Hybrids With Other Solanum Species In contrast to the normal meiosis of hybrids within Lycopersicon, meiosis in hybrids involving the more distantly related Solanum species is partially disrupted. Observations in this area are based primarily on F1 L. esculentum x S. lycopersicoides hybrids, of which the first were synthesized by Rick (1951). Detailed studies were conducted on comparative chromosome morphology and associations in the 2x and 4x intergeneric hybrids (Menzel 1962, 1964, Menzel and Price 1966). Chromosome behavior during early prophase of the 2x hybrid is relatively normal: chromosomes are completely synapsed and form normal synaptonemal complexes at pachytene. However, occasional inversion or deficiency configurations are observed, and the total pachytene complement length of S. lycopersicoides is nearly 1.5 times that of the cultivated tomato. Chromosomes 4, 9, and 10 of S. lycopersicoides were found to be longer than the corresponding chromosomes of L. esculentum, and the resultant bivalents showed unequal pairs. During meiosis, 2x hybrids undergo reduced chiasma formation and produce about four univalents/cell at metaphase I. In 4x allotetraploids, pairing occurs preferentially among homologous chromosomes, resulting in mostly bivalents and a few multivalents. The 4x hybrids also exhibit greater pollen fertility than diploids, and produce a few viable seeds. In allotriploid (sesquidiploid) hybrids, consisting of two genomes of L. esculentum and one of S. lycopersicoides, preferential pairing of the L. esculentum homologues produces 12 bivalents, with the S. lycopersicoides chromosomes forming 12 univalents (Rick et al. 1986). In addition, the condensation of S. lycopersicoides chromosomes during early diakinesis of the sesquidiploids is significantly delayed with respect to their L. esculentum counterparts. These observations of incomplete chromosome pairing and lack of synchronization during meiosis indicate the chromosomes of L. esculentum and S. lycopersicoides are homeologous.
|Original language||English (US)|
|Title of host publication||Genetic Improvement of Solanaceous Crops Volume 2|
|Subtitle of host publication||Tomato|
|Number of pages||70|
|State||Published - Jan 1 2006|
All Science Journal Classification (ASJC) codes
- Agricultural and Biological Sciences(all)