The genus Poa comprises approximately 500 species that occur throughout the world, including the widely grown Kentucky bluegrass (P. pratensis L.). Hybridization and polyploidization have played a prominent role in the evolution of this complex genus, but limited information is available regarding genome relationships in Poa. Thus, we amplified, cloned, and compared the DNA sequences of 2 nuclear genes (CDO504 and thioredoxin-like protein) and 2 chloroplast genome loci (ndhF and trnT-trnF) from 22 Poa species. Four distinct classes of sequences corresponding to 4 putative homoeologous loci from each nuclear gene were found within polyploid P. pratensis. Nuclear sequences from 15 other Poa species were found to group with at least 1 P. pratensis homoeolog, whereas 6 species displayed sequences not present in P. pratensis. The nuclear genome phylogenies presented here show the first evidence of diverse and related genomes in the genus Poa.

A series of poly(4-tert-butylstyrene-block-2-vinylpyridine) [P(tBuSt-b-2VP)] block copolymers (BCPs) with varying volume fractions, molecular weights, and narrow dispersities were synthesized from the commercially available monomers by sequential living anionic polymerization. The copolymers were thoroughly characterized by 1H NMR spectroscopy, size exclusion chromatography, thermal gravimetric analysis, and differential scanning calorimetry (DSC). To examine the effect of the tert-butyl group on the effective interaction parameter (χeff) relative to poly(styrene-block-2-vinylpyridine) [(P(S-b-2VP)], the self-assembly of symmetric copolymers was studied by small-angle X-ray scattering (SAXS) and transmission electron microscopy. Order-to-disorder transitions (ODTs) were identified by both DSC and SAXS on five copolymers, to define the equation χeff(T) = (67.9 ± 1.3)/T – (0.0502 ± 0.0029), which shows a higher enthalpic contribution to χeff than P(S-b-2VP) and approximately 1.5 times larger χeff. This enables a minimum full pitch of 9.6 nm for the symmetric copolymers. Asymmetric copolymers were also examined for bulk self-assembly by SAXS and TEM, exploring both P2VP and PtBuSt cylindrical phases with diameters as small as 6 nm. Feasibility of thin film assembly by thermal annealing was demonstrated for a P2VP cylinder forming BCPs to yield parallel cylinders that were seeded with Pt ions and etched to yield Pt nanowires with diameters as small as 5.8 nm.

Molecular genetic maps were constructed for two full-sib populations, TTC1 and TTC2, derived from two Leymus triticoides x Leymus cinereus hybrids and one common Leymus triticoides tester. Informative DNA markers were detected using 21 EcoRI-MseI and 17 PstI-MseI AFLP primer combinations, 36 anchored SSR or STS primer pairs, and 9 anchored RFLP probes. The 164-sib TTC1 map includes 1069 AFLP markers and 38 anchor loci in 14 linkage groups spanning 2001 cM. The 170-sib TTC2 map contains 1002 AFLP markers and 36 anchor loci in 14 linkage groups spanning 2066 cM. Some 488 homologous AFLP loci and 24 anchor markers detected in both populations showed similar map order. Thus, 1583 AFLP markers and 50 anchor loci were mapped into 14 linkage groups, which evidently correspond to the 14 chromosomes of allotetraploid Leymus (2n = 4x = 28). Synteny of two or more anchor markers from each of the seven homoeologous wheat and barley chromosomes was detected for 12 of the 14 Leymus linkage groups. Moreover, two distinct sets of genome-specific STS markers were identified in these allotetraploid Leymus species. These Leymus genetic maps and populations will provide a useful system to evaluate the inheritance of functionally important traits of two divergent perennial grass species.

Intermediate wheatgrass [IWG; Thinopyrum intermedium (Host) Barkworth & D.R. Dewey subsp. intermedium] is being developed as a new perennial grain crop that has a large allohexaploid genome similar to that of wheat (Triticum aestivum L.). Breeding for increased seed weight is one of the primary goals for improving grain yield of IWG. As a new crop, however, the genetic architecture of seed weight and size has not been characterized, and selective breeding of IWG may be more intricate than wheat because of its self-incompatible mating system and perennial growth habit. Here, seed weight, seed area size, seed width, and seed length were evaluated across multiple years, in a heterogeneous breeding population comprised of 1126 genets and two clonally replicated biparental populations comprised of 172 and 265 genets. Among 10,171 DNA markers discovered using genotypingby-sequencing (GBS) in the breeding population, 4731 markers were present in a consensus genetic map previously constructed using seven full-sib populations. Thirty-three quantitative trait loci (QTL) associated with seed weight and size were identified using association mapping (AM), of which 23 were verified using linkage mapping in the biparental populations. About 37.6% of seed weight variation in the breeding population was explained by 15 QTL, 12 of which also contributed to either seed length or seed width. When performing either phenotypic selection or genomic selection for seed weight, we observed the frequency of favorable QTL alleles were increased to >46%. Thus, by combining AM and genomic selection, we can effectively select the favorable QTL alleles for seed weight and size in IWG breeding populations. Intermediate wheatgrass (2n = 6x = 42) is a new perennial grain crop (Wagoner, 1990;Kantar et al., 2016). Compared with annual grain crops, it has an extended growing season and deep roots, which increase carbon sequestration and help prevent runoff and improve water quality (Glover et al., 2010;Culman et al., 2013). Moreover, Core Ideas• Twenty-three shared QTL were identified using linkage and association mapping• Overlapped QTL explained the high genetic correlation among seed weight and size• QTL responded positively to either phenotypic selection or genomic selection• Combining association mapping and genomic selection would increase genetic gain

Bluebunch wheatgrass (Pseudoroegneria spicata [Pursh] A. Löve = Agropyron spicatum Pursh: Poaceae) is a cross‐pollinating perennial grass native to western North America. Two bluebunch wheatgrass cultivars, Goldar and Whitmar, are currently available for large‐scale rangeland seeding. However, cultivars may lack the genetic diversity and adaptation necessary for dynamic non‐local environments. The objective of this study was to quantify and compare genomic DNA variation within and between Goldar, Whitmar, and Generation 2 of P‐7, a multiple‐origin polycross (MOPX2) of 25 naturally diverse bluebunch wheatgrass collections. We assayed 1043 polymorphic amplified fragment length polymorphism (AFLP) products and 88 monomorphic AFLP products from three sample populations of 22 plants. The number of polymorphic loci (and unique alleles) within sample populations of P‐7, Goldar, and Whitmar was 898 (99), 813 (49), and 746 (59), respectively. Conversely, the number of fixed AFLP loci within sample populations of P‐7, Goldar, and Whitmar was 233, 318, and 385, respectively. The overall nucleotide‐sequence diversity [π ± SE (×1000)] estimated for P‐7, Goldar, and Whitmar was 100.2 ± 7.1, 80.1 ± 6.6, and 79.4 ± 6.7, respectively. By all measures, genetic variation within P‐7 is significantly higher than genetic variation within cultivars. However, the estimated number of inter‐population nucleotide differences per site [dX ± SE (×1000)] between Goldar and Whitmar, e.g., 36.6 ± 1.6, is only slightly higher than π within these cultivars, therefore the net nucleotide‐sequence divergence [dA ± SE (× 1000)] between these cultivars is relatively small, e.g. 2.5 ± 0.3. These results indicate that selectively neutral genetic diversity has not been dramatically reduced or inadvertently lost via genetic drift that may have occurred since the divergence of Goldar and Whitmar. No AFLP markers completely distinguish Goldar and Whitmar, therefore discrete morphological differences between these cultivars (e.g., the presence and absence of awns) most likely result from natural or artificial selection.