Protocols for the micropropagation of several chestnut cultivars

Explants of different chestnut cultivars have been introduced and maintained in vitro in the Laboratory of Micropropagation of the Lugo Polytechnic School of Engineering. Currently, stocks of the Galician cultivars ‘Negral’, ‘Branca’, ‘Amarelante’, ‘Longal’ and ‘Ventura’, and of the Andalusian cultivars ‘Temprana’ and ‘Comisaria’ are completely stabilized in vitro and preserved in in vitro conditions. This paper describes the general conditions for their establishment, and some propagation and rooting experiments. The factors studied in the propagation stage include, depending on the cultivar, medium formulation (WPM, GD), BAP concentration, and light regime (fluorescent lamps vs. LEDs). In cultivars showing symptoms of endogenous bacterial contamination (‘Longal’ and ‘Ventura’), the effect of supra-optimal concentrations of Cu (1 µM -standard-, 30 µM, 60 µM CuSO₄) was tested. After stabilization of the cultures, the cultivars were subjected to rooting induction by dipping in 4.9 mM IBA solution, to test their rooting ability. The cultivars tested responded better, or with no significant differences in multiplication rates, in WPM medium + 0.1 mg L^‑1 BA. Regarding light source, multiplication rates under LEDs or fluorescent lamps were similar for the cultivars tested. Regarding the rooting ability, some cultivars showed low rooting percentages (0 to 25%) while others, such as ‘Branca’ and ‘Negral’ showed rooting percentages above 50%. Interestingly, LED lighting, significantly improved rooting rates and root quality compared to fluorescent lamps. In cultures showing endogenous bacterial contamination, the addition of 60 µM CuSO₄ was detrimental. There were no differences in multiplication rates between cultures in 1 or 30 µM CuSO₄ after three successive subcultures.