Genome analysis of Thinopyrum intermedium and Thinopyrum ponticum using genomic in situ hybridization

Genomic in situ hybridization (GISH) using genomic DNA probes from Thinopyrum elongatum (Host) D.R. Dewey (genome E, 2n = 14), Thinopyrum bessarabicum (Savul. & Rayss) A. Love (genome J, 2n = 14), and Pseudoroegneria strigosa (M. Bieb.) A. Love (genome S, 2n = 14), was used to examine the genomic constitution of Thinopyrum intermedium (Host) Barkworth Sr D.R. Dewey (2n = 6x = 42) and Thinopyrum ponticllm (Podp.) Barkworth Sr D.R. Dewey (2n = 10x = 70). Evidence from GISH indicated that hexaploid Tit, intermedium contained the J, J(s), and S genomes, in which the J genome was related to the E genome of Th. elongatum and the J genome of Th. bessarabicum. The S genome was homologous to the S genome of Ps. strigosa, while the J(s) genome referred to modified J- or E-type chromosomes distinguished by the presence of S genome specific sequences close to the centromere. Decaploid Th. ponticum had only the two basic genomes J and J(s). The J(s) genome present in Th. intermedium and Th. ponticum was homologous with E or J genomes, but was quite distinct at centromeric regions, which can strongly hybridize with the S genome DNA probe. Based on GISH results, the genomic formula of Th. intermedium was redesignated JJ(s)S and that of Th. ponticllm was redesignated JJJJ(s)J(s). The finding of a close relationship among S, J, and J(s) genomes provides valuable markers for molecular cytogenetic analyses using S genome DNA probes to monitor the transfer of useful traits from Th. intermedium and Th. ponticum to wheat.