Mitotic and meiotic irregularities in somatic hybrids of Lycopersicon esculentum and Solanum tuberosum

Abstract

Chromosome numbers were determined in metaphase complements of root-tip meristems of 107 tomato (+) potato somatic hybrids, obtained from five different combinations of parental genotypes. Of these hybrids 79% were aneuploid, lacking one or two chromosomes in most cases. All four hybrids that were studied at mitotic anaphase of root tips showed laggards and bridges, the three aneuploids in a higher frequency than the single euploid. Hybrid K2H2-1C, which showed the highest percentage of aberrant anaphases, possessed 46 chromosomes. Fluorescence in situ hybridization with total genomic DNA showed that this hybrid contained 23 tomato, 22 potato, and 1 recombinant chromosome consisting of a tomato chromosome arm and a potato chromosome arm. The potato parent of K2H2-1C was aneusomatic in its root tips with a high frequency of monosomic and trisomic cells and a relatively high frequency of cells with one fragment or telosome. Meiotic analyses of three tomato (+) potato somatic hybrids revealed laggards, which occurred most frequently in the triploid hybrids, and bridges, which were frequently present in pollen mother cells (PMCs) at anaphase I of hypotetraploid K2H2-1C. We observed putative trivalents in PMCs at diakinesis and metaphase I of eutriploid A7-82A and quadrivalents in part of the PMCs of hypotetraploid K2H2-1C, suggesting that homoeologous recombination between tomato and potato chromosomes occurred in these hybrids. All three hybrids showed a high percentage of first division restitution, giving rise to unreduced gametes. However, shortly after the tetrad stage all microspores completely degenerated, resulting in exclusively sterile pollen.

Analysis of chromosomal and organellar DNA of somatic hybrids between Triticum aestiuvm and Haynaldia villosa Schur

“…By genomic in situ hybridization (GISH), it was possible to identify unequivocally the parental chromosomes in the somatic hybrids. Intergeneric translocations have previously been observed in asymmetric hybrids obtained after irradiation of the donor (Piastuch et al 1990;Parokonny et al 1992;Xia et al 1998) as well as in symmetric hybrids obtained without irradiation (White et al 1985;Wolters et al 1994;Buiteveld et al 1998). The results of our GISH analysis of 7 cell clones showed that intergenomic translocations were also present in the symmetric somatic hybrids of common wheat and H. villosa.…”

Preparation of tomato meiotic pachytene and mitotic metaphase chromosomes suitable for fluorescencein situ hybridization (FISH)

“…1994. As for plants, FISH has seen so far different types of applications (for review see Jiang & Gill 1994), ranging from the detection of alien chromosomes or segments in cereals (Schwarzacher et al 1992a, Mukai et al 1993) and the detection of parental chromosomes in (a)symmetric somatic hybrids (Parokonny et al 1992, Schwarzacher et al 1992b, Wolters et al 1994, Jacobsen et al 1995, to the mapping of repetitive and low-copy DNA sequences in various species (Leitch et al 1991, Maluszynska & Heslop-Harrison 1991, Albini & Schwarzacher 1992, Xu & Earle 1994.…”

Meiotic behaviour and pollen fertility in sexual and somatic hybrids ofPassifloraspecies

“…The presence of two nucleoli (one of them condensed) in the pachytenic phase of the somatic hybrid has also been observed in other somatic hybrids (WOLTERS et al 1994), and may represent a form of dose compensation, leading to the inactivation of one nucleolus during microsporogenesis.…”

“…Gene introgression between species, rather than the combining of complete genomes, is usually the preferred approach (WOLTERS et al 1994). However, Passiflora edulis f. flavicarpa Deg.…”

“…and other species of this genus show self-incompatibility, which raises methodological difficulties (KNIGHT Jr. and WINTERS 1962;BRUCKNER 1994) and results in low fertility of the interspecific F1 hybrids (RÊGO et al 1999). Somatic hybridization may provide an efficient method for overcoming barriers between incompatible species (WOLTERS et al 1994;LEFRANCOIS 1993;OTONI et al 1995;BARBOSA and VIEIRA 1997).…”