The pattern of homoeologous recombination in triploid hybrids of Lolium multiflorum with Festuca pratensis

Homoeologous chromosomes of Lolium-Festuca hybrids are capable of frequent meiotic pairing and recombination. The frequency and distribution of recomb ination was studied by genomic in situ hybridization in backcross progenies of reciprocal triploid hybrids of Lolium multiflorum with Festuca pratensi s. Significant differences in the male transmission of the parental and tra nslocated chromosomes were observed depending on the cytoplasm of the F-1 h ybrids and the ploidy level of the female test cross partner. The frequency of intergeneric translocations in the progeny indicated that, on average, there must have been at least 4.5 homoeologous arms paired in the F-1 hybri ds; the actual frequency might have been higher because of pre- or post-zyg otic selection against the F. pratensis chromatin, which probably eliminate d certain gametes with Festuca-Lolium translocations. Both parental species are known for localized distal chiasmata, but the intergeneric translocati on breakpoints were distributed along the entire lengths of the chromosome arms. The change in the distribution of homoeologous recombination might ha ve been related to different pairing initiation of homologues and homoeolog ues. It probably resulted from allocation of additional chiasmata to chromo some arms and produced a net increase in recombination.