Kevin B. Jensen

Merits of native and introduced Triticeae grasses on semiarid rangelands

Experiments were conducted on four semiarid range sites to compare stand establishment, productivity, and persistence of several introduced perennial Triticeae grasses with that of their native counterparts. On Intermountain sites with severe water limitations (< 300 mm), native grasses were more difficult to establish, less productive, and less persistent than the introduced grasses. Stands of native grasses declined most rapidly under defoliation. At locations where moisture conditions were more favorable, particularly where more summer precipitation occurred, native Triticeae grasses established and persisted relatively well compared with the introduced entries. Although difficult to establish, stands of the rhizomatous native, western wheatgrass [Pascopyrum smithii (Rydb.) A. Love] in creased during the seasons after establishment. Choice of plant materials to be used in range seeding programs should be based on objective criteria. To do otherwise will perpetuate degradation of soil resources, especia...

Population structure in Pseudoroegneria spicata (Poaceae: Triticeae) modeled by Bayesian clustering of AFLP genotypes.

Pseudoroegneria spicata (Poaceae: Triticeae) is an abundant, allogamous species widely adapted to the temperate, semiarid steppe and open woodland regions of western North America. Amplified fragment length polymorphism (AFLP), model-based Bayesian clustering, and other methods of hypothesis testing were used to investigate genetic diversity and population structure among 565 P. spicata plants from 82 localities representing much of the species distribution. Comparisons with four Asiatic Pseudoroegneria species and two North American Elymus wawawaiensis accessions demonstrate cohesiveness in P. spicata. However, P. spicata genotypes group by locality and geographic region based on genetic distance analysis. Average DNA polymorphism among P. spicata localities was significantly correlated (r = 0.58) with geographical distance. The optimum Bayesian cluster model included 21 P. spicata groups, indicating that dispersal among sampling locations was not sufficient to group genotypes into one unstructured population. Approximately 18.3% of the DNA polymorphism was partitioned among the 21 regional groups, 14.9% among localities within groups, and 66.8% within accessions. Average DNA polymorphism among Bayesian groups was correlated (r = 0.53) with the average geographic distance among Bayesian groups, which partly reflects isolation by distance. However, conspicuous regional boundaries were discernable among several divergent genetic groups.

Cytological and molecular evidence for transferring Elymus coreanus from the genus Elymus to Leymus and molecular evidence for Elymus californicus (Poaceae : Triticeae)

Elymus coreanus and Elymus californicus were studied to describe (1) their genomic composition and (2) correct taxonomic alignment based on genomic relationships. The hybrids E. coreanus x Psathyrostachys stoloniformis (NsNs), E. coreanus x Leymus ambiguus (NsNsXmXm), E. coreanus x Leymus salinus ssp. salmonis (NsNsXmXm), and E. coreanus x Leymus innovatus NsXmXm) averaged 5.80, 13.74, 13.15, and 13.58 bivalents per cell, respectively. Genome-specific RAPD assay results indicate that E. californicus and E. coreanus have the Ns genome but lack the St genome from the genus Pseudoroegneria and the Eb genome from the genus Thinopyrum. Therefore, these two species have the same genome constitution as other Leymus species and should be transferred to the genus Leymus. The following new name combination is proposed for Leymus coreanus (Honda) K. B. Jensen & R. R-C. Wang comb. nov., based on Elymus coreanus Honda (1930 [J. Fac. Sci. Univ. Tokyo 3, 3:17], cited in Love 1984). However, until further cytological data are available, the new name combination transferring E. californicus into Leymus will be made in a later publication.

Cytogenetics and Morphology of Elymus panormitanus var. Heterophyllus and Its Relationship to Elymus panormitanus var. Panormitanus (Poaceae: Triticeae)

