Search

In the Texas Rolling Plains, cool-season perennial grasses may complement limited forage availability in March-May and October-December. In two experiments conducted at Vernon, TX, on a sandy loam soil (fine-loamy, mixed, thermic Udic Paleustalfs), we evaluated productivity and persistence of crested [Agropyron cristatum (L.) Gaertn. x A. desertorum (Fisch. ex Link) J.A. Schultes], hybrid [Elytrigia repens (L.) Nevski × Pseudoroegneria spicata (Pursh) L've], intermediate [Thinopyrum intermedium (Host) Barkworth & D.R. Deweyl, pubescent [T. intermedium ssp. barbulatum (Schur) Barkw. & D.R. Dewey], and tall wheatgrass [T. ponticum (Podp.) Barkworth & D.R. Dewey] under combinations of 3- or 6-wk defoliation frequency at 7.5- or 15-cm. About 64% more herbage yield was harvested from all species at the 7.5- vs. 15-cm defoliation height in the first, but only from crested, hybrid, and pubescent wheatgrass in the second growing season. Frequent defoliation increased herbage by 22% in Experiment A or 37% in Experiment B only in the first growing season. Tiller survival increased with frequent defoliation in intermediate wheatgrass by 33% in Experiment A and up to 70% in Experiment B, but decreased by 52% in hybrid and by 33% in pubescent wheatgrass in Experiment A, and up to 50% in Experiment B. Lower nighttime soil temperatures increased tiller survival during summer in swards defoliated at the 7.5- vs. 15-cm height. Wheatgrass productivity increased under intensive or frequent defoliation in the first, but declined in several species in the subsequent growing season, making their potential to complement forage base limited.

Thinopyrum intermedium (2n = 6x = 42, JJJsJsSS) is potentially a useful source of resistance to wheat streak mosaic virus (WSMV) and its vector, the wheat curl mite (WCM). Five partial amphiploids, namely Zhong 1, Zhong 2, Zhong 3, Zhong 4, and Zhong 5, derived from Triticum aestivum × Thinopyrum intermedium crosses produced in China, were screened for WSMV and WCM resistance. Zhong 1 and Zhong 2 had high levels of resistance to WSMV and WCM. The other three partial amphiploids, Zhong 3, 4, and 5, were resistant to WSMV, but were susceptible to WCM. Genomic in situ hybridization (GISH) using a genomic DNA probe from Pseudoroegneria strigosa (SS, 2n = 14) demonstrated that two partial amphiploids, Zhong 1 and Zhong 2, have almost the identical 10 Th. intermedium chromosomes, including four Js, four J, and two S genome chromosomes. Both of them carry two pairs of J and a pair of Js genome chromosomes and two different translocations that were not observed in the other three Zhong lines. The partial amphiploids Zhong 3, 4, and 5 have another type of basic genomic composition, which is similar to a reconstituted alien genome consisting of four S and four Js genome chromosomes of Th. intermedium (Zhong 5 has two Js chromosomes plus two Js–W translocations) with six translocated chromosomes between S and Js or J genomes. All three lines carry a specific S–S–Js translocated chromosome, which might confer resistance to barley yellow dwarf virus (BYDV-PAV). The present study identified a specific Js2 chromosome present in all five of the Zhong lines, confirming that a Js chromosome carries WSMV resistance. Resistance to WCM may be linked with J or Js chromosomes. The discovery of high levels of resistance to both WSMV and WCM in Zhong 1 and Zhong 2 offers a useful source of resistance to both the virus and its vector for wheat breeding programs.Key words: GISH, genomic composition, J, Js and S genomes, Thinopyrum intermedium, partial amphiploid, WSMV, WCM resistance.

Wheatgrasses (Thinopyrum, Agropyron and Pascopyrum spp.) are a ubiquitous group of cool-season grasses used throughout much of the semiarid temperate world. In order to explore the potential of biotechnology to accelerate conventional breeding efforts, we developed an efficient plant regeneration system for different wheatgrass species: tall wheatgrass [Thinopyrum ponticum (Podp.) Liu and Wang], intermediate and pubescent wheatgrass [Thinopyrum intermedium (Host) Barkw. and D.R. Dewey], crested wheatgrass [Agropyron cristatum (L.) Gaertner], and western wheatgrass [Pascopyrum smithii (Rydb.) Love]. Embryogenic callus was induced from mature and immature embryos and immature inflorescence with an induction frequency in the range of 0.5–8.3% for the different wheatgrass species tested. Individual embryogenic calluses were then used to establish single genotype-derived suspension cultures. Efficient plant regeneration was achieved from the established em-bryogenic suspensions with regeneration frequencies in the range of 20–65% for tall wheatgrass, 21–40% for intermediate and pubescent wheatgrasses, 32–51% for crested wheatgrass, and 25–48% for western wheatgrass. The cell suspension-derived wheatgrass plants were fertile and phenotypically normal in the field. The efficient plant regeneration system provides a solid basis for genetic transformation of wheatgrasses.

Although the unique properties of wheat α-gliadin gene family are well characterized, little is known about the evolution and genomic divergence of α-gliadin gene family within the Triticeae. We isolated a total of 203 α-gliadin gene sequences from 11 representative diploid and polyploid Triticeae species, and found 108 sequences putatively functional. Our results indicate that α-gliadin genes may have possibly originated from wild Secale species, where the sequences contain the shortest repetitive domains and display minimum variation. A miniature inverted-repeat transposable element insertion is reported for the first time in α-gliadin gene sequence of Thinopyrum intermedium in this study, indicating that the transposable element might have contributed to the diversification of α-gliadin genes family among Triticeae genomes. The phylogenetic analyses revealed that the α-gliadin gene sequences of Dasypyrum, Australopyrum, Lophopyrum, Eremopyrum and Pseudoroengeria species have amplified several times. A search for four typical toxic epitopes for celiac disease within the Triticeae α-gliadin gene sequences showed that the α-gliadins of wild Secale, Australopyrum and Agropyron genomes lack all four epitopes, while other Triticeae species have accumulated these epitopes, suggesting that the evolution of these toxic epitopes sequences occurred during the course of speciation, domestication or polyploidization of Triticeae.

Two wheat–Thinopyrum substitution lines X479 and X482 selected from the progenies of wheat “Mianyang26 (MY26)” × wheat–Thinopyrum intermedium ssp. trichophorum partial amphiploid were characterized by seed storage protein electrophoresis, genomic in situ hybridization (GISH), fluorescence in situ hybridization (FISH), and PCR-based molecular markers. Seed storage protein analysis showed that X479 expressed some of Th. intermedium ssp. trichophorum-specific gliadin and glutenin bands. Chromosome counting and GISH probed by Pseudoroegneria spicata genomic DNA indicated that two pairs of Thinopyrum-derived chromosomes (St genome and St–JS translocated chromosomes) substituted for two pairs of wheat chromosomes in both X479 and X482. FISH using pAs1 and pHvG38 as probes showed that chromosomes 1B and 4B, and 4D and 6D were absent in X479 and X482, respectively. Using the newly isolated JS chromosome-specific repetitive sequence pDb12H as a probe, the FISH signals revealed that the translocation of St–JS chromosomes in X479 and X482 occurred in repetitive sequence regions of the short arm. The molecular markers based on wheat–rice colinearity confirmed that the chromosome constitutions of X479 and X482 were 1St (1B) + 4St–4JS (4B) and 4St–JS (4D) + 6St (6D), respectively. The substitution lines were both fully fertile which suggests that the Th. intermedium chromosomes in X479 and X482 substitute well for the corresponding wheat chromosomes. The rust resistance and novel agronomic traits revealed that the substitution lines will be potentially useful for genetic improvement of wheat.

