Allotriploid somatic hybrids of diploid tomato (Lycopersicon esculentum Mill.) and monoploid potato (Solanum tuberosum L.)

Abstract

Allotriploid somatic hybrids were obtained from fusions between protoplasts of diploid tomato and monohaploid potato. The selection of fusion products was carried out in two different ways: (1) The fusion of nitrate reductase-deficient tomato with potato gave rise only to hybrid calli if selection was performed on media lacking ammonium. Parental microcalli were rarely obtained and did not regenerate. (2) The fusion of cytoplasmic albino tomato with potato gave rise to albino and green hybrid calli and plants. Allotriploids were identified from the two somatic hybrid populations by counting chloroplast numbers in leaf guard cells and by flow cytometry of leaf tissue. Although some pollen fertility of allotriploids and pollen-tube growth of tomato, potato andLycopersicon pennellii into the allotriploid style were observed, no progeny could be obtained. The relevance of allotriploid somatic hybrids in facilitating limited gene transfer from potato to tomato is discussed.

Fine Mapping of ui6.1, a Gametophytic Factor Controlling Pollen-Side Unilateral Incompatibility in Interspecific Solanum Hybrids

“…For example, diploid F 1 hybrids between cultivated tomato and SI accessions of S. habrochaites, S. pennellii, S. peruvianum, or S. chilense are all SI and reject pollen of cultivated tomato (McGuire and Rick 1954;Martin 1961Martin , 1963Hardon 1967). Allotriploids composed of two genomes from tomato and one from potato (S. tuberosum, SI) also reject pollen of S. lycopersicum and accept pollen of S. pennellii LA0716 (Schoenmaker et al 1993), i.e., the same crossing relationships we report herein. In other solanaceous genera, including Nicotiana (Murfett et al 1996) and Capsicum (Pickersgill 1997), self-and unilateral incompatibility are also dominant in interspecific SC 3 SI hybrids.…”

Genomic in situ hybridization (GISH) and RFLP analysis for the identification of alien chromosomes in the backcross progeny of potato (+) tomato fusion hybrids

“…Unlike sexual hybridization, through protoplast fusion it should be possible to exploit individual organelle genomes in addition to the nuclear genome. With this aim, somatic fusion hybrids between potato and tomato have been successfully made in the past (Shepard et a!., 1983;Wolters et a!., 1991;Jacobsen et a!., 1992;Schoenmakers et al, 1994). If such somatic hybrids are to be used further in breeding, the following aspects have to *Correspondence 250 be considered: (i) the possibility of backcrossing the fusion hybrid to the parents; (ii) the transmission of the individual genomes, or individual chromosomes from somatic hybrids to the progeny in the subsequent generations; (iii) the occurrence and extent of any genetic recombination between the homoeologous chromosomes; (iv) the structural integrity of individual chromosomes in an alien genomic background and the possibility of producing lines with alien chromosome additions and/or substitutions from either the potato or the tomato.…”

Somatic hybridization as a tool for tomato breeding

“…However, in many cases a selectable marker was present in one parent, and selection against the parent carrying the marker was either based on its poor callus growth and regeneration capacity and/or because it was metabolically inactivated by irradiation or chemical treatment . Mutations in tomato chloroplast DNA that can be selected for are the cytoplasmically inherited albino mutation isolated by Hosticka & Hanson (1984) and introduced in a genotype showing better regeneration (Schoenmakers et al ., 1993) and the Pl-alb] albino mutation described by Ratushnyak et al . (1993) .…”

“…Isozyme analyses have often been used to confirm the hybrid nature of the regenerated plants . Since in the case of dimeric enzymes an intermediate hybrid band is found, this analysis distinguished hybrids unambiguously from chimaeric plants (Handley et al ., 1986 ;Wijbrandi et al ., 1990c ;Schoenmakers et al ., 1993) . Mutations in genes affecting leaf shape, anthocyanin accumulation, etc .…”

“…However, in such combinations hexaploids, which originate either by triple fusions 2 7 1 or by fusion of a tetraploid protoplast with a diploid protoplast, are rather common (Handley et al ., 1986 ;Wijbrandi et al, 1990a ;Gavrilenko et al ., 1992) . When fusions were made between a diploid tomato and a monohaploid potato, the expected triploid hybrids were rare (Schoenmakers et al ., 1993) . In somatic hybrids of tomato with L. peruvianum euploids were most common at the tetraploid level ; at the hexaploid level, however, most plants were hypoploid (Wijbrandi et al ., 1990a) .…”