The use of in vitro techniques as a supplement to conventional methods for potato breeding is discussed. The literature on protoplast, isolation, culture and somatic hybridisation is reviewed. The materials and methods used are described. Meristem-tip cultures of three S. tuberosum lines were used to initiate shoot cultures. Plants grown under different environmental regimes were assessed as protoplast sources. Isolations from shoot cultures were more reproducible but gave lower protoplast yields than leaves from growth room grown plants. Protoplasts from a tetraploid cultivar (Fortyfold) from both shoot cultures and leaves of whole plants were successfully cultured and regenerated to plants. Isolated protoplasts from two monohaploid lines failed to respond to the culture conditions used. Shoot cultures of S. brevidens were suitable for the isolation of high yields of viable protoplasts, from which fertile plants were regenerated. Isolated protoplasts of S. brevidens were used in attempts to improve the plating characteristies of cultured Solanum protoplasts. A protocol enabling the culture of protoplasts at low population densities and subsequently, more efficient regeneration of plants from protoplast-derived calluses was developed. The final protocol was applied to the culture of protoplasts from a range of S. tuberosum genotypes. Plants regenerated from protoplasts of S. brevidens and S. tuberosum showed phenotypic variation. Cytological analysis revealed some of this variation correlated with changes in ploidy, aneuploidy and chromosome structural changes. Variation was also present among plants with the normal chromosome number. Unstable changes in the phenotype of regenerated plants were also observed. The final protocol described in this thesis is discussed in perspective with other methods for protoplast culture. The uses of potato protoplasts are discussed.
|Date of Award||1983|