Grazing by herbivores affects grass species both morphologically and physiologically. A study was conducted on an irrigated pasture near Outlook, Saskatchewan, Canada during the summer of 1991 to determine leaf regrowth after grazing of reed canarygrass (Phalaris arundinacea L.), slender wheatgrass [Elymus trachycaulus (Link) Gould ex Shinners subsp. trachycaulus], intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey subsp. intermedium], orchardgrass (Dactylis glomerata L.), meadow bromegrass (Bromus beibersteinii Roem. & Schult.), smooth bromegrass (Bromus inermis Leyss.), tall fescue [Festuca arundinacea (Schreb.) Wimm.] and timothy (Phleum pratense L.) in order to evaluate the suitability of these species for grazing. All eight species were mob-grazed by sheep at a stocking density of 30 animals ha-1. Physiological stage of leaf development was determined at 7, 14 and 21 d following defoliation. Smooth bromegrass and timothy consistently produced the greatest number of leaves for all regrowth periods. Tall fescue produced the least number of leaves at all time periods. Fifty-five percent of slender wheatgrass tillers and 19% of intermediate wheatgrass tillers were reproductive 21 d after defoliation. Based on leaf regrowth after grazing measured by leaf appearance, the grasses were ranked into three groupings – meadow bromegrass, smooth bromegrass and reed canarygrass ranked highest; intermediate wheatgrass, slender wheatgrass and orchardgrass ranked intermediate; and timothy and tall fescue ranked lowest. Key words: Leaf, regrowth, grass, grazing

Perennial grain crops were examined in pure stands and in various mixtures for their grain yield potential in, and suitability for, low-input systems on marginal land. The investigation was based on field experiments conducted at two sites characterized by marginal environmental conditions in south-west Germany in 1999 and 2000. The experiments included perennial species of rye (Secale cereale x Secale montanum), intermediate wheatgrass (Thinopyrum intermedium), lupin (Lupinus polyphyllus) and linseed (Linum perenne). In some stands, white clover (Trifolium repens) was included as an undersown intercrop for improved N supply. It was found that maturation of the species differed by up to almost 6 weeks, and consequently the threshability of most mixed stands was not satisfactory. Nevertheless, mixtures of either of the grasses (rye or wheatgrass) with lupin or undersown clover proved to be more suitable than pure stands in most cases, for measures such as grain yield, weed suppression and stability of grain yield over years. The grain yield harvested in the experiments in 1999 was low, reaching about 2.7 t ha -1 with rye, and decreased for most species in 2000. If improved genotypes were available, perennial grain crops could provide an alternative for arable cropping and set-aside areas under marginal conditions.

Cox, C. M., Murray, T. D., and Jones S. S. 2002. Perennial wheat germ plasm lines resistant to eyespot, Cephalosporium stripe, and wheat streak mosaic. Plant Dis. 86:1043-1048. A perennial wheat cropping system on the Palouse Prairie of eastern Washington may provide an alternative to the Federal Conservation Reserve Program and reduce soil erosion while providing a harvestable crop for growers. Twenty-four perennial wheat germ plasm lines resulting from crosses between wheat and wheatgrass were evaluated under controlled environment conditions for resistance to Wheat streak mosaic virus (WSMV), Cephalosporium gramineum, and Tapesia yallundae (anamorph Pseudocercosporella herpotrichoides var. herpotrichoides). Perennial wheat lines SS452, SS103, SS237, MT-2, and PI 550713 were resistant to all three pathogens. Eight lines (33%) were resistant to WSMV at 21°C and 25°C; AT3425 was resistant to WSMV at 21°C but not at 25°C. Thirteen lines (54%) were highly to moderately resistant to C. gramineum. Thirteen lines (54%) were resistant to T. yallundae in each experiment, but the reactions of four lines differed between experiments. The wheatgrasses Thinopyrum intermedium (PI 264770) and Thinopyrum ponticum (PI 206624) are reported as new sources of resistance to T. yallundae. Perennial wheat must have resistance to these diseases in order to be feasible as a crop in the Pacific Northwest.

The production and subsequent feeding of forage during winter is a major expense for livestock producers. Fourteen perennial range forage grasses including crested wheatgrass (WG) [Agropyron cristatum and A. desertorum] , intermediate WG [Thinopyrum intermedium], tall WG [T. ponticum], quackgrass [Elytrigia repens] × bluebunch WG [Pseudoroegneria spicata] RS hybrids, Altai [Leymus angustus] wildrye (WR), basin [L. cinereus] WR, smooth bromegrass [Bromus inermis], and orchardgrass [Dactylis glomerata] were evaluated from 1992 to 1994 for total dry matter (DM) production (November harvest only), crude protein (CP), neutral (NDF), and acid (ADF) detergent fiber from November through March in northern Utah. Mean species DM production rankings (P < 0.01) combined across years were: RS hybrids > smooth bromegrass > basin WR > Altai WR > intermediate WG > orchardgrass > tall WG > crested WG. Mean species CP rankings (P < 0.01) combined across years and harvests were tall WG > intermediate WG > orchardgrass > RS hybrids > crested WG > Altai WR > basin WR > smooth bromegrass. Levels of CP remained constant from November through March for all species and entries. Trends in NDF and ADF remained constant from November through January, but NDF increased slightly in March. Crude protein of the dormant grasses was below the level necessary to maintain ruminal function so protein supplementation would be necessary. Key words: Range grasses, winter forage quality, yield, extending the grazing season

The wheat – Thinopyrum intermedium addition lines Z1 and Z2 carry 21 pairs of wheat chromosomes and one pair of Th. intermedium chromosomes (2Ai-2) conferring resistance to barley yellow dwarf virus (BYDV). GISH results using the genomic DNA of Pseudoroegneria strigosa (S genome) as the probe indicated that the 2Ai-2 chromosome in Z1 and Z2 is an S–J intercalary translocation. Most of the 2Ai-2 chromosome belongs to the S genome, except for about one third in the middle region of the long arm that belongs to the J genome. The results of detailed RFLP analyses confirmed that the 2Ai-2 chromosome is extensively homoeologous to wheat group 2 chromosomes. Some new RFLP markers specific to the 2Ai-2 chromosome were identified. A RAPD marker, OP-R16340, specific to the 2Ai-2 chromosome, was screened. We converted the RAPD marker into a sequence-characterized amplified region (SCAR) marker (designated SC-R16). The study establishes the basis for selecting translocation lines with small segments of the 2Ai-2 chromosome and localizing the BYDV resistance gene when introgressed into a wheat background.Key words: Thinopyrum intermedium, barley yellow dwarf virus (BYDV), genomic in situ hybridization (GISH), RFLP, SCAR, homoeologous group 2.