Elymus panormitanus var. heterophyllus, PI-235086, was collected in Israel and became part of the National Plant Germplasm System as Elymus caninus L. in 1956. Bivalent pairing at metaphase I (MI) in E. panormitanus var. heterophyllus (2n = 42) was typical of other allohexaploids within the Triticeae. However, chromosome pairing analysis at MI of the tetraploid hybrids with Pseudoroegneria spicata (2n = 14, SS) and the pentaploid hybrids with Pseudoroegneria stipifolia (2n = 28, SSSS), Elymus lanceolatus (2n = 28, SSHH), E. panormitanus (2n = 28, SSYY), and Elymus nevski (2n = 28, SSYY) indicated that two of the three genomes of E. panormitanus var. heterophyllus were at least partially homologous to the S genome and confirmed the presence of a Y genome. Cluster analysis of 18 key characters separated E. panormitanus var. heterophyllus from E. panormitanus However, the continuous variation between the two taxa made taxonomic separation difficult unless the samples represented the two extremes. In this unique case, two taxa-E. panormitanus var. heterophyllus and E. panormitanus-were very close morphologically but different genomically. Elymus panormitanus var. heterophyllus is a hexaploid (SSSSYY; 2n = 42) and E. panormitanus is an allotetraploid (SSYY; 2n = 28).

Analyses of Thinopyrum bessarabicum, T. elongatum, and T. junceum chromosomes using EST-SSR markers.

Wild Thinopyrum grasses are important gene pools for forage and cereal crops. Knowledge of their chromosome organizations is pivotal for efficient utilization of this important gene pool in germplasm enhancement programs. Expressed sequence tags derived simple sequence repeat (EST-SSR) markers for Thinopyrum bessarabicum, T. elongatum, and T. junceum chromosomes were identified among amplicons produced from three series of wheat-Thinopyrum addition lines using 193 primer pairs designed from the Leymus EST unigenes. The homology of T. junceum chromosomes in 13 wheat addition lines was tentatively established to reveal that homologous groups 3, 4, 5, 6, and 7 were represented by HD3515, HD3505, AJDAj11, AJDAj1, and HD3508, whereas groups 1 and 2 were represented by AJADj7-AJDAj9 and AJDAj2-AJDAj4, respectively. AJDAj5 and AJDAj6 had complexly reconstituted T. junceum chromosomes that might have resulted from fusion or translocations of large chromosomal segments from two or more chromosomes, that is (1+5) and (2+5+1), respectively. The identified EST-SSR markers will be useful in comparative gene mapping, chromosome tracing, taxonomic studies, gene introgression, and cultivar identification.

Genome Analysis of Eurasian Elymus thoroldianus, E. melantherus, and E. kokonoricus (Triticeae: Poaceae)

Elymus thoroldianus (Oliver) G. Singh, E. melantherus (Keng) A. Löve, and E. kokonoricus (Keng) A. Löve are short-lived perennial grasses of the tribe Triticeae distributed throughout the upper and middle mountain ranges of central Asia. Analyzer species used to produce interspecific hybrids with the three target taxa were Pseudoroegneria spicata (Pursh) A. Löve (SS), E. lanceolatus (Scribn. & Smith) Gould (SSHH), Psathyrostachys juncea (Fisch.) Nevski (NN), E. batalinii (Krasn) A. Löve (SSYYPP), E. alatavicus (Drob.) Tzvelev (SSYYPP), E. grandiglumis (Keng) A. Löve (SSYYPP), and E. kengii (Tzvelev) A. Löve (SSYYPP). Elymus thoroldianus, E. melantherus, and E. kokonoricus are self-fertile allohexaploids (2n = 42). Analysis of metaphase I pairing configurations in the F1 indicate that E. thoroldianus, E. melantherus, and E. kokonoricus possess the S, Y, and P genomes, with only minor structural rearrangements. Chromosome pairing in interspecific hybrids with the target species and hexaploid accessions of E. batalinii, E. alatavicus, E. kengii, and E. grandiglumis supports the inclusion of E. thoroldianus, E. melantherus, and E. kokonoricus in the genus Elymus section Hyalolepis.

Notice of Release of NBR-1 Germplasm Basalt Milkvetch

A selected-class pre-variety germplasm of basalt milkvetch (Astragalus filipes Torr. ex A. Gray [Fabaceae]) has been released for reclamation, rehabilitation, and restoration of semiarid rangelands in the northern Great Basin Region of the western US.Johnson DA, Jones TA, Connors KJ, Bhattarai K, Bushman BS, Jensen KB. 2008. Notice of release of NBR-1 Germplasm basalt milkvetch. Native Plants Journal 9(2):127–132.

