Meiosis of triploid Lolium. III. Synaptonemal complex formation in the two inverse autoallotriploids of L. temulentum and L. multiflorum, TTM and TMM

The inverse types of autoallotriploid of Lolium temulentum × L. multiflorum have different trivalent frequencies and the possible causes were investigated by analysis of synaptonemal complex (SC) formation at zygotene. There is less synchrony in axial element (AE) formation in the TMM type than TTM. There are two autonomous pairing sites (APS) in the terminal regions, one at the end of the AE (telomeric) and one in a subterminal position. In the TMM combination, the L. temulentum subterminal APS cannot compete effectively with the pair of L. multiflorum APSs at synapsis and SCs are initiated between L. multiflorum AEs, but in TTM the L. multiflorum site competes with the pair of L. temulentum sites and SCs are frequently formed between homoeologous AEs. The L. temulentum chromosomes seem to be later in reaching a ready-to-pair stage and the results are taken to support the idea that genome asynchrony can lead to preferential pairing of chromosomes in polyploids.