Development of wheat (Triticum aestivum L.) cultivars resistant to Wheat streak mosaic virus (WSMV) that remain productive in the absence of the disease would benefit wheat growers. A wheat germplasm (KS93WGRC27) carrying a Thinopyrum intermedium (Host) Barkworth and Dewey chromosome 4J s translocation conferring WSMV resistance was used to develop spring wheat populations segregating for WSMV resistance. Four populations, consisting of a total of 22 translocation-positive (WSMV-resistant), 36 translocation-negative (WSMV-susceptible), and eight parental lines, were grown as a randomized complete block with three replications at Bozeman and Conrad, MT, in 1998 and 1999. Treatments were arranged as a split plot with populations as main plots and progeny and parents as subplots. The agronomic performance of resistant and susceptible lines was compared under inoculated and noninoculated conditions to assess the effectiveness of the WSMV resistance gene and to determine the effects of the Thinopyrum translocation in the absence of disease. A small but significant decrease in yield was observed for noninoculated resistant lines in contrast to susceptible lines. However, the yield range of resistant entries suggests that the recovery of parental yield was possible. The resistance source was highly effective in limiting virus accumulation and yield losses to WSMV, resulting in only a 5% yield reduction in resistant lines under inoculated conditions compared with 32% for susceptible lines. In all instances where WSMV was introduced to field trials, the Thinopyrum translocation provided a significant benefit for resistant lines when compared with susceptible lines. The T. intermedium translocation present in resistant lines had no detrimental effects on end-use quality or other agronomic traits.

Barley yellow dwarf (BYD) is the most important viral disease of small cereal grains. True resistance to the disease is not found in wheat (Triticum aestivum L.), but it has been introgressed from Thinopyrum intermedium (Ti) on chromosome 7DL of recombinant wheat lines designated TC. The objectives of our study were to identify a high through-put scoring tool for the presence of the translocated Th. intermedium fragment and to assess its suitability for evaluating resistance to BYDV in segregating populations. Segregation of the Ti fragment was followed in the F2 population of an Anza (bread wheat) by TC14/2*Spear (TC14) cross. Resistance to BYDV isolates PAV-Mex and MAV-Mex in F3, F4, and F5 populations was evaluated under field and/or greenhouse conditions by measuring the virus titers of infected plants using ELISA, and the number of infected plants per plot. The SSR marker gwm37 was polymorphic for the translocation. In F4 lines it was associated with the physical presence of an intact translocation on chromosome 7DL and with low virus titers of BYDV-PAV. Reductions in virus titer of 27% and 55% in the F3 and 18% and 45% in the F5 populations were observed when the fragment was present in the heterozygous and homozygous states, respectively, confirming a dosage effect of the resistance allele. A lower proportion of infected individuals in the field was associated with the presence of the fragment, indicating a mechanism that may interfere with aphid feeding or virus translocation within infected plants. Despite significant differences between groups with and without the fragment, the OD values of infected lines overlapped, and it was not possible to definitively detect the fragment based solely on ELISA. We conclude that gwm37 is a reliable marker for the Ti translocation that will allow efficient detection of the translocation in breeding populations and greatly assist in selecting BYDV-resistant wheats in the absence of the disease.

Intergeneric hybrids (ABDJJsS genomes) were made between Triticum aestivum cv. Chinese Spring (CS) and Thinopyrum intermedium. Genomic in situ hybridization (GISH) using genomic DNA probes from Pseudoroegneria libanotica (Hackel) D.R. Dewey (genome S, 2n = 14) was used to study chromosome pairing among J, Js, S and wheat ABD genomes in the hybrids. It was shown that in the hexaploid (ABDJJsS) hybrids, high pairing occurred among wheat chromosomes and among Thinopyrum chromosomes. A closer relationship was observed among the three genomes of Th. intermedium than among the three genomes of T. aestivum. It was further discerned that S genome chromosomes paired with J- and Js-genome chromosomes at a high frequency. The frequency of heterologous pairing between S and J or S and Js chromosomes was higher than those between J and Js chromosomes, indicating that the S-genome was more closely related with these two genomes. Our results provided direct molecular cytogenetic evidence for the hypothesis that S-genome chromosomes are genetically similar to the J-genome chromosomes and, therefore, genetic exchange between these genomes is possible. The discovery of a close relationship among S, J and Js genomes provides valuable markers for molecular cytogenetic analyses using S-genomic DNA probes in monitoring the transfer of useful traits from Thinopyrum species into wheat.

To introduce useful genes from the wild species Thinopyrum intermedium into cultivated wheat, a wheat-Th. intermedium disomic addition line (TAI27) was used as source material for tissue culture. TAI27 contains, beside the 42 wheat chromosomes, a pair of smaller chromosomes that is cytologically discernible. Based on restriction fragment length polymorphism (RFLP) analysis, this chromosome pair was determined to be a recombinant one, comprising segments with homoeology to at least two chromosome groups of wheat, i.e., group 2 and 7. Sixty-eight green plants were regenerated from six month-old embryogenic calli initiated from immature embryos of TAI27. Four of the plants were found to have only 42 cytologically normal-looking chromosomes. Southern blot analysis using a Th. intermedium-enriched repetitive probe showed that one of the plants had hybridization fragments specific to Th. intermedium, indicating introgression of chromatin during the cell culture process.

We developed some wheat-Th. intermedium translocation lines,Yw642, Yw443 and Yw243, etc., showing good BYDV resistance from L1by induced homoeologous pairing using CS ph mutant. Characterization ofthese wheat lines was carried out by GISH and RFLP analysis. The resultsof GISH showed that the lines, YWw42, Yw443 and Yw243, etc., arehomozygous wheat-Th. intermedium translocation lines, in which thechromosome segments of Th. intermedium were transferred to thedistal end of a pair of wheat chromosomes. RFLP analysis indicated that thetranslocation chromosome of the wheat lines is T7DS · 7DL-7XL. Thebreakpoint of the translocation is located on the distal end of 7DL, betweenXpsr965 and Xpsr680 about 90–99 cm from the centromere. The BYDVgene is located on the distal end of 7XL around Xpsr680, Xpsr687 andXwg380. The RFLP markers of psr680, psr687 and wg380 werecosegregated with the BYDV resistance respectively and could be used formolecular assisted selection (MAS) in wheat breeding program for BYDVresistance.

Ayala, L., van Ginkel, M., Khairallah, M., Keller, B., and Henry, M. 2001. Expression of Thinopyrum intermedium-derived Barley yellow dwarf virus resistance in elite bread wheat backgr ounds. Phytopathology 91:55-62. Resistance to Barley yellow dwarf virus (BYDV) is not found in wheat but is available in a Thinopyrum intermedium translocation (Ti) carried on chromosome 7DL of bread wheat recombinant lines. We used one of those lines (TC14/2*Spear) to introgress the Ti into bread wheat cultivars and to determine the influence of wheat backgrounds, with and without known tolerance to BYDV, on the expression of resistance. Two single and three backcross populations, segregating for the presence of the alien fragment, were tested under field conditions and artificial inoculation with BYDV isolates MAV-Mex and PAV-Mex. Lines containing the fragment were identified using the microsatellite marker gwm37. Tillering, biomass, grain yield, thousand-kernel weight, and seed qua lity were evaluated in inoculated and noninoculated plots. Resistance was assessed by enzyme-linked immunosorbent assay. In early generations, the alien fragment followed expected Mendelian segregation, whereas in the advanced ones a slight bias against its transmission was observed. No positive nor negative effects of Ti on agronomic performance and quality were found. A significant optical density reduction in individuals carrying the fragment was observed after PAV infection in crosses with lines Anza and Baviacora but not with Milan. In addition, the fragment was associated with a lower frequency of infected plants for both PAV and MAV isolates. The reduced yield loss associated with the presence of the translocation was due largely to the lower infection rate.

