Chromosome pairing in allotetraploid hybrids of Festuca pratensis × Lolium perenne revealed by genomic in situ hybridization (GISH)

Abstract

Genomic in situ hybridization (GISH) was used to make a detailed study of chromosome pairing at metaphase I (MI) of meiosis in six F(1) hybrid plants of the allotetraploid Festuca pratensis x Lolium perenne (2n = 4x = 28; genomic constitution FpFpLpLp). The mean chromosome configurations for all hybrids analysed were 1.13 univalents + 11.51 bivalents + 0.32 trivalents + 0.72 quadrivalents, and the mean chiasma frequency was 21.96 per cell. GISH showed that pairing was predominantly intragenomic, with mean numbers of L. perenne (Lp/Lp) and F. pratensis (Fp/Fp) bivalents being virtually equal at 5.41 and 5.48 per cell, respectively. Intergenomic pairing between Lolium and Festuca chromosomes was observed in 33.3% of Lp/Fp bivalents (0.62 per cell), in 79.7% of trivalents - Lp/Lp/Fp and Lp/Fp/Fp (0.25 per cell), and in 98.4% of quadrivalents - Lp/Lp/Fp/Fp and Lp/Lp/Lp/Fp (0.71 per cell). About 4.0% of the total chromosome complement analysed remained as univalents, an average 0.68 Lp and 0.45 Fp univalents per cell. It is evident that in these hybrids there is opportunity for recombination to take place between the two component genomes, albeit at a low level, and this is discussed in the context of compromising the stability of Festulolium hybrid cultivars and accounting for the drift in the balance of the genomes over generations. We speculate that genotypic differences between hybrids could permit selection for pairing control, and that preferences for homologous versus homoeologous centromeres in their spindle attachments and movement to the poles at anaphase I could form the basis of a mechanism underlying genome drift.

Chromosome pairing of individual genomes in tall fescue (<i>Festuca arundinacea </i>Schreb.), its progenitors, and hybrids with Italian ryegrass (<i>Lolium multiflorum </i>Lam.)

“…Similarly, a 9: 1 ratio of homologous vs. homoeologous pairing was detected in tetraploid F1 F. pratensis ! L. perenne hybrids (Zwierzykowski et al, 2008). An even lower frequency of homoeologous association (14: 1 ratio of homologous vs. homoeologous pairing) was reported in our previous study in tetraploid F1 L. multiflorum !…”

Differences in leaf proteome response to cold acclimation between Lolium perenne plants with distinct levels of frost tolerance

“…Meadow fescue (Festuca pratensis Huds., Fp), a species closely related to Lp, has lower nutritive value but is one of the most winter-hardy species within the Lolium-Festuca complex (Humphreys, 1989). The transfer of the genes governing winter-hardiness (WH) from Fp to Lp is achievable, as both species hybridize readily and their homologous chromosomes pair and recombine at high frequency during meiosis (Zwierzykowski et al, 2008). However, not all the physiological bases of WH, expressed differently in Fp and Lp, have been identified and comprehensive research is still required to dissect this complex trait.…”

Research Article Contributions of classical and molecular cytogenetic in meiotic analysis and pollen viability for plant breeding.

“…The frequency was 21.96 chiasmata per cell. GISH showed that the pairing was predominantly intragenomic (Zwierzykowski et al, 2008).…”