Patterns of meiosis in ABDR amphihaploids depend on the specific type of univalent chromosome division.

Meiosis in wide F hybrids in the tribe Triticeae is complex and irregular. Despite extensive research, the meiotic pathways in such hybrids remain largely unknown. In this study, the effect of the genotypes of disomic wheat-rye substitution lines on the regulation of meiosis in ABDR amphihaploids was analysed by comparing microsporogenesis and seed set under self pollination in hybrids of normal bread wheat ( Triticum aestivum L.) and wheats with single chromosome substitutions 1R(1A), 1Rv(1A), 2R(2D), 2R(2D), 2R(2D), 5R(5D), 5R(5A), 6R(6A) with rye ( Secale cereale L.). Three types of meiotic pathways were identified in the hybrids: reductional, equational, and equational+reductional. During the reductional type division, chromosomes randomly moved toward the poles at Anaphase I (AI) and separated sister chromatids at AII. Meiosis ended with tetrad formation, and the resulting plants were sterile ((2R(2D) × R, 2R(2D) × R). In the equational type division, the chromosomes aligned along the equator at Metaphase I and at AI separated into chromatids that moved toward the poles. This meiotic pathway led to dyad formation and partial fertility (especially in hybrids of 1Rv(1A) and 6R(6A)). In the equational+reductional pathway, some chromosomes divided in an equational manner while others were segregated reductionally within the same microsporocyte and this led to formation of tetrads with groups of uncoiled chromosomes. Comparison of the frequencies of each of the three meiotic pathways in different hybrid combinations suggests differences in contributions of individual chromosomes to the control of the entire meiotic process. [ABSTRACT FROM AUTHOR]