PRODUCTION AND CYTOGENETIC ANALYSIS OF BC1, BC2, AND BC3 PROGENIES OF AN INTERGENERIC HYBRID BETWEEN TRITICUM-AESTIVUM (L) THELL AND TETRAPLOID AGROPYRON-CRISTATUM (L) GAERTN

Intergeneric hybrids between Triticum aestivum cv 'Chinese Spring' and Agropyron cristatum 4x (2n = 5x = 35, ABDPP genomes) with a high level of homoeologous meiotic pairing between the wheat chromosomes were backcrossed 3 times to wheat. Pollination of the F, hybrid with 'Chinese Spring' resulted in 22 BC1 seeds with an average seed set of 1.52%. Five BC1 plants with 39-41 chromosomes were raised using embryo rescue techniques. Chromosome pairing in the BC1 was characterized by a high frequency of multivalent associations, but in spite of this there was no evidence of homoeologous pairing between chromosomes of wheat and those of Agropyron. All of the plants were self sterile. The embryo rescue technique was again essential to produce 39 BC2 plants with chromosome numbers ranging from 37 to 67. The phenomenon of meiotic non-reduction was also observed in the BC3 progenies. In this generation male and female fertility greatly increased, and meiotic pairing was fairly regular. Some monosomic (2n = 43) and double monosomic (2n = 44) lines were produced. Analysis of these progenies should permit the extraction of the seven possible wheat-Agropyron disomic addition lines including those with the added chromosomes carrying the genes involved in meiotic non-reduction and in suppression of Ph activity.