Genome evolution of intermediate wheatgrass as revealed by EST-SSR markers developed from its three progenitor diploid species

Intermediate wheatgrass (Thinopyrum intermedium (Host) Barkworth & D.R. Dewey), a segmental autoallohexaploid (2n = 6x = 42), is not only an important forage crop but also a valuable gene reservoir for wheat (Triticum aestivum L.) improvement. Throughout the scientific literature, there continues to be disagreement as to the origin of the different genomes in intermediate wheatgrass. Genotypic data obtained from newly developed EST-SSR primers derived from the putative progenitor diploid species Pseudoroegneria spicata (Pursh) Á. Löve (St genome), Thinopyrum bessarabicum (Savul. & Rayss) Á. Löve (J = J(b) = E(b)), and Thinopyrum elongatum (Host) D. Dewey (E = J(e) = E(e)) indicate that the V genome of Dasypyrum (Coss. & Durieu) T. Durand is not one of the three genomes in intermediate wheatgrass. Based on all available information in the literature and findings in this study, the genomic designation of intermediate wheatgrass should be changed to J(vs)J(r)St, where J(vs) and J(r) represent ancestral genomes of present-day J(b) of Th. bessarabicum and J(e) of Th. elongatum, with J(vs) being more ancient. Furthermore, the information suggests that the St genome in intermediate wheatgrass is most similar to the present-day St found in diploid species of Pseudoroegneria from Eurasia.

Potential of new tetraploid germplasm in Russian wildrye.

Induced and natural tetraploids have been proposed as promising sources of germplasm in breeding programs to improve Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski]. Studies were conducted under semiarid conditions to evaluate the potential of tetraploid (2n=4x=28) Russian wildrye germplasm recently obtained from Kazakhstan. The teraploids had significantly heavier seeds, greater seedling vigor, and they were significantly taller, and had longer and wider leaves than standard diploid (2n=2x=14) cultivars. Carbon isotope discrimination, which has been negatively correlated with water-use efficiency in cool-season grasses, was significantly lower in the tetraploid accessions than the diploid cultivars. Dry matter and seed yield of these unselected tetraploid accessions were superior to the diploid cultivar Vinall and equivalent to more recently developed diploid cultivars, Bozoisky-Select and Syn-A. In general, relative phenological development and forage quality of the tetraploid populations did not differ significantly from the diploid cultivars; however, water content, which has been associated with greater succulence, was significantly higher in the tetraploid accessions. Significant variation was found among entries within ploidy levels for most characters indicating that genetic variability is available for additional improvement through selection. Results indicate that these tetraploid accessions can be used in the development of promising breeding populations and support earlier conclusions that tetraploid germplasm should receive emphasis in future Russian wildrye breeding programs.

Molecular Marker Analysis of Leymus flavescens and Chromosome Pairing in Leymus flavescens Hybrids (Poaceae: Triticeae)1

Leymus flavescens (Scribner & Smith) Pilger, yellow wild rye, is a long‐lived, strongly rhizomatous, tetraploid (2n=4x=28) perennial grass of the tribe Triticeae distributed throughout central Washington, eastern Oregon, and the Snake River plains of Idaho. Our objectives were (1) to describe chromosome pairing and fertility in F1 hybrids between L. flavescens and North American tetraploids (2n=4x=28) L. triticoides and L. cinereus and Eurasian tetraploids L. secalinus, L. racemosus, and L. alaicus subsp. karataviensis and (2) to utilize genome‐specific random amplified polymorphic DNA (RAPD) markers to verify the genomic composition of L. flavescens. The hybrids L. flavescens × L. triticoides (NsNsXmXm), L. flavescens × L. secalinus (NsNsXmXm), L. flavescens × L. racemosus (NsNsXmXm), L. flavescens × L. cinereus (NsNsXmXm), and L. flavescens × L. alaicus subsp. karataviensis (NsNsXmXm) averaged 13.9, 13.8, 13.6, 13.1, and 11.9 bivalents per cell, respectively. Genome‐specific RAPD assay indicates that L. flavescens has the Ns genome but lacks the St genome from the genus Pseudoroegneria and the H genome from the genus Hordeum. On the basis of the bivalent chromosome pairing frequency in the F1 hybrids of L. flavescens, the genomic formula of L. flavescens is NsNsXmXm. The presence of the Ns genome was verified by molecular characterization.