PACHYTENE CHROMOSOMES OF THE INTERGENERIC HYBRID LYCOPERSICON ESCULENTUM x SOLANUM LYCOPERSICOIDES

Abstract

MENZEL, MARGARET Y. (Florida State U., Tallahassee.) Pachytene chromosomes of the intergeneric hybrid Lycopersicon esculentum X Solanum lycopersicoides. Amer, Jour. Bot. 49 (6): 605-615. Illus. 1962.-Pachytene bivalents of the hybrid were compared with those of the parents to determine whether the chromosome differentiation assumed to underlie chiasma failure and sterility of the F1 and preferential pairing in the corresponding amphidiploid was reflected in visible differences or failure of synapsis between homeologues. The total pachytene complement length of S. lycopersicoides Dun. was nearly 1.5 times that of the 'Pearson' tomato parent; the complement of the hybrid was of intermediate length. Pairing in the hybrid showed that the chromosomes of the parents were visually similar and completely synapsed in 43 of the 47 identifiable regions into which the pachytene complement may be divided. The similar regions included all 23 distal, achromatic segments in which chiasmata were localized, and 20 of the proximal, chromatic segments. The other 4 chromatic segments differed in length and hence exhibited a "deficiency" configuration. According to Barton's system of numbering, these were the short (nucleolar) arm of chromosome 2, the proximal segments of the long arms of chromosomes 4 and 9, and the proximal segments of the short arm of chromosome 10. Sporadic inversion, deletion and translocation configurations found in about 1-5% of pachytene nuclei of the hybrid probably represented newly-arisen spontaneous aberrations rather than constant differences between the parental genomes, No evidence was found that the chromosomes of the parents differed by small structural rearrangements. Either the rearrangements were below the resolving power of the methods employed, or differentiation has affected some property or properties of the chromosomes other than linear order. Evidence from metaphase I suggested that inequalities in chromatic regions of hybrid bivalents inhibited chiasma formation in adjacent achromatic segments but enhanced it in achromatic segments of the opposite arm. The mean number of bivalent arms having chiasmata at metaphase I was nearly as high in the hybrid as in the 'Pearson' parent Univalents at metaphase I in the hybrid result not from failure of synapsis or lowered chiasma frequency but from an unbalanced distribution of chiasmata among the chromosome arms. ABSTRACT A~UJo;RSO:'\, EUWARU F. (Pomona ColI., Claremont, California.) A reVISiOn of Ariocarpus (Cactaeeae l. II. The status of the proposed genus Neog;omesia. Amer. Jour. Bot. 49(6): 615-622. Illus. 1962.-The proposed monotypic genus Neogomesia is found to be similar to Ariocarpus in seed structure, seedling development, habitat, certain significant internal characters, chemistry,

Unique meiotic behaviourin F1 plants from a cross between a non-tuberous and a tuberous Solanum species in section Petota

“…1 and 2). These unpaired heterochromatic parts are similar to those observed in intergeneric hybrids between Lycopersicon esculentum x S. lycopersicoides (MENZEL, 1962) and L. esculentum x S. pennellii (KHUSH & RICK, 1963).…”

“…1 and 2). Similar observations have been reported in the F,'s of intergeneric and interspecific hybrids (MENZEL, 1962, KHUSH & RICK, 1963, RAMANNA & HERMSEN, 1976. Apart from such small structural differences, MARKS (1968)reported a rare case of the presence of a reciprocal translocation in an interspecific Solanum hybrid.…”

“…DISCUSSION A widely recognized fact about the tuber-bearing Solanum species is that most of the well recognized species are in general easily crossable, and the meiosis in most of the F,'s is nearly normal. Let alone the interspecific hybrids of Solanums, even the intergeneric hybrids such as Lycopersicon esculentum x S. lycopersicoides and L. esculentum x S. pennelliihave been found to show nearly 'normal'chromosome pairing at pachytene and metaphase I of meiosis in F, (MENZEL, 1962;KHUSH & RICK, 1963). This means that the chromosomes of Solanums in general are not structurally differentiated enough to result in failure of chromosome pairing in any of the interspecific or intergeneric hybrids that have been studied so far.…”

Molecular analysis of single copy and repetitive genes on chromosome 2 in intergeneric tomato somatic hybrid plants

“…R45s is visible cytologically as the nucleolus organizer region (NOR). Menzel [16] studied chromosomal pairing in sexual diploid hybrids between tomato and S. lycopersicoides and found one NOR in both tomato and S. lycopersocoides. Synapsis of the achromatic regions of this chromosome also occurred.…”

Tomato: a crop species amenable to improvement by cellular and molecular methods

“…In fact, Hawkes & Smith, (1965) have argued that the genus Solanum and its relatives have evolved at least for 100 million years . The similarities between the karyotypes of Solanum and Lycopersicon species are also evident from the cytology of intergeneric hybrids (Menzel, 1962 ;Klush & Rick, 1963) .…”