Citrus TISSUE CULTURE WITH TWO DIFFERENT APPROACHES

Citrus is an important genius for economy and human health but a susceptible genius against biotic and abiotic stresses, so it needs to improved programs. Different basal media (MS, ½MA, ?MS and DKW) and different kind and concentrations of plant growth regulators i.e. BA, KIN, 2ip, ZE and TDZ (0 – 2 mg/l) and NAA, IAA and IBA (0 – 2 mg/l) added with 30 g/l sucrose, 3 g/l active charcoal and 7.5 g/l bacteriological agar] were used for organogenesis include shooting and rooting, also callusing from nodal explant of Citrus latifolia. MS medium supplemented with 1 mg/l BA, and 0.01 mg/l NAA is the best media for multiple shoot induction on nodal explants and elongation of them. Other cytokinins had not significant effects on shoot induction and multiplication. Using of 0.01 mg/l IBA instead of 0.01 mg/l NAA on medium with 1 mg/l BA, led to multiple shoot induction on nodal explant indirectly. Rooting was induced on DKW medium plus 1.5 mg/l NAA in the best way compared another media. Both direct and indirect organogenesis (multiple shoot induction) were carried out on media with very similar contents. So we can use very simple and practical methods tissue culture for different improved programs in Citrus genius genius.

Citrus tissue culture: regulation of stylar abscission in excised pistils

Lemon pistil explants were obtained by cutting just above the region of the hypogynous disc (A type explant) or at the base of the pistil (B type explant) and cultured on test medium containing Murashige and Skoog salts, 50 g sucrose/L, 100 mg myo-inositol/L, 5 mg thiamine–HCl/L, and 0.5 mg kinetin/L, plus or minus supplements. Under appropriate conditions an abscission zone formed and styles abscised after 6–8 days of culture; in the field stylar abscission occurred 12–15 days postanthesis. Abscission in A type explants was markedly inhibited by 9 μM 2,4-dichlorophenoxyacetic acid but was unaffected by indole-3-acetic, 1-naphthaleneacetic, gibberellic, abscisic, caffeic, or p-coumaric acids. The response to 2,4-dichlorophenoxyacetic acid was reduced in B type explants. In an atmosphere containing 35–200 ppm ethylene, cell division occurred in the zone of stylar abscission producing a proliferating callus, and the content of cellulase increased from 0.6 to 53.7 enzyme units/g fresh weight compared with fresh explants. Stylar abscission was inhibited by 2,4-dichlorophenoxyacetic acid in A type explants of Washington navel orange, Valencia orange, and mandarin pistils, but not of grapefruit pistils. B type explants of Washington navel orange and mandarin pistils were less responsive to 2,4-dichlorophenoxyacetic acid.