GENOMIC CONSTITUTIONS OF 4 CHINESE ENDEMIC ELYMUS SPECIES - ELYMUS-BREVIPES, E-YANGII, E-ANTHOSACHNOIDES, AND E-ALTISSIMUS (TRITICEAE, POACEAE)

The objectives of this study were to determine the genomic constitutio n and to explore the genomic variation within four Chinese endemic Ely mus species, i.e., E. brevipes (Keng) Love (2n = 4x = 28) and E. yangi i B.R. Lu (2n = 4x = 28), E. anthosachnoides (Keng) Love (2n = 4x = 28 ), and E. altissimus (Keng) Love (2n = 4x = 28). Intraspecific crosses between different populations of the four Elymus species, as well as interspecific hybridizations among the four target species, and with s ix analyzer species containing well-known genomes, i.e., E. caninus (L .) L. (2n = 4x = 28, SH), E. sibiricus L. (2n = 4x = 28, SH), E. semic ostatus (Lees ex Steud.) Melderis (2n = 4x = 28, SY), E. parviglumis ( Keng) Love (2n = 4x = 28, SY), E. tsukushiensis Honda (2n = 6x = 42, S HY), and E. himalayanus (Nevski) Tzvelev (2n = 6x = 42, SHY), were ach ieved through the aid of embryo rescue. Chromosome pairing behaviors w ere studied in the parental species and their hybrids. Numerical analy sis on chromosome pairing was made on the interspecific hybrids. With one exception, each meiotic configuration at metaphase I in the hybrid s involving the target taxa and the analyzer species containing the '' SH'' genomes fit a 2:1:1 model with x-values ranging between 0.91 and 1.00; chromosome pairing in the hybrids involving analyzer parents wit h the ''SY'' genomes match a 2:2 model, with x-values between 0.97 and 0.99. All pentaploid hybrids with a genomic formula ''SSYYH,'' except for two crosses having unexpected low c-values, had pairing patterns fitting the 2:2:1 model with x-values varying between 0.96 and 1.00. I t is concluded based on hybridization, fertility, and chromosome pairi ng data that (i) the four target Elymus species are strictly allotetra ploid taxa, (ii) they are closely related species, all comprised of th e ''SY'' genomes, (iii) minor genomic structural rearrangements have o ccurred within the four Elymus species, and (iv) meiotic pairing regul ator(s) exists in some of the Elymus taxa studied.