Genomic in situhybridization (GISH) to root-tip cells at mitotic metaphase, using genomic DNA probes from Thinopyrum intermedium and Pseudoroegneria strigosa, was used to examine the genomic constitution of Th. intermedium, the 56-chromosome partial amphiploid to wheat called Zhong 5 and disease-resistant derivatives of Zhong 5, in a wheat background. Evidence from GISH indicated that Th. intermedium contained seven pairs of St, seven JS and 21 J chromosomes; three pairs of Th. intermedium chromosomes with satellites in their short arms belonging to the St, J, J genomes and homoeologous groups 1, 1, and 5 respectively. GISH results using different materials and different probes showed that seven pairs of added Th. intermedium chromosomes in Zhong 5 included three pairs of St chromosomes, two pairs of JS chromosomes and two pairs of St-JS reciprocal tanslocation chromosomes. A pair of chromosomes, which substituted a pair of wheat chromosomes in Yi 4212 and in HG 295 and was added to 21 pairs of wheat chromosomes in the disomic additions Z1, Z2 and Z6, conferred BYDV-resistance and was identical to a pair of St-JS tanslocation chromosomes (StJS) in Zhong 5. The StJS chromosome had a special GISH signal pattern and could be easily distinguished from other added chromosomes in Zhong 5; it has not yet been possible to locate the BYDV-resistant gene(s) of this translocated chromosome either in the St chromosome portion belonging to homoeologous group 2 or in the JS chromosome portion whose homoeologous group relationship is still uncertain. Among 22 chromosome pairs in disomic addition line Z3, the added chromosome pair had satellites and belonged to the St genome and homoeologous group 1. Disomic addition line Z4 carried a pair of added chromosomes which was composed of a group-7 JS chromosome translocated with a wheat chromosome; this chromosome was different to 7 Ai-1, but was identical to 7 Ai-2. The leaf rust and stem rust resistance genes were located in the distal region of the long arm, whereas the stripe rust resistance gene(s) was located in the short arm or in the proximal region of the long arm of 7 Ai-2. A pair of JS-wheat translocation chromosomes, which originated from the WJS chromosomes in Z4, was added to the disomic addition line Z5; the added chromosomes of Z5 carried leaf and stem rust resistance but not stripe rust resistance; Z5 is a potentially useful source for rust resistance genes in wheat breeding and for cloning these novel rust-resistant genes. GISH analysis using the St genome as a probe has proved advantageous in identifying alien Th. intermedium in wheat.

Thirty-six wheat-Agropyron intermedium (host) Beauv. [Syn. Trichopyrum intermedium (host) A. Love, Elytrigia intermedia (host) Nevski, Thinopyrum intermedium (host) Barkworth and Dewey] 7A/7Ai-1 recombinant chromosomes were characterized using DNA markers. Analysis of recombinant chromosomes using 15 restriction fragment length polymorphism probes identified the homoeologous crossover products that had varying length of A. intermedium chromatin introgressed onto chromosome 7A of common wheat. The linear order of the probe loci was established along the lengths of the chromosomes. The short arm recombinants that had A. intermedium chromatin distal to the locus Xpsr108 and proximal to the locus Xpsr119 were resistant to wheat stem rust, indicating that the rust resistance gene (Sr44) was located on the distal part of chromosome arm 4Ai-1s. The barley yellow dwarf virus (BYDV) resistance gene reported to be present on the long arm of chromosome 7Ai-1 was found to be ineffective against the BYDV serotype used in the present study.

greater stand longevity than legume or grass monocultures (Droslom and Smith, 1976). Yield and forage quality of kura clover (Trifolium ambiguum Although exceptions exist, compatible legume‐grass Bieb.) and intermediate wheatgrass [Thinopyrum intermedium mixtures usually yield more than any single component (Host.) Barkw. & D.R. Dewey] mixtures compared with commonly grown in monoculture (Roberts and Olson, 1942; Aberg grown forages such as alfalfa (Medicago sativa L.) and smooth bromegrass (Bromus inermis Leyss.) have not been fully explored. Our et al., 1943). Wilsie (1949) noted, however, that alfalfa‐ objective was to evaluate the effects of alfalfa, birdsfoot trefoil (Lotus grass mixtures did not yield more forage than alfalfa corniculatus L.), and kura clover grown in binary mixtures with or- alone when alfalfa was seeded at a high rate; Wilsie also chardgrass (Dactylis glomerata L.), smooth bromegrass, and interme- concluded that alfalfa was the best legume to grow with diate wheatgrass on seasonal distribution of forage yield and quality. smooth bromegrass. Even though alfalfa‐grass mixtures Plots of each species in monoculture and binary legume‐grass mix- have received much acclaim, several studies (Fuelleman tures were established in a randomized complete block design in 1994 et al., 1943; Rather and Harrison, 1944; Koonce, 1946; near Boone, IA. Yield was measured monthly during the 1995 and Mooso and Wedin, 1990) concluded that mixtures offer 1996 seasons. In vitro dry matter digestibility (IVDMD), neutrallittle yield advantage over alfalfa monocultures when detergent fiber (NDF), and crude protein (CP) concentrations were harvested as hay.

Barley yellow dwarf virus (BYDV) is the most serious viral disease affecting wheat and genes for BYDV resistance have not been found in wheat. BYDV-resistant alien addition and alien substitution lines produced from a wheat × Thinopyrum intermedium (species of Agropyron complex) cross were characterized. Chromosome pairing in the hybrids between two substitution lines showed that they had the same Th. intermedium chromosome. Likewise, two addition lines involved the same alien chromosome. In situ hybridization of chromosomes, confirmed that line P29 is a disomic substitution line. Double monosomic seeds and self-pollinated seeds from monosomic addition plants were irradiated to induce translocations between wheat and Th. intermedium chromosomes. Putative translocations were selected on the basis of BYDV resistance and studied by chromosome analysis, Southern hybridization using Thinopyrum specific probe and RFLP markers. A BYDV-resistant translocation was identified.

Genomic in situ hybridization (GISH) using genomic DNA probes from Thinopyrum elongatum (Host) D.R. Dewey (genome E, 2n = 14), Thinopyrum bessarabicum (Savul. & Rayss) Á. Löve (genome J, 2n = 14), and Pseudoroegneria strigosa (M. Bieb.) Á. Löve (genome S, 2n = 14), was used to examine the genomic constitution of Thinopyrum intermedium (Host) Barkworth & D.R. Dewey (2n = 6x = 42) and Thinopyrum ponticum (Podp.) Barkworth & D.R. Dewey (2n = 10x = 70). Evidence from GISH indicated that hexaploid Th. intermedium contained the J, Js, and S genomes, in which the J genome was related to the E genome of Th. elongatum and the J genome of Th. bessarabicum. The S genome was homologous to the S genome of Ps. strigosa, while the Js genome referred to modified J- or E-type chromosomes distinguished by the presence of S genome specific sequences close to the centromere. Decaploid Th. ponticum had only the two basic genomes J and Js. The Js genome present in Th. intermedium and Th. ponticum was homologous with E or J genomes, but was quite distinct at centromeric regions, which can strongly hybridize with the S genome DNA probe. Based on GISH results, the genomic formula of Th. intermedium was redesignated JJsS and that of Th. ponticum was redesignated JJJJsJs. The finding of a close relationship among S, J, and Js genomes provides valuable markers for molecular cytogenetic analyses using S genome DNA probes to monitor the transfer of useful traits from Th. intermedium and Th. ponticum to wheat.Key words: genomic in situ hybridization, GISH, Thinopyrum intermedium, Thinopyrum ponticum, genomic analysis, Js genome.

