| Abstract: |
In establishment stage the sterilized buds of Dieffenbachia picta cv. Tropica (1×1cm) were cultured on MS medium supplemented with 16 ppm 2-ip + 2 ppm IAA + 1 ppm DPU. The resulted shoots from establishment stage (about 2 cm length) were used for multiplication stage.The growth regulators Benzyladenine, Kinetin and Triiodobenzoic acid at 0, 4, 8 and 16 ppm, also cassien hydrolysate at 2, 4 and 8 gm/l or malt extract at 2, 4 or 8 gm/l were used to investigate their effect on shoot multiplication and growth.The effective treatments in enhancing shoot number, shoot length and leaves number/shoot were 4 ppm Benzyladenine or 4 ppm triiodobenzoic acid. Disadvantage of 4 ppm Benzyladenine treatment is callus formation on explant base which may produce variation in the resultant plants, while 4 ppm triiodobenzoic acid did not cause callus formation, moreover, both treatments resulted in similar number of roots/shoot and root length during this stage which lead to avoiding rooting stage. The resultant plantlets could be acclimatized in peat moss media or peat moss + vermiculite (1:1, v:v) with 100% survival percentage.In vitro proliferated shoots of Dieffenbachia picta cv. Tropica were subjected to chemical mutagenic treatment with N-nitroso-N-methylurea (NMU) through either immersion of explants in different concentrations (0.0, 0.1, 0.2, 0.3 and 0.4 %) or by supplementation MS medium with different concentrations (0.0, 0.01, 0.02, 0.03, 0.04 and 0.05 %). The obtained results showed that survival percentage, number of shoots/explant and number of leaves/shoot were decreased with increasing the concentration of NMU agitation concentration. In this experiment, the lethal dose causing 50% reduction in explant survival (LD50) ranged between 0.3 - 0.4% concentrations of NMU. Increasing of NMU concentration in MS medium decreased number of shoots/explant and number of leaves/shoot without affecting the survival percentage. Screening of the second mutated generation showed that the highest NMU agitation concentration (0.4%) was efficient in increasing the number of shoots/explant. Supplementation of medium with NMU did not significantly affect the second mutated generation shoot characters except the shoot length which increased significantly by addition of 0.03% NMU to the culture medium. Successfully acclimatized plantlets will be subjected to further screening for selection any mutated plants.
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