High molecular karyotype variation revealed in indigenous Elymus nutans in the Qinghai Plateau

The karyotypes of 27 individuals of Elymus nutans from eight wild populations in the Qinghai Plateau were analyzed using sequential FISH and GISH. High FISH pattern polymorphism and karyotype variation were detected within and among populations. The chromosome variations were mainly characterized as repeat deletions and amplifications along with inter-genomic translocations. The chromosomes of the St and Y genomes demonstrated higher polymorphism than those of the H genome. Six different intergenomic translocations were identified in 33.3% of individuals; type Ⅰ and Ⅱ translocations were detected with higher frequency. Further analysis revealed that type Ⅰ and Ⅱ translocations were distributed in different geographic regions. The origin of high karyotype variation of E. nutans in the Qinghai plateau is further discussed.

Molecular cytogenetic study on the plants of Elymus nutans with varying fertility on the Qinghai-Tibet Plateau

A molecular cytogenetic investigation was conducted on plants of the allohexaploid species Elymus nutans with varying fertility on the Qinghai-Tibet Plateau.Molecular karyotyping revealed that chromosome variants were distributed unevenly among genomes and among different homologue chromosomes in each genome.The plants with varying fertility exhibited significantly higher numbers of chromosome variants than did the normal fertility samples,although both kinds of plants showed the same pattern of high-to-low polymorphism from the Y to St and H genomes.Heterozygosis and karyotype heterozygosity in the plants with varying fertility were 3-and 13-fold higher than those in normal samples,respectively.Significant negative correlations were found not only between seed setting rates and total genome heterozygosity but also between seed setting rates and heterozygosity of each genome in the plants of varying fertility.Chromosome pairing analysis was performed using genomic in situ hybridization in selected plants of different fertility levels.The pairing of chromosomes at meiotic metaphase I was mostly bivalent,although univalent,trivalent,quadrivalent,and other polyvalents also occurred;in addition,chromosome configuration forms and frequencies varied among the studied samples.ANOVA results showed that the average number of ring bivalents in the Y genome was significantly higher than those in the St and H genomes.Significant positive correlations between pollen grain fertility and ring bivalent number were found in the St and H genomes but not in the Y genome.Furthermore,chromosome configuration parameters(total bivalents,numbers of ring and rod bivalents)were found to be significantly correlated with heterozygosity and seed setting rates in the St and H genomes,respectively,but not in the Y genome.It was inferred that the seed setting rate and pollen grain fertility in E.nutans are strongly influenced by the heterozygosity of each genome,but the Y genome differs from the St and H genomes due to chromosome pair alterations.The St and H genomes may contain more chromosome structural variations than the Y genome in E.nutans.