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  • Author or Editor: A. El-Banna x
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The present study was carried out for developing an efficient in vitro callus induction and plant regeneration system in four different tomato genotypes (Solanum lycopersicum Mill., previous name: Lycopersicon esculentum), Advantage II, Edkawy, Castle Rock and Super Strain B, using hypocotyl and cotyledon explants. The effects of two cytokinins, BA (benzyl adenine) and Kin (kinetin), on callus induction and plant regeneration frequency were investigated when added to MS medium in combination at varying concentrations. All concentrations of the two cytokinins were suitable for callus induction and plant regeneration. The frequency of callus induction and plant regeneration from both cotyledon and hypocotyl explants reached 100% for all tested genotypes. Cotyledons produced a higher average number of shoots per explants than hypocotyls for all the genotypes in the five concentrations of combined cytokinins. The average number of shoots per explant in Super Strain B was found to be the highest (42 and 60 for the hypocotyl and cotyledon explants, respectively). Supplementing MS medium with 1.0 mg L−1 kinetin and 1.0 mg L−1 benzyl adenine was found to be optimum for producing the highest number of shoots per explant from hypocotyls and cotyledons in the tomato genotypes investigated. The proposed medium showed a significant superiority over the reference media.

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Fasciated and normal stem segments of Opuntia microdasys, Opuntia cylindrica, Huernia primulina and Euphorbia lactea were collected from the same plant and compared for their anatomy, water relations and genetic variations. Anatomical differences in terms of thickness of cuticle, vascular bundle, xylem and phloem were analyzed in both normal and fasciated stems. The mucilage cells were higher in the fasciated form of Opuntia microdasys than that in the normal form. Water status in terms of total water content (TWC), water deficit and relative water content (RWC) was influenced by fasciation. Genetic variations were tested in normal and fasciated stems using randomly amplified polymorphic DNA (RAPD) fingerprints and SDS-PAGE of soluble protein extracts. SDS-PAGE protein and RAPD analysis confirmed that normal and fasciated tissues were genetically different. Polymerase chain reaction (PCR) yielded different polymorphic banding patterns that were unique to each primer and distinguishable over all samples. The PCR results of normal and fasciated samples were significantly different in cases of primers P1, P2 and P3. These results indicate that occurrence of fasciation in Opuntia microdasys, Opuntia cylindrica, Huernia primulina and Euphorbia lactea is an epigenetic mutation of tissues.

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