Wheatgrass (Thinopyrum intermedium) possesses a high level of resistance to barley yellow dwarf virus (BYDV) subgroup I and subgroup II strains. A wheat line (P29), in which the 7D chromosome has been substituted with a group 7 chromosome from T. intermedium, was examined for the level of resistance to two subgroup I and two subgroup II BYDV strains. In P29 plants inoculated with the subgroup I PAV strains, the titer of virus in leaf and stem tissue was typically reduced 42 to 52% when compared with the BYDV-susceptible cv. Abe. P29 and ‘Abe’ had the same content of PAV in roots. These results and the absence of detectable virus in inoculated T. intermedium plants indicate that the complete resistance to subgroup I possessed by the wheatgrass has not been introgressed into P29. In contrast, P29 was completely resistant throughout the plant to the subgroup II strains, NY-RPV and NY-RMV, demonstrating that the complete resistance to subgroup II in T. intermedium was incorporated into P29. Further analysis of this resistance to NY-RPV showed that NY-RPV can replicate in mesophyll protoplasts of P29 and ‘Abe’, suggesting that this resistance is not operating at the single-cell level. Molecular marker analysis confirmed that the T. intermedium chromosome present in P29 is a different group 7 wheatgrass chromosome than that present in L1, a wheat line with BYDV resistance properties similar to those of P29.

Excessive seed shattering of perennial grasses in the Triticeae tribe results in major economic losses to seed producers. In this 4-yr field study, heat units expressed as growing degree-days (GDD) after anthesis were related to seed development in tetraploid crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schultes], Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski], intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey], and western wheatgrass [Pascopyrum smithii (Rydb.) A. Love]. Seed quality at different stages of development was assessed by germination percentage and emergence of seedlings from a 5.0-cm planting depth in a Parshall fine sandy loam soil (coarse-loamy, mixed Pachic Haploborolls). Water concentration of the seed at maximum seed mass (dry wt. basis) ranged from 303 g kg -1 for intermediate wheatgrass to 376 gkg -1 for western wheatgrass. Seed mass was closely associated with seed vigor in all four grass species, as evidenced by correlation coefficients between seed mass and seedling emergence of 0.88 ** for crested wheatgrass, 0.93 ** for Russian wildrye, 0.92 ** for intermediate wheatgrass, and 0.77 ** for western wheatgrass. Plots sampled at the stiff-dough stage had a water concentration of approximately 350 g kg -1 (dry wt. basis), and the seed sample was at or near maximum seed mass. Seed mass and germination would not be seriously compromised and seed yield losses from shattering would be reduced if windrowing were completed about 50 GDD or 2 to 3 calendar days before maximum seed mass is attained.

Wheat streak mosaic virus (WSMV), vectored by the wheat curl mite (WCM), is one of the most important viral diseases of wheat (Triticum aestivum) in the world. Genetic resistance to WSMV and the WCM does not exist in wheat. Resistance to WSMV and the WCM was evaluated in five different partial amphiploids namely Agrotana, OK7211542, ORRPX, Zhong 5 and TAF 46, which were derived from hybrids of wheat with decaploid Thinopyrum ponticum or with hexaploid Th. intermedium. Agrotana was shown to be immune to WSMV and the WCM; the other four partial amphiploids were susceptible to the WCM. Genomic in situ hybridization (GISH) using genomic DNA probes from Th. elongatum (EE, 2n=14), Th. bessarabicum (JJ, 2n=14), Pseudoroegneria strigosa (SS, 2n=14) and T. aestivum (AABBDD, 2n=42) demonstrated that three of the partial amphiploids, Agrotana, OK7211542 and ORRPX, have almost identical alien genome constitutions: all have 16 alien chromosomes, with 8 chromosomes being closely related to the Js genome and 8 chromosomes belonging to the E or J genomes and no evidence of any S-genome chromosomes. GISH confirmed that the alien genomes of Agrotana and OK7211542, like ORRPX, were all derived from Th. ponticum, and not from Th. intermedium. However, in contrast to Agrotana, ORRPX and OK7211542 were susceptible to the WCM and WSMV. The partial amphiploid Zhong 5 had a reconstituted alien genome composed of 4 S-and 4 Js-genome chromosomes of Th. intermedium with 6 translocated chromosomes between the S and Js genomes. This line was highly resistant to WSMV, but was susceptible to the WCM. TAF 46, which contained a synthetic genome consisting of 3 pairs of S-genome chromosomes and 4 pairs of E- or J-genome chromosomes in addition to the 21 pairs of wheat chromosomes, was susceptible to the WCM, but moderately resistant to WSMV. Agrotana offers great potential for transferring WSMV and WCM resistance into wheat.

Long-term control of downy brome with an integrated approach is needed in order to sustain range productivity. Studies were conducted to study the effectiveness of a combination of downy brome control practices. In two studies, glyphosate and paraquat were evaluated at various rates for up to three successive years for control of downy brome in rangeland. A third study evaluated the competitiveness of perennial cool-season grasses against downy brome in the absence of herbicides. Glyphosate, at 0.55 kg/ha, and 0.6 kg/ha paraquat provided selective downy brome control on rangeland when applications were combined with intensive grazing. Downy brome control was greater than 90% following two sequential years of 0.6 kg/ha paraquat at either the two- to eight-leaf stage or bloom stage at both study locations. At one study location, 0.55 kg/ha glyphosate provided 97% control after the first application at both growth stages. In the second study, control averaged greater than 92% following three sequential applications of glyphosate. When perennial cool-season grasses were seeded in the spring following fall tillage (no herbicides) and allowed to establish for three growing seasons, three of the five species were effective in reducing the reesta- blishment of downy brome. 'Luna' pubescent wheatgrass, 'Hycrest' crested wheatgrass, 'Sodar' streambank wheatgrass, 'Bozoisky' Russian wildrye, and 'Critana' thickspike wheatgrass controlled 100, 91, 85, 45, and 32% of the downy brome, respectively. Yields of perennial grass dry matter were 1,714, 1,596, 1,135, 900, and 792 kg/ha. Replacing noncompetitive annual grasses with com- petitive cool-season perennials will provide a longer term solution to a downy brome problem than the use of herbicides alone or with intensive grazing. Nomenclature: Glyphosate, N-(phosphonomethyl)glycine; paraquat, 1,1'-dimethyl-4,4'-bipyridinium ion; downy brome, Bromus tectorum L. #3 BROTE; pubescent wheatgrass, Thinopyrum intermedium (Host. Barkworth & Dewey) Nevski 'Luna'; thickspike wheatgrass, Elymus lanceolatus (Scribn. & Smith) Gould 'Critana'; Russian wildrye, Psathyrostachys juncea (Fisch) Nevski 'Bozoisky'; stream- bank wheatgrass, Elymus lanceolatus (Scribn. & J. G. Smith) Gould 'Sodar'; crested wheatgrass, Agropyron cristatum (L.) Gaertn. X (Agropyron desertorum (Gaertn.) 'Hycrest'. Additional index words: Plant competition, rangeland weed control, annual grass control in range- land, cool-season grasses.

A combination of genomic in situ hybridization (GISH) and meiotic pairing analysis of crosses between a series of 2n = 56 partial amphiploids confirmed that the alien genome of the BYDV-immune Agrotricum line OK7211542 is derived from Thinopyrum ponticum and not from Thinopyrum intermedium. The evidence from meiotic pairing analysis indicated that the chromosome constitution of OK7211542 is similar to another Agrotricum line, ORRPX, which was derived from a cross of wheat and Th. ponticum, but different from other Agrotricum lines, Zhong 5 and TAF 46 which were derived from the crosses between wheat and Th. intermedium. The GISH analysis confirmed that OK7211542 contained one complete set of 14 Th. ponticum chromosomes, in which no S chromosome was present in the alien genome. GISH also detected a small alien translocation attached to one of the wheat chromosomes, a result that was consistent with the pairing data.

