Results of cytogenetic analysis of microsporogenesis in rye-triticale F1 hybrids (RRABR, 5x = 35) are presented. Meiosis of pentaploids is described as the key stage in the synthesis of secalotriticum, lines with intergenomic substitutions of chromosomes, or alloplasmic rye and wheat lines. Properties of meiotic processes and cytological mechanisms in formation of functional gametes and plants of various genomic and chromosomal composition are discussed.