Tomato genotypes superior in regenerating plants from protoplast and callus cultures were obtained by transferring regeneration capacity from Lycopersicon peruvianum into L. esculentum by classical breeding. The genetics of regeneration and callus growth have been studied in selfed and backcross progenies of a selected plant (MsK93) which has 25% L. peruvianum in its ancestry. Segregation data showed that the favourable cell culture traits of L. peruvianum are dominant. Regeneration capacity from established callus cultures was controlled by two dominant genes. Callus growth on primary expiants, callus growth of established cultures and shoot regeneration from explants had high heritabilities (0.47, 0.78, 0.87, respectively). Callus growth and regeneration capacity were not correlated within the populations studied.

A genetic analysis of cell culture traits in tomato.

The commercial tomato belongs to a species most frequently referred to as Lycopersicon esculentum Miller. The correct Latin name for this species has been the subject of much discussion which has not been fully resolved. The alternative names Solanum lycopersicum L., or Lycopersicon lycopersicum (L.) Karsten have appeared in the literature. Lycopersicon esculentum was first proposed for the tomato by Miller in 1768, replacing the earlier Linnean name Solanum lycopersicum. However, Karsten in 1900 suggested that Lycopersicon lycopersicum should be adopted. Under the rules of the International Code of Botanical Nomenclature the original specific name ‘lycopersicum’ should have been retained following the creation of the new genus Lycopersicon. The arguments on either side have been most recently summarized by Broome, Terrell and Reveal (1983). These authors conclude that because of its long and popular usage, the name Lycopersicon esculentum Mill. should be preserved. This is the name which will be used throughout this chapter.

Biosystematics of the tomato

The seed is the primary organ for the perpetuation of germplasm and propagation in all flowering plants. It contains the embryo which develops from the zygote following the fertilization of the egg cell by one of the male gametes. Gene recombination during the formation, as well as the fusion, of the gametes plays a critical role in the evolution of the angiosperms. During its development the embryo is nourished by the endosperm, which itself is formed as a result of the fusion of the second male gamete with two nuclei (in most of the angiosperms) of the central cell of the embryo sac. During the course of evolution many species have developed special means of propagation to overcome physical, environmental and genetic factors that prevent flowering and seed formation. These include the formation of perennial structures such as tubers, rhizomes, bulbs, stolons, etc (see Sharma and Thorpe, this volume). An advanced form of perennation is found in many apomictic species which produce embryos from unfertilized gametic or somatic cells. Like the zygotic embryos, the apomictic embryos develop within the seed and are protected and dispersed like natural seed. Apomictic embryos of all genotypes — irrespective of heterozygosity — developing from unreduced and unfertilized somatic or gametic cells (agamospermy, adventive embryony, apospory, diplospory) breed true and give rise to clonal populations. Apomixis is known to be under genetic control, but environmental conditions such as temperature and photoperiod may also promote a switch from sexual to apomictic development [1,2].

https://link.springer.com/content/pdf/10.1007/978-94-011-0485-2_10

Somatic Embryogenesis in Herbaceous Dicots

Somatic embryos and plantlets have been obtained in quite a direct way from mesophyll protoplasts isolated from androgenetic plants of two cultivars (“Loras” and “Tower”) of Brassica napus. The procedure consists of four steps. Proembryos were induced in a medium supplemented with a cytokinin and an auxin at comparatively high concentrations. They developed to mature embryos when the auxin was reduced or omitted.

Somatic embryogenesis in quite a direct way in cultures of mesophyll protoplasts of Brassica napus L.

Plant regeneration from protoplasts: a literature review

One to five percent of Lycopersicon peruvianum (L.) Mill. leaf mesophyll protoplasts undergo cell division and concomitant organization to form embryogenic-like structures when cultured in Murashige and Skoog medium (1962) containing 3% sucrose, 9% mannitol, 1.0 mg/l kinetin (K) and 1.0 mg/l naphthalene acetic acid (NAA) at pH 5.6–5.8 (medium A). These embryogenic structures, after passing through developmental stages similar to those observed in zygotic embryogeny, are capable of forming shoots on hormone-free medium A. In medium B, wherein 0.5 mg/l of 2,4-dichlorophenoxyacetic (2,4-D) replaced the hormones (K and NAA), embryogenic structures did not develop. However, callus originating in medium B retained morphogenetic capacity as was evidenced by subsequent shoot regeneration when they were transferred to medium A with K and NAA replaced by 1.0 mg/l zeatin (Z). The potential value of incorporating this regeneration trait into Lycopersicon species and cultivated lines for use in tissue culture programs is discussed.

F. J. Zapata

Papers

Somatic embryogenesis from Lycopersicon peruvianum leaf mesophyll protoplasts.