Siberian wild rye (Elymus sibiricus L.), an allotetraploid species, is a potentially high-quality perennial forage crop native to temperate regions. We used fluorescently conjugated oligonucleotides, representing ten repetitive sequences, including 6 microsatellite repeats, two satellite repeats, and two ribosomal DNAs, to characterize E. sibiricus chromosomes, using sequential fluorescence in situ hybridization and genomic in situ hybridization assays. Our results showed that microsatellite repeats (AAG) 10 or (AGG) 10 , satellite repeats pAs1 and pSc119.2, and ribosomal 5S rDNA and 45S rDNA are specific markers for unique chromosomes. A referable karyotype ideogram was suggested, by further polymorphism screening, across different E. sibiricus cultivars with a probe mixture of (AAG) 10 , Oligo-pAs1, and Oligo-pSc119.2. Chromosomal polymorphisms vary between different genomes and between different individual chromosomes. In particular, two distinct forms of chromosome E in H genome were identified in intra-and inter-populations. Here, the significance of these results, for E. sibiricus genome research and breeding, and novel approaches to improve fluorescence in situ hybridization-based karyotyping are discussed.
Abstract. This study was carried out to evaluate the vulnerability of the herders in the grassland areas of Northern China. The results showed that, as a consequence of less capital accumulation, the herders in this area were vulnerable as a whole, and that gender, grassland area, livestock numbers and net incomes have significant effects on the vulnerability of grazer households. The families with female householders tended to be more vulnerable and they were characterised as owning less grassland, smaller houses, fewer or no vehicles, fewer young livestock and numbers of livestock slaughtered annually, whereas the families with low vulnerability had a higher net income. Geographically, household vulnerability showed a decreasing trend from west to east in Northern China at the county or region scale, which was positively correlated with grassland productivity. Social resources played a less important role than natural resources in decreasing the herders' vulnerability. Educational level of the household members and the household labour capacity played important roles in reducing vulnerability. Increasing the enrolment rate and the education background in grassland regions may decrease the vulnerability of the herders. It is argued that the use of vulnerability indices can be helpful to increase the herders' adaptation to climate change and to improve the sustainability of rural pastoral regions.
The genomes of five Agropyron Gaertner, 1770 species were characterized using all potential di- or trinucleotide simple sequence repeat (SSR) motifs and four satellite DNA repeats as fluorescence in situ hybridization (FISH) probes. The sites of 5S and 45S rDNA were relatively conserved among the diploid and tetraploid species. A number of sites for the dinucleotide SSRs AC, AG, and pSc119.2 was detected in all investigated species except A. mongolicum Keng, 1938. Several different trinucleotide SSRs were identified in different tetraploid species. All Agropyron species were suggested to include the basic P genome, although genome differentiation was still observed. The P genome of A. mongolicum was distinct from that of the diploid A. cristatum (Linnaeus, 1753) Gaertner, 1770. and other tetraploid species, with no hybridizations for AC, AG, or pSc119.2 observed. This finding supports designation of the P genomes of A. cristatum and A. mongolicum as Pc and Pm, respectively. An exceptional 5S rDNA site revealed in one set of homoeologous chromosomes strongly supports the allopolyploid origin of A. desertorum (Fischer ex Link, 1821) Schultes, 1824. However, the diploid donors to A. desertorum need further investigation. Similarly, the unique FISH pattern of a pair of 5S rDNA-carrying chromosomes was indicative of a potential allopolyploid origin for A. fragile (Roth, 1800) Candargy, 1984. The conserved distribution of 5S and 45S rDNA suggests A. cristatum (4x) and A. michnoi Roshevitz, 1929 are closely related. Two forms of B chromosomes were identified among individuals A. mongolicum and A. desertorum plants.
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