicular-arbuscular mycorrhiza fungi

Summary Mycorrhizal colonization and growth dependency were studied at a single rate of phosphorous application in wild and cultivated primitive and modern wheats, inoculated with Glomus intraradices Schenck & Smith. Mycorrhizal colonization found in Triticum timopheevii var. araraticum (AAGG) was higher than that found in the other tetraploid wheats (AABB). Mycorrhizal dependency was higher in representatives of the D genome donor — Aegilops squarrosa, compared with representatives of the A and possible B genome donors T. monococcum and Ae. sharonensis, Ae. longissima and Ae. speltoides, respectively. The nature of response to VAM in hexaploid wheat was controlled by factors of the A and B genomes which are epistatic over those located in the D genome. The high mycorrhizal colonization and dependency which was found in T. timopheevii var. araraticum may indicate special genomic affinity possessed by the G genome of wheat in VAM interaction. Based on the 27 wheat lines and species tested in this study only low correlation between G. intraradices colonization and its contribution to plant growth can be suggested.     

Genetic diversity of wheat wild relatives in the Near East detected by AFLP

In order to reveal the molecular genetic diversity of wheat wild relatives, an AFLP analysis was conducted with 16 accessions of five Triticum andAegilops species originating from the Near East. Variation within population was studied with at least seven individuals per accession. Four primer combinations were used for selective amplification. Based on the scored bands, we estimated percentage of polymorphic bands, 1 – proportion of shared bands (1-psb) and nucleotide diversity (π). Of the five species used in this study, Ae. speltoides had the highest level of `within population' variation. This species had also the highest value of the variation among populations. As for Triticum species, the level of variation within population was low in diploid species (T. urartu and T. boeoticum),whereas two tetraploid species (T. dicoccoides and T. araraticum) had relatively high levels of variation within population. While the two diploid Triticum indicated a clear interspecific divergence, the two tetraploid wild wheats were not clearly divergent in this study. The variance portioning analysis indicated that the variation detected for diploid Triticum species was mainly composed of `between species' variation, on the other hand that for tetraploid Triticum was mostly composed of `within population' variation. In conclusion, AFLP analysis reveals molecular variation in all accessions used in this study, suggesting a potential genetic diversity of the wheat wild relatives in natural populations. These results have implications for the design of strategies to maintain genetic diversity within genebank collections. This revised version was published online in August 2006 with corrections to the Cover Date.     

The introduction into bread wheat of a major gene for resistance to powdery mildew from wild emmer wheat

Summary A new source of resistance to wheat powdery mildew caused by Erysiphe graminis has been transferred to hexaploid bread wheat, Triticum aestivum, from the wild tetraploid wheat, Triticum dicoccoides. The donor was crossed to bread wheat and the pentaploid progeny was then self-pollinated. Plants having a near stable hexaploid chromosome complement were selected in the F₃ progeny and topcrossing and backcrossing of these to a second wheat cultivar to improve the phenotype was undertaken. Monosomic analysis of early backcross lines showed the transferred gene to be located on chromosome 4A. The gene has been designated Pm16.     

Morphology,geography and infraspecific taxonomics of Triticum dicoccoides Körn. A retrospective of 80 years of research

Summary Research on the morphology, geography and infraspecific taxonomics of Triticum dicoccoides Körn. performed during the 80 years since its rediscovery by Aaronsohn is reviewed. T. dicoccoides is a vluable genetic resource for the improvement of cultivated wheat. Its intraspecific structure is, however, not known sufficiently. It is evident that T. dicoccoides is subdivided into two morphologically and geographically distinct forms. The intepretations of these forms by various authors are diverse. There is also no consensus concerning their geographical within the general range of T. dicoccoides. It is necessary to carry out a detailed morphological study in order to define their taxonomical rank and specify their ranges. It would be expedient to perform comparative genetic, biochemical and agronomic investigations of the two T. dicoccoides infraspecific types.     

Cytoplasmic homology between Aegilops mutica Boiss. and Ae. ovata L.

