Origins and chromosome differentiation of Thinopyrum elongatum revealed by PepC and Pgkl genes and ND-FISH

Thinopyrum elongatum is an important gene pool for wheat genetic improvement. However, the origins of the Thinopyrum genomes and the nature of the genus' intraspecific relationships are still controversial. In this study, we used single-copy nuclear genes and non-denaturing fluorescence in situ hybridization (NDFISH) to characterize genome constitution and chromosome differentiation in Th. elongatum. According to phylogenetic analyses based on PepC and Pgk1 genes, there was an E genome with three versions ([E.sup.e],[E.sup.b],[E.sup.x])and St genomes in the polyploid Th. elongatum. The ND-FISH results of pSc119.2 and pAs1 revealed that the karyotypes of diploid Th. elongatum and Th. bessarabicum were different, and the chromosome differentiation occurred among accessions of the diploid Th. elongatum. In addition, the tetraploid Th. elongatum has two groups of ND-FISH karyotype, indicating that the tetraploid Th. elongatum might be a segmental allotetraploid. In summary, our results suggested that the diploid Th. elongatum, Th. Bessarabicum,andPseudoroegneria were the donors of the [E.sup.e],[E.sup.b], and St genomes to the polyploid Th. elongatum, respectively. Key words: Thinopyrum elongatum,phylogeny,PepC, Pgk1,ND-FISH. Le Thinopyrum elongatum constitue une importante ressource genetique pour l'amelioration du ble. Cependant, les origines et la nature des relations intraspecifiques des genomes presents au sein du genre Thinopyrum demeurent controversees. Dans ce travail, les auteurs ont employe l'hybridation in situ en fluorescence en conditions non-denaturantes (ND-FISH), en utilisant des genes nucleaires a simple copie comme sondes, pour etudier la composition genomique et la differenciation chromosomique chez le Th. elongatum. Sur la base d'analyses phylogenetiques realisees a l'aide des genes PepC et PgK1, trois versions d'un genome E ([E.sup.e],[E.sup.b] et [E.sup.x]) et des genomes St ont ete documentes chez le Th. elongatum polyploide. Les resultats des analyses ND-FISH a l'aide des sondes pSc119.2 et pAs1 ont revele que les caryotypes des Th. elongatum et Th. bessarabicum diploides etaient differents et qu'une differentiation chromosomique existait au sein des accessions diploides du Th. elongatum. De plus, le Th. elongatum tetraploidepresentedeux sortesde caryotypesND-FISH,cequi indique que le Th. elongatum tetraploide pourrait etre un allotetraploide segmentaire. En resume, les resultats obtenus suggerent que les especes diploides Th. elongatum, Th. bessarabicum et Pseudoroegneria seraient respectivement a l'origine des genomes [E.sup.e],[E.sup.b] et St presents chez les especes polyploides du Th. elongatum.[Traduit par la Redaction] Mots-cles : Thinopyrum elongatum, phylogenie, PepC, Pgk1, ND-FISH.
Introduction The genus Thinopyrum is a perennial herb in the Triticeae, but the taxonomic status of this genus has been changed many times. The species in Thinopyrum were first classified [...]