Phylogeny of Triticeae (Poaceae) Based on Three Organelle Genes, Two Single-Copy Nuclear Genes, and Morphology

Triticeae are renowned for their complicated taxonomy, but their phylogeny is equally intricate and perplexing, and remains largely unresolved. Based on morphology and nucleotide sequences from two plastid genes (rbcL, rpoA), one mitochondrial gene (coxII), and two single-copy nuclear genes (DMC1, EF-G), the most comprehensive hypothesis (both with respect to taxa and data points) of the phylogeny of diploid Triticeae to date is presented. The incongruence length difference tests clearly indicate that the four logical data partitions (morphology and the three genome compartments) are mutually incongruent, except the mitochondrial and nuclear sequences. Nonetheless, a total evidence approach results in a highly resolved, strongly supported consensus tree, though partitioned Bremer support points to a high level of conflict among the individual data sets

Path and Ridge Regression Analysis of Seed Yield and Seed Yield Components of Russian Wildrye (Psathyrostachys juncea Nevski) under Field Conditions

The correlations among seed yield components, and their direct and indirect effects on the seed yield (Z) of Russina wildrye (Psathyrostachys juncea Nevski) were investigated. The seed yield components: fertile tillers m-2 (Y1), spikelets per fertile tillers (Y2), florets per spikelet- (Y3), seed numbers per spikelet (Y4) and seed weight (Y5) were counted and the Z were determined in field experiments from 2003 to 2006 via big sample size. Y1 was the most important seed yield component describing the Z and Y2 was the least. The total direct effects of the Y1, Y3 and Y5 to the Z were positive while Y4 and Y2 were weakly negative. The total effects (directs plus indirects) of the components were positively contributed to the Z by path analyses. The seed yield components Y1, Y2, Y4 and Y5 were significantly (P<0.001) correlated with the Z for 4 years totally, while in the individual years, Y2 were not significant correlated with Y3, Y4 and Y5 by Peason correlation analyses in the five components in the plant seed production. Therefore, selection for high seed yield through direct selection for large Y1, Y2 and Y3 would be effective for breeding programs in grasses. Furthermore, it is the most important that, via ridge regression, a steady algorithm model between Z and the five yield components was founded, which can be closely estimated the seed yield via the components

The Study on N Genome of Leymus Species

Leymus Hochst. is a perennial genus of Triticeae. All species in Leymus have the genomes NX. The genome N is from the genus Psathyrostachys. Two Psathyrostachys species, diploid P. huashanica Keng ex Kuo and P. juncea (Fische.) Nevski (2n= 14), were hybridized with allotetraploid, Leymus secalinus (Georgi.) Tzvelev and L. multicaulis (Kar. & Kir.) Tzvelev. Meiotic behavior of the synthetic hybrids was studied. The chromosome pairings indicated that one L. secalinus genome and one L. multicaulis genome were closely homologous with both P. huashanica and P. juncea genomes. The data of genomic analysis in the hybrids of P. huashanica crossed with L. secalinus and L. multicaulis are so similar to those in the hybrids of P. juncea crossed with L. secalinus and L. multicaulis, there is no significant difference between them. Both P. huashanica and P. juncea are possible donors of the N genome of L. secalinus and L. multicaulis

Introgression of Chromosome 3Ns from Psathyrostachys huashanica into Wheat Specifying Resistance to Stripe Rust

Wheat stripe rust is a destructive disease in the cool and humid wheat-growing areas of the world. Finding diverse sources of stripe rust resistance is critical for increasing genetic diversity of resistance for wheat breeding programs. Stripe rust resistance was identified in the alien species Psathyrostachys huashanica, and a wheat- P. huashanica amphiploid line (PHW-SA) with stripe rust resistance was reported previously. In this study, a P. huashanica 3Ns monosomic addition line (PW11) with superior resistance to stripe rust was developed, which was derived from the cross between PHW-SA and wheat J-11. We evaluated the alien introgressions PW11-2, PW11-5 and PW11-8 which were derived from line PW11 for reaction to new Pst race CYR32, and used molecular and cytogenetic tools to characterize these lines. The introgressions were remarkably resistant to CYR32, suggesting that the resistance to stripe rust of the introgressions thus was controlled by gene(s) located on P. huashanica chromosome 3Ns. All derived lines were cytologically stable in term of meiotic chromosome behavior. Two 3Ns chromosomes of P. huashanica were detected in the disomic addition line PW11-2. Chromosomes 1B of substitution line PW11-5 had been replaced by a pair of P. huashanica 3Ns chromosomes. In PW11-8, a small terminal segment from P. huashanica chromosome arm 3NsS was translocated to the terminal region of wheat chromosomes 3BL. Thus, this translocated chromosome is designated T3BL-3NsS. These conclusions were further confirmed by SSR analyses. Two 3Ns-specific markers Xgwm181 and Xgwm161 will be useful to rapidly identify and trace the translocated fragments. These introgressions, which had significant characteristics of resistance to stripe rust, could be utilized as novel germplasms for wheat breeding