Summary Triticum aestivum L. em Thell. (2n=42; AABBDD), and T. durum Desf. (2n=28; AABB) genomes were substituted into the cytoplasms of Aegilops mutica Boiss. (2n=14; M_tM_t), Ae. heldreichii Holzm. (2n=14; MM), Ae. uniaristata Vis. (2n=14; M^uM^u), and Ae. ovata L. (2n=28; C^uC^uM^oM^o), to identify the M-genome diploid cytoplasm donor of Ae. ovata. Substitution of the T. durum genome into Ae. uniaristata cytoplasm resulted in a large proportion of shriveled inviable seeds. A few plump viable seeds were obtained all of which produced male-sterile plants having one univalent or telocentric chromosome from Ae. uniaristata. The T. aestivum plants having Ae. uniaristata or Ae. mutica cytoplasms were fertile. However, Ae. mutica was similar to Ae. ovata in the induction of delayed maturity and tall robust growth habit to the T. durum and T. aestivum plants. Cytoplasms of the other C- and M-genome diploids Ae. umbellulata Zhuk. (2n=14; C^uC^u) and, Ae. heldreichii (2n=14; MM) earlier had been shown to differ from that of Ae. ovata. Therefore, Ae. mutica is the most likely cytoplasm and M-genome donor to Ae. ovata.     

Identification of Aegilops germplasm with multiple aphid resistance

The greenbug, Schizaphis graminum(Rondani), the Russian wheat aphid, Diuraphis noxia (Mordvilko), and the bird cherry oat aphid, Rhopalosiphum padi(L.), annually cause several million dollars worth of wheat production losses in Europe and the United States. In this study, Triticum and Aegilops accessions from the Czech Research Institute of Crop Production and the Kansas State University Wheat Genetic Resources Center were evaluated for resistance to these aphids. Accessions with aphid cross-resistance were examined for expression of the antibiosis, antixenosis, and tolerance categories of resistance. Aegilops neglecta accession 8052 exhibited antibiotic effects toward all three aphids in the form of reduced intrinsic rate of increase (r_m). The r_m of greenbug (biotype I) on Ae. neglecta 8052 was significantly lower than that of greenbugs on plants of the susceptible U. S. variety Thunder bird. The r_m of Russian wheat aphids was significantly lower on foliage of both Ae. neglecta 8052 and T. araraticum accession 168 compared to Thunderbird. The r_m values of bird cherry oat aphids fed both Ae. neglecta 8052 and T. araraticum 168 were also significantly lower than those fed the susceptible accession T. dicoccoides 62. Neither Ae. neglecta 8052 or T. araraticum 168 exhibited tolerance to either greenbug biotype I or Russian wheat aphid. Preliminary data suggest that T. araraticum 168 may also possess tolerance to bird cherry oat aphid. New genes from Ae. neglecta 8052 and T. araraticum 168 expressing aphid antibiosis can be used to develop multiple aphid resistant wheat in the U. S. and Central Europe. This revised version was published online in July 2006 with corrections to the Cover Date.     

Peroxidase isozyme differences in tall fescue cultivars and allopolyploid accessions

Summary The use of isoelectric focusing for the isozymic identification of cultivars and wild forms in tall fescue (Festuca arundinacea Schreb.) and determination of ploidy effects was investigated. Peroxidase zymograms from allopolyploid accessions (4x, 6x, 8x, and 10x, x=7) and randomly sampled plants of the cultivars Kenhy, Kentucky 31, and Missouri 96, were compared for band number, position, and staining intensity. There was little isozymic variation among plants in the tetraploid and hexaploid, but considerably more in the octoploid and decaploid members of the series. Yet no significant effects of ploidy on isozyme complexity or band number were observed. There were no consistent differences in band number, position, or frequencies among the three cultivars in spite of their diverse parentage. Isoclectric focusing can be used successfully in tall fescue, but the limited variability of the peroxidases encourages investigation of other isozyme systems in the future.Contribution from the Missouri Agricultural Experiment Station. Journal Series No. 8627. Research supported by USDA-SEA Competitive Research Grant 5901-0410-9-0366-0.     

Genetics of morphological traits in wild wheat,Triticum turgidum var.dicoccoides

Summary The mode of inheritance, linkage groups, and chromosomal location of 23 morphological and 4 biochemical traits were characterized in the wild tetraploid emmer wheat,Triticum turgidum var.dicoccoides. These traits were described and their mode of inheritance was determined by their segregation in four F₂ populations derived from crosses between four var.dicoccoides accessions and a tetraploiddurum cultivar. Linkage groups among the genes encoding for these traits were determined or postulated, and their chromosomal location was deduced by linkage to previously located genes. The genetic control of the following traits was characterized and is first reported here: black keel; hairy leaf sheath; hairy auricles; hairy rachilla; hairy kernel brush; obtuse flag leaf; and curved neck/peduncle. The linkage data indicated that developmentally-related genes tended to occur in clusters.     

