Homoeologous pairing and recombination in Solanum lycopersicoides monosomic addition and substitution lines of tomato

Abstract

We compared meiotic pairing and recombination between tomato ( Lycopersicon esculentum) and homoeologous Solanum lycopersicoides chromosomes in monosomic additions (MAs) and substitution lines (SLs), each representing a single chromosome of the nightshade in a tomato background. Three configurations of each alien chromosome and its two tomato homoeologues were detected by genomic in situ hybridization in MA-7, -8, and -10 at diakinesis/metaphase-I: 1 trivalent (III), 1 bivalent + 1 univalent (II+I), and 3 univalents (3I). The II+I category was by far the most common, and the univalent was from S. lycopersicoides 91-99.5% of the time, indicating a high degree of preferential (homologous) pairing. In the corresponding substitution lines, association of homoeologous chromosomes was much higher (up to 90% of the cells), presumably due to the absence of homologous partners. However, SL-10 showed a surprisingly high frequency of univalents (about 73%). Genome-wide analysis of chromosome pairing revealed a decrease in the average chiasma frequency for both monosomic additions and substitution lines. Recombination between tomato and the nightshade was restricted in all cases, the reduction being more severe in each monosomic addition than in the corresponding substitution line. Recombination rates in the substitutions were less than those observed for the same chromosomes in the first backcross generation. Chromosomes 8 and 10 showed the highest and the lowest rates of homoeologous recombination, respectively. No recombination was detected between markers on the long arm of chromosome 10, presumably due to the presence of a paracentric inversion differentiating the two genomes in this region. The frequency of homoeologous pairing at diakinesis/metaphase-I was significantly higher than the rate of homoeologous recombination detected in the progeny, suggesting a strong selection against recombinant products in meiotic or post-meiotic stages.

Homeologous Recombination in Solanum lycopersicoides Introgression Lines of Cultivated Tomato

“…The result would be to increase the overall frequency of recombinant progeny relative to the rate of crossing over. We previously quantified the rate of pairing failure, as indicated by univalent formation, in heterozygous substitution lines, and found that it had a relatively small effect on recombination estimates (Ji and Chetelat 2003).…”

“…The parental genotypes and breeding strategy used for selecting the lines were described previously ( Ji and Chetelat 2003;Canady et al 2005). Briefly, both types of prebreds were derived from S. lycopersicoides accession LA2951 by backcrossing to L. esculentum cv.…”

“…Heterozygous substitution lines, in which one tomato chromosome is substituted with one homeologous S. lycopersicoides chromosome, recombine at ,50% of the rate observed in the F 1 interspecific hybrid, indicating strong background effects (Ji and Chetelat 2003). Recombination is even lower (0-2% of normal) in corresponding monosomic addition lines, in which the S. lycopersicoides chromosome is present as an extra (i.e., 2n 1 1), suggesting that exchange between homeologous chromosomes is antagonized by homologous associations.…”

Pairing analysis and in situ Hybridisation reveal autopolyploid-like behaviour in Solanum commersonii × S. tuberosum (potato) interspecific hybrids

“…These markers have proved useful to analyse the behaviour of the corresponding chromosomes or chromosome regions during mitosis and meiosis (Schubert et al 2001;Lysak et al 2003;McKee 2004). They also constitute a powerful tool for karyotyping in species with small chromosomes or across related species (Dong et al 2000) and to identify extra chromosomes in aneuploids (Ji 2014) or chromosomes containing genes responsible for resistance traits (Tek et al 2004). When GISH was combined with chromosome-specific molecular markers the transmission and segregation of individual chromosomes could be traced in potato (?)…”

Production of alien chromosome additions and their utility in plant genetics

“…Generally, additions derived from wide interspecific or intergeneric hybrids display little or no homoeologous recombination at all, and hence leave the alien chromosomes as univalents at metaphase I. In the corresponding substitution lines, association of homoeologous chromosomes may be far higher due to the absence of homologous partners (Ji and Chetelat, 2003). Transfer of desired chromosome regions to wheat is generally most successful in the Ph1 background of wheat allowing high levels of homoeologous recombination (Ceoloni, 1984).…”