Theor Appl Genet (1997) 95 : 1084—1091  Springer-Verlag 1997 L. L. Qi · S. L. Wang · P. D. Chen · D. J. Liu B. Friebe · B. S. Gill Molecular cytogenetic analysis of Leymus racemosus chromosomes added to wheat Received: 2 May 1997 / Accepted: 20 May 1997 Abstract Five disomic, two double-disomic, and two ditelosomic addition lines and one disomic substitution line derived from the crosses of ¹riticum aestivum (2n" 6x" 42, AABBDD)¸eymus racemosus (2n" 4x" 28, JJNN) were identified by C-banding analysis. The homoeology of the added ¸eymus chromosomes was determined by RFLP analysis. Four of five disomic addition lines belonged to group 2, 5, 6 and 7 chro- mosomes of ¸. racemosus; these were designated as 2Lr1(NAU516), 5Lr1(NAU504, NAU514), 6Lr1 (NAU512), and 7Lr1(NAU501). Two additional chromosomes, 1Lr1 and 3Lr1, were present in double-disomic addition lines 1Lr1# 5Lr1 (NAU525) and 3Lr1# 7Lr1(NAU524), respec- tively. In the disomic substitution line wheat chromo- some 2B was replaced by ¸. racemosus chromosome 2Lr1 (NAU551). Two telocentric chromosomes, 2Lr2S (NAU509) and 7Lr1S (NAU511), were iso- lated as ditelosomic addition lines. The study presented here provides the first evidence of homoeology of the added ¸. racemosus chromosomes with wheat chromo- somes using DNA markers. Our data provide the basis for further directed chromosome engineering aimed at producing compensating wheat-¸. racemosus translo- cation lines. Key words ¹riticum aestivum · ¸eymus racemosus · Chromosome addition lines · C-banding · RLFP analysis · Homoeology Communicated by G. Wenzel L. L. Qi · S. L. Wang · P. D. Chen · D. J. Liu Department of Agronomy, Nangjing Agricultural University, Nangjing, 210095, P.R. China B. Friebe · B. S. Gill ( ) Department of Plant Pathology, Kansas State University, Throckmorton Hall, Manhattan, KS 66506-5502, USA Introduction The genus ¸eymus consists of about 30 species, all previously belonging to the genus Elymus. ¸eymus species are long-lived perennials with drought and salt tolerance, disease resistance, and a high number of seeds per spike (Dewey 1984). Attempts were made in the early 1940s to incorporate useful genes from ¸eymus into wheat. Some ¸eymus species were success- fully crossed with wheat (Petrova 1960; Mujeeb-Kazi and Rodriguez 1980; 1981; Majeeb-Kazi et al. 1983; Comeau et al. 1985; Plourde et al. 1989 a, b, 1992). Evaluations of barley yellow dwarf virus resistance (BYDV) in the BC  and BC  F  derivatives of ¹. aesti- vum¸. multicaulis and the F  of ¹. aestivum¸. angustus indicated that ¸eymus species may have potential in improving the BYDV resistance of bread- wheat (Plourde et al.1989, 1992). ¸eymus racemosus (syn. Elymus giganteus ) is a tetraploid species (2n" 4x" 28, genomically JJNN) distributed throughout central Asia. The first ¹. aestivum (AABBDD)¸. racemosus (JJNN) hybrid (ABDJN) was reported in 1981 (Mujeeb- Kazi and Rodriguez 1981). ¸. racemosus was later found to be a potential resource of resistance to wheat scab (Mujeeb-Kazi et al. 1983), but addition or substitution lines were not developed. In 1984, a program was initiated in China aimed at introducing the genes for scab resistant from ¸. racemosus into common wheat. The cytology of the F  hybrid of ¹. aestivum/¸. racemosus and its BC  and BC  deriva- tives had been reported previously (Wang et al. 1986, 1991), and seven disomic addition lines and two ditelosomic addition lines were developed from BC  F  —BC  F  and screened for scab resistance. (Chen et al. 1993, 1995; Ren et al. 1996; Sun et al. 1997a, b) One disomic addition line and one double disomic addition-substitution line were developed using anther culture (Lu et al. 1995).