Thesis (M.Sc.) - Cairo University - Faculty of Agriculture - Department of Vegetable

The present research was conducted in tissue culture lab., veg. crops department, Fac. of Agric., Cairo Univ., Giza, Egypt. It aimed to reach the proper protocol for in vitro production of virus-free microtubers of potato cvs. Santana, Herms, and Spunta under light or dark conditions, through applications of silver thiosulfate, abscisic acid, humic acid, maltose and sucrose. Tip meristems were excised from potato tuber seeds. All cultivars were repropagated after 4 weeks for 2 subcultures. At the first experiment, explants were cultured on MS medium with 0, 0.4, 0.8, 1.2, 1.6 or 2 mM of STS under dark or light. STS at 0.4 and 0.8 mM recorded the tallest microplants. The highest number of leaflets and branches per plantlet were obtained with 0.4mM STS. The highest microtuberazation % was recorded with STS at 0.4 mM under dark conditions, and at 2 mM under light one. At the second experiment, explants were cultured on MS medium with 0, 0.5, 1.0 or 1.5 mM of ABA under dark or light. The highest value of plantlet height was recorded at 0 mM ABA. In dark condition, the highest microtuberazation % was recorded in cvs. Santana and Spunta with 0.5 and 0 mM ABA, respectively. The untreated microplantlets under dark recorded the highest number of microtubers/plantlet in cv. Herms At the third experiment, 0, 2,4,6,8 ml HA/l were applied at MS medium. Untreated microplantlets (0 ml HA/l) recorded the highest values of plant height, number of leaflets and branches/plantlet. The application with 2 ml/lHA obtained the highest microtuberazation % either under dark or light conditions. The application with 6 ml HA recorded the lowest number of microtuber/plantlet under dark

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