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Protocols for Micropropagation of Woody Trees and Fruits

Protocols for Micropropagation of Woody Trees and Fruits

Protocols for Micropropagation of Woody Trees and Fruits

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274<br />

2.3. Rooting<br />

O. PÉREZ-TORNERO AND L. BURGOS<br />

2.3.1. Culture Medium <strong>and</strong> Conditions<br />

QL macronutrients diluted to half strength, DKW micronutrients, organics <strong>and</strong><br />

vitamins (Table 1), plus 40 mg/l phloroglucinol, are used <strong>for</strong> the rooting <strong>of</strong> apricot<br />

shoots. Sucrose is used at 2%, agar at 0.6% (Hispanlab, S.A.) <strong>and</strong> IBA at 1 to 3 µM,<br />

depending on genotype (Pérez-Tornero & Burgos, 2000).<br />

Figure 6. Bottom cooling system.<br />

Medium is prepared, dispensed <strong>and</strong> sterilized as described previously. Culture<br />

conditions are as described above. Proliferating shoots should be at least 2 cm long.<br />

The basal callus is eliminated <strong>and</strong> shoots are cultured <strong>for</strong> 21 days in the rooting<br />

medium, where induced adventitious roots grow (Figure 7).<br />

Although rooting <strong>of</strong> micropropagated apricot shoots is not a problem, a high percentage<br />

<strong>of</strong> shoots shows symptoms <strong>of</strong> apical necrosis on the rooting media, sometimes<br />

exceeding 80% <strong>and</strong> also affecting axillary buds. Plantlets with necrotic apices<br />

frequently are unable to grow <strong>and</strong> cannot be acclimatized. This effect is highly<br />

genotype-dependent.<br />

2.3.2. Apical Necrosis during Rooting<br />

Apical necrosis can be related to lower endogenous cytokine concentration in the<br />

shoot apex (Kataeva et al., 1991) in apricot (Pérez-Tornero & Burgos, 2000). Apical<br />

necrosis during rooting can be solved by immersing shoot tips in concentrated BA<br />

solution (22.19 to 44.38 µM) just be<strong>for</strong>e explanting shoots on the rooting media. It is<br />

necessary to dry the excessive BA solution to avoid any interference with rooting.

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