Genome Constitution And Classification Of Roegneria Calcicola Keng(Poaceae: Triticeae)

Roegneria calcicola Keng is a perennial species of Roegneria in Triticeae（Poaceae）.The morphological characters of R.calcicola were characterized by a single spikelet per rachis node which is the character of genus Roegneria,while the longer palea（compared with the lemma） makes the species more similar to genus Elymus.The taxonomy of R.calcicola remains uncertain.Some taxonomist classified R.calcicola into Roegneria while some others treated it in Elymus.The main reason for the taxonomical controversy of R.calcicola is that the chromosome ploidy and the chromosome composition of R.calcicola were still unknown.In order to clarify the genome constitution and classification of R.calcicola,in this study we carried out through（1）identifying and analyzing themorphological characteristics of R.calcicola;（2）studying the karyotype and chromosome ploidy of R.calcicola;（3）hybridizing R.calcicola with species with known genome constitutions（Pseudoroegneria stipifolia（Zern.ex Nevski）A.L?ve（St）,Hordeum bogdanii Wilensky（H）,Elymus wawawaiensis J.R.Carlsen et Barkworth（St H）,Roegneria ciliaris（Trin.）Nevski（St Y）and Campeiostachys kamoji Ohwi（St YH））,and determining the genome composition of R.calcicola by observing and analyzing the chromosome pairing at the meiotic metaphase I of the pollen cell of hybrid F₁;and（4）validating the genome composition of R.calcicola by using the genome in situ hybridization（GISH）.The main results are listed as follows:1.Roegneria calcicola is a species with a single spikelet in a per rachis node,glume narrow and lanceolate and the longer palea compared with the lemma.2.Roegneria calcicola is hexaploid（2n=6x=42）and the karyotype formula is 2n=6x=36 m（2 sat）+6 sm（2 sat）.There are two satellite chromosomes on chromosomes19 and 21,respectively.The karyotype type is 2B.3.The chromosome pairing at the hybrid F₁from R.calcicola with Campeiostachys kamoji（2n=6x=42,St YH）were observed.An average of 1.16 univalents（varied from0 to 4）,19.18 bivalents（varied from 17 to 21）and 0.62 tetravalents（varied from 0 to 1）were observed in pollen mother cells of R.calcicola with Campeiostachys kamoji.The C-value is 0.94.The results indicated that the genome constitution of R.calcicola is St YH.4.In GISH analysis of R.calcicola,14 chromosomes showed green fluorescence signal when probed with H.bogdanii（H）and blocked with R.ciliaris（St Y）.The result showed that the R.calcicola contains the H genome.28 chromosomes showed red fluorescence signal when probed with the R.ciliaris（St Y）and blocked with the H.bogdanii（H）,suggesting that R.calcicola contains the St Y genome.Therefore,the genome constitution of R.calcicola is St YH based on GISH analysis.5.According to results of karyotype,chromosome pairing at meiotic metaphase I and GISH in this study,R.calcicola is a hexaploid species with genome constitutions of St YH.On the basis of the principle of genome classification in the tribe Triticeae,R.calcicola should be treated as the species in the genus Campeiostachys Drobov,and be treated as Campeiostachys calcicola（Keng）Y.H.Zhou,H.Q.Zhang et M.Q.Deng.