Variations arising through tissue culture in soft fruits

The study mainly concerns the potential of the tissue culture for mass propagation and to evaluate the trueness to type of regenerated plants from tissue culture using appropriate molecular markers. Three soft fruits species Ribes, Fragaria and Rubus were used in this study. The study has three main sections dealing with an evaluation of appropriate molecular marker systems to study the plants regenerated via micropropagation, callus culture and regeneration and tissue culture and regeneration.The first section evaluates the potential of SDS-PAGE protein electrophoresis and RAPD-PCR as markers to distinguish among clonally propagated cultivars of R. nigrum. SDS-PAGE was able to distinguish only four out of ten cultivars tested. RAPD-PCR was able to distinguish all the cultivars studied using only two primers. The data generated by RAPD-PCR and from pedigree information was used to examine the relatedness among the cultivars studied. RAPD-PCR was further used to examine the purity of the cultivar Baldwin collected at various locations in the UK. Polymorphism was detected and differences were found between the sub-samples of a single cultivar.The second section deals with the multiplication of Rubus, Ribes and Fragaria by micropropagation. The effect of culture cycle on the plants regenerated was evaluated using RAPD-PCR. Ribes did not show any variation until the 14th generation cycle but in the 15th and 16th cycles variation was detected from 6.2% and 13.4% respectively. Considerable variation was detected in Rubus starting with the 4th sub-culture and was at a maximum in the 7th sub-culture. In Fragaria. all plants at sub-culture 3 were evaluated and variation was detected between them. The relevance of such variation on the release of material of all three species is discussed in relation to certification scheme requirements.The third experimental section evaluates the potential of callus as explant source for the multiplication and regeneration of plants in Ribes and Fragaria species. The study also describes investigations in the optimum growth regulators concentrations for callus culture and subsequent plant regeneration. Both the explant type leaf disc and leaf petiole showed successful callus induction in Ribes cultivars. However, plant regeneration was not successful in the cultivars and explant sources studied. In Fragaria regeneration was easily achieved from leaf disc callus and the plants were evaluated for trueness to type using RAPD-PCR This indicated variation ranges from 0.68 to 22.80%.The final discussion reviews micropropagation, callus culture and regeneration and their application to mass propagation. The use of molecular marker systems to evaluate multiplication methodology is discussed both in terms of the needs of the soft fruits industry and as the general approach to the evaluation of progeny of clonally propagated species