Molecular Cytogenetics of an Amphiploid Trigeneric Hybrid between Triticum durum, Thinopyrum distichum and Lophopyrum elongatum

In situ hybridization of total genomic DNA was used to analyselines derived from an amphiploid between tetraploid wheat,Triticumdurum Desf. (2n =4x =28), and the wheatgrassesThinopyrum distichum(Thunb.) A. Löve (2n =4x =28) andLophopyrum elongatum (Host)A. Löve (2n =2x =14). A range of chromosome numbers wasdetected, arising from loss or gain of chromosomes. Total genomicDNA probes fromThinopyrum species,L. elongatum andTriticum monococcumL. were able to discriminate chromosomes from the A and B genomesof tetraploid wheat and those of wheatgrass-origin. The methoddid not discriminate the two wheatgrass genomes, J and E, indicatingtheir close similarity. Chromosomal aberrations—includingtelocentric and ring chromosomes—were frequent. Distalinter-genomic translocations of parts of A and B genome chromosomearms, unusual in wheat itself, were more frequent than translocationsbetweenT. durum and wheatgrass.In situ hybridization of an rDNAprobe most frequently revealed four sites associated with secondaryconstrictions onT. durum chromosomes and four onTh. distichumorL. elongatum chromosomes, although there was variation inthe number of loci between and within plants. Within interphaseand prophase nuclei, the three genomes were not intermixed andoften lay in distinct sectors. Wheat; hybrids; Triticum ; Triticeae; evolution; introgression; nuclear architecture; rDNA; in situ hybridization