Genetic resources of wild cereals in Israel and vicinity. I. Phenotypic variation within and between populations of wild wheat,Triticum dicoccoides

Summary Populations of wild emmer wheat, Triticum dicoccoides, in Israel, originating from diverse habitats, and tested earlier for allozyme (Nevo et al., 1982) and disease resistance polymorphisms (Moseman et al., 1983a, 1983b; Nevo et al., 1984a, 1984b), were compared and contrasted for performance in agronomically important phenotypic traits. The traits compared involved 10 variables comparing germination, earliness, biomass and yield variables. The field experiments were conducted in 1980, 1981 and 1982 in two relatively standardized and contrasting environments: mesic (Mount Carmel, Haifa) and xeric (Acedat Farm, and Sede Boqer, in the northern Negev desert). The experimental design involved 12 population quadrangles at Avedat Farm in 1980, and rows of randomized genotypes of five populations in both Haifa and Sede Boqer in 1981 and 1982.The results indicate that the characters studied are partly genetically determined. Striking genetic variation was found between and, at least in some characters, also within populations in each site, whereas remarkable environmental variation including genetic-environmental interaction was found between the mesic and the xeric sites. We conclude that natural populations of wild emmer wheat in Israel vary not only in genetic polymorphisms of allozymes and disease resistance, but also in quantitative traits of agronomic importance. These traits are economically significant and should be conserved and utilized in wheat crop improvement.     

Influence of selected wheat and rye genotypes on the direct synthesis of hexaploid triticale

Summary In the synthesis of primary hexaploid triticale, a cross-incompatibility barrier exists when tetraploid wheat (4X) is crossed with diploid (2X) rye. Fertilization may occur, however, abnormal endosperm development usually leads to premature embryo death. Four selected tetraploid wheat lines were crossed as females with seven open-pollinated rye lines and the resulting embryos were rescued in vitro 13–16 days after pollination. The wheat genotypes showed a major influence on crossability (seed set), embryo development and plant recovery. The highest efficiency of amphihaploid plant recovery (18.3 plants per 100 pollinated florets) was obtained from one 4X wheat line originally selected from the cross T. carthlicum × T. dicoccoides. Some of the 3X amphihaploid plants (ABR) derived from two wheat lines showed relatively high level of partial fertility presumably as a result of meiotic restitution. Correlation analysis showed that crossability (seed set), normal hybrid embryo development in vivo and embryo culturability were independent of each other.     

Plant nitrogen distribution in wild tetraploid (Triticum turgidum dicoccoides) and hexaploid wheat (Triticum aestivum)

Summary Differences were found in total nitrogen uptake and its pattern of distribution in the main tiller amongst five lines of wild tetraploid wheat (Triticum turgidum dicoccoides) and between it and two hexaploid wheats (Triticum aestivum) under low (48 ppm) and higher (240 ppm) levels of soil nitrogen.Under the low soil nitrogen level the hexaploids had higher amounts of total nitrogen in the main tiller than the dicoccoides lines, but under the higher soil nitrogen level, three of the dicoccoides lines had significantly (P<0.01) higher, and the other two lines, similar amounts as the hexaploids. The total amount of grain nitrogen in the hexaploids was significantly (P<0.01) higher than the five dicoccoides under the low nitrogen soil level but under the higher level, two of the dicoccoides lines had similar amounts as one of the hexaploids (cv. Bencubbin) but significantly (P<0.01) lower than the other (cv. Argentine IX).The efficiency of nitrogen translocation to the grain was significantly (P<0.01) lower in a primitive, compared with four cereal forms of dicoccoides under both low and high levels of soil nitrogen. The cereal forms of dicoccoides, while similar in nitrogen translocation efficiency under low soil nitrogen as the lower translocation efficiency hexaploid (cv. Bencubbin), were significantly (P<0.01) and substantially lower than it under the higher soil nitrogen level.     

