Characterization of an Agropyron elongatum chromosome conferring resistance to cephalosporium stripe in common wheat

Related wheat (Triticum aestivum L.) breeding lines, PI 561033, REA 9232, REA 9257, and CI 13113 were analyzed cytogenetically to characterize the association of resistance to cephalosporium stripe (caused by Cephalosporium gramineum Nis. & Ika.) with Agropyron elongatum chromatin. One pair of A. elongatum chromosomes was detected in PI 561033, REA 9232, and CI 13113 by genomic in situ hybridization. The sib line of PI 561033 and REA 9232, REA 9257, which is not resistant to this disease, lacked this pair of A. elongatum chromosomes. PI 561033 was characterized as a disomic T. aestivum - A. elongatum 6Ae#2(6A) chromosome substitution line using test crosses and C-banding. In situ hybridization and test crosses showed that the donor parent, CI 13113, also had chromosome 6A substituted by A. elongatum chromosome 6Ae#2. The C-banding pattern of 6Ae#2 showed two subterminal bands on the long arm and one small band proximal to the centromere on the short arm. Based on chromosome pairing and compensation, chromosome 6Ae#2 shows a close homoeologous relationship with wheat chromosome 6A. Key words : Cephalosporium gramineum, Agropyron elongatum, in situ hybridization, C-banding, chromosome substitution.