Genome characterization of MT-2 perennial and OK-906 annual wheat x intermediate wheatgrass hybrids

Montana-2 (MT-2; X Agrotriticum intermediodurum Khizhnyak) is a variable perennial F-5:15 line derived from hybridization between durum wheat (Triticum turgidum L. var. durum, AABB) and Thinopyrum intermedium (Host) Barkw. & D.R. Dewey (StStEEEE). OK-906 is a uniform annual line derived from hybridization between hexaploid wheat (Triticum aestivum L,, AABBDD) and an unknown Thinopyrum sp. followed by backcrossing to wheat and several generations of selling and selection. We wished to characterize perennial (Thinopyrum) and annual (Triticum) chromosome content of MT-2 and OK-906 to determine how chromosome content corresponds to perenniality. When DNA of genomes ABD (T. aestivum) + E-b [Thinopyrum bessarabicum (Savul & Rayss) Love] was used as the block and DNA of the genome St [Pseudoroegneria stipifolia (Czern. ex Nevski) A. Love] was used as the probe, the average chromosome content among15 MT-2 lines was 26.2 wheat + 9.4 St + 18.8 E + 1.5 St/E translocation = 55.9 chromosomes (8x). Variation for genomic content was found within as well as among MT-2 lines, indicating that instability remains in the material. OK-906 exhibited about 40 wheat + 6 St + 8 E + 2 St/E translocation = 56 chromosomes (8x), but some aneuploidy was present. Its chromosome content is similar to 'Agrotana', another wheat X Thinopyrum annual. Perenniality in MT-2 may relate to its higher perennial chromosome dosage (about 30 of about 56 chromosomes) than OK-906 or Agrotana (16 of 56 chromosomes). Alternatively, specific genes or chromosome segments may confer perenniality. Development of stable breeding populations from MT-2 is improbable because of its variable chromosome constitution. However individual lines could be useful for forage if they could be stabilized with improved seed yield.