Thinopyrum intermedium is a promising source of resistance to wheat streak mosaic virus (WSMV), a devastating disease of wheat. Three wheat germplasm lines possessing resistance to WSMV, derived from Triticum aestivum×Th. intermedium crosses, are analyzed by C-banding and genomic in situ hybridization (GISH) to determine the amount and location of alien chromatin in the transfer lines. Line CI15092 was confirmed as a disomic substitution line in which wheat chromosome 4A was replaced by Th. intermedium chromosome 4Ai?2. The other two lines, CI17766 and A29-13-3, carry an identical Robertsonian translocation chromosome in which the complete short arm of chromosome 4Ai?2 was transferred to the long arm of wheat chromosome 4A. Fluorescence in situ hybridization (FISH) using ABD genomic DNA from wheat as a probe and S genomic DNA from Pseudoroegneria stipifolia as the blocker, and vice versa, revealed that the entire short arm of the translocation was derived from the short arm of chromosome 4Ai?2 and the breakpoint was located at the centromere. Chromosomal arm ratios (L/S) of 2.12 in CI17766 and 2.15 in A29-13-3 showed that the translocated chromosome is submetacentric. This translocated chromosome is designated as T4AL ⋅ 4Ai?2S as suggested by Friebe et al. (1991).

Intermediate and pubescent wheatgrasses (Thinopyrum intermedium) are potentially useful as dryland forage grasses in New Zealand. The recent literature on their international and local use in pasture and cropping situations is reviewed. Under semi-arid conditions at Bendigo Station over a 13-year period, cv. Luna wheatgrass has spread several metres from the original drill lines and it provides very high ground cover. In terms of dryland soil resource conservation this contrasts with adjacent cocksfoot and, to a lesser extent, lucerne plots which have wide-spaced plants interspersed with litter and much bare ground. In a mixed drilling containing wheatgrass, hairy dorycnium, birdsfoot trefoil and sheep's burnet, the first two species now dominate. At Takapau, central Hawke's Bay, annual yields from intermediate and pubescent wheatgrasses produced over 80% of the yield of 10 New Zealand cultivars in spring, summer and autumn, and 65% in the winter. Of the wheatgrasses, cv. Topar intermediate wheatgrass and a pubescent wheatgrass (unnamed line) were the lowest yielding, whereas cv. Oahe and cv. Mandan produced the highest yields. Cv. Greenleaf pubescent wheatgrass had higher foliar nitrogen content than all other species, but in vitro organic matter digestibility was less than 700 g OM/kg DM. Although the wheatgrasses had satisfactory herbage yield and nutritional value, better alternative species are available for pastoral farming in central Hawke's Bay. On Belfield in the Hakataramea Valley, cv. Rush has been the most vigorous wheatgrass for establishment and it seems to handle cold winds and frost well. Hay made from a wheatgrass/ lucerne mix is considered better than that from the individual species as this can increase production by 40-50%, depending on soil and climatic conditions. Usually only one cut per year is taken from the mixed pasture. Crop maintenance includes the application of 200 kg/ha of sulphur super extra every 3-4 years and the pH is maintained at about 5.9-6.4 by liming. A significant advantage is that no stock health, pest or plant disease problems have been noted as yet with any of the wheatgrass varieties available in New Zealand. Keywords: dryland agriculture, New Zealand, Thinopyrum, wheatgrass

Efficient testing procedures are needed to identify superior parents for improved cultivars of cross-pollinated forage species. The primary objective of this study was to compare clonal and open-pollinated (OP) progeny testing in the selection of parents from an intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & Dewey] population. A second objective was to examine experimental error control from a partially-balanced lattice design and a nearest-neighbor analysis relative to a randomized complete block statistical design (RCBD). Parent clones were evaluated in plots that consisted of 30 closely spaced ramets, and progenies were sown in single-row plots 6.0 m long spaced 0.6 m apart at adjacent sites near Mandan, ND. Based on 3-yr means from one location, narrow-sense heritability. estimates from 81 parent clones and their respective open-pollinated progenies averaged 50% for heading date, 45% for plant height, and 69% for dry matter yield. Extreme high- and low-ranked entries for all three traits generally were in common for clonal and progeny tests. A lattice design and nearest-neighbor analysis reduced experimental error but did not improve rank correlations between parent clones and their progenies or heritability estimates compared with a randomized complete block design. These results suggest that clonal and open-pollinated progeny tests should be used to select superior parents of intermediate wheatgrass, as both test procedures have unique attributes. Clonal tests are useful in selecting for traits with relatively high herita-bility, while extensive progeny testing is more appropriate for complex traits such as dry-matter yield.

Genomic in situ hybridization (GISH) was used to distinguish autosyndetic from allosyndetic pairing in the hybrids of Thinopyrum intermedium and Th. ponticum with Triticum aestivum cv ‘Chinese Spring’ (CS). All hybrids showed high autosyndetic pairing frequencies among wheat chromosomes and among Thinopyrum chromosomes. The high autosyndetic pairing frequencies among wheat chromosomes in both hybrids suggested that Th. intermedium and Th. ponticum carry promoters for homoeologous chromosome pairing. The higher frequencies of autosyndetic pairing among Thinopyrum chromosomes than among wheat chromosomes in both hybrids indicated that the relationships among the three genomes of Th. intermedium and among the five genomes of Th. ponticum are closer than those among the three genomes of T. aestivum.

Fertile hybrids were produced with genetic material transferred from Th. intermedium into a wheat background and supply a source of genetic variation to wheat improvement. Both symmetric and asymmetric somatic hybrids have been obtained from the combination of wheatgrass (Thinopyrum intermedium) and bread wheat (Triticum aestivum). Two wheat protoplast populations, one derived from embryogenic calli and the other from a non-regenerable, rapidly dividing cell line, were fused with Th. intermedium protoplasts which had been (or not been) pre-irradiated with UV. Among the 124 regenerated calli, 64 could be categorized as being of hybrid origin on the basis of plant morphology, peroxidase isozyme, RAPD DNA profiling and karyological analysis. Numerous green plantlets were regenerated from 13 calli recovered from either the symmetric hybrid (no UV pre-treatment) or the asymmetric one (30 s UV irradiation). One of these hybrid plants proved to be vigorous and self-fertile. The regenerants were all closer in phenotype to wheat than to Th. intermedium. Genomic in situ hybridization analysis showed that the chromosomes in the hybrids were largely intact wheat ones, although a few Th. intermedium chromosome fragments had been incorporated within them.

