Bivalent formation and chromosome dynamics in hexaploid triticate and rye crosses

Twelve hexaploid triticale lines were crossed with diploid rye (Secale ceveale L.) to study the extent and pattern of bivalent formation in hybrid and F2 generations. The number of bivalents in hybrid plants ranged from four to seven. This was used as a criterion to determine the number of D-chromosomes substituted for R-chromosomes in triticale parents. The implications of R/D chromosome substitutions in triticale breeding are discussed. Observations on the number of bivalents and their segregation pattern in seven F2 plants indicated recovery of tetraploid triticale types in later generations.