Phylogeny and evolutionary history of Leymus (Triticeae; Poaceae) based on a single-copy nuclear gene encoding plastid acetyl-CoA carboxylase

<p>Abstract</p> <p>Background</p> <p>Single- and low- copy genes are less likely subject to concerted evolution, thus making themselves ideal tools for studying the origin and evolution of polyploid taxa. <it>Leymus </it>is a polyploid genus with a diverse array of morphology, ecology and distribution in Triticeae. The genomic constitution of <it>Leymus </it>was assigned as NsXm, where Ns was presumed to be originated from <it>Psathyrostachys</it>, while Xm represented a genome of unknown origin. In addition, little is known about the evolutionary history of <it>Leymus</it>. Here, we investigate the phylogenetic relationship, genome donor, and evolutionary history of <it>Leymus </it>based on a single-copy nuclear <it>Acc1 </it>gene.</p> <p>Results</p> <p>Two homoeologues of the <it>Acc1 </it>gene were isolated from nearly all the sampled <it>Leymus </it>species using allele-specific primer and were analyzed with those from 35 diploid taxa representing 18 basic genomes in Triticeae. Sequence diversity patterns and genealogical analysis suggested that (1) <it>Leymus </it>is closely related to <it>Psathyrostachys</it>, <it>Agropyron</it>, and <it>Eremopyrum</it>; (2) <it>Psathyrostachys juncea </it>is an ancestral Ns-genome donor of <it>Leymus </it>species; (3) the Xm genome in <it>Leymus </it>may be originated from an ancestral lineage of <it>Agropyron </it>and <it>Eremopyrum triticeum</it>; (4) the <it>Acc1 </it>sequences of <it>Leymus </it>species from the Qinghai-Tibetan plateau are evolutionarily distinct; (5) North America <it>Leymus </it>species might originate from colonization via the Bering land bridge; (6) <it>Leymus </it>originated about 11-12MYA in Eurasia, and adaptive radiation might have occurred in <it>Leymus </it>during the period of 3.7-4.3 MYA and 1.7-2.1 MYA.</p> <p>Conclusion</p> <p><it>Leymus </it>species have allopolyploid origin. It is hypothesized that the adaptive radiation of <it>Leymus </it>species might have been triggered by the recent upliftings of the Qinghai-Tibetan plateau and subsequent climatic oscillations. Adaptive radiation may have promoted the rapid speciation, as well as the fixation of unique morphological characters in <it>Leymus</it>. Our results shed new light on our understanding of the origin of Xm genome, the polyploidization events and evolutionary history of <it>Leymus </it>that could account for the rich diversity and ecological adaptation of <it>Leymus </it>species.</p

Multigenic phylogeny and analysis of tree incongruences in Triticeae (Poaceae)

Background: Introgressive events (e.g., hybridization, gene flow, horizontal gene transfer) and incomplete lineage sorting of ancestral polymorphisms are a challenge for phylogenetic analyses since different genes may exhibit conflicting genealogical histories. Grasses of the Triticeae tribe provide a particularly striking example of incongruence among gene trees. Previous phylogenies, mostly inferred with one gene, are in conflict for several taxon positions. Therefore, obtaining a resolved picture of relationships among genera and species of this tribe has been a challenging task. Here, we obtain the most comprehensive molecular dataset to date in Triticeae, including one chloroplastic and 26 nuclear genes. We aim to test whether it is possible to infer phylogenetic relationships in the face of (potentially) large-scale introgressive events and/or incomplete lineage sorting; to identify parts of the evolutionary history that have not evolved in a tree-like manner; and to decipher the biological causes of genetree conflicts in this tribe. Results: We obtain resolved phylogenetic hypotheses using the supermatrix and Bayesian Concordance Factors (BCF) approaches despite numerous incongruences among gene trees. These phylogenies suggest the existence of 4-5 major clades within Triticeae, with Psathyrostachys and Hordeum being the deepest genera. In addition, we construct a multigenic network that highlights parts of the Triticeae history that have not evolved in a tree-lik