Stripe rust resistance transferred from Thinopyrum intermedium into common wheat was controlled by a single dominant gene, which mapped to chromosome 1B near Yr26 and was designated YrL693. Stripe rust caused by Puccinia striiformis f. sp. tritici (Pst) is a highly destructive disease of wheat (Triticum aestivum). Stripe rust resistance was transferred from Thinopyrum intermedium to common wheat, and the resulting introgression line (L693) exhibited all-stage resistance to the widely virulent and predominant Chinese pathotypes CYR32 and CYR33 and to the new virulent pathotype V26. There was no cytological evidence that L693 had alien chromosomal segments from Th. intermedium. Genetic analysis of stripe rust resistance was performed by crossing L693 with the susceptible line L661. F1, F2, and F2:3 populations from reciprocal crosses showed that resistance was controlled by a single dominant gene. A total 479 F2:3 lines and 781 pairs of genomic simple sequence repeat (SSR) primers were employed to determine the chromosomal location of the resistance gene. The gene was linked to six publicly available and three recently developed wheat genomic SSR markers. The linked markers were localized to wheat chromosome 1B using Chinese Spring nulli-tetrasomic lines, and the resistance gene was localized to chromosome 1B based on SSR and wheat genomic information. A high-density genetic map was also produced. The pedigree, molecular marker data, and resistance response indicated that the stripe rust resistance gene in L693 is a novel gene, which was temporarily designated YrL693. The SSR markers that co-segregate with this gene (Xbarc187-1B, Xbarc187-1B-1, Xgwm18-1B, and Xgwm11-1B) have potential application in marker-assisted breeding of wheat, and YrL693 will be useful for broadening the genetic basis of stripe rust resistance in wheat.

We employed sequencing of clones and in situ hybridization (genomic and fl uorescent in situ hybridization [GISH and rDNA-FISH]) to characterize both the sequence variation and genomic organization of 45S (herein ITS1-5.8S-ITS2 region) and 5S (5S gene + nontranscribed spacer) ribosomal DNA (rDNA) families in the allohexaploid grass Thinopyrum intermedium. Both rDNA families are organized within several rDNA loci within all three subgenomes of the allohexaploid species. Both families have undergone different patterns of evolution. The 45S rDNA family has evolved in a concerted manner: internal transcribed spacer (ITS) sequences residing within the arrays of two subgenomes out of three got homogenized toward one major ribotype, whereas the third subgenome contained a minor proportion of distinct unhomogenized copies. Homogenization mechanisms such as unequal crossover and/or gene conversion were coupled with the loss of certain 45S rDNA loci. Unlike in the 45S family, the data suggest that neither interlocus homogenization among homeologous chromosomes nor locus loss occurred in 5S rDNA. Consistently with other Triticeae, the 5S rDNA family in intermediate wheatgrass comprised two distinct array types—the long- and short-spacer unit classes. Within the long and short units, we distinguished five and three different types, respectively, likely representin gh omeologous unit classes donated by putative parental species. Although the major ITS ribotype corresponds in our phylogenetic analysis to the E-genome species, the minor ribotype corresponds to Dasypyrum. 5S sequences suggested the contributions from Pseudoroegneria, Dasypyrum ,a ndAegilops. The contribution from Aegilops to the intermediate wheatgrass’ genome is a new finding with implications in wheat improvement. We discuss rDNA evolution and potential origin of intermediate wheatgrass.

The disease take-all, caused by the fungus Gaeumannomyces graminis, is one of the most destructive root diseases of wheat worldwide. Breeding resistant cultivars is an effective way to protect wheat from take-all. However, little progress has been made in improving the disease resistance level in commercial wheat cultivars. MYB transcription factors play important roles in plant responses to environmental stresses. In this study, an R2R3-MYB gene in Thinopyrum intermedium, TiMYB2R-1, was cloned and characterized. The gene sequence includes two exons and an intron. The expression of TiMYB2R-1 was significantly induced following G. graminis infection. An in vitro DNA binding assay proved that TiMYB2R-1 protein could bind to the MYB-binding site cis-element ACI. Subcellular localization assays revealed that TiMYB2R-1 was localized in the nucleus. TiMYB2R-1 transgenic wheat plants were generated, characterized molecularly, and evaluated for take-all resistance. PCR and Southern blot analyses confirmed that TiMYB2R-1 was integrated into the genomes of three independent transgenic wheat lines by distinct patterns and the transgene was heritable. Reverse transcription-PCR and western blot analyses revealed that TiMYB2R-1 was highly expressed in the transgenic wheat lines. Based on disease response assessments for three successive generations, the significantly enhanced resistance to take-all was observed in the three TiMYB2R-1-overexpressing transgenic wheat lines. Furthermore, the transcript levels of at least six wheat defence-related genes were significantly elevated in the TiMYB2R-1 transgenic wheat lines. These results suggest that engineering and overexpression of TiMYB2R-1 may be used for improving take-all resistance of wheat and other cereal crops.

Perennial cereals may offer a novel forage source in mixed farming enterprises while improving the sustainability of grain farming. There has been limited analysis of the quality of this forage type and its likely value to mixed grazing/cropping farming systems. This study evaluated the biomass and grain production of four wheat × wheatgrass hybrid experimental lines under four simulated grazing regimes; nil defoliation (grain only; D0), defoliate once (D1), defoliate twice (D2) and defoliate twice followed by a simulated hay cut (D3), and compared performance to a winter wheat, Wedgetail, and the perennial grass Thinopyrum intermedium. Early biomass production of the perennial entries was significantly less than Wedgetail (P = 0.01). Grain yield from Wedgetail was generally higher (P

The grazing season in the central and northern Great Plains could be extended by use of adapted cool-season grass pastures for spring and fall grazing to augment the native warm-season range. A grazing trial was conducted to evaluate the forage quality of four intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Dewey] populations for use in forage-livestock systems. The cultivars Slate and Oahe and two populations selected for improved IVDMD, 'Manska'and NE TI 1, were evaluated. Each population was seeded in the fall of 1987 in three replicated 0.4-ha pastures arranged in a randomized complete block design. Pastures were stocked with three beef yearlings for 28 d in spring 1989 and 42 d in spring 1990 to provide a stocking rate of 7.5 steers ha -1 . Duration of grazing was shorter in 1989 because of inadequate soil moisture. Average daily gain (ADG) and gain per hectare were higher (P ≤ 0.10) in 1989 than 1990, despite the lower (P ≤ 0.10) forage availability and lesser number of grazing days in 1989. Steers grazing Manska in 1989 gained 1.59 kg d -1 , compared with 1A2, 1.27, and 1.43 for Oahe, Slate, and NE TI 1, respectively. There were no differences (P > 0.10) in ADG or gain per hectare among populations in 1990. The improvement in ADG resulted in 30 to 65 kg more gain per hectare from Manska compared with the other populations in 1989. These results demonstrate the excellent quality of intermediate wheatgrass for grazing livestock and the impact that modest improvements in forage quality can have on animal performance.

Wheatgrasses (species of Agropyron complex) have previously been reported to be resistant to barley yellow dwarf virus (BYDV). To introgress this resistance into wheat, Triticum aestivum × Thinopyrum (Agropyron) intermedium hybrids were advanced through a backcrossing program and reaction to BYDV, as determined by enzyme-linked immunosorbent assay (ELISA), is reported for the first time in backcross populations of wide hybrids between wheat and wheatgrasses. ELISA values revealed highly resistant to highly susceptible segregants in backcrosses. BYDV resistance was expressed in some backcross derivatives. Continued selection, based on cytology and ELISA in each generation, eliminated most of the unwanted wheatgrass chromosomes and produced self-fertile BYDV resistant wheat lines. The BYDV resistant lines with 2n = 42 had normal chromosome pairing similar to wheat, and their F1 hybrids with wheat had two univalents. DNA analyses showed that the source of alien chromatin in these BYDV resistant wheat lines is distinguishable from that in other Th. intermedium derived BYDV resistant wheat lines. Chromosome pairing and restriction fragment length polymorphism analyses indicated that the 42 chromosome resistant Purdue wheat lines are substitution lines in which chromosome 7D was replaced by a chromosome from Th. intermedium that was carrying gene(s) for BYDV resistance.Key words: BYDV, Agropyron, Thinopyrum, wheat, backcrosses, Southern blots.

