Abstract
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.
Highlights
The genus Agropyron Gaertner, 1770, referred to as the crested wheatgrass complex, includes 10–15 species (Asay and Jensen 1996)
Genomic characterization of the P genome in Agropyron using repetitive sequences In this study, all potential dinucleotide and trinucleotide simple sequence repeat (SSR) and four satellite DNA repeats were used to characterize the P genome of five Agropyron species. Unlike other genomes such as the H, I, A, B, and D genomes in Triticeae (Cuadrado et al 2007; 2008; Dou et al 2016), which include a number of SSR hybridization signals based on fluorescence in situ hybridization (FISH), the P genome in Agropyron harbored only the dinucleotide SSRs a high number of (AG) and AC in all species, except A. mongolicum, and fewer trinucleotide SSRs in the different species
The distribution of AAG corresponded to the distribution of N bands, which are composed of heterochromatin in Triticeae (Pedersen et al 1996)
Summary
The genus Agropyron Gaertner, 1770, referred to as the crested wheatgrass complex, includes 10–15 species (Asay and Jensen 1996). The genus is distributed in Eurasia and comprises a series of diploid (2n = 14), tetraploid (2n = 28), and hexaploid (2n = 42) species (Löve 1982, 1984, Dewey 1984). The taxonomy of Agropyron spp. has been characterized as “a multitude of taxonomic binomials” (Dewey and Pendese 1967). All crested wheat grasses are considered to share the same basic genome; this was previously termed the C genome and is currently referred to as the P genome (Dewey and Pendese 1967)
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