Cytological and microsatellite mapping of the genes determining liguleless phenotype in durum wheat

Liguleless phenotypes of wheat lack ligule and auricle structures on all leaves of the plant. Two recessive genes principally control the liguleless character in tetraploid wheat. The F₂ progenies of k17769 (liguleless mutant)/Triticum dicoccoides and k17769/T. dicoccum segregated in a 15:1 ratio, whereas the F₂ progenies of k17769/T. durum and k17769/T. turgidum segregated in a 3:1 ratio. A new gene, lg₃, was found on chromosome 2A. Segregation of F₂ progenies between k17769 and chromosome substitution lines for homoeologous group 2 chromosomes suggested that the liguleless genotype had occurred by mutation at the lg₃ locus on chromosome 2A, and then by mutation at the lg₁ locus on chromosome 2B, in the process of domestication of tetraploid wheat. The gene (lg₁) was linked to Tc₂ (11.9 cM), which determines phenol colour reaction of kernels, on the long arm of chromosome 2B. The distance of lg₁ to the centromere was found to be 60.4 cM, and microsatellite mapping established the gene order, centromere – Xgwm382 – Xgwm619 – Tc₂ – lg₁ on the long arm of chromosome 2B.     

Resistance of Triticum dicoccoides to infection with Erysiphe graminis tritici

Summary The reactions of 233 Triticum dicoccoides acessions, collected at 10 sites in Israel and elsewhere, to infection with cultures of Erysiphe graminis tritici, were determined. The reactions indicated that the number of sources of resistance to E. graminis tritici which can be obtained from T. dicoccoides plants growing wild in Israel and elsewhere is almost unlimited. One hundred and fourteen or 49% of the accessions were resistant, and 137 or 59% of the accessions were resistant or moderately resistant to infection with four cultures of E. graminis tritici which possess the virulence genes corresponding to most of the identified resistance genes in wheat. Accessions collected at sites with marginal habitats where T. dicoccoides grows poorly and has lower grain weight, were more susceptible than were accessions collected at sites with an optimal habitat for growth of T. dicoccoides. The results agreed with those in a previous study with Hordeum spontaneum, and indicate that to obtain H. spontaneum or T. dicoccoides accessions with the highest level of resistance to the powdery mildew pathogens, plants should be collected at sites in ecological and geographic regions where those two species occupy optimum habitats and are exposed to the powdery mildew pathogens.     

An assessment of the potential of 4DS.4DL-4s l L translocation lines as a means of eliminating tall off types in semi-dwarf wheat varieties

Summary Wheat varieties tend to be chromosomally unstable producing on average 2–3% of plants with abnormal chromosome numbers. A number of semi dwarf wheat varieties, carrying the gibberellic acid insensitive dwarfing genes Rht1 or Rht2, have been seen to produce distinct tall off types due to reduction in dosage of the chromosome carrying the dwarfing gene. The UK variety Brigand, carrying Rht2 on chromosome 4D, produced very distinct tall off types when this chromosome was reduced in dosage. The frequency of tall off types was sufficiently high to cause the variety to fail United Kingdom statutory uniformity tests. An attempt to prevent the loss of chromosome 4D was made by constructing translocation chromosomes involving the short arm of chromosome 4D, which carries Rht2, and the long arm of chromosome 4S ^l from Aegilops sharonensis, which carries a gene(s) conferring preferential transmission. The work in this paper describes the field evaluation of two lines carrying 4DS.4DL-4S ^l L translocations, and demonstrates their success in preventing spontaneously occurring monosomy of chromosome 4D in semi-dwarf wheats.     

Variation of high-molecular-weight glutenin subunits amongst cultivars of Triticum turgidum L. from Portugal

Summary Variation in high-molecular-weight (HMW) glutenin subunit composition amongst 63 varieties of Triticum turgidum L. from Portugal was investigated using SDS-PAGE. A total of thirteen Glu-A1 and Glu-B1 alleles were identified, and three of them were found to be different from those previously described in the literature. A number of the tetraploid wheats examined contained subunits known to have a beneficial effect of the bread-making properties of T.aestivum. Camara, a tetraploid wheat cultivar carrying a 1D/1B chromosomal substitution, is proposed as a bridge for the transfer of Glu-D1 alleles and of other protein fractions controlled by the 1D chromosomes (Gli-D1 locus) from hexaploid to tetraploid wheat.