Physical Distribution of Homoeologous Recombination in Individual Chromosomes of <i>Festuca pratensis </i>in <i>Lolium multiflorum</i>

Abstract

Crossing over-based recombination is a powerful tool for generating new allelic combinations during sexual reproduction. It usually occurs between homologous chromosomes. However, under some conditions, homoeologues may also be capable of crossing over. Whether homologous and homoeologous crossovers are equivalent and governed by the same rules has never been established. Here we report on chromosome distribution of homoeologous crossovers in a unique system of Festuca × Lolium hybrids. Unlike in most other hybrids, in these intergeneric hybrids, homoeologous chromosomes are capable of pairing and crossing over with frequencies approaching that of homologues. At the same time, genome divergence makes cytological detection of chromosome recombination feasible. We analyzed the distribution of homoeologous recombination along individual chromosomes in a complete set of intergeneric single chromosome substitutions fromF. pratensisinto tetraploid L. multiflorum. Homoeologous recombination sites were not evenly distributed along the chromosomes, being concentrated in intercalary regions of the arms and reduced in proximal and distal regions. Several recombination hotspots and cold spots were found along individual chromosomes and the recombination was not affected by the presence of a secondary constriction. Our results indicate that despite the uneven distribution of homoeologous recombination, introgression of any part of the F. pratensis genome into L. multiflorum is feasible.

Flow Sorting and Sequencing Meadow Fescue Chromosome 4F

“…1). All seven chromosomes of meadow fescue can be individually identified based on their specific patterns of hybridization with various DNA probes (Kopecký et al, 2010). This permitted the identification of particles sorted from individual peaks on flow karyotype.…”

“…A total of 85,351,865 paired-end sequence reads with lengths of 101 bp were generated, yielding 28,553 Mb of sequence. Considering the size of chromosome 4F at 543 Mb (Kopecký et al, 2010), this represented approximately 503 coverage.…”

“…Genomic studies in meadow fescue are complicated by the large genome size (3,175 Mb/1C; Kopecký et al, 2010) and a rather symmetrical karyotype. Relative to cereals, and even to closely related ryegrasses, genetic and genomic resources of meadow fescue are limited.…”

“…So far, two bacterial artificial chromosome (BAC) libraries have been developed for meadow fescue. Donnison et al (2005) constructed a five-genome coverage library and used it to clone candidate orthologous sequences to the CONSTANS-like rice (Oryza sativa) Heading date1 (Hd1; Photosensitivity1 [Se1]) gene in Lolium perenne and meadow fescue, while Kopecký et al (2010) used a partial genomic BAC library (about one genome coverage) as a source of cytogenetic markers. The only existing DNA array was developed by Kopecký et al (2009) using DArT technology (Jaccoud et al, 2001), and it consists of 7,680 probes derived from methyl-filtered genomic representations of five species from the FestucaLolium species complex (L. perenne, L. multiflorum, F. pratensis, Festuca arundinacea, and Festuca glaucescens).…”

An Increasing Need for Productive and Stress Resilient Festulolium Amphiploids: What Can Be Learnt from the Stable Genomic Composition of Festuca pratensis subsp. apennina (De Not.) Hegi?

“…Unfortunately, for such a breeding approach the outcome reported from all cytogenetic studies that involved amphiploid Festulolium varieties was that unbalanced genome complements had arisen over generations of seed multiplication which had resulted in a shift toward a Lolium genome, accompanied by loss of Festuca chromosomes (Canter et al, 1999;Kopecký et al, 2006;Zwierzykowski et al, 2006). This outcome was aided by frequent homoeologous pairing and recombination between Festuca and Lolium chromosomes and possibly by the self-incompatibility of the species involved (Kopecký et al, 2008a(Kopecký et al, , 2010Harper et al, 2011).…”