Zhong 5 is a partial amphiploid (2n = 56) between Triticum aestivum (2n = 42) and Thinopyrum intermedium (2n = 42) carrying all the chromosomes of wheat and seven pairs of chromosomes from Th. intermedium. Following further backcrossing to wheat, six independent stable 2n = 44 lines were obtained representing 4 disomic chromosome addition lines. One chromosome confers barley yellow dwarf virus (BYDV) resistance, whereas two other chromosomes carry leaf and stem rust resistance; one of the latter also confers stripe rust resistance. Using RFLP and isozyme markers we have shown that the extra chromosome in the Zhong 5-derived BYDV resistant disomic addition lines (Z1, Z2, or Z6) belongs to the homoeologous group 2. It therefore carries a different locus to the BYDV resistant group 7 addition, L1, described previously. The leaf, stem, and stripe rust resistant line (Z4) carries an added group 7 chromosome. The line Z3 has neither BYDV nor rust resistance, is not a group 2 or group 7 addition, and is probably a group 1 addition. The line Z5 is leaf and stem rust resistant, is not stripe rust resistant, and its homoeology remains unknown.Key words: Agropyron, intermediate wheatgrass, leaf rust, stem rust, stripe rust, luteovirus.

Speciation and allopolyploidization in cereals may be accompanied by dramatic changes in abundance of centromeric repeated transposable elements. Here we demonstrate that the reverse transcriptase part of Ty3/gypsy centromeric retrotransposon (RT-CR) is highly conservative in the segmental hexaploid Thinopyrum intermedium (JrJvsSt) and its possible diploid progenitors Th. bessarabicum (Jb), Pseudoroegneria spicata (St) and Dasypyrum villosum (V) but the abundance of the repeats varied to a large extent. Fluorescence in situ hybridization (FISH) showed hybridization signals in centromeric region of all chromosomes in the studied species, although the intensity of the signals drastically differed. In Th. intermedium, the strongest signal of RT-CR probe was detected on the chromosomes of Jv, intermediate on Jr and faint on Js and St subgenome suggesting different abundance of RT-CR on the individual chromosomes rather than the sequence specificity of RT-CRs of the subgenomes. RT-CR quantification using real-time PCR revealed that its content per genome in Th. bessarabicum is ~ 2 times and P. spicata is ~ 1,5 times higher than in genome of D. villosum. The possible burst of Ty3/gypsy centromeric retrotransposon in Th. intermedium during allopolyploidization and its role in proper mitotic and meiotic chromosome behavior in a nascent allopolyploid is discussed.

Trigeneric hybrids offer opportunities to transfer alien traits into cultivated wheat. In this study, a new trigeneric hybrid involving species of Triticum , Psathyrostachys , and Thinopyrum was synthesized by crossing Triticum aestivum L. (wheat) – Thinopyrum intermedium (Host) Barkworth & D.R. Dewey amphiploid Zhong 3 with wheat – Psathyrostachys huashanica Keng ex Kuo amphiploid PHW-SA. Crossability of the two amphiploids was 19.74%, and the fertility of the hybrid was 16.20%. The mean meiotic configuration of the trigeneric hybrid (2n = 56) was 13.06 I + 17.24 IIring + 3.73 IIrod + 0.28 III + 0.04 IV. GISH analysis indicated that the trigeneric F1had seven P. huashanica chromosomes and seven Th. intermedium chromosomes. The mean chromosome numbers of F2, F3, and F4progenies were 2n = 49.24, 2n = 48.13, and 2n = 46.78, respectively, a gradual decrease. GISH analysis revealed that most F2and F3plants had 2–10 Th. intermedium chromosomes and 0–4 P. huashanica chromosomes. In the F4progenies, 1–7 Th. intermedium chromosomes were labeled, but no P. huashanica chromosomes were detected. It seems that Th. intermedium chromosomes are more likely than P. huashanica chromosomes to be transmitted to the progenies. The stripe rust response of PHW-SA was expressed in the F1and some F2and F3progenies. The trigeneric hybrid could be a useful bridge for transfering P. huashanica and Th. intermedium chromosomes to common wheat.

Knowledge of heritability and inheritance of nutritive quality traits in intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & D.R. Deweys would be helpful in choosing effective selection techniques. This study assess variation and heritability of traits associated with hay quality in intermediate wheatgrass, ascertains the relative magnitude of general and specific combining ability (SCA and GCA) for these traits, and examines relationships among important agronomic and quality traits. Six parent clones and the 15 progenies from a diallel cross (reciprocal crosses not included) were evaluated in a replicated field test for in vitro digestible organic matter (IVDOM), neutral detergent fiber (NDF), and N concentration of whole plants, leaf blades, and stems (stem plus leaf sheath)

Background The wheat tribe Triticeae (Poaceae) is a diverse group of grasses representing a textbook example of reticulate evolution. Apart from globally important grain crops, there are also wild grasses which are of great practical value. Allohexaploid intermediate wheatgrass, Thinopyrum intermedium (2n = 6x = 42), possesses many desirable agronomic traits that make it an invaluable source of genetic material useful in wheat improvement. Although the identification of its genomic components has been the object of considerable investigation, the complete genomic constitution and its potential variability are still being unravelled. To identify the genomic constitution of this allohexaploid, four accessions of intermediate wheatgrass from its native area were analysed by sequencing of chloroplast trnL-F and partial nuclear GBSSI, and genomic in situ hybridization. Results The results confirmed the allopolyploid origin of Thinopyrum intermedium and revealed new aspects in its genomic composition. Genomic heterogeneity suggests a more complex origin of the species than would be expected if it originated through allohexaploidy alone. While Pseudoroegneria is the most probable maternal parent of the accessions analysed, nuclear GBSSI sequences suggested the contribution of distinct lineages corresponding to the following present-day genera: Pseudoroegneria, Dasypyrum, Taeniatherum, Aegilops and Thinopyrum. Two subgenomes of the hexaploid have most probably been contributed by Pseudoroegneria and Dasypyrum, but the identity of the third subgenome remains unresolved satisfactorily. Possibly it is of hybridogenous origin, with contributions from Thinopyrum and Aegilops. Surprising diversity of GBSSI copies corresponding to a Dasypyrum-like progenitor indicates either multiple contributions from different sources close to Dasypyrum and maintenance of divergent copies or the presence of divergent paralogs, or a combination of both. Taeniatherum-like GBSSI copies are most probably pseudogenic, and the mode of their acquisition by Th. intermedium remains unclear. Conclusions Hybridization has played a key role in the evolution of the Triticeae. Transfer of genetic material via extensive interspecific hybridization and/or introgression could have enriched the species' gene pools significantly. We have shown that the genomic heterogeneity of intermediate wheatgrass is higher than has been previously assumed, which is of particular concern to wheat breeders, who frequently use it as a source of desirable traits in wheat improvement.

Genetic differences among cultivars or strains for specific traits can be significantly reduced or increased by differential genotypic responses to environments. The objective of this study was to determine the relative magnitude of genotype and genotype × environment interaction effects, which are due to differential responses, on forage yield and quality of intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] when grown in seeded swards in the central Great Plains. Thirty-four strains (genotypes), which included cultivars, experimental strains, and PI lines, were grown in replicated trials at Mead, North Platte, and Alliance, NE (.)