Cytogenetic And EF-G Sequences Analysis Of Species And Hybridizations With The StH Genome In Triticeae (Poaceae)

The group of Triticeae species with the StH genome is important plants in the tribe Triticeae. At present, there are about35species in the world as known. Most species with the StH genome are fine herbages, and some of them have disease resistance, stress tolerance and insect resistance, which are precious germplasm resources in forage breeding and crop improvement.The St and H genome were evolved from Pseudoroegnaria and Hordeum, respectively. Alougth having the same StH genomes, these species with the StH genome show different morphological characters, habits and distributions. Some of the morphological characters, such as the number of spikelet per node, glume, lemma, are different in species with the StH genome.The species with the StH genome exhibit different morphological characters, such as, having one (Elymus lanceolatus) to two (Hystrix patula) to three～four (Elymus canadensis) spikelets per node, and with narrow and long (Elymus elymoides) to reduced (Hystrix patula) glumes. Geographically, the species with the StH genome are mainly distributed in the temperate and warm temperate regions, from Eurasia to North America in the word. They are growing in valley, grassland, and forest. The species with the StH genome were once involved in different genera because of their morphological variation, such as Hystrix, Elymus, Elytrigia and Sitanion, and they were treated as the type species of the four genera.In order to inspect the interspecific and phylogenetic relationships among the species with the StH genome, interspecific and intergeneric hybridizations in company with morphological comparison, cytological study, fertility, and EF-G sequences analysis of species with the StH genome and their related species were carried out in this study. The main results are showed as follows:1. Interspecific hybridizations were carried out among the species with the StH genomes. Four intergeneric hybridizations (E. glaunus x E. wawawaiensis, E. wawawaiensis×E. virginicus, E. virginus×E. wawawaiensis, E. virginus×E. multisetus) were obtained successfully. Chromosome configuration of E. glaunus×E. wawawaiensis, E. wawawaiensis×E. virginicus, E. virginus×E. wawawaiensis, E. virginus×E. multisetus were0.2I+13.9Ⅱ,0.41+13.8Ⅱ,0.43Ⅰ+13.74Ⅱ+0.01Ⅲ+0.01IV and1.13~+13.29Ⅱ+0.04Ⅲ+0.04Ⅳ, respectively. The results indicate that higher genome homology existed among genomes of the four Elymus species. Meiotic pairing in E. virginus x E. multisetus was relatively lower than the other three hybridizations, indicating that the StH-genome of E. multisetus was different from those in other Elymus species.2. Intergeneric hybridizations were carried out among the species with the StH genomes and the genus Pseudoroegneria and Hordeum. In the present study, one intergeneric hybridizations (E. wawawaiensis (2n=4x=28, StH)×P.libanotica (2n=2x=14, St)) was obtained. Meiotic pairing in E. wawawaiensis×P.libanotica were relatively high with average of6.35bivalents per cell, indicating that high genome homology existed between StH genomes of E. wawawaiensis and the St genome of Pseudoroegneria.3. Based on EF-G sequences, phylogenetic analysis was performed on sixteen species with StH genome, seven Pseudoroegneria (St) species and four Hordeum (H) species in the tribe Triticeae. Phylogenetic analysis showed that:(1) The species with the StH genome from the same areas are closely related to each other;(2) Pse. gracillima, Pse.libanotica, Pse. strigosa, Pse. stipifolia, Pse. spicata and Pse. ferganensis formed parallel branches, which indicates that differentiation occurred of among the St genome in Pseudoroegneria;(3) The EF-G sequences of the species with the StH genome distributed in North and Eurasian